US3620294A

US3620294A - Semiautomatic metal casting apparatus

Info

Publication number: US3620294A
Application number: US841019A
Authority: US
Inventors: Frank L Hetzel; Stuart T Schy
Original assignee: TRW Inc
Current assignee: Northrop Grumman Space and Mission Systems Corp
Priority date: 1969-07-11
Filing date: 1969-07-11
Publication date: 1971-11-16
Anticipated expiration: 1988-11-16

Abstract

A program-controlled semiautomatic metal casting process and apparatus involving a series of successive working and checking operations, including preliminary semiautomatic startup operations and final fully automatic melting, pouring, and shutdown operations. Commencement of each operation requires proper completion of the preceding operation. Certain of the operations proceed in accordance with a preselected casting program which may be varied, either by total program substitution or by manual adjustment of the individual program parameters, to provide the optimum program for the particular metal being poured and the particular shape being cast.

Description

United States Patent [72] Inventors Frank L. Hetzel 3,008,855 11/1961 Swenson 164/256 UX Manhattan Beach; 3,478,808 1 1/1969 Adams 164/4 Stuart T. Schy, Reseda, both of Calif. 3,525,382 8/1970 Devol 164/154 9Y1; 3 1:2 FOREIGN PATENTS 1 e u y [45] Patented Nov. 16 1971 467,475 6/1937 Great Bntam 164/157 [73] Assignee TRW Inc. Primary ExaminerR. Spencer Annear One Space Park, Redondo Beach, Calif. A!trneys Daniel T. Anderson, Donald R. Nyhagen and Jerry A. Dinardo 4 EM l 3 s: CASTING APPARATUS ABSTRACT: A program-Controlled semiautomatic metal casting process and apparatus mvolvmg a series of successive [52] US. Cl 164/155, working and checking operations, including preliminary /258 semiautomatic startup operations and final fully automatic [51] Int. Cl 822d 37/00 m lti g, ouring, and shutdown operations. Commencement [50] Field ol Search 164/4, 61, of ea h o eration requires proper completion of the preceding I55 operation. Certain of the operations proceed in accordance with a preselected casting program which may be varied. [56] References cued either by total program substitution or by manual adjustment UNITED STATES PATENTS of the individual program parameters, to provide the optimum 2,713,183 7/1955 Winkler 164/258 p g for the p r l me l ing p re nd th par- 2,932,069 4/1960 Takahashi et al 164/256 ticular h p eing a t.

VAC POWER CONTROLLER 52 SUPPLY 5o 28 TEMP 3 MOLD MONITOR l POLBHON CON ROLLER CARD :2 PROGRAMMER |2 L, VAC

54 PUMPING MEANS 42 PROGRAM 401 SEOUENCER ;1 C

MASTER CONTROL MANUAL CIRCUIT PROGRAMMER L 1s LECEL 34 MOLD on F I I 44 56 GU58 CRUCIBLE SSi TROLLER 430 434 45 4,2 432 436 0% o 0 0 HEAT CONTROL PANEL CONTROLLER PATENTEDuuv 16 an SHEET 07 0F 250 Frank L Hefzel Stuart T Schy 24s INVENTORS Fig 50 ATTORNEY PATENTEDuuv 16 I97! 3, 20,294

sum 12 0F 12 SOOb - 7 o 282A-F Frank L; Hetzel Flg- L Stuart T Schy I NVENTORS ATTORNEY SEMIAUTOMATIC METAL CASTING APPARATUS BACKGROUND OF TI-IE'INVENTION l. Field of the Invention This invention relates generally to the metal casting art. More particularly, the invention relates to a programmed, semiautomatic metal casting method and apparatus involving successive semiautomatic and fully automatic working and checking operations, certain of which proceed in accordance with a casting program which may be varied to provide the optimum program for the particular metal and shape being cast.

2. Prior Art As will appear from the ensuing description, the present invention may be utilized for both atmospheric and vacuum casting applications. However, the invention is primarily concerned with and will be disposed in relation to vacuum casting.

Heretofore, vacuum casting of super alloys and other exotic metals has generally required manual control and manipulation of the casting apparatus. As a consequence, evaluation of the various steps of the casting process often vary from one operator to the next with the result that castings of uniform quality are difiicult to obtain. Moreover, these manually controlled casting processes are excessively tedious and time consuming to practice owing to the numerous manual working and checking operations which the operator must perform properly, and in the proper sequence to obtain satisfactory casting. However, even with the utmost care on the part of the operator, errors and improperly performed casting operations often occur which result in substandard or totally unacceptable cast parts, as well as other adverse occurrences, such as excessive splash and hence loss of the metal being poured.

Another disadvantage of the existing manual casting techniques resides in the fact that many of the manual operations performed during the casting cycle are not subject to audit until completion of the cycle. Consequently, slight variations in the various operations introduced by different operators cannot be detected until the casting cycles are completed and then only by detection of variations in the cast parts. This method of detecting and correcting operator-induced variations in the casting process is very inefiicient, at best, and relatively costly because of the nature of the equipment involved, the necessity of checking each casting, and the relatively high scrap rate.

SUMMARY OF THE INVENTION According to one of its aspects, the invention provides a semiautomatic, precisely repeatable program controlled casting method and apparatus which avoid the above-noted and other disadvantages inherent in the existing manual casting techniques. To this end, the present casting method and apparatus involve a number of successive programmed working and checking operations, including initial semiautomatic startup operations and final fully automatic chamber pumpdown, melting, pouring, and shutdown operations. By way of example, a typical programmed casting cycle proceeds from initial conditioning of the casting apparatus for operation through loading of the metal charge into the crucible, evacuation of the vacuum chamber, checking of the chamber vacuum level, melting and superheating of the metal charge in the crucible, preheating of the crucible pouring lip, checking of the chamber vacuum level and the temperature of the molten charge, uncovering the preheated mold, pouring of the molten charge, venting of the vacuum chamber, shutdown of the apparatus, and final return of the apparatus to its initial state in readiness for the next casting cycle. Each step or operation of the casting cycle must occur to proper completion before the next operation can proceed. In some cases, this requires merely the performance of certain mechanical actions. In other cases, occurrence of an operation to proper completion requires expiration of a measured time delay. In yet other cases, proper completion of an operation necessitates the attainment of a predetermined temperature level or vacuum level.

Certain operations of the present casting process proceed in accordance with a preselected casting program which establishes the optimum casting parameters for the particular metal being cast, such as minimum chamber vacuum level, alloying temperature, and pouring temperature. The program also establishes other optimum parameters associated with the pouring operation including the optimum pouring angle and angular velocity profile of the crucible for the particular metal charge within the crucible to obtain accurate entrance of the molten stream into the mold with virtually no splash or contact of the molten metal with the rim of the mold.

According to one programming feature of the invention, the casting process is programmed with an information storage medium, such as a program card, which is coded to define a selected casting program. A number of these program cards, defining optimum casting programs for different metals and/or cast shapes may be prepared for selective insertion into the casting apparatus, depending upon the particular metal to be poured and the cast shape to be produced. According to another programming feature of the invention, the casting apparatus is provided with a substitute or manual programmer which permits manual adjustment or setting of the individual casting parameters during a test program, to produce any desired casting program. This manual programmer is useful in determining, by the experimental process of trial and error, an optimum casting program for a particular metal or shape to be cast. The apparatus may also be equipped with certain manual override switches to be selectively operated at any stage of the casting cycle to assume manual control of the cycle.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. I is a diagrammatic illustration of the present casting apparatus;

FIG. 2 is a circuit diagram of the control panel of the apparatus;

FIGS. 3a, 3b, and 3c are circuit diagrams of the apparatus;

FIG. 4 illustrates a casting program card for use in the casting apparatus;

FIG. 5 is a perspective view of a card reader employed in the casting apparatus;

FIG. 5a is an enlarged section through contacts of the card reader;

FIG. 6 is a circuit diagram of the card reader;

FIG. 7 is a circuit diagram of the card reader timing circuit;

FIG. 8 is a circuit diagram of the crucible drive controller;

FIG. 9 is a circuit diagram of the vacuum system for the vacuum casting chamber;

FIG. I0 is a circuit diagram of the temperature monitor;

FIG. I l is a circuit diagram of the heat controller;

FIG. 12 is a circuit diagram of the mold lid position controller; and

FIG. I3 is a circuit diagram of the manual programmer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference is made first to FIG. 1 diagrammatically illustrating a semiautomatic metal casting apparatus 10 according to the invention. The casting apparatus includes a vacuum chamber 12 and vacuum pumping means 14 for evacuating the chamber. Exposed to the interior of the vacuum chamber is a vacuum level detector 16 for sensing the vacuum level within the chamber. At the bottom of the chamber is a mold 18 supported on a mold positioning table 20. A crucible 22, having an induction heating coil 23, is pivotally mounted over the mold and is coupled to a crucible tilt drive motor 25 for rotating the crucible through a range of angular positions. Associated with the mold I8 is a combination lid and positioning target 26 coupled to a lid operator 28. This operator may be actuated to move the mold lid between its broken and solid line positions of FIG. I. The solid line position of the lid is its retracted position, wherein the lid is situated to permit pouring of metal from the crucible 22 into the mold I8. The

broken line position of the lid is its target position, wherein the lid closes the mold, which is preheated, to aid in retaining heat in the mold and serves as a target for positioning the mold 18 properly to receive molten metal from the crucible. At the top of the vacuum chamber 12, over and in a position to view the interior of the crucible 22, is an optical thermal sensor 30. Access to the interior of the vacuum chamber 12 to introduce, position, and remove the mold l8 and to load a metal charge into the crucible 22 is provided by a door 32. This door, when closed, hermetically seals the chamber.

Operation of the casting apparatus is controlled by a semiautomatic control system 34 powered from an electrical power supply 36. This control system includes a programmer 38 into which may be inserted an information storage medium containing a preselected casting program, and a substitute or manual programmer 40 which may be operated manually to adjust the individual casting cycle parameters, thus to preset into the control system any selected casting program. In the particular embodiment of the invention selected for presentation in this disclosure, the programmer 38 is designed to receive casting program cards which are prepared or coded to define difi'erent preselected casting programs. For this reason, the programmer 38 is hereinafter referred to as a card programmer. It will be understood, however, that other types of I information storage media may be utilized to store the preselected casting programs. Also included in the control system is a program sequencer 42, a control panel 44, a crucible drive controller 45 for the crucible drive motor 25, a vacuum controller 46 for the vacuum pumping means 14, a heat controller 48 for the crucible heating coil 23, a mold lid position controller 50 for the lid operator 28, and a temperature monitor 52 for the thermal sensor 30. A master control circuit 54 interconnects the several components of the casting apparatus to accomplish the semiautomatic casting or pouring cycle of the invention. As noted earlier, this cycle involves a series of successive working and checking operations or steps, including preliminary semiautomatic startup operations and subsequently fully automatic melting, pouring, and shutdown operations. Certain of these operations proceed in accordance with the casting program stored in the card programmer 38 or preset into the manual programmer 40 in a manner such that the casting cycle occurs under the optimum conditions for the particular metal being poured and shape being cast.

A detailed description of the casting apparatus 10 will be presented shortly. In order to facilitate a full and complete understanding of the later description, however, it is advisable to discuss at this point an exemplary casting cycle in step-by-step sequence.

It will become evident from the later description, that the casting cycle is caused to proceed from one step to the next by stepping of the program sequencer 42. Each step of the cycle must occur to proper completion before the next step can occur. Accordingly, any malfunction during the casting cycle will automatically terminate the sequence until the malfunction is corrected. Moreover, as noted earlier and explained in detail later, manual control of the casting cycle may be assumed at any point in the cycle. In the ensuing discussion of the casting cycle, reference is made to various programmed functions or parameters, such as programmed crucible positions and tilt speeds, programmed time delays, programmed temperatures, programmed heating power levels, and so on. As will appear from the later description, these are parameters which are dictated or established by the selected casting program inserted into the card reader 38.

Attention is directed to the fact that the following steps define a typical casting program and are not to be construed as necessarily occuring in the order listed, as the order of seqbence is versatile and changeable by simple resetting of the sequence order in the programmer sequencer 42. Moreover, the actual steps involved in the casting cycle may be varied by eliminating and/or adding steps.

PRECONDITION OF THE CASTING APPARATUS FOR AUTOMATIC CASTING OPERATION Automatic operation of the casting apparatus 10 requires the execution of certain preliminary manual operations to condition the apparatus for its automatic casting cycle which are represented in this disclosure by actuation of automatic mode switches 56, 58 on the control panel 44. These actions energize the control system 54 and produce a stepping impulse which steps the program sequencer 42 from its initial or home position to initiate the first step of the casting cycle.

STEP l STEP 2 During this step of the casting cycle, bars or ingots of the metal to be cast are loaded into the crucible 22, and the mold lid operator 28 is actuated manually by button 59 on the changeable panel 44 to lower the mold lid 26 to its broken line target position of FIG. 1. In this regard, it should be noted that the mold lid is thus lowered only after the mold 18 has been placed in the vacuum chamber 12 and that the act of lowering the lid is utilized, in effect, as a control function to indicate the presence of the mold within the chamber. Arrival of the lid at its lower target position produces a stepping impulse for stepping the program sequencer 42 to the third step of the casting cycle.

STEP 3 STEP 4 This step is the final manual step of the casting cycle and involves closing and locking of the vacuum chamber door 32 to hermetically seal the vacuum chamber 12. Closing of the door produces a stepping impulse which advances the program sequencer 42 to the fifth step of the casting cycle. The latter step constitutes the beginning of the fully automatic portion of the casting cycle during which the successive steps of the cycle occur automatically in sequence in response to proper completion of the preceding steps.

STEP 5 During this first automatic step of the casting cycle, the

vacuum controller 46 and the heat controller 48 are energized to commence evacuation of the vacuum chamber 12 and condition the heat controller for the subsequent crucible heating step. The crucible drive controller 45 is activated to rotate the crucible 22 to a programmed melt position. Relation of the crucible to this position produces a stepping impulse for advancing the program sequencer 42 to the sixth step of the casting cycle.

STEP 6 This step activates the vacuum level detector 16 to check the vacuum level in the vacuum chamber 12. When this vacuum level reaches a programmed heat-start vacuum level, a stepping impulse is produced which advances the program sequencer 42 to the seventh step of the casting cycle.

STEP 7 In this step, the heat controller 48 is activated to energize the crucible heating coil 23 to programmed melt power level. Simultaneously, a programmed melt time delay is initiated and programmed superheat temperature information is fed to the temperature monitor 52. The programmed melt time delay represents the approximate heating time, less a selected fixed time interval such as one minute, required at the programmed melt power level to melt the metal charge within the crucible 22 and bring the molten metal to a temperature level which is less, by a preselected temperature difference, than the programmed superheat temperature. At the expiration of the melt time delay, a stepping impulse is produced to step the sequencer 42 to the eighth step ofthe casting cycle.

STEP 8 During this step, the crucible drive controller 45 is activated to rotate the crucible 22 at a relatively slow creep rate to an upright position in which the molten metal in the crucible is exposed to the thermal sensor 30. Also, control of the heat controller 48 is effectively transferred from the card programmer 38, which supplies the programmed melt power information for controlling the power level setting of the heat controller in step 7, to the temperature monitor 52. The temperature monitor activates the heat controller 48 to energize the crucible heating coil 23 at a preselected full controlled power level. Simultaneously, an additional fixed melt time delay, equal to the selected time delay interval referred to in step 7, i.e. 1 minute, is initiated. At the expiration of this fixed melt time delay, a stepping impulse is produced to advance the sequencer to its ninth step.

STEP 9 This step involves resumption of control of the heat controller 48 by the card programmer 38 and reduction of the power level setting of the heat controller to a programmed hold power level. After a short delay to permit thermal stabilization, the temperature monitor 52 is activated to compare the temperature of the molten metal with the programmed superheat temperature level and to determine the heating power level required to heat the metal to the superheat temperature. If the required heating power level is less than the programmed hold power level, a forward stepping impulse is produced which advances the program sequencer 42 to the following lOth step of the casting cycle. On the other hand, if the required power level is greater than the hold power level, a backstepping impulse is produced which returns the sequencer to the preceding eighth step of the casting cycle to repeat the latter step at controlled power level proportional to the temperature error. After expiration of the fixed heating time delay of the eighth step, the sequencer is again advanced to repeat the ninth step. This procedure is repeated, at a controlled heating power level which gradually drops as the metal temperature increases, until the heating power level required to achieve the programmed superheat temperature closely approaches the hold power level, indicating an acceptable temperature error, whereupon the sequencer advances to the 10th step.

STEP 10 In this step, the power level of the heat controller is reduced to a preset low level and the crucible drive controller 45 is activated to rotate the crucible 22 at the creep rate to a programmed lip heat position, wherein the molten metal within the crucible contacts but does not overflow the crucible pouring lip. Also, a programmed lip heat delay is initiated. This lip heat delay represents the time period required to heat the pouring lip at the power level to the proper pouring temperature and cool the molten metal from its superheat temperature to a temperature slightly above, i.e. on the order of 25 above, a programmed pouring temperature of the metal. A stepping impulse is produced at the expiration of the lip heat delay to advance the sequencer 42 to the 1 1th step of the casting cycle.

STEP 1 I In this step, the crucible 22 is returned at the creep rate to its upright position and the heat controller 48 is activated by the temperature monitor 52 to energize the crucible heating coil at a controlled power level proportional to the temperature error between the metal temperature and the programmed pouring temperature. A fixed heating delay, such as 1 minute delay is initiated, after which a stepping impulse is produced to advance the sequencer 42 to the 12th step.

STEP l2 This step again activates the temperature monitor 52 to read the temperature of the molten metal within the crucible 22 after a brief delay to permit thermal stabilization and to compare the temperature of the molten metal with its programmed pouring temperature. If the temperature of the metal is less than its programmed pour temperature, a backstepping impulse is produced to return the sequencer 42 to its 11th step to repeat the latter step at a power level proportional to the temperature error. If the metal temperature exceeds the programmed pour temperature on the other hand, the system waits, applying heating power to the crucible at a preset minimum power level, until the metal temperature cools to the programmed pour temperature. When the exact pour temperature is attained, a stepping impulse is produced to advance the sequencer 42 to its 13th step.

STEP 13 This step returns the heat controller 48 to its programmed hold power level and verifies the existence of a programmed minimum pour vacuum level within the vacuum chamber 12. A stepping impulse is then produced to step the sequencer 42 to the following 14th step of the casting cycle.

STEP l4 During this step, the mold lid operator 28 is actuated by the mold lid position controller 50 to raise the mold lid 26 to its solid line retracted position of FIG. 1. The crucible drive controller 45 is actuated to rotate the crucible 22 to a final programmed pour angle at a programmed pour speed which is selected to cause entrance of the molten stream into the mold 18 with virtually no splash or contact of the molten metal with the rim of the mold. Rotation of the crucible to its final pouring position produces a stepping impulse for advancing the sequencer 42 to the final 15th step of the casting cycle.

STEP 15 This step is a cooling step during which all heating power to the crucible is turned ofi, and a programmed vent delay time is initiated. This vent delay time represents the time required for cooling of the poured metal under vacuum within the mold 18 to a selected reduced temperature. At the expiration of the delay, a stepping impulse is produced to advance the programmed sequencer 42 to its initial home position. Return of the sequencer to its home position cuts power to the vacuum and

heat controllers

46, 48 to shutdown the vacuum pumping system 14 and automatically vent the vacuum chamber 12 to atmosphere and thereby complete the casting cycle.

The casting apparatus 10 of the invention which has been selected for illustration will now be described in greater detail by initial reference to FIG. 3. In the ensuing description, programmed control infonnation is referred to in terms which connote the functions to which the information relates. For example, programmed information relating to a crucible position is referred to as angle select information. Melt angle selection information, for instance, is programmed crucible position information which dictates the angular position in which the crucible 22 is to be located during the melt phase of the casting cycle. Programmed information relating to heating power level, temperatures, time delays, crucible tilt rate, etc., is referred to in similar terms. Pour temperature select information, for example, is control information which dictates a preselected temperature at which the molten metal is to be poured. As it will appear from the later description, this control information is electrical information in the form of voltage signals. In a similar manner, certain mechanical elements of the casting apparatus are referred to in terms which indicate the functions performed by the respective elements. By way of example, a melt angle select switch is referred to in the ensuing description. This is a switch for feeding melt angle select information from the card programmer 38 to the crucible drive controller 24. It will be understood, of course, that the various functions referred to in the description are those mentioned in the earlier discussion of the casting cycle.

Turning now to FIG. 3, the illustrated program sequencer 42 is a rotary stepping drum-type sequencer, such as that marketed by the Tenor Company of Milwaukee, Wis., under the name Tenor Programmer. This sequencer is diagrammatically illustrated in FIG. 3 as comprising a number of switches 60, a rotary drum 62 having changeable pins 63 for actuating the switching in a desired sequence as the drum rotates, and an electrical stepping actuator 64 for rotating the drum in stepwise fashion through a number of successive positions or steps. In this instance, the sequencer drum 62 uses 16 positions or steps corresponding to the initial conditioning step and working steps of the casting cycle described earlier. Fewer or additional steps may be employed, depending upon the number of steps in the casting cycle.

In connection with actuation of the sequencer switches 60 by the sequencer drum 62, it will appear from the ensuing description that each switch has a normal position and a second position to which the switch is operated by the drum. In some cases, the drum may operate a switch in only one drum stepping position. In other cases, the drum may operate a switch in a number of stepping positions, either consecutive stepping positions or spaced stepping positions. The switch operating pins 63 on the drum may be so arranged that a switch which is operated in a number of consecutive stepping positions remains in its drum actuated position continuously throughout these positions including the intervals during which the drum steps from one position to the next. Attention is directed to the bracketed numerals below the broken lines representing the drum pins 63 in FIG. 3. These numerals identify the stepping position or positions of the drum in which the corresponding drum switch 60 is actuated.

Power supply 36 provides both AC and DC power for operating the casting apparatus in the manner explained in the ensuing description. In this regard, attention is directed to the fact that the casting apparatus and its operation are described below in relation to the typical or exemplary casting cycle discussed earlier. Accordingly, it should be understood that the invention contemplates within its scope various modifications, which will become obvious as the description proceeds, to accommodate variations in the casting cycle.

The stepping actuator 64 of program sequencer 42 has two normally

open switches

72, 76 and opens a normally closed switch 74. Switch 72 is a load angle select switch. This switch, when closed, completes a circuit from a load angle select terminal of the card programmer 38 through a lead 80, the switch contacts, and a lead 82 to the crucible drive controller 45. As it will appear from the later description, this circuit is utilized to feed programmed load angle information to the drive controller for energizing the crucible drive motor 25 to rotate the crucible 22 to a programmed loading position. Sequencer switch 74 is a creep relay switch. This switch, when closed, completes an energizing circuit from a low voltage lead 83 of the power supply 36 through a lead 84, the switch contacts, and a lead 86 to the crucible controller 45 for energizing a creep relay within the controller. As explained later, the creep relay, when thus energized, conditions the drive controller to energize the crucible drive motor at a relative slow creep rate in response to angle select information, such as the load angle select information just mentioned, for rotating the crucible 22 at this rate to the position represented by the information. Programmer switch 76 is an automatic power-on check switch. This switch, and a set of normally open contacts 56a are connected in electrical series between the low voltage supply lead 83 and the sequencer forward stepping lead 68. Closure of the contacts 56a thus applies a forward stepping voltage to the program sequencer 42 which steps the latter from its home position H to its first stepping position. As will be explained presently, contacts 560 are contacts of the automatic mode switch 56 on the control panel 44 which are closed by actuation of the switch. Actuation of switch 58 energizes the control system including lead 83 from the power supply 36. Thus, actuation of both switches conditions the casting apparatus for its casting cycle and steps the sequencer from its home position to its first stepping position.

As indicated in FIG. 3, the load angle select switch 72 remains closed from the home position H through the fourth stepping position and is then reclosed from the l5th stepping position back to the home position H of the sequencer 42. Creep relay switch 74 is open in the home position of the sequencer and closes to energize the creep relay when the sequencer advances to its first stepping position. The switch reopens to deenergize the creep relay in the l3th and l4th stepping positions. The automatic power-on check switch 76 is closed only in the sequencer home position and opens when the sequencer steps from this position.

It is now evident that actuation of the

switches

56, 58 in the home position of the sequencer 42 feeds programmed crucible load angle information from the card programmer 38 to the crucible drive controller 45, supplies operating power to the control system and closes the sequencer stepping contacts 560 to advance the program sequencer 42 to its first stepping position.

Stepping of the program sequencer 42 to its first stepping position closes the creep relay switch 74 to energize the creep relay in the crucible drive controller 45. The programmed crucible load angle information which is currently being fed to the controller through the closed sequencer load angle select switch 72 then actuates the controller to drive the crucible 22 at the creep rate to the programmed load angle. In its first stepping position, the sequencer 42 also closes a normally open MLC (main line contactor) check switch 90. Switch 90 and a set of nonnally open contacts 920 are connected in electrical series between the supply lead 83 and the sequencer forward stepping lead 68. Accordingly, closure of the contacts 92a applies a forward stepping voltage to the sequencer 42 which steps the latter from its first stepping position to its second stepping position. Contacts 92a are contacts of an MLC (main line contactor) relay embodied in the heat controller 48. As explained later, this relay is energized to close its contacts upon proper completion of the precondition steps at the outset of the casting cycle. Accordingly, if these precondition steps have been properly completed, closure of the MLC check switch 90 by the sequencer drum 62 upon stepping of the latter to its first position results in immediate stepping of the drum to its second stepping position. The MLC check switch reopens upon stepping of the drum.

From the earlier description of the typical casting cycle, it will be recalled that in the second step of the cycle, the mold lid 26 is lowered to its broken line position of P16. 3 to signify that the mold 18 has been placed in the vacuum chamber 12 and to permit use of the lid as a target for placement of the mold in proper pouring position relative to the crucible 22. Arrival of the lid in its lower target position closes a normally open lid-down limit switch 94 actuated by the mold lid operator. Switch 94, and a normally open switch 96 of the program sequencer 42 are connected in electrical series between the low voltage supply lead 83 and the sequencer forward stepping lead 68. Sequencer switch 96 is a lid-down check switch which is closed in the second stepping position of the sequencer. Thus, with the sequencer in its second stepping position, lowering of the mold lid 26 to its target position applies a forward stepping voltage to the sequencer which steps the latter to its third stepping position. The lid-down check switch 96 reopens when the sequencer steps.

In the third stepping position of the program sequencer 42, the card programmer 38 is opened and a previously prepared casting program card is inserted. In FIG. 3, the card programmer is diagrammatically illustrated as having a hinged cover 100 which may be rotated to open position for insertion of the program card. After the card has been properly inserted into the programmer, the latter is closed by rotation of its cover 100 to closed position. The card programmer 38 and the casting program card will be described in detail presently. Suffice it to say at this point that the card programmer embodies normally

open switches

102, 103 which are closed by proper placement of a program card in the programmer and by closure of the programmer cover 100, respectively. These switches and a normally open switch 104 in the program sequencer 42 are connected in electrical series between the supply lead 83 and the sequencer forward stepping lead 68. Switch 104 is a normally open card programmer check switch which closes in response to stepping of the sequencer to its third stepping position. It is now evident, therefore, that insertion of a program card into the card programmer 38 and closure of the latter with the program sequencer 42 in its third stepping position applies a forward stepping voltage to the sequencer which steps the sequencer to its fourth stepping position.

Stepping of the sequencer 42 to its fourth stepping position closes a normally open vacuum chamber door check switch 106. Switch 106 and a switch 108 are connected in electrical series between the supply lead 83 and the sequencer forward stepping lead 68. Switch 103 is operated by the door 32 of the vacuum chamber 12 in such a way that the switch closes when the door is closed to seal the chamber. Thus, closure of the chamber door 32 during the fourth step of the casting cycle steps the program sequencer 42 to its fifth stepping position. In this regard, it is significant to recall that the first four steps of the casting cycle require manual operations for their completion. The remaining steps of the cycle, commencing with step number 5, are fully automatic.

Stepping of the sequencer 42 to its fifth stepping position closes a normally open switch 110 which is hereinafter referred to as a vacuum-heat controller switch. One terminal of this switch is connected to the low voltage power supply lead 83. The other terminal of the switch is connected through a lead 1 13 to the vacuum controller 46 and heat controller 48. Accordingly, closure of the vacuum-heat controller on switch 110 in stepping position of the program sequencer 42 connects the vacuum and heat controllers to the supply lead 83. The vacuum and heat controllers will be described in detail presently. Suffice it to say at this point that connection of the controllers to the supply lead 83 activates the controllers. The vacuum controller 46, when thus activated, immediately energizes the vacuum pumping means 14 to commence evacuation or pump-down of the vacuum chamber 12. The heat controller 48, when activated, on the other hand, is merely conditioned to energize the crucible heat coil 23. In this regard, it will be seen that the MLC contacts in the heat controller, which were closed at the start of the casting cycle, are reopened in response to activation of the heat controller at this point to open the energizing circuit between the controller and the heating coil. The MLC contacts are reclosed to energize the coil in the seventh step of the sequencer. It is significant to note here that the sequencer switch remains closed, and hence the vacuum and heat controllers remain in their activated or on condition, from the fifth stepping position through the 15th stepping position of the program sequencer 42.

Stepping of the program sequencer 42 to its fifth stepping position also closed a pair of normally

open switches

114 and 116. Switch 114 is a melt-angle select switch which completes a circuit from a melt-angle terminal of the card programmer 38, through a lead 118, the switch contacts, and a lead to the lead 82 extending to the crucible drive controller 45. As will appear presently, this circuit is utilized to feed a programmed crucible melt-angle signal from the card programmer to the crucible drive controller. This signal activates the controller to energize the crucible drive motor 25 for rotating the crucible 22 at its creep rate from its current loadangle position to the programmed melt-angle position. The melt-angle select switch 114 remains closed, so that the crucible remains in its programmed melt-angle position, from the fifth stepping position through the seventh stepping position'of the program sequencer 42.

Associated with the crucible drive system is a normally open switch 121 which is momentarily closed in response to rotation of the crucible 22 from its load angle position to its meltangle position as well as in response to later rotation of the crucible to its pour-angle position. In the particular embodiment of the invention selected for illustration, the switch 121 closes in response to rotation of the crucible through an 80 position (i.e. a position displaced 80 from the horizontal and 10 from the vertical). For this reason, the switch 121 is referred to for convenience as an 80 switch. The 80 switch 121 and a fixed delay timer 122 are connected in electrical series to the supply lead 83 so that closure of the switch energizes the timer to commence running of a fixed delay time to be discussed presently. The timer has normally open contacts 122a in series with a sequencer switch 116 which closes in the fifth stepping position. At the expiration of its fixed delay, timer closes its contacts to connect lead 83 to the sequencer forward stepping lead 68. Closure of the 80 switch 121 in response to rotation of the crucible 22 through its 80 position with the sequencer in its fifth stepping position thus applies a forward stepping voltage to the sequencer for advancing the latter to its sixth stepping position.

As noted in FIG. 3 of the drawings, sequencer switch 116, hereinafter referred to as an 80 stepping switch, opens upon stepping of the sequencer and subsequently recloses in the 14th stepping position of the sequencer.

lt is now evident, therefore, that stepping of the program sequencer 42 to its fifth stepping position turns on the vacuum controller 46 to commence pumpdown of the vacuum chamber 12 and turns on the heat controller 48 to condition the latter for energizing the crucible heating coil 23 in the seventh step of the sequencer. The crucible drive controller 45 is also activated to drive the crucible 22 from its programmed load-angle position to its programmed melt-angle position. Rotation of the crucible through its 80 position on its way to its melt-angle position advances the program sequencer 42 to its sixth stepping position.

In the sixth stepping position of the program sequencer 42, a normally open vacuum-step switch 124 is closed. This switch completes a stepping circuit from a vacuum-step terminal of the card programmer 38, through a lead 126 and the switch contacts to the sequencer forward stepping lead 68. As will appear from the later description, the chamber vacuum level detector 16 and the card programmer 38 cooperate to produce a stepping voltage at the latter programmer terminal in response to reduction of the pressure within the vacuum chamber 12 to or below a programmed heat-start vacuum level. This stepping voltage is applied to the sequencer stepping lead 68 through the circuit 124, 126 to step the sequencer 42 to its seventh stepping position. In this regard, it is significant to recall that evacuation of the vacuum chamber 12 commences in the preceding stepping position of the sequencer 42 by closure of its vacuum-heat controller on switch 1 10.

From the foregoing discussion, it will be understood that in the sixth stepping position of the program sequencer 42, the vacuum chamber 12 is pumped down by the vacuum pumping means 14, thereby reducing the pressure within the chamber. When the vacuum chamber is finally evacuated at least to the programmed heat start vacuum level, the sequencer 42 is advanced to its seventh stepping position.

Stepping of the program sequencer 42 to its seventh stepping position closes a group of five normally

open switches

130, 132, 134, 136, and 138. Switch 130 is a heating power-on switch which completes a circuit from the low voltage power supply lead 83 through the switch contacts and a lead 140 to the heat controller 148. As will appear from the later description, the voltage which is thus applied to the heat controller recloses the MLC contacts in the heat controller to energize the crucible heating coil 23. The switch 130 remains closed through the 14th stepping positions of the sequencer. Sequencer switch 132 is a melt power select switch. Closure of this switch completes a circuit from a melt power terminal of the card programmer 38 through a lead 142, the switch contacts, and a lead 144 to the heat controller 48. From the later description, it will be seen that a programmed melt power level signal is thereby fed from the card programmer 38 to the heat controller 48. This signal adjusts the controller to energize the crucible heating coil 23 at the programmed melt power level. Switch 132 opens in response to stepping of the sequencer 42 to its next stepping position. The third switch 134 to be closed in the seventh stepping position of the sequencer 42 is a superheat temperature select switch which remains closed through the ninth stepping position. Closure of this switch completes a circuit from a superheat temperature terminal of the card programmer 38, through a lead 146, the switch contacts, and a lead 148 to the temperature monitor 52. A programmed superheat temperature signal is thereby fed from the card programmer 38 to the monitor to be utilized in the manner explained below.

The two remaining

switches

136 and 138 which close in the seventh stepping position of the program sequencer 42 are utilized to effect a timing function. Thus, switch 136 is a heating time delay start switch having one terminal connected to the power supply lead 83. The other terminal of the switch is connected through a lead 150 to a melt time delay power terminal of the card programmer 38. Closure of the switch 136 energizes a timing circuit embodied in the card programmer to commence running of a programmed melt time delay, as explained later. At the expiration of this delay, the timing circuit produces a stepping voltage at a melt time delay step terminal of the card programmer. This stepping voltage is applied to the sequencer stepping lead 68 through a lead 152 and the currently closed sequencer switch 138 to advance the sequencer to its eighth stepping position. This latter switch is hereinafter referred to as a time delay stepping switch. It will be noted that the melt time delay start switch 136 is closed only in the seventh stepping position of the sequencer 42, while the time delay stepping switch 138 is closed in stepping positions Nos. 7, l0, and 15.

From the foregoing description. it will be understood that the seventh stepping position of the program sequencer 42 energizes the crucible heating coil 23 to a programmed melt power level to commence melting of the metal within the crucible 22. Simultaneously, programmed superheat temperature information is fed to the temperature monitor 52 and a programmed melt time delay is started. The length of this delay is selected to equal the time duration, less a fixed time interval of typically 1 minute duration, required to melt the metal charge in the crucible and heat the molten metal to a temperature on the order of less than the programmed superheat temperature. At the expiration of the melt time delay, the sequencer 42 is advanced to its eighth stepping position.

In its eighth stepping position, the sequencer 42 closes a normally open switch 154. Closure of this switch completes a circuit from the power supply lead 83 through the switch contacts and a lead 156, to a fixed delay timer 158 having normally open contacts 1580. A voltage is thereby applied to the timer to commence running of a fixed time delay. At the expiration of this delay, which is equal to the fixed time interval, i.e. l minute, referred to in the preceding stepping position of the sequencer 42, the timer contacts 158a close. These timer contacts are connected in electrical series between the supply lead 83 and the sequencer stepping lead 68. Accordingly, closure of the timer contacts steps the sequencer 42 to its ninth stepping position. Lead 156 also extends to the temperature monitor 52. Accordingly, a voltage is applied to the monitor concurrently with energizing of the fixed delay timer 158. As will be explained presently, this voltage and the programmed superheat temperature signal which is currently being applied to the temperature monitor through the sequencer switch 134 cooperate to effect electrical connection of the temperature monitor to the heat controller 48 and actuation of the monitor to transmit a programmed heating power level signal from a full controlled power level terminal of the card programmer 38, through a lead 1590 the temperature monitor. and a lead 15% to the heat controller. This power level signal, hereafter referred to as a full controlled power level signal, adjusts the heat controller to energize the crucible heating coil 23 at the programmed full controlled power level. As will appear from the later description, the above actuation of the temperature monitor 52 in response to closure of the sequencer switch 154 involves a controlled power level locking function in the monitor. For this reason, the switch is hereafter referred to as a controlled power level lock switch or simply a power lock switch.

ln the eighth stepping position of the sequencer 42, then, the crucible heating coil 23 is energized at the programmed full controlled power level for a fixed period of time, in this instance l minute. The sequencer 42 then advances to its ninth stepping position. The power lock switch 154 reopens when the sequencer steps and subsequently recloses in the 11th sequencer stepping position. Reopening of switch 154 deenergizes the fixed delay timer 158, which then resets automatically in readiness for its next timing cycle, and disconnects the temperature monitor 52 from the heat controller 48 to terminate energizing of the heating coil 23 at the full controlled power level.

In its ninth stepping position, the program sequencer 42 closes a pair of normally open switches and 162. Switch 160 is a hold power level select switch which reopens when the sequencer steps and subsequently recloses in the 13th and 14th stepping positions. Closure of this switch completes a circuit from a hold power level tenninal of the card programmer 38, through a lead 164, the switch contacts, and a lead 166 and the lead 144 to the heat controller 48. As will be explained later, a programmed hold power level signal is thereby fed from the card programmer 38 to the heat controller 48. This signal adjusts the heat controller to energize the crucible heating coil 23 at the programmed hold power level which is selected to produce a crucible heating temperature approximating a programmed pouring temperature of the molten metal in the crucible. Sequencer switch 162 is a temperature interrogate switch which closes in the ninth stepping position only to complete a circuit from the power supply lead 83 through the switch contacts and a lead 168 to a fixed delay timer 170 having normally open contacts 1700. Accordingly, closure of the switch 162 energizes the timer to commence a fixed time delay. At the expiration of this delay, the timer contacts 170a close to connect the lead 168 to a lead 172 extending to the temperature monitor 52. As explained later, the voltage signal which is thus applied to the temperature monitor 52 effectively interrogates the monitor to determine the heating power level required to heat the molten metal in the crucible to its programmed superheat heat temperature. The fixed delay introduced by the timer 170 permits stabilization of the temperature monitoring system. Extending from the temperature monitor are

leads

174 and 176. Lead 174 connects to the forward stepping lead 68 and lead 176 to the backstepping leads 70 of the program sequencer 42. As will also appear from the later description, the temperature monitor 52 responds to the incoming interrogate signal by applying a forward stepping voltage to the lead 174 if the required heating power level is less than the programmed hold power level and a backstepping voltage to the lead 176 if the required power level exceeds the hold power level.

it will now be understood that in the ninth stepping position of the sequencer 42, the temperature monitor 52 is interrogated concerning the heating power level required to heat the molten metal within the crucible 22 to its programmed superheat temperature. If the required heating power level change exceeds 50 percent of the programmed full controlled power level, the sequencer is returned to its eighth stepping position to repeat the l-minute heating step of this position. As explained later, however, during this reheating step, the crucible heating coil 23 is energized at a controlled power level proportional to the temperature error between the programmed superheat temperature and the actual metal temperature. On the other hand, if the required heating power is less than 50 percent of the full controlled power level, the sequencer is advanced to its th stepping position.

In its 10th stepping position, the sequencer 42 closes three normally

open switches

178, 180, and 182. Switch 178 is a lip heat angle select switch. Closure of this switch completes a circuit from a lip heat angle terminal of the programmer 38, through a lead 184, the switch contacts, lead 186 and the lead 82 to the crucible drive controller 24. From the later description, it will appear that this action feeds a programmed lip heat angle signal from the card programmer 38 to the crucible drive controller 24. The drive controller energizes the crucible drive motor 25 in response to this signal to rotate the crucible 22 at its slow creep rate to a programmed lip heat angle position. In this position, the molten metal within the crucible contacts but does not overflow the crucible pouring lip. Switch 180 is a lip heat delay start switch. Closure of this switch connects the power supply lead 83 to a lip heat delay power terminal of the card programmer 38 through the switch contacts and a lead 188. A voltage is thereby applied to the card programmer which activates the timing circuit in the programmer to generate a programmed lip heat delay time. This lip heat delay is selected to equal the time duration, less a fixed time interval such as 1 minute, required to heat the crucible pouring lip to the proper pouring temperature and cool the molten metal in the crucible from its current superheat temperature to a temperature slightly above, typically on the order of 25 F. above, a programmed pouring temperature. In this regard, it is significant to note that in the 10th stepping position, no heating power level signal is supplied to the heat controller 48. As will be seen later, under these conditions, the heat controller energizes the crucible heating coil 23 at a reduced power level which permits cooling of the metal as just stated. Switch 182 is a pour temperature select switch which remains closed through the 12th stepping position. Closure of this switch completes a circuit from a pour temperature terminal of the card programmer 38 through a lead 189, the switch contacts, a lead 190 and the lead 148 to the temperature monitor 52. Programmed pour temperature signal is then fed from the card programmer to the monitor to be utilized in the manner explained below.

At the expiration of the programmed lip heat delay, which commences to run in response to closing of the sequencer lip heat delay start switch 180, the timing circuit in the card programmer 38 produces a sequencer stepping voltage at a lip heat delay step terminal of the programmer. This terminal is connected through a lead 191 and the lead 152 to the time delay step switch 138 of the sequencer 42. It will be recalled that this switch closes in the 10th stepping position of the sequencer. Accordingly, the stepping voltage produced by the card programmer advances the sequencer to its l lth stepping position.

It will now be understood that in the 10th stepping position of the sequencer 42, the heating power level of the crucible 22 is reduced to the programmed hold power level, the crucible is reduced, the crucible is rotated to a programmed lip heat angle to heat the crucible pouring lip and cool the molten metal within the crucible to a temperature slightly above a programmed pouring temperature, and a programmed pour temperature signal is fed to the temperature monitor. At the expiration of the programmed lip heat delay, the sequencer 42 is advanced to its 1 lth stepping position.

In its llth stepping position, the program sequencer 42 recloses the controlled power lock switch 154 for the heat controller 48 and reenergizes the fixed delay timer 158 to commence running of the fixed, i.e. 1 minute, delay. Closure of switch 154 returns control of the power level setting of the heat controller 48 to the temperature monitor 52 which is currently being supplied with a programmed pour temperature signal from the card programmer. The heat controller is then adjusted to energize the crucible heating coil 23 at a controlled power level proportional to the temperature error between the temperature of the molten metal and the programmed pour temperature.

From the preceding discussion, it will be understood that in the l lth stepping position of the program sequencer 42, the crucible heating coil 23 is energized at a controlled power level, proportional to the temperature error between the molten metal temperature and the programmed pour temperature for a fixed heating delay time, i.e. 1 minute. At the expiration of this fixed delay, the sequencer 42 is advanced to its 12th stepping position.

Stepping of the program sequencer 42 to its 12th stepping position closes a normally open temperature interrogate switch 196. Closure of this switch connects a fixed delay timer 198 to the power supply lead 83 through a lead 200 and the switch contacts. The timer is thus energized by closing of the switch 196 to commence running of a fixed time delay. This time delay is selected to permit thermal stabilization of the temperature monitoring system. At the expiration of the fixed stabilization delay, the timer contacts 1980 close to connect the power supply lead 83 to the temperature monitor 52 through the lead 200 and a lead 202. As will be explained later, the voltage thus applied to the temperature monitor conditions the latter to compare the temperature of the molten metal within the crucible 22 to the programmed pour temperature and to generate a sequencer backstepping voltage, forward stepping voltage, or no stepping voltage depending upon the relationships of these temperatures. Thus, if the metal temperature is less than the programmed pour temperature, the temperature monitor generates a backstepping voltage which is applied through the lead 176 to the sequencer backstepping lead 70. Under these conditions the program sequencer 42 returns to the proceeding 1 lth stepping position to repeat the fixed time heating step of that position at a heating power level proportional to the temperature error between the actual metal temperature and the programmed pour temperature. If the metal temperature exactly equals the programmed pour temperature, the temperature monitor 52 generates a forward stepping voltage which is applied through the lead 174 to the sequencer forward stepping lead 68 to advance the sequencer 42 to its 13th stepping position. Finally, if the metal temperature exceeds the programmed pour temperature, the temperature monitor produces no stepping voltage until the molten metal cools to the exact programmed pour temperature. When this occurs, the temperature monitor produces a forward stepping voltage for advancing the sequencer 42 to its 13th stepping position, as just explained.

Claims

1. Automatic casting apparatus comprising: a crucible for containing a metal to be cast; a motor for driving said crucible through a range of angular positions; an induction heater for heating said metal to the molten state; means for sensing and generating a signal related to the angular position of said crucible; means for sensing and generating a signal representing the temperature of the molten metal in said crucible; programmer means including means for storing information providing a casting program representing preselected program parameters including melt and pour angles for said crucible, a heating power level for said heater, and a metal pouring temperature and selectively actuable means for reading said parameters in sequence in response to successive actuations of said programmer means and producing a signal representing each parameter; and automatic control means including means for operating said motor and heater in response to said signals and means for actuating said programmer means to advance said program from one parameter to the next at the completion of each operation in response to a parameter signal to cause said apparatus to proceed through an automatic casting cycle involving initial operation of said motor in response to the melt angle signal to drive said crucible to said melt angle, operation of said heater in response to the heating power level signal to heat said metal to the molten state at said heating power level while said crucible occupies said melt angle and to thereafter heat the molten metal to said pouring temperature in response to the pouring temperature signal, and operation of said motor in response to the pour angle signal following heating of the molten metal to said pouring temperature to rotate said crucible to said pour angle.

2. Automatic casting apparatus according to claim 1, wherein: said program parameters include a parameter representing a rate of rotation of said crucible to said pour angle; said programmer means produces a tilt rate signal representing said rotation rate; means for sensing and generating a signal representing the rotational speed of said crucible; and said control means operates said motor in response to said signals to cause rotation of said crucible to said pour angle at said rotation rate.

3. Automatic casting apparatus according to claim 1, wherein: said crucible has a pouring lip; said program parameters include a parameter representing a lip heat angle for said crucible wherein the molten metal within the crucible contacts but does not overflow said pouring lip and a parameter representing a lip heat delay time; said programmer means produces a signal representing said lip heat angle and a signal representing said lip heat delay time; and said control means operates said motor in response to said signals to rotate said crucible to and retain the crucible at said lip heat angle for said lip heat delay time following heating of said metal to the molten state and prior to rotation of said crucible to said pour angle, thereby to heat said lip prior to pouring of the molten metal.

4. Automatic casting apparatus according to claim 3, wherein: said program parameters include a parameter representing a superheat temperature in excess of said pouring temperature; said programmer means produces a signal representing said superheat temperature; and said control means opeRates said heater in response to said signals to heat said metal to the molten state and then heat the molten metal to said superheat temperature while said crucible occupies said melt angle and to thereafter bring the temperature of the molten metal to said pouring temperature following heating of said crucible pouring lip.

5. Automatic casting apparatus according to claim 3, wherein: said control means includes means for operating said heater at a reduced heating power level during heating of said pouring lip; and said superheat temperature, lip heat delay time, and reduced power level are selected to effect heating of said pouring lip to a given lip temperature and concurrent cooling of said molten metal approximately to said pouring temperature.

6. Automatic casting apparatus according to claim 1, wherein: said program parameters include a parameter representing an initial temperature of said molten metal and a parameter representing a heating delay time at said heating power level required to heat the molten metal to a selected temperature less than said initial temperature; said programmer means produces a signal representing said initial temperature and a signal representing said heating delay time; and said control means includes means for operating said heater in response to said power level signal to initially heat said metal at said heating power level for said heating delay time, heating said metal for an additional fixed delay time, and then alternately comparing the temperature of said molten metal to said initial temperature and heating said metal for said fixed delay time at a power level related to the temperature error between the metal temperature and said initial temperature until the temperature of the molten metal approximately equals said initial temperature, all prior to rotation of said crucible to said pour angle.

7. Automatic casting apparatus according to claim 6, wherein: said crucible has a pouring lip; said program parameters include a parameter representing a lip heat angle of said crucible wherein the molten metal within the crucible contacts but does not overflow said pouring lip and a parameter representing a lip heat delay time; said programmer means produces a signal representing said lip heat angle and a signal representing said lip heat delay time; said control means includes means for operating said heater at a reduced heating power level during heating of said pouring lip; said control means operates said motor in response to said signals to rotate said crucible to and retain the crucible at said lip heat angle for said lip heat delay time following heating of said metal to the molten state and prior to rotation of said crucible to said pour angle, thereby to heat said lip prior to pouring of the molten metal; said initial temperature is a superheat temperature in excess of said pouring temperature; and said superheat temperature, lip heat delay time, and reduced power level are selected to effect heating of said pouring lip to a given lip temperature and concurrent cooling of said molten metal approximately to said pouring temperature.

8. Automatic casting apparatus according to claim 7, wherein: said control means includes means for comparing the temperature of the molten metal to said pouring temperature and operating said heater to bring said molten metal to said pouring temperature after expiration of said lip heat delay.

9. Automatic casting apparatus according to claim 8, wherein: said program parameters include a parameter representing a rate of rotation of said crucible to said pouring angle; said programmer means produces a signal representing said rotation rate; means for sensing and generating a signal representing the rotational speed of said crucible; and said control means operates said motor in response to said signals to rotate said crucible from said upright position to said pour angle at said rotaTion rate.

10. Automatic casting apparatus comprising: a vacuum chamber; vacuum pumping means for evacuating said chamber; a vacuum level detector for producing signals related to the vacuum level within said chamber; a crucible within said chamber for containing a metal to be cast; a motor for driving said crucible through a range of angular positions; means for sensing and generating a signal representing the angular position of said crucible; an induction heater for heating said metal to the molten state; means for sensing and generating a signal representing the temperature of the molten metal in said crucible; programmer means including means for storing information providing a casting program representing preselected program parameters including a heat start vacuum level for said chamber, melt and pour angles for said crucible, a heating power level for said heater, and a metal pouring temperature, and selectively actuable means for reading said parameters in sequence in response to successive actuations of said programmer means and producing a signal representing each parameter; and control means including means for operating said motor and heater in response to said signals and means for actuating said programmer means to advance said program from one parameter to the next at the completion of each operation in response to a parameter signal to cause said apparatus to proceed through an automatic casting cycle involving initial operation of said pumping means to evacuate said chamber, operation of said motor in response to the melt angle signal to drive said crucible to said melt angle, operation of said heater in response to the heating power level signal to heat said metal to the molten state at said heating power level while said crucible occupies said melt angle and thereafter heat the molten metal to said pouring temperature in response to the pouring temperature signal, and operation of said motor in response to the pour angle signal following heating of the molten metal to said pouring temperature to rotate said crucible to said pour angle.

11. Automatic casting apparatus according to claim 10, wherein: said program parameters include a parameter representing a pour vacuum level for said chamber; said programmer means produces a signal representing said pour vacuum level; and said control means operates said motor in response to said signals to rotate said crucible to said pour angle following heating of said metal to said pour temperature and reduction of the chamber pressure to said pour vacuum level.

12. Automatic casting apparatus according to claim 10, wherein: said program parameters include a parameter representing a rate of rotation of said crucible to said pour angle; said programmer means produces a signal representing said rotation rate; means for sensing and generating a signal representing the rotational speed of said crucible; and said control means operates said motor in response to said signals to cause rotation of said crucible to said pour angle at said rotation rate.

13. Automatic casting apparatus according to claim 10, wherein: said crucible has a pouring lip; said program parameters include a parameter representing a lip heat angle for said crucible wherein the molten metal within the crucible contacts but does not overflow said pouring lip and a parameter representing a lip heat delay time; said programmer means produces a signal representing said lip heat angle and a signal representing said lip heat delay time; and said control means operates said motor in response to said signals to rotate said crucible to and retain the crucible at said lip heat angle for said lip heat delay time following heating of said metal to the molten state and prior to rotation of said crucible to said pour angle, thereby to heat said lip prior to pouring of the molten metal.

14. Automatic casting apparatus according to claiM 13, wherein: said program parameters include a parameter representing a superheat temperature in excess of said pouring temperature; said programmer means produces a signal representing said superheat temperature; and said control means operates said heater in response to said signals to heat said metal to the molten state and then heat the molten metal to said superheat temperature while said crucible occupies said melt angle and to thereafter bring the temperature of the molten metal to said pouring temperature following heating of said crucible pouring lip.

15. Automatic casting apparatus according to claim 14, wherein: said control means includes means for operating said heater to heat said molten metal at a reduced heating power level during heating of said pouring lip; and said superheat temperature, lip heat delay time, and reduced power level are selected to effect heating of said pouring lip to a given lip temperature and concurrent cooling of said molten metal approximately to said pouring temperature.

16. Automatic casting apparatus according to claim 10, wherein: said program parameters include a parameter representing an initial temperature of said molten metal and a parameter representing a heating delay time at said heating power level required to heat the molten metal to a selected temperature less than said initial temperature; said programmer means produces a signal representing said initial temperature and a signal related to said heating delay time; and said control means includes means for operating said heater in response to said signals to initially heat said metal at said heating power level for said heating delay time, heating said metal for an additional fixed delay time, and then alternately comparing the temperature of said molten metal to said initial temperature and heating said metal for said fixed delay time at a power level related to the temperature error between the metal temperature and said initial temperature until the temperature of the molten metal approximately equals said initial temperature, all prior to rotation of said crucible to said pour angle.

17. Automatic casting apparatus according to claim 16, wherein: said crucible has a pouring lip; said program parameters include a parameter representing a lip heat angle of said crucible wherein the crucible contacts but does not overflow said pouring lip and a parameter representing a lip heat delay time; said programmer means produces a signal representing said lip heat angle and a signal representing said lip heat delay time; said control means operates said motor in response to said signals to rotate said crucible to and retain the crucible at said lip heat angle for said lip heat delay time following heating of said metal to the molten state and prior to rotation of said crucible to said pour angle, thereby to heat said lip prior to pouring of the molten metal; said initial temperature is a superheat temperature in excess of said pouring temperature; and said superheat temperature, lip heat delay time, and reduced power level are selected to effect heating of said pouring lip to a given lip temperature and concurrent cooling of said molten metal approximately to said pouring temperature.

18. Automatic casting apparatus according to claim 17, wherein: said control means includes means for comparing the temperature of the molten metal to said pouring temperature, and operating said heater to bring said molten metal to said pouring temperature after expiration of said lip heat delay.

19. Automatic casting apparatus according to claim 10, wherein: said program parameters include a parameter representing a rate of rotation of said crucible to said pouring angle; said programmer means produces a signal related to said rotation rate; means for sensing and generating a signal representing the rotational speed of said crucible; and said control means operates said motor in response to said signals to rotate said crucible to said pour angle at said rotation rate.

20. Automatic casting apparatus comprising: a crucible for containing a metal to be cast; a motor for driving said crucible through a range of angular positions; an induction heater for heating said metal to the molten state; means for sensing and generating a signal related to the angular position of said crucible; means for sensing and producing a signal representing the temperature of the molten metal in said crucible; programmer means including means for storing information providing a casting program representing preselected program parameters including melt and pour angles of said crucible, a heating power level for said heater, and a metal pouring temperature, and selectively actuable means for reading said parameters in sequence in response to successive actuations of said programmer means and producing a signal representing each parameter; a crucible drive controller responsive to said crucible angle signals and connected to said motor for operating said motor to rotate said crucible to said melt and pour angles in response to said melt and pour angle signals; a temperature monitor connected to said thermal sensor and responsive to said pour temperature and metal temperature signals for generating a controlled power level signal related to the error between said pour and metal temperatures; a heat controller responsive to aid heating power level and controlled power level signals and connected to said heater for operating said heater at said heating power level in response to said heating power level signal and at a heat power level related to said temperature error in response to said controlled power level signal; means for applying said angle signals to said drive controller and said heating power level and controlled power level signals to said heat controller to produce a casting cycle having successive steps involving operation of said motor to drive said crucible to said melt angle, operation of said heater following rotation of said crucible to said melt angle to heat said metal to the molten state at said heating power level while said crucible occupies said melt angle and to thereafter heat the molten metal to said pouring temperature, and operation of said motor following heating of the molten metal to said pouring temperature to rotate said crucible to said pour angle; and means for actuating said programmer means to advance said program from one parameter to the next at the completion of each operation in response to a parameter signal to cause said apparatus to proceed through said casting cycle.