326:
metals the mold life is longer but thermal fatigue and erosion usually limit the life to 10,000 to 120,000 cycles. The mold life is dependent on four factors: the mold material, the pouring temperature, the mold temperature, and the mold configuration. Molds made from gray cast iron can be more economical to produce but have short mold lives. On the other hand, molds made from H13 tool steel may have a mold life several times greater. The pouring temperature is dependent on the casting metal, but the higher the pouring temperature the shorter the mold life. A high pouring temperature can also induce shrinkage problems and create longer cycle times. If the mold temperature is too low
268:) casting uses a gas at low pressure, usually between 3 and 15 psi (20 to 100 kPa) to push the molten metal into the mold cavity. The pressure is applied to the top of the pool of liquid, which forces the molten metal up a refractory pouring tube and finally into the bottom of the mold. The pouring tube extends to the bottom of the ladle so that the material being pushed into the mold is exceptionally clean. No risers are required because the applied pressure forces molten metal in to compensate for shrinkage. Yields are usually greater than 85% because there is no riser and any metal in the pouring tube just falls back into the ladle for reuse.
257:
20:
149:. The process is then started all over again, but preheating is not required because the heat from the previous casting is adequate and the refractory coating should last several castings. Because this process is usually carried out on large production run work-pieces automated equipment is used to coat the mold, pour the metal, and remove the casting.
301:
The main advantages are the reusable mold, good surface finish, good dimensional accuracy, and high production rates. Typical tolerances are 0.4 mm for the first 25 mm (0.98 in) for the first inch) and 0.02 mm for each additional centimeter (0.002 in per in); if the dimension
165:
resistance, but other materials include steel, bronze, and graphite. These metals are chosen because of their resistance to erosion and thermal fatigue. They are usually not very complex because the mold offers no collapsibility to compensate for shrinkage. Instead the mold is opened as soon as the
325:
There are three main disadvantages: high tooling cost, limited to low-melting-point metals, and short mold life. The high tooling costs make this process uneconomical for small production runs. When the process is used to cast steel or iron the mold life is extremely short. For lower melting point
205:. In the process the material is poured into the mold and allowed to cool until a shell of material forms in the mold. The remaining liquid is then poured out to leave a hollow shell. The resulting casting has good surface detail but the wall thickness can vary. The process is usually used to cast
152:
The metal is poured at the lowest practical temperature in order to minimize cracks and porosity. The pouring temperature can range greatly depending on the casting material; for instance zinc alloys are poured at approximately 370 °C (698 °F), while Gray iron is poured at approximately
247:
is used in automotive dashboard manufacture, for soft-panel interiors with artificial leather, where a free-flowing (which behave like a liquid) powder plastic compound, either PVC or TPU, is poured into a hot, hollow mold and a viscous skin forms. Excess slush is then drained off, the mold is
173:
As stated above, the mold is heated prior to the first casting cycle and then used continuously in order to maintain as uniform a temperature as possible during the cycles. This decreases thermal fatigue, facilitates metal flow, and helps control the cooling rate of the casting metal.
288:
Vacuum permanent mold casting retains all of the advantages of LPPM casting, plus the dissolved gases in the molten metal are minimized and molten metal cleanliness is even better. The process can handle thin-walled profiles and gives an excellent
310:. A draft of 2 to 3° is required. Wall thicknesses are limited to 3 to 50 mm (0.12 to 1.97 in). Typical part sizes range from 100 g to 75 kg (several ounces to 150 lb). Other advantages include the ease of inducing
330:
are produced, but if the mold temperature is too high then the cycle time is prolonged and mold erosion is increased. Large differences in section thickness in the mold or casting can decrease mold life as well.
177:
Venting usually occurs through the slight crack between the two mold halves, but if this is not enough then very small vent holes are used. They are small enough to let the air escape but not the molten metal. A
185:
Mechanical ejectors in the form of pins are used when coatings are not enough to remove casts from the molds. These pins are placed throughout the mold and usually leave small round impressions on the casting.
271:
The vast majority of LPPM casting are from aluminum and magnesium, but some are copper alloys. Advantages include very little turbulence when filling the mold because of the constant pressure, which minimizes
240:. It uses less material than solid casting, and results in a lighter and less expensive product. Hollow cast figures generally have a small hole where the excess liquid was poured out.
129:
The gravity process begins by preheating the mold to 150–200 °C (302–392 °F). to ease the flow and reduce thermal damage to the casting. The mold cavity is then coated with a
280:
formation. Mechanical properties are about 5% better than gravity permanent mold castings. The disadvantage is that cycles times are longer than gravity permanent mold castings.
636:
293:. Mechanical properties are usually 10 to 15% better than gravity permanent mold castings. The process is limited in weight to 0.2 to 5 kg (0.44 to 11.02 lb).
598:
314:
by changing the mold wall thickness or by heating or cooling portions of the mold. The fast cooling rates created by using a metal mold results in a finer
629:
161:
Molds for the casting process consist of two halves. Casting molds are usually formed from gray cast iron because it has about the best
437:
622:
591:
550:
529:
510:
901:
659:
818:
584:
145:
is then poured into the mold. Soon after solidification the mold is opened and the casting removed to reduce chances of
674:
256:
102:
306:
add an additional 0.25 mm (0.0098 in). Typical surface finishes are 2.5 to 7.5 μm (100–250 μin)
311:
711:
319:
875:
206:
273:
777:
757:
566:
752:
716:
701:
221:, from low-melting-point materials. A similar technique is used to make hollow chocolate figures for
137:, which prevents the casting from sticking to the mold and prolongs the mold life. Any sand or metal
798:
182:
must also be included to compensate for shrinkage. This usually limits the yield to less than 60%.
90:
691:
664:
441:
134:
121:
There are four main types of permanent mold casting: gravity, slush, low-pressure, and vacuum.
850:
845:
767:
684:
679:
546:
525:
506:
35:
166:
casting is solidified, which prevents hot tears. Cores can be used and are usually made from
307:
462:
772:
742:
179:
162:
438:"A Dinky Life, the illustrated history of a passion by a long-time collector of die-cast"
793:
290:
214:
138:
895:
747:
721:
645:
106:
31:
762:
726:
706:
607:
303:
167:
142:
98:
42:. The most common process uses gravity to fill the mold, however gas pressure or a
19:
540:
669:
315:
237:
210:
870:
865:
233:
130:
571:
860:
855:
226:
55:
51:
318:
structure than sand casting. Retractable metal cores can be used to create
46:
are also used. A variation on the typical gravity casting process, called
218:
146:
79:
880:
840:
808:
327:
222:
110:
59:
43:
813:
803:
277:
94:
39:
18:
823:
86:
75:
71:
67:
618:
580:
576:
63:
260:
Schematic of the low-pressure permanent mold casting process
501:
Degarmo, E. Paul; Black, J. T.; Kohser, Ronald A. (2003),
197:
is a variant of permanent molding casting to create a
50:, produces hollow castings. Common casting metals are
539:
Todd, Robert H.; Allen, Dell K.; Alting, Leo (1994),
786:
735:
652:
484:
424:
386:
371:
141:are then installed and the mold is clamped shut.
16:Metal casting process that employs reusable molds
403:
248:cooled, and the molded product is stripped out.
352:
467:Dictionary of Scientific & Technical Terms
630:
592:
8:
480:
478:
476:
420:
418:
416:
414:
412:
399:
397:
395:
382:
380:
367:
365:
363:
361:
520:Kalpakjian, Serope; Schmid, Steven (2006),
637:
623:
615:
599:
585:
577:
522:Manufacturing Engineering and Technology
503:Materials and Processes in Manufacturing
255:
85:Typical products are components such as
542:Manufacturing Processes Reference Guide
340:
322:while maintaining a quick action mold.
38:("permanent molds"), usually made from
348:
346:
344:
7:
236:in 1893 for the production of lead
14:
572:Article on Permanent Mold Process
567:Efunda: Engineering Fundamentals
485:Degarmo, Black & Kohser 2003
425:Degarmo, Black & Kohser 2003
387:Degarmo, Black & Kohser 2003
372:Degarmo, Black & Kohser 2003
62:alloys. Other materials include
153:1,370 °C (2,500 °F).
819:Semi-finished casting products
34:process that employs reusable
1:
353:Todd, Allen & Alting 1994
264:Low-pressure permanent mold (
404:Kalpakjian & Schmid 2006
297:Advantages and disadvantages
243:Similarly, a process called
232:The method was developed by
78:and steel are also cast in
918:
312:directional solidification
836:
614:
545:, Industrial Press Inc.,
524:(5th ed.), Pearson,
109:, and automotive engine
902:Casting (manufacturing)
505:(9th ed.), Wiley,
107:fuel injection housings
261:
28:Permanent mold casting
24:
23:Permanent mold casting
876:Tools and terminology
692:Investment (Lost wax)
259:
22:
469:. McGraw-Hill. 2003.
675:Evaporative-pattern
406:, pp. 303–304.
355:, pp. 258–262.
262:
209:products, such as
25:
889:
888:
832:
831:
909:
712:Semi-solid metal
639:
632:
625:
616:
601:
594:
587:
578:
555:
535:
516:
488:
482:
471:
470:
459:
453:
452:
450:
449:
440:. Archived from
434:
428:
422:
407:
401:
390:
384:
375:
369:
356:
350:
917:
916:
912:
911:
910:
908:
907:
906:
892:
891:
890:
885:
828:
794:Casting defects
782:
731:
648:
643:
610:
605:
563:
553:
538:
532:
519:
513:
500:
497:
492:
491:
483:
474:
463:"Slush Molding"
461:
460:
456:
447:
445:
436:
435:
431:
423:
410:
402:
393:
385:
378:
370:
359:
351:
342:
337:
299:
286:
254:
234:William Britain
192:
163:thermal fatigue
159:
127:
125:Gravity process
119:
17:
12:
11:
5:
915:
913:
905:
904:
894:
893:
887:
886:
884:
883:
878:
873:
868:
863:
858:
853:
848:
843:
837:
834:
833:
830:
829:
827:
826:
821:
816:
811:
806:
801:
796:
790:
788:
784:
783:
781:
780:
775:
770:
765:
760:
755:
750:
745:
739:
737:
733:
732:
730:
729:
724:
719:
714:
709:
704:
699:
697:Permanent mold
694:
689:
688:
687:
682:
672:
667:
662:
656:
654:
650:
649:
644:
642:
641:
634:
627:
619:
612:
611:
606:
604:
603:
596:
589:
581:
575:
574:
569:
562:
561:External links
559:
558:
557:
551:
536:
530:
517:
511:
496:
493:
490:
489:
487:, p. 328.
472:
454:
429:
427:, p. 326.
408:
391:
389:, p. 325.
376:
374:, p. 327.
357:
339:
338:
336:
333:
298:
295:
291:surface finish
285:
282:
253:
250:
199:hollow casting
191:
188:
158:
155:
133:material or a
126:
123:
118:
115:
15:
13:
10:
9:
6:
4:
3:
2:
914:
903:
900:
899:
897:
882:
879:
877:
874:
872:
869:
867:
864:
862:
859:
857:
854:
852:
849:
847:
844:
842:
839:
838:
835:
825:
822:
820:
817:
815:
812:
810:
807:
805:
802:
800:
797:
795:
792:
791:
789:
785:
779:
776:
774:
771:
769:
766:
764:
761:
759:
756:
754:
751:
749:
748:Cope and drag
746:
744:
741:
740:
738:
734:
728:
725:
723:
722:Shell molding
720:
718:
715:
713:
710:
708:
705:
703:
700:
698:
695:
693:
690:
686:
683:
681:
678:
677:
676:
673:
671:
668:
666:
663:
661:
658:
657:
655:
651:
647:
640:
635:
633:
628:
626:
621:
620:
617:
613:
609:
602:
597:
595:
590:
588:
583:
582:
579:
573:
570:
568:
565:
564:
560:
554:
552:0-8311-3049-0
548:
544:
543:
537:
533:
531:0-13-148965-8
527:
523:
518:
514:
512:0-471-65653-4
508:
504:
499:
498:
494:
486:
481:
479:
477:
473:
468:
464:
458:
455:
444:on 2010-01-15
443:
439:
433:
430:
426:
421:
419:
417:
415:
413:
409:
405:
400:
398:
396:
392:
388:
383:
381:
377:
373:
368:
366:
364:
362:
358:
354:
349:
347:
345:
341:
334:
332:
329:
323:
321:
317:
313:
309:
305:
296:
294:
292:
283:
281:
279:
275:
269:
267:
258:
251:
249:
246:
245:slush molding
241:
239:
235:
230:
228:
224:
220:
216:
212:
208:
204:
200:
196:
195:Slush casting
189:
187:
183:
181:
175:
171:
169:
164:
156:
154:
150:
148:
144:
140:
136:
132:
124:
122:
116:
114:
112:
108:
104:
103:pipe fittings
100:
99:gear housings
96:
92:
88:
83:
81:
77:
73:
69:
65:
61:
57:
53:
49:
48:slush casting
45:
41:
37:
33:
32:metal casting
29:
21:
763:Molding sand
717:Shaw process
702:Plaster mold
696:
608:Metalworking
541:
521:
502:
495:Bibliography
466:
457:
446:. Retrieved
442:the original
432:
324:
304:parting line
302:crosses the
300:
287:
274:gas porosity
270:
265:
263:
252:Low-pressure
244:
242:
238:toy soldiers
231:
211:candlesticks
202:
198:
194:
193:
184:
176:
172:
160:
151:
143:Molten metal
128:
120:
84:
47:
27:
26:
846:Fabrication
787:Terminology
660:Centrifugal
217:bases, and
203:hollow cast
74:alloys and
866:Metallurgy
736:Components
665:Continuous
448:2009-11-04
335:References
207:ornamental
170:or metal.
131:refractory
861:Machining
856:Jewellery
685:Lost foam
680:Full mold
653:Processes
320:undercuts
227:Christmas
147:hot tears
135:mold wash
56:magnesium
52:aluminium
896:Category
871:Smithing
219:statuary
80:graphite
881:Welding
851:Forming
841:Casting
809:Foundry
768:Pattern
646:Casting
328:misruns
117:Process
111:pistons
91:splines
82:molds.
549:
528:
509:
284:Vacuum
223:Easter
95:wheels
70:, and
60:copper
58:, and
44:vacuum
814:Ingot
804:Dross
799:Draft
778:Sprue
773:Riser
758:Flask
743:Chill
316:grain
278:dross
190:Slush
180:riser
139:cores
87:gears
40:metal
36:molds
30:is a
824:Slag
753:Core
727:Spin
707:Sand
547:ISBN
526:ISBN
507:ISBN
276:and
266:LPPM
225:and
215:lamp
168:sand
157:Mold
76:iron
72:lead
68:zinc
670:Die
308:RMS
201:or
64:tin
898::
475:^
465:.
411:^
394:^
379:^
360:^
343:^
229:.
213:,
113:.
105:,
101:,
97:,
93:,
89:,
66:,
54:,
638:e
631:t
624:v
600:e
593:t
586:v
556:.
534:.
515:.
451:.
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
