US2368718A

US2368718A - Method of making molds having accommodation cores

Info

Publication number: US2368718A
Application number: US467088A
Authority: US
Inventors: Raymond J Miller
Original assignee: Miller Engineering Corp
Current assignee: Miller Engineering Corp
Priority date: 1942-11-27
Filing date: 1942-11-27
Publication date: 1945-02-06
Anticipated expiration: 1962-02-06

Description

R. J. MILLER Feb. 6, 1945.

,METHOD OF MAKING MOLDS HAVING ACCOMMODATION CORES F'ld NOV. 27, 1942 3 sheets-sheet 2 1N V EN TOR.

METHOD OF MAKING MOLDs HAVING ACCOMMODATION coREs R.- J. MILLER Feb. 6, 1945.

Filed Nov. 27, 1942 5 Sheets-Sheet 3 av s I INVENTOR. ,64k/vamo ZM/Lee BY A arme/ww v 'of the flask Iby the use of transition cores.

Patented Feb. 6,' 1945 lUNITED STATES PATENT .oFFl'c-E METHOD OF MAKING MOLDS HAVING ACCOMMODATION CORES Raymond J..Miller, Detroit, Mich., assigner, by"v direct and mesne assignments, to Miller Engineering Corporation,v Detroit, Mich., a corporation of Michigan Application November 27, 1942, Serial No. 467,088

7 claims. (ol. zza- 193) This invention relates to the art of casting,4 and more particularly to the use of cores formed by a reproductive process for forming mold cavities of articles having irregular contours where back draft would be .encountered in the formation of mold cavities in the methods heretofore employed. l These core members may be of the transition type to extend a parting line throughout the usable mold-forming substance in both the cope and drag sections of a mold.

In certain types of casting equipment now being used commercially, such for example as the Capaco process as disclosed in Patent No. 2,201,037, issued May 14, 1940, molds of accurate external dimensions are formed from separate die patterns. Each die pattern consists of a pattern or a group of patterns positioned in a ask. Where a plurality of patterns are used in a single flask, each pattern member is carried on a baseof accurate external dimensions to accurately locate the pattern in the flask to assure proper alignment of the mold cavities of the cooperating nold members formed from the separate die pat-l erns.

In this and other types of casting equipment being used commercially, it is impossible to form mold cavities of articles having irregular surfaces where back draft would be encountered. As pointed out in my copending application Serial No. 459,106 filed September 21, 1942, it is impos sible in the Capaco process to extend a parting Iof cooperating core box and pattern members of an article embodying back draft lby applying` to thesurface of a pattern of the article to be beyond the usable mold-forming substance of one vmold plus the majority of the depth ofl a single pattern base member. Y

My copending application Serial No. 459,106 discloses a method whereby a parting line may be extended throughout the usable mold-forming substance of both the cope and the drag sections By the method disclosed in said application it is difcult to accommodate'articles having contoured surfaces where a substantial amount of back draft would be encountered. 'Ihis invention is directed primarily to the use of accommodation cores to permit the formation of mold cavities of articleshaving contoured surfaces embodying lback draft. The accommodation cores may lbe in 4the formof transition cores to exten'd a parting vthroughout the usable mold- ,forming substance in both the cope and. drag sections of a mold. e

An object of this invention resides in the, de'- velopment of an improved method whereby articles having contoured surfaces embodyingy back draft maybe tion.

readily formed by a casting operaformed fa parting material to eliminate back draft and forming pattern members of the combined pattern member and the parting material .by a

reproductive method, and forming core boxes v from the parting material by a reproductive method. Y y

Another object of the invention is t0 provide transition` accommodation cores to permit the 1 casting of articles having back draft and to extend a parting throughout the entire usable moldforming substance of the cope and drag sections of a mold.

A further object resides in the use of a plurality of interlocked core members to form a portion of the surface of a casting cavity of an article j having contoured surfaces or projections in the form of bosses, etc., whereby back draft would be encountered.

Another object of the invention isto form a plurality of core boxes bya reproductive method from segments of interlocked parting material applied to a pattern surface to eliminate back.-

draft and lto accommodate irregularities in the surface of the articleto be formed.Y

Other objects and advantages of this invention Vwill be apparent from the following detailed vdescrlption considered in connection with the ac-v` companying drawings, submitted' for purposes of illustration only, and not intended to d'ene the scope of the invention, reference being had for l that purpose to the subjlned claims.

In the drawings wherein similar reference characters refer to similar parts throughout the several views:

Fig. 1- is a perspective view of a master pattern* formed by of an article having back draft to be a casting operation.

Fig. 2 is a llongitudinal .sectional pattern illustrated in Fig. 1.

view 0f the!" Fig. 3 is a perspective view illustrating the first step in the practice of this invention wherein separable parting material is applied to the surface of the master pattern'to eliminate back draft and to forman accommodation core-forming vexposed pattern member and accommodation core-forming'member in-a frame aligned with the frame surrounding the female impression.v

formed in the step illustrated in Fig. 4.

Fig. 6 is a sectional view illustrating the formation of a production pattern member of the pattern and accommodation core members from 'the female impression formed in the step illustrated in Fig. 4.

Fig-'1 is a'view similar to Fig. 6 illustrating the formationv of a production pattern from the female impression o'fnthe pattern and accommodation core members formed in the step illustrated in Fig. 5.

Fig. 8 is a sectional view illustrating the step of forming the rst half of theaccommodation core box member from the core-formingmember posi- Fig. 16 is a sectional view taken substantially on the line l6-I6 of Fig. 15 looking in the direction ofthe arrows preparatory to forming corebox members for making the accommodation.

Fig. 17 is a sectional view illustrating the formation of the first half of a core-box member for forming one of the accomodation core segments.

Fig. 18'is a sectional view illustrating the for- I mation of the other half of the core box for making one of the accommodation core segments.

Fig. 19 is a sectional View illustrating the corebox members in assembled position with the pouring and venting means in place for forming one of the accommodation core segments.

Fig. 20 is a sectional View illustrating the step of forming the first half of a core box for making another of the accommodation core segments to eliminate back draft in a plurality of directions.

Fig. 21 is a sectional view illustrating the formation of the second half of this core-box member.

Fig. 22 is a sectional view illustrating the corebox members assembled with the pouring and -ventingmeans in place in operative position to form the segment of the accommodation core segment. c

Before explaining in detail the present invention it is to be understood that the invention is not limited in its'application to the details of construction and arrangement of parts illustrated in the .accompanying drawings, since the inventioned in the female impression formedin the step illustrated in Fig. 5 with additional parting material added to ll the space formerly occupied by the master pattern and to eliminate back draft.

Fig. 9 is also a sectional view illustrating the formation of the second halffof the accommodation core-box member from the rst half of the accommodation core-box member, the parting material applied in the step illustrated in Fig. 6

being removed.

Fig. 10 is a sectional view illustratingthe corebox members assembled to form the accommodation core member. Y

Fig. 11 is an assembled view showing ,the accommodation core member in place in drag and cope mold members formed from the production pattern equipment illustrated in Figs. 6 and -7 and showing the methodof feeding molten alloy or metal to themold cavity.

Fig. 12 is a perspective view similar to Fig. 1 showing a modied form of the invention wherein the article to be formed is provided with a boss projecting from one side wherein back draft ina plurality of directions would be encountered.

Fig. 13 is a perspective view illustrating the formation of an accommodation, core-forming segment to eliminate back draft in a plurality of directions encoimtered in the surfaces of the master pattern and the extending boss 4carried thereby.

Fig. 14 is a fragmentary sectional view illusments.

Fig. 15 is a perspective view illustrating the master pattern and accommodation. core-forming segments embedded in parting material preparatory to forming-core-box members for making the accommodation core segments.

tion is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or vterminology employed herein is for the purpose 'of description and not of limitation.

Refen'ing nowto the drawings, Figs. 1 and 2 are illustrative'of a pattern of any article I0 having back draft which may be formed byv a casting operation. 'I'he article I0 may, for exam-A ple, be a cone-shaped member having an upwardly tapering cuter surface I2 terminating in a radially-extended flange [4 at its upper or smaller end. The article I0 may be cored internally as illustrated in Fig. 2,. and an inwardly-extended web I6 may support an axially-extending hub I8.

By the methods .heretofore employed in the casting art, it would be'extremely dimcult, if not impossible.' to cast this type of article, since it would be necessary to extend the parting longitudinally of the article I0, and hanging cores f would be required to form the hub i8 and web I8.

v'I'liese difliculties may be readily eliminated by the use of an accommodation core-forming member surrounding the pattern of the article l0 to eliminate back draft. The core box for forming the accommodation core may be conveniently and accurately formed by a reproductive process trating one suitable form of locating means between the accommodation core-forming seg- 4from the surfaces of any suitable partingma.-

terial applied to the pattern to provide Vau accommodation core-forming member to eliminate back draft.

As illustrated in Fig. 3, suitable parting material 20 is. applied to the tapered outer surface t2 of .the pattern of the article Hlv to eliminate back draft between the tapered surface and the flange Il.: The material 20 may be any substance suitable for making pax-tinge, such as lmolding clay. Plaster, wax, parailin, an alloy of the Woods metal group, or the Cerro alloys consisting for exampleof 42% tin and 58% bismuth.

The parting material'n should closely adhere to the surface of the pattern of the 'article Ill to form an accurate female impression of the area of the accommodation core-forming mem` bers may be 4applied to this sprayed layer.

The parting material 26 is preferably split longitudinally to form two accommodation-coreformingsegments'22 and 24 capable of being separated to remove them from the pattern of thearticle I0. The outer surfaces of the

coreforming segments

22 and 24 are shaped to eliminate back draft on the surface of the pattern and to provide upper and lower sections 26 and 128 respectively tapering in-opposite directions from a point 30 positioned approximately midway of the length of the pattern of the article I8. If desired, an inwardly-extended flange 32 may be formed on the core-forming

segments

22 and 24 at the point 30 to more definitely locate the positioning of the accommodation core in the cope and drag sections of themold at the time castings are formed.

Referring now to Fig. 4 it will be observed thatv accommodation core-forming

segments

22 and 24 in any convenient manner.

A frame 36 preferably having smooth, accurately-dimensioned outer edges is positioned on the parting material 34 to surround the upper section 26 of the accommodation core-forming members'22 and 24 and the pattern of the article I0.

Any suitable moldable substance 38 is introframes 36-and 42 respectively by the frictional accommodation core-forming

members

22 and 24. The substance 46 may; like the substance'38, be any material capable of being applied and solidifying to form the female impression 48 of the pattern and core-forming members. I The substance 46 may be the same type of material as the substance 38, suitable'precautions being taken to guard against fusion`with .the solidified substance 3B. Where the substances 38 and 4'6 are alloys applied in the molten state, the block of the solidied'substance 38 acts to chill the molten substance 46 to prevent fusion of the blocks having the

female impressions

40 and 48 of spaced portions of the pattern and accommodation core-forming members.

The blocks formed by soudincauon of the

substances

38 and 46 are retained in their associated contact of the outer surfaces of the blocks and the inner surfaces of the frames. parent thatv if desired, an `inwardly-extending bead may be carried bythe frames to engage and securely hold the blocks in place.

' fication of the substance 46, the frames 36 and duced into the space. within the frame 36 to form a female impression 48 of the exposed surfaces of the pattern. Ill and the upper section y26 of the accommodation core-forming

members

22 and 24. The substance 38 may be virtually any material capable of flowing and solidifying to form within the frame 36 the female impression 40 of the core-forming and pattern members.

ting or thermoplastic types, and the so-called Cerro alloys consisting for example of 42% tin and 58% bismuth. The cerro alloys possess the characteristics of flowing and hardening with substantially no change of volume; When these v alloys are employed th female impression 40 accurately conforms to the shape and contour of the core-forming and pattern members. event that the -substance employed does not pos- 42 having the female impressions and 48 respectively therein may be separated from the pattern and accommodation core-forming members.

Where the pattern equipment is to be used in the so-called Capaco process of molding, the

female impressions

48 and 48 may be used as illustrated in Figs. 6 and-7 to form production pattern equipment of the pattern and accommodation core-forming members. A production pattern frame 50, preferably of the same external dimensions as the frame 36, is superimposed on the frame 36 land is accurately aligned therewith by means of the 'right angle 44 as illustrated in Fig. 6.

Any suitable pattern-forming moldable mate' rial 52 is introduced into the space within the frame to form thereon va production pattern 54 accurately' conforming to the contour of the female impression 40 of the pattern and accommoclation core-forming members. If desired, a

riser frame 56 may be superimposed on the pro- Suitable materials for this purpose are the various Woods4 or type metals, white metal, plaster, plastics either of the thermoset In the sess the characteristics of maintaining substantially constant volume upon change of state, suitable allowance should be made to compensate the variation of volume. l

After solidiiication of the moldable substance l 38, the entire assembly may be invertedI and the parting material 34 removed. Another lframe 42 preferably having smooth, accurately-dimensioned outer edges is superimposed on the frame 36 and is accurately aligned therewith by means of a right angle 44 adapted to engage the side walls of the

frames

36 and 42.

duction `pattern frame 50, as more fully disclosed in my copending application Serial No. 454,831, filed August 14, 1942.

Where the production pattern equipment is to be mounted in a flask to form a die pattern as in the Capaco process of molding, the `pattern frame 50 is 'formed to accurate external dimension's conforming to the required dimension of the pattern equipment under consideration. It will be apparent that the pattern frame can be of any desired shape and dimensions to adopt the production pattern equipment for use in any type of molding process.

A production pattern frame 58.may be super;

' imposed on the frame 4 2, and moldable material of the article I8 and the lower section 28 of the 'I Where substances other than alloys are used, suitable parting materials may be employed.

After soiidimade to compensate variations of'volume of the substances 52 and 60 upon change of state from liquid to solidin the event that said substances do not possess the characteristic of substantially constant volume upon change from liquid to solid states.

The accommodation core-forming members 22 and V24 may be removed from the pattern of the article I and used in the formation of a core box for making an accommodation core to be used with molds formed from the production patterns 54 and 62 to form a casting cavity conforming with the contour of the pattern of the article I0.

The

members

22 and 24 of the accommodation core former may be positioned in the female impression. 48 of the substance 46 in the frame 42 as illustrated in Fig. 8. Suitable parting material 64 may be introduced into the space within the

members

22 and 24 of the accommodation core former to fill the space occupied by the patvendent because the core-

box members

12 and 16 must be assembled and disassembled each time an accommodation core member is formed.

After the substance 80 has solidified, the second half 16 of the core box may be removed from the Vfirst half 12 and the accommodation coreforming members'22 'and 24 removed. Suitable riser and feeder apertures 82 and 84 may be extendedthrough the walls of the/ first and second halves of the corel box to permit the introduction of a suitable core-forming substance into the accommodation core cavity 86, as illustrated in Fig. 10. A

Where the pattern and core-forming members are used in processes such as the Capaco process of plaster molding a gypsum compound having Vsuitable strengthening ingredients is introduced Locator means such for example as the dowel `A pins 66 may be positioned in .the substance 46 outside the female impression 48 of the pattern y and accommodation core-forming members. A frame 68 may be superimposed on the frame42 and a moldable substance 18 applied to form the first half 12 of the core box. The moldable substance 16 may be any suitable material such asthose discussed above for the making of the female impressions or for the making of the production patterns. The core box half 12 embodies the-contour of the upper section 26 of the

coreforming members

22 and 24, the contour. of the parting material 64, and the contour of the exposed upper surface of the substance 46 having the female impression 48 therein.

As illustrated in Fig. 8 the upper ends of the dowel or locator pins 66 have contoured portions 14 to engage within the moldable substance 18 to lock the dowelsl to the first half 12 of the core box. l y

Aftr the substance 18 .has solidified, the entire assembly may be inverted and the framer 42 A with the female impression 48 in the substance 46A removed. The dowel or locator members 66 remain in the substance 10. 'I'he parting material 64 may also be removed from the inside of the accommodation core-forming

members

22 and 24.

The second half 16 of th core box may be formed f rom the first core box half 12 and the

accommodation coreforming members

22 and 24, as illustrated in Fig. 9.A Another frame 18 may be superimposed on the frame 68 and any suitable substance introduced intothe space within the frame 18 to provide the second half 16 of the core box with a surface fconformin'g with the remainder of the contour of the accommodation core-forming

members

22 and 24 previouslv covered by the female impression 48 and the parting material 64.

The substance .88 surrounds the exposed portions of the dowel pins 66 to form dowel impressions to locate the second half 16 of the core box the

frames

68 and 18 of the rst and second halves of the

core box members

12 and 16 may be located by means of the right-angle frame 44. The use of the dowel pins 66 is more vcon- 76 wX method of casting. If desired. the 1111181116-l *I 7.0 with reference to the first half 12. If desired.

l a relatively porous core having a highly calendered surface.

The productionpatterns 54 and 62 formedin the step illustrated in Figs. 6 and 7 are mounted in flasks to form die patterns. A -gypsum compound similar to that of which the accommodation core 88 was formed may be applied to the4 die patterns having the production patterns 54 and 62 to, form cope and drag molds 90 and 9| having

female impressions

92 and 93 respectively of the patternof the article I8 and the Paccommodation core 88.

The accommodation core 88 may be positioned inthe

mold impressions

92 and 93 in the cope V and drag sections of the mold to provide a casting cavity 94 accurately conforming to the contour of the pattern of the article I8.

'The casting cavity 94 may be supplied with molten'alloy or metal by means of asuitable feeder passage 95 communicating with agate impression 96 formed inthe cope or drag sections of the mold. The feeder passage 95 communica tes with a downwardly-extending passageway 91 terminating in asurge pool 98. The surge pool 98 communicates with the casting cavity 94 through a restricted feeder 99 positioned at the bottom thereof. The impressions of the feeder passageways may be formed in the mold and accommodation core members by means of suitable pattern members applied to the production pattern and core-box members before the accommodation core 88 and the cope and drag mold 1 members and 9| are formed.

It will be noted that molten alloy or metal is introduced into the mold cavity 94 at .the bottom. No turbulence is caused during-.the filling of the mold and the envelop'e formed on the surface of the molten alloy or metal during the pouring operation is progressively expanded and is not ruptured. Entrained airand gases formedduring the pouring operation are ldispelled through the relatively porous walls of the'accommodation core and' mold members surrounding the casting cavity 94.

It will be apparent that the pattern and accommodation core-'box members may be used to form molds and 'accommodation core members for -use in any type ofmolding operation, and the complete mold assembly, including the accommodation core member, may be employed to make wax patterns for use in the so-called Lost segment.

tion patterns 54 and 62 may be used in the Capaco process to form patterns in the harder and more durable alloys, such as Beryllium brass, etc.

. This invention is not limited to the formation of accommodation cores to eliminate back draft in a single direction, since a plurality of accommodation core mem-bers may be formed to eliminate back draft in several directions. The accommodation core memlber may be divided into a plurality of smaller segments, each segment being capable of relieving back draft in a portion only of the surface ofthe pattern. Core boxes for forming each accommodation core seg-ment may be formed by the reproductive process directly from the accommodation core-'forming The accommodation core-forming members may be provided with registering means to locate each segment accurately relative to the other segments employed-to form the complete accommodation core member. 'l

Figs, 12 to 22 illustrate the formation of two separate accommodation core-'forming seg-ments, one of which embodies back draft in two directions. It will of course be apparent that any desired number of segments may be employed to eliminate back draft. An accommodation core member formed of a plurality yof segments is necessary where back draft in a plurality of directions is encountered, because it would be impossible to open a single core box embodying double back draft after the formation of the accommodation core member.

As illustrated in Fig. 12, a radially-extended boss projects outwardly from the conicallyshaped surface I2 of the pattern |0. .Because of the radially-extended flange |4 the conically- ||1 are positioned in the parting material outside the contour of the accommodation coreforming member |03. A frame `|I9 is superimposed. on the frame H5, and lmoldable substance 2| similar to the moldable Asubstance 10 and 80 illustrated in Figs. 8 and 9 is introduced into the space within the frame ||9 to form a female impression of the exposed surface of the coreforming segment |05 and thepartinlg material I and I |3. The substance |2| engages the exposed ends of the dowel pins ||1 to securely lock'them `to the first half |23 of the core-box member for making the core segment conforming to the shape of the accommodation core-forming member |05.

Upon solidification of the substance |2| the entire assembly may be inverted, the frame ||5 y The core box may then .be used in the manner previously indicated'to form acommodation core shaped surface |2 embodies back draft in one, 'A

forming members |03 and |05 in place thereon maybe used in the manner illustrated in Figs. 4 to 7 to form production pattern equipment of 4 the 'pattern :and accommodation core-forming members. Y

Core boxes for making cooperating accommo- 'daton core segments conforming to the shape and contour of the core-forming members |03 and I 05 may be formed as' illustrated in Figs. 15 to 22 inclusive.

The core-forming segments |03 and |05 may be separated from the pattern |0, reassembled by means of the registering means |01 and |09, and embedded in parting material as illustrated in Figs. 15 and 16. The parting material should be extended to cover the core-forming segment |03, and additional parting material |3 may be employed .to fill the space Ibetween the segments 03 and |05 formerly occupied by the pattern I0 and to eliminate back draft.- The parting material is preferably positioned in a frame I5 to insure more accurate results in the formation of the core-'box members.

As illustrated in Fig. 17. dowel or locator pins segments accurately -conforming to the shape and contour of the accommodation core-forming segment |05.

The core box for making accommodation core segments embodying the shape and contourof the segment |03 may be formed by'the reproductive method from the core-forming segment |03. Additional dowel or locator pins |31 :may be positioned in the openings in the parting material formerly occupied by the dowel pins I1. -A frame |39 may be superimposed on the vframe ||5 and suitable core box-forming moldable substance |4| introduced into the space within the frame |39 to form-the first half |43 of the ycore-box member for' forming accommo-v dation core segments conforming to the shape and contour ofthe core-forming member |03.

After the substance |4| solidies, the assembly may be inverted and the frame l5l with the parting' material removed. As disclosedin Fig. 21 a frame |45 may be superimposed on the frame |39 and core :box-forming moldable substance |41 introduced to form the second half |49 of the core box Afor forming accommodation cores embodying the contour of the accommodation core-forming member-|03.

The accommodation core-forming member |03 may be removed from the core box and suitable feeding and venting passageways |5| and |53 -extendedthrouqh the core-box member to communicate with the accommodation core cavity |55 conforming to the contour of the accommodation core-forming member |03.

Accommodation core segments conforming tothe shape and `contour of the accommodation core-forming segments 03 and formed in the core boxes.v These segments may be located by their cooperating registering means |05 may bel I`claim: y f

1. The method vof forming accommodation core boxes comprising applying to a pattern of an article embodying back draft anioldable sub-v stance capable of conforming to"th e.contour of 'the pattern, shaping the external? surfaces of -the moldable substance to eliminate back draft and provide accommodation core-forming members, forming cope and drag patterns 'of the pattern member and core-forming members, removing the core-forming members from the pattern member, assembling the reforming members' and applying parting' matenartnminate back draft, forming a rst half ofa core-box member by a reproductive processfrom thecoreforming members and parting-material, inverting the assembly and removing-the'. parting material, and forming a second hanf the core-box member bya reproductive'process from the coreforming members and rst half of the core b jox.A

2. The method of forming cooperative pattern' and core-boxmembers for casting an article having back draft comprising applying to a patternY of the article to be formed a moldable substancato eliminate back draft and provide separable core-forming members, forming female' impressions of the pattern and core-forming members, forming production patterns from the L'female impressions, separating the core-forming 1 members from the pattern, assembling the coreforining members in one of the female impressions and applying parting material to the coreforming members to eliminate back draft, formlf core-box member bya reproductive ing-.Lal

from the core-forming members. removin'gtl''e 'female impression and parting material,

forming theother half of the core-box member from the core-forming members, removing the female impression and parting material, forming ing the core-forming members from the pattern member, applying parting material to the corel forming members to eliminate back draft, forming a rst half of a core box member by a. reproductive process fromv the core-forming members and parting material,A removing the parting material, -and forming a second half of the core box member by a, reproductive'process from the core-forming members and rst half of -a plurality of accommodation core-forming segments, separating the core-forming segments from the pattern, reassembling the core-forming segments with the pattern removed, applying parting'material to ll the-space occupied by the pattern and to eliminate back draft, forming core .box portions from the core-forming segments and parting material by a casting operation, re-

moving the parting material and casting the remainder of the, core box members from the core-forming segments and said initially formed core box portions. v

6. The method of forming cooperating mold and accommodation core members for casting an article having-'back draft comprising applying to a pattern of the article to be formed a moldable substance to eliminate back draft and provide separable core-forming members, forming impressions of spaced portions of the vpattern and core-forming members, forming production patterns from said impressions, separat.-

the other halfof the core-box member from the 40 core-formingmembers, removingthe core-forming members from the core box, and providing afeedingopening communicating with the accom,

modtitn core cavity.

' method of making cooperating pattern afrdf'coreabox members to form aicasting cavity embodying back draft comprising applying to a pattern of `the=article to be formed a'moldable substance capable'ofA assuming thecontour of` the pattern, contourlng the external siufaces of v the mfdable substance Ito eliminate back draft and'zpoyide accommodation core-forming members, forming production pattern members of the assembled pattern and core-forming members,

separating the core-forming members from the pattern, reassembling the core-forming members with the pattern removed, applying partingmaspace occupied bythe pattern and to eliminate back draft and forming core boxes by a repro'- ductive processfrom the core-forming members and parting material. Y

` terial to the core forming members to flll the.

ing the core-forminglmembers from the pattern, applying parting material to the core-forming members to eliminate back' draft, forming portions of core box members by a reproductive process from the core-forming members and Aparting material, removing the parting material, forming the remainder of the core box members from the core-forming members and said portions of the core box members, and forming cooperating mold and accommodation core members from vsaid pattern and core box members;

7. The method of forming cooperating-pattern and core box members to eliminate back draft in a plurality of directions comprising applying moldable substance to a pattern, shaping the external surfaces of the moldable substance -to eliminate back -draft and to provide a plurality ofvspaced interlocked core-forming members, forming pattern members of the pattern and core-forming members by a reproductive process,

separating the core-forming members from the pattern, applying parting material toeach seg-` ment :to fill the space occupied by thev pattern,

4. The method of forming core boxes for makhaving back draft comprising applying to a pattern of said article a moldable substance capable of conforming to the contour of the pattern, shaping the external surfaces of the moldable substance to ehminate hack draft and provide accommodation core-forming members, separat- 70 l 'ing accommodation cores for casting an article forming a core box portion from each coreforming 'segment and its applied parting material by a reproductive process, removing the part ing material, andforming the remainder'ot the core box for eachv core segment by a reproductive process from the core-forming member and the previously formed core boxportion.

' RAYMOND J.