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Direct
Shell Production Casting (DSPC) is a proprietary fabrication process
for metal parts which combines the advantages of both casting and
machining and eliminates the disadvantages of both processes.
The patternless
DSPC process produces functional cast metal parts directly from your
CAD file. In addition to shortening lead time and saving cost, eliminating
casting tools add tremendous design flexibility of complex cast parts
which is essential during the development phase. Soligen has combined
DSPC, conventional casting techniques and a modern CNC machine shop
to yield a "one stop-shop" for cast and machined metal parts and supply
them as ready for assembly.
ALLOYS:
DSPC enables
casting parts from any castable alloy. A partial list of alloys:
- Aluminums: 206, 319,
328, 356, 357, 390
- Magnesium: AZ91
- Copper, Brass, Bronze
- Irons: ductile, austempered
gray, malleable, Si moli
- Stainless Steels: 3xx,
4xx, 17-4ph, 15-5ph
- Super Alloys
SURFACE FINISH:
DSPC and production
castings are normally shot blasted. Our default DSPC parts surface
finish is "as printed". As these DSPC molds are cast, some of the
surfaces of DSPC parts contain "stair steps" of approximately 0.005"
to 0.007". Shot blasting and gating removal removes most of the stair
steps from external surfaces and near areas of gating. When required
Soligen can provide hand finishing of DSPC castings to a finish of
approximately 125 to 150 micro-inches rms. Proprietary ceramic coatings
that are compatible with metal casting can improve surface finish
of internal cavities and other areas when access to hand finishing
is restricted. Casting appearance can be improved with your express
instruction and at additional cost (please consult with Soligen technical
team on available finishing processes).
ACCURACY AND FEATURE
SIZES:
Soligen uses
either gravity or low pressure casting processes to produce DSPC parts,
therefore casting rules of thumb should be observed. The DSPC process
is capable of producing a net shape casting. When you send a file,
unless you otherwise instruct us in writing, we will produce a cast
metal part that will match your STL file (except for un-castable features)*.
While the DSPC process tends to produce molds that are more accurate
than standard sand casting, in order to make your parts more produceable,
you should generally assume that the accuracy of the part will conform
to standard casting tolerances. For tolerances on non-heat treated
DSPC cast parts, refer to the following table: Dimension Tolerance
(inches) Equal or smaller than 1 inch +/- 0.021" Between 1" and 6"
0.021 + 0.002" per inch Greater than 6" 0.031 + 0.003" per inch over
six inches Angles +/- 30' * If we detect non castable features, Soligen
will contact you to receive your authorization prior to any modification
of the CAD file.
DRAFTING, BLENDING AND
FILLETS:
DSPC castings
do not require drafting and fillets, because there is no tooling per
se which must draw. The DSPC part will therefore be identical to your
STL file in this respect, i.e., if drafts and fillets will be in the
part only if they are in the part file. Sand castings are often modified
from the original geometry so that the tooling can be withdrawn from
the sand without damaging the imprint. So, if you plan to order multiple
pieces i.e., sand casting or low pressure permanent mold casting (short
production runs) and are not aware of the constraints under which
a pattern maker will operate, please make your requirements clear
and indicate so at the time that the request for quotation (RFQ) is
placed. To avoid casting defects, which result from sharp corners,
we recommend that you include fillets and avoid sharp corners in intersection
of walls. Our technical team will be happy to assist you. Another
important consideration in cast part design is to make an effort to
keep the walls thickness of the part as uniform as practically possible.
That is because a transition from thick to thin wall section is sensitive
to shrinkage due to uneven solidification. Sharp corners and unblended
transitions are the most sensitive. You should therefore attempt to
blend and fillet intersecting sections. To increase the likelihood
of getting a sound casting the design should call for smooth blending
and as large a fillet diameter as possible.
VACUUM
CASTING:
DSPC shells are suitable for vacuum casting which enables high definition,
wall thickness that is thinner and a higher aspect ratio than those
achieved in gravity casting. Since DSPC yields a solid ceramic mold
(no organic binders) it does not outgas. It also allows pouring at
elevated shell temperatures (similar to investment casting).
CASTING GRADES:
Designing the gating in CAD enables us to feed the cast part in more
directions and entries than conventional casting. Embedding metal
chills is an additional feature that DSPC incorporates freely. These
enable us to better control the direction and rate of solidification
of the part as well as eliminating shrinkage and other casting defects.
Thus DSPC is a perfect process to develop high grades of casting.
PART SIZE:
This is not a limitation. The printing envelope of our DSPC machines
is 14"x18"x14" inches. However since ceramic molds can be assembled
from multiple ceramic pieces, the final casting mold can be much larger.
We have successfully made castings as large as instrument panels for
SUV vehicles and as heavy as a Tomahawk missile body. (weighing hundreds
of pounds)
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