TOOLING OR 3-D PRINTING?
Certain conditions in which short leadtimes and a small
production order is required for a complex part can make a case for the use of 3-D printed molds.
OLIV ER JOHNSON, TOOLING AND EQUIPMENT INTERNATIONAL CORP., LIVONIA, MICHIGAN; TOM MUELLER, VOXELJET USA, CANTON, MICHIGAN; MIKE LINDBERG, ILMOR ENGINEERING, PLYMOUTH, MICHIGAN.
T
he 3-D printing of cores and complete molds, without any requirement for tooling, is revolutionizing the indus- try of fast prototype casting manufacturing but it also off ers distinct advantages for certain production castings. A recent case study of a complex thermal command
center casting for a high performance marine powertrain illustrates the calculation metalcasters and end-users may take in determining the cost factors that would
promote the use of 3-D printed molds over conventional soft tooling. T e thermal command center, which combines a water pump, thermostat
housing, and a series of bypass valves into one single casting was required for early mechanical development testing (Fig. 1). T e part’s overall dimensions were 29 x 13 x 6 in. (736 mm x 330 mm x 152 mm), and it weighed 14 lbs. (6.35 kg). Two castings were needed on an accelerated timeline. T e fi rst cast and machined
part was needed in four weeks. More parts would be required after development testing, and it was likely the design would be modifi ed based on the results of dyna- mometer testing. T e casting was to be made in A356 alloy and heat treated to a T6 condition prior to CNC machining. T e designer communicated information to the
36 | METAL CASTING DESIGN & PURCHASING | Sept/Oct 2016
metalcasting facility strictly through 3-D data in order to accelerate the manufacturing process by eliminating two-dimensional drawings. 3-D printing the entire sand mold
holds many advantages: • Backdraft and zero draft present no obstacles and considerably reduce time for the product designer.
MACHINED
• T e ability to make a casting, quickly evaluate the casting size and alter the shrink factor for the second casting is possible with 3-D printing, but not with tool- ing where remanufacturing the tools at great expense is necessary. • Complex in-gate and riser geom-
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