Fig. 1. The thermal command center integrated a water pump, thermostat housing and bypass valves in a single complex cast assembly.
• Design features can be quickly revised without any cost of tool- ing updates.
etries can be created more easily with 3-D printing than tooling.
• Internal core positions are ac- curate as cores can be grouped together or printed directly into the cope and drag, eliminating core clearances and the resulting core shift in the casting.
• Reduction in weight or heavy sections of the casting is possible because it is not necessary to be able to draw sand components from molds. T is leads to im- proved casting quality by elimi- nating heavy sections vulnerable to porosity.
However, 3-D printing holds some disadvantages compared to conven-
tional tooling: • T e cost per sand mold is much higher, and the time to manufac- ture is generally much longer.
• T e cost per printed sand com- ponent generally is linked to the size of the cuboid containing the printed part. As is the case for the core depicted in Figure 2, a small 3-D printed compo- nent occupying a large volume of unprinted sand would be expensive. T is is because cur-
• Once soft tooling is made, it is possible to manufacture castings at a much quicker rate for most cores and mold components than by 3-D printing.
Because only two parts were re- quired at fi rst, it was decided to manu-
rent 3-D printing machines use activated sand for which only a small percentage can be recycled. Similarly, large molds will be much more expensive than their tooled equivalents if the cost of the tooling is eliminated from the comparison. Future develop- ments with phenolic binders may improve the cost eff ectiveness of low printed density cores since the sand can be recycled.
facture these castings using 100% 3-D printed sand molds.
Computer Aided Engineering Crucial
T e cost of 3-D printed sand is
high in comparison to sand molds and cores produced by soft tooling, making the use of simulation upfront critical. Simulations assist the engineer in gat- ing and chilling strategies for com- plex castings. T is strategy leverages preemptive casting development rather than trial and error development. For the thermal command center,
a variety of analysis techniques were conducted through the use of solidifi - cation modeling software. First, a 3-D mesh of the casting was built, and a
Fig. 2. This 3-D printed oil gallery core is currently expensive as a large amount of activated sand has to be wasted during its manufacture.
Fig. 3. A natural solidifi cation of the thermal command center was predicted.
Sept/Oct 2016 | METAL CASTING DESIGN & PURCHASING | 37
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