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| vtsteam:
Just thought I'd post some pics of lost foam patterns and casting I have made. The intent was tto produce a homemade linear bearing housing for a simple CNC turn mill. Similar to the linear bearing housings illustrated by Dave Kush, a lost foam casting pioneer at his buildyouridea.com. The drawing (in Google Sketchup): |
| vtsteam:
Using a plugin to produce a .dxf file output in Sketchup 7 (free edition, and run in WINE on Puppy Linux) I transferred the profile to Jedicut (also free, and running on WINE) and cut the foam patterns on a CNC hot wire cutter I built, using an old 4 axis HobbyCNC controller and steppers. Here are the foam patterns: |
| vtsteam:
The patterns were attached to a split sprue -- trying out the Dave Kush methods: |
| vtsteam:
Then the pattern was dipped in wallboard compound (sheetrock mud) diluted to a yogurt consistency, and then hung to dry. In summer Vermont weather this takes 1 to 2 days for complete drying. Unfortunately this can't be done in a kitchen oven, since the foam might melt. |
| vtsteam:
The bearing housing pattern was placed in a large tin of loose sand. The 4 sprues were cut off short, and a hinged split riser, similar to Dave Kush's was placed on top of the sand. A hot wire was poked down the sprues to clear them a little in advance of the pour. The aluminum was poured quite hot compared to my usual practice, because the sections were long and thin, as were the sprues. In addition, the heat must do the work of flashing the polystyrene to gas, and getting rid of the gas bubbles before solidifying. The first casting was shorted, and a second was poured with even hotter metal, successfully. I don't have photos of the pour, as I was working alone, but here is the finished casting from the second pour. |
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