Fifth Attempt: Foam pattern success, casting failure...

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Here we go! Finally got all the bugs worked out of the hot wire cnc machine. Backlash is way down, so the patterns are nearly perfect. Here is a shot of my complete cnc machining center.

 

Resolution is excellent with the guitar wire. Slow speed and the coolest setting on the wire that you can get away with is essential.

 

Making the radius.

 

Another view showing the fixture that I built to hold the foam billet square with the wire. The rubber bands keep the billet locked in place.

 

4" foam billet from the insulation place. This stuff is $30 for a 2'x8' piece. A bit pricey, but well worth it if I can get this working.

 

The new profile of the part. I guess this would be generation 274 if you are keeping track of how many times the design has changed!

 

To make the bolt holes, I built another fixture from MDF. This clamps to my drill press table, and I use the heated rod to melt the holes. Very precise and accurate.

 

Another shot of the hot shaft punch.

 

Two patterns ready to go.

 

These patterns were invested in silica flour, but it was a total disaster. Out of three pours, none of them turned out. Back to the drawing board...