Second Attempt: More foam cutting trial and error...

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To build a 3d model of the HBLB, I cut out 5 different shapes with the cnc router, then glued them together to form an extrusion that will be the pattern for the casting. This was a very time consuming process, and ultimately did not work. The problem was aligning the layers. There was just too much error introduced into the system when building a part this way. I learned loads about cutting foam with the cnc router, though!

A shot of the many foam pieces that I made until I figured out that TurboCNC wasn't configured properly for my machine. Once I fixed that, the part scaled perfectly.

 

I assembled this piece to test the lost foam casting process before I went through the effort of making a full bearing. It worked like a charm.

 

The edges are a bit fuzzy, but I think that this is because my feed rate is too slow. Even so, a bit of sanding cleans them right up.

 

Test piece.

 

Test piece.

 

This foam machines very well. The spiral saw bit cuts a smooth and accurate hole in the foam.

 

Testing the fit of the bearings on one of the test cuts.

 

Try doing that with an xacto-knife! Here are two of the three different layers that are needed to form one HBLB

 

The HBLB all hot glued together and ready for a bit of touch up.

 

Another shot of the HBLB.

 

After a bit of sanding, the foam model is ready for the sand.

 

Investing the foam model in the sand. I left out the pictures from the test piece where I used a plastic 5 gallon bucket for a flask. While pouring the aluminum, I missed the sprue and a bunch of molten aluminum melted the bucket and started burning. The aluminum continued to flow down and catch the grass on fire. I guess I need to make a sand pit or get a steel flask. I think I'm going to get a big stainless pot from the thrift store.

 

Sprue and riser visible just before the pour.

 

The HBLB hot out of the mold. I love the lost foam process. There is no shakeout or cleanup. You just dump the sand out of the flask and there is your part.

 

The finish is quite good considering that I used sand blasting sand for the mold.

 

After a bit of clean up and washing the sand off, the HBLB is done. The finish is a light grey color, not like the finish when using Petrobond.

 

Another shot of the finished HBLB.

 

Although this process worked well, it took too long to make just one part and the finish wasn't that great. I just have to try something else...