NWSL & SLM Critter – Pt V

Molds and Castings
This was my first attempt at casting the sideframe. It came out .. ok. There is a lot of flash as this was a open face mold. The slight warp I had in the sideframe really didn’t lend itself to a two-piece mold. I thought about trying to flatten the sideframe but .. instead glued the 3d print to a flat surface and made the mold as you see.

Couple things I learned. One was that I needed to seal the edges better .. that’s where the rough edge you see came from. With the casting you can see that the ‘bolt heads’ didn’t cast well. I figured that was because of air trapped in the small mold of the bolt heads.

Overall though I was happy .. generally. I could have drilled out the messed up bolts here and glued in brass or styrene ones.

I then turned to the bearing assembly. In the photo you can see how small this sucker is .. that’s the 3D print sitting on the penny. The mold was a two-part (my first) and it worked .. pretty much. I got a casting but wasn’t happy with it. I made the mistake of pressing the print into the clay too far .. ended up with the parting line through the bolt heads. Not a good thing. But hey .. lessons learned.
Not being satisfied with the first mold for the sideframes I redid it. This one came out pretty good. Of course .. if you solve one problem then a second is bound to raise it’s head (evidently a corollary of Murphy’s Law). The resin doesn’t get into all the small crevices and pockets easily. This can bee seen with the bearing casting sitting between the two sideframe castings. The areas that are supposed to be a bolt head have a hole in the center. Again .. I think that was because air was trapped under the resin so it didn’t fill the void completely.
Part IV Part VI

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