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[NZFoamer]

I have been trialing this for some time now and need to go to next level to achieve the result that is the sample sitting on my bench.

Casting Endurathane has been interesting and I have finally managed to get it to skin properly. The last one failed but did skin very well, perhaps a 2mm skin. Realising that the mold needs to be overfilled and warmed did that.

For the mold I have used an acrylic 10mm sheet, laminated to 40mm thick. And cut the mold sides out with a CNC Router. Then put a hinge on one end. The item I am making or trying to make is about 250mm x 50mm.

Where I am falling short is the finish I want to achieve on the skin of the foam. My last attempt I actually heated up some vinyl and pressed it into my mold using contact adhesive. It did impact on the skin of the foam the pattern I am looking for. But the edges where the mold comes together looked rough. It really doesn't matter what the pattern is on the skin, it just needs to look decent and proper - you know - professionally made. I am unsure how to achieve this? I have thought about scribing a pattern into the mold with my cnc but yeh, that is easier said than done. Would really like or actually I need some help here on this one. I found the foam is actually so particular to the mold that even the very small endmill patterns from cutting it out show. I have seen some spray textures but am not that keen to use something like that.

If I can get this correct, I will end up machining a mold out of alloy. But then I still need to get this skin pattern correct.

Thanks in advance.

[Jim]

Good morning NZFoamer,
Any 2 pc mold such as yours will have parting lines. The edges of the mold need to be as sharp as possible without a burr and line up perfectly to give you the cleanest parting line. Your hinge most likely has play in it allowing misalignment on your edges. While it may be small, it’s enough to allow foam to flow over. I would suggest removing the hinge and doing alignment dowels at the corners on the faces of the mold. Then use good clamps all the way around. You may need a hole somewhere in the mold to allow air to escape as you are filling. As for finish, once you get to the final mold material, you can sand and polish the alloy to a smooth surface.