Sunday, 6 October 2013

Dome on the range part two.

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I make sensor domes for my Milestag guns using 2mm acrylic sheet heated in the oven and press formed over a mold using a 3d printed ring which is designed to fit over the mold. You can see the mold and the forming ring here:

The ring fits into an MDF sheet that allows me to push down enough force to deform the acrylic over the mold:

I wanted to experiment with polycarbonate sheet. It is cheaper and tougher than acrylic. However, it has a higher glass transition temperature (147C) than acrylic (107C) and this caused the ABS plastic of the forming ring to soften and leave deposits on the egde of the dome during the deformation process.

I decided to make a replacement forming ring from aluminium. I bought a billet from ebay for about £6.

I used a combination of drills and boring bars on the lathe to turn a replacement ring. It came out rather well:

It fits nicely into the MDF sheet and works slightly better than the ABS ring when forming the sheet as it has a narrower rim which allows me to apply more pressure to the sheet.

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