Dome on the range part two.

Visit Tagbits to see the full range of tagger products described in this blog.

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.

Dome Mount Redesign

Visit Tagbits to see the full range of tagger products described in this blog.

I've been unhappy with my design for mounting acrylic domes to my sensor bases:

I designed the domes to be held in place by three #2 self tapping screws that push against the inside of the dome. I've since found that putting acrylic in tension can cause it to crack. Resulting in the destruction of at least one dome as I tightened the mounting screws. To fix this I've redesigned the dome mount to have a ring that fastens around the outside of the dome, keeping it in compression rather than tension. However, to accomplish this I've had to redesign the dome bases to allow this ring to be fastened with screws:

Here is the full assembly:

And sprayed and mounted with PCB on a gun:

Clearly I need to change the position of the clamping ring screw holes for this design. I'm going to roll this design out to the other dome bases available at Tagbits over the next few days.