Laser cutting electrode holders

Because my applied electronics lab will have labs of 50 students (25 stations), I’ve needed to make a number of new setups. The lab will be taught in a space that is not normally a lab, so I’ll need to wheel in the equipment and set it up before the lab sessions and pack it all back up and wheel it out every Tuesday and Thursday.  Luckily, the lab is not very expensive—equipping all 25 stations, including storage tubs and the cart, cost lest than $10,000.  That is less than the cost of one station in the lab that we used in the past.

Some of the setups for the lab require me to build some equipment (pressure sensor breakout boards, stainless steel electrodes, electrode holders for silver wire electrodes, … ).  I made the stainless steel electrodes over the summer, and this week I made new electrode holders.

The electrode holders are laser cut from acrylic sheet.  Earlier this quarter I tried cutting them from 3mm acrylic from the hardware store, but that did not turn out well.  The lines that were supposed to be etched only partway through the pieces ended up cutting all the way through, even though I was using the laser cutter on its lowest setting and highest speed.

This week I used some 5.3mm thick acrylic sheet.  I cut at 8mm/s at the highest setting, and made the marking lines at 180mm/s at 20–25% power (the lowest setting).

A holder as it came from the laser cutter, with the protective paper still covering the acrylic.

The same holder with protective paper removed.

The holder with 6″ silver wire mounted so that alligator clips can attach to the wires at the top, while the bottom is immersed in salt water.

The marking worked fine, and the first few holders I cut were fine, but several of them did not get cut all the way through, which I did not notice until I had removed the acrylic from the laser cutter (so I couldn’t just cut the lines again).  I ended up having to snap several of the partially cut holders from the waste material.

One of the failed cuts—the ear broke off when I tried snapping the holder from the waste material around it.

I made enough spares that the two for which the ears broke off can be discarded, but I will have to use my rifflers to smooth some of the edges and open up notches on a few of the holders.