I spent some time after class in the Physical Computing Lab repairing the hot glue guns. During class students told me that the triggers didn’t seem to work, and they had to push the glue into the gun by hand to get anything out the hot-end.
I removed all the screws (about 8 of them) and opened one up and it’s a lot of plastic inside, besides the hot bits. There’s a plastic piece that snapped, due to (I’m assuming) pulling the trigger too hard. It’s a poor design, but I was able to repair it by drilling holes in the two pieces and adding some wire through the holes and twisting it tight. This was enough to pull the pieces close together. (I contemplated using cyanoacrylate, but didn’t have any, and wasn’t convinced it would work.)
Two of the guns were in good condition, except for the snapped piece of plastic, but the third one must have been repaired before, because the rubber retaining ring and a tiny spring were missing, and the larger spring had been replaced by a not-quite correct replacement spring. The third one (once assembled) didn’t do a very good job of pushing the glue forward. I may have to try further repairs, but at least we have two working better now.
The other issue, which may have cause some of the problems, is a “HIGH/LOW” switch on the handle. When I held the gun, I ended up switching it to LOW. If someone had been using it on HIGH and accidentally switched it to LOW, they might have kept pressing hard on the trigger while the temperature dropped, and snapped the plastic bit inside.
I added some tape to the switches so they don’t get accidentally set to LOW. We only have high temperature glue anyway…
The third gun, which doesn’t work very well, got labeled “Not Great” so we remember which one is the crappy one., which can still be used, as long as you don’t mind (possibly) pushing the glue forward with your hand.
Reminder: Hot Glue is Hot!