USB heat gun for shrink tubing

thingiverse

I had some spare parts lying around and had the idea for a very simple heat gun. I don't have a heat gun with a fan yet, it's on the list of tools to buy along with a million others... Anyway, I would always use my soldering iron to shrink tubing after making a joint, but that would melt the rubber and leave junk all over my iron, a crappy system born out of laziness. This device uses 15 watts, and doesn't get hot enough to melt the rubber, just to shrink it, and heats up in seconds. I can also leave it sitting on a table without burning most surfaces. I used a variation of the power equation P = V^2/R and solved for L, R(total) = R*Length I had some 20 AWG nichrome wire(it's used for heaters because of much higher resistance than copper) on hand which is .635 Ohms per foot. Using 5 volts and 15 watts I solved for the length of wire, this turns out to be 2.6 feet (31in). A thinner(and thus shorter) wire would work better for this but I'm working with what I have. You can change it for the materials you have. I used 15 watts because I have a 3A USB wall charger I can use with this, 5V * 3A = 15W. I also found a USB wall panel in my house that goes up to 4.2 A for quite a bit more power but this is plenty. I found a small rocker switch, and a very nice and long, but frayed and broken iPhone charging cable to reuse, eliminating some e-waste. The wires running through most of the handle are 14AWG solid, again, a little thinner would be better, but this helps keep the nichrome loops rigid, and works as a heat sink to not melt the PLA. I then modeled a handle to hold everything together, which is always a little more challenging than it should be when trying to stuff wiring inside. It kind of looks like it was bought off aliexpress but works well. An Adam Savage (half) day build if there ever was one. I included the Solidworks parts, they are a little rough around the edges but you won't run into any errors changing the size for the wire channels if you need to. Screws together with an M3 bolt. Rocker switch: https://www.aliexpress.com/item/4001165826718.html?spm=a2g0o.productlist.0.0.265375e83FdoKU&algo_pvid=1b9110f2-e1d6-4900-b788-b589d70e1824&algo_exp_id=1b9110f2-e1d6-4900-b788-b589d70e1824-20&pdp_ext_f=%7B%22sku_id%22%3A%2210000014982124403%22%7D&pdp_pi=-1%3B0.98%3B-1%3B-1%40salePrice%3BUSD%3Bsearch-mainSearch