Hot glue has become widespread for quite a long time and has become almost indispensable both among home-made and needlewomen, and in everyday life in general. It is easy to apply to surfaces, has good adhesion, comes in different colors, and creates a fairly strong adhesive seam.
However, most thermo guns for applying such glue have a PTC PTC heater in the cheapest and very unreliable design. Basically it is a ceramic heating element sandwiched between two conductive plates to which the mains wires are connected. When heated, brass plates expand and deform, which sooner or later leads to their closure.
And yet this is not a reason to buy a new instrument. The gun can still be repaired and even made safer. You just need to modify it a little.
DIY repair-modernization of a hot melt glue gun
Photo of the burned out “patient”:
- The schematic diagram of the future device is as simple as possible:
It will take
In order to alter an existing or repair an already burnt out thermal gun, you need only a few parts, which can be bought at any radio parts store or ordered via the Internet:
- resistor MLT-2 with a resistance of 20 ohms;
- copper wire approximately 1 mm in diameter;
- power supply unit 9-16 volts, with an output current of 1 or more amperes (for example, from a laptop);
- suitable power connector.
- any 3-5 mm LED and 3 kΩ resistor;
- heat-resistant kapton tape.
A 20-ohm resistance will replace a heater, and it is advisable to use a domestic resistor with an MLT-2 case. Firstly, it is designed for power much more than the nominal 2 watts and is able to withstand prolonged heating without any consequences for itself. Secondly, in size, it ideally fits the place of the old heater.
We disassemble the glue gun (remembering to pull the plug out of the socket) and remove the nozzle with the heater attached to it. Usually everything here is covered with a thick layer of hardened hot melt glue, so we take a clerical knife and carefully clean the nozzle from the outside. You can use a lighter to loosen the glue residue.
ATTENTION! Observe safety precautions when working with a knife!
Then remove the old heater. Usually it is wrapped in Kapton tape – a special colored (usually orange or green) film that can withstand temperatures up to 400 ° C. This tape can also be bought with the rest of the radio components in the form of a skein like this:
If you don’t have this, it doesn’t matter. Carefully remove the old tape from the heater and set it aside. The heater itself can now be thrown away, no longer needed.
The resistor leads should be bent with rings and connected to the wires with screws. For reliability, I also fixed the screws on the PCB plate (any other non-combustible insulating material will do). Now we wrap the resistor in a Kapton, put it in the place of the heater and tightly wire it to the nozzle. Additionally, wire the junction of the nozzle and the rubber tube into which the glue stick is inserted – this will prevent the glue from flowing into the body.
The other ends of the wires must be soldered to the power connector – here the polarity does not matter, so you can connect as you like. Optionally, to indicate the inclusion of a thermal gun, you can add an LED with a current-limiting resistor, as in the above diagram. It is better if it is dim, so that its light does not hit the eyes and does not distract when working. Remember that LEDs have an anode (plus) and a cathode (minus):
It remains to expand the hole for the power cable with a file so that you can install the power connector in its place, and drill (or pierce with a heated awl) somewhere a hole for the LED.
After assembly, you can test the glue gun in action. It should only be borne in mind that the resistor takes a little more time to heat up to the desired temperature.
After such a modification, the mains voltage is no longer in the instrument, which makes it much safer and practically eliminates the possibility of electric shock. Video of the glue gun:
Watch the video
Also read how to make a soldering iron with instant heating from a glue gun – https://sdelaysam-svoimirukami.ru/6061-momentalnyj-pajalnik-iz-kleevogo-pistoleta-i-jenergosberegajuschej-lampy.html