Teardown Of A Cheap Glue Gun

A hot glue gun is one of those standard tools of the hardware hacker’s bench, called upon to provide adhesion between an astonishing range of materials, and to provide a handy filler and strain relief in the form of blobs of polymer glue. We’ve all got one, but how many of us have taken a look inside it?

[Andrew Lorimer] bought a super-cheap eBay glue gun, and subjected it to a teardown. As you might expect, he found it to be a pretty simple device with only a trigger mechanism and a dumb heating element, but his write-up is of passing interest because he’s characterised its heating element. It has a positive temperature coefficient, which means that its resistance increases from around 2.5 kΩ at room temperature to about 7 kΩ at its 150 ºC operating temperature. This limits the current, and provides a very simple thermostat action.

The build quality is surprisingly good for such a cheap appliance, and he notes a surfeit of screws holding its shell together. But the quality of the insulation and strain relief leaves a lot to be desired, and he wonders whether it truly qualifies for its double-insulated logo. The LED pilot light is simply fed from the 240 V mains supply through a 250 kΩ resistor which he replaces with a 12 kΩ component for a brighter result.

We cover plenty of teardowns here at Hackaday. Often they are of extremely expensive and complex devices, but sometimes they are of much simpler subjects.

25 thoughts on “Teardown Of A Cheap Glue Gun

      1. Maybe you got crappy glue stick? Mine sticks to everything pretty well. I get glue stick from local Walmart so it’s probably better quality than the cheapest stuff one finds on eBay.

  1. Normally I don’t buy craft items from the local drug store like Rite Aid and prefer to support craft and hobby stores, but did buy an inexpensive glue gun there once. Used it for a kids project (bridge to support weight) and it worked well for plastic, wood, and foam board. Just need to make sure it’s on the high heat setting (pretty much useless at low setting) and warmed up enough.

    1. If I bue something, I buy it where I get it cheapest in an acceptable amount of time. If I can wait, I order online from Aliexpress (slow, cheapest) or Amazon (little more expensive but faster) and if I need it immediately I go into a store.

  2. My two glue guns are from the $1 store. I also have a lot of different sticks from the $1 store. For a quick tack I use one of he guns I am happy with them, though I would not turn my back on one for an extended amount of time. For bigger jobs I put a few sticks in a steel can that something from the store came in and use my induction heater to melt it. I can accurately control the temperature to get it exactly where I want it and I can change the temperature almost instantly.

  3. Interesting! Could we see a soldering iron teardown too?

    My glue gun is dual-voltage 110V and 220V.

    Unfortunately, my soldering iron is only single-voltage. I haven’t found a dual-voltage soldering iron in the stores nearby.

    Both are just heating elements, right? Why would the soldering iron not allow the full range of AC voltage?

    1. because in a simple heating element, the resistance, and hence power, is chosen based on the supplied voltage. So plugging it into the other supply, 110 or 220VAC it will either halve, or double the power output.

      And for temperature controlled soldering stations, the transformer (judging by the weight mass of mine) is chosen in function of the supplied voltage, also doubling/halving the voltage at the secondary winding. Some brands might have a multiple tap transformer with a selection switch on the back.

      1. visiting your website now (GP post) (who knew some of these username links actually go to anything other than a dead wordpress site) it seems you obviously knew that already, so i must have misunderstood your question ?

  4. I see these a lot when perusing random taobao sellers. They’re usually like, 7 yuan which is about $1.

    Hey, I guess once you have the injection molds, you basically just pay for the materials and lab- uh, yeah, just the materials.

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