I am trying to understand and maybe repair cheap hot glue guns.

[flat5]

Google has not been helpful so far.

The element seems to be a ceramic crystal I think.
It is sandwiched between two brass or copper plates that connect directly to the 100-240v power.
This assembly is wrapped in a plastic film for insolation and clamped to the aluminum headpiece with the hole for the glue.

One of my cheap guns measures 7k ohms cold. This one does not warm up at all.
One measures 4k and heats but not enough to work properly.
One measures 200k ! and gets plenty hot but has no trigger. Rather confusing.

I need more info on the heat element.
I have thought of lightly sanding/smoothing the surfaces that contact the side copper plates.

 

[Paul_L]

I just measured mine. It is at least 30 years old and measures 1K.

 

[flat5]

Thank you, Paul_L.
All of mine are supposed to be 20 watt models.

I have not found an article explaining how the element works.
I want more than "You push electrons thru it and it gets hot"

 

[Paul_L]

Mine is a 40 watt model.

 

[Paul_L]

I would have to take one apart to see what makes it tick.

 

[MrAl]

Hello,

Mine is 40 watts and somewhat new. It was advertized as 80 watts and very fast warm up, but it is 40 watts made by Stanley.
The heater inside is a dual coil for low and high settings, and i think it is partly inductance so probably should not be run on DC.
The two windings will act as a very light duty transformer, but i am not sure if it actually has a magnetic core or just a coil as i can not see inside the coil construction.

 

[tunedwolf]

I have only ever owned 1 glue gun, a Bostik Handy or something like that, Blue in colour with orange trigger and silicone rubber inserts. It is rated at 45 watts allegedly. It heats rapidly, in fact, it continues to do so, until the glue is really too hot and begins running out of the nozzle on its own. This excess heat eventually melts the remaining glue stick still protruding from the feed side of the chamber, which of course then drips into the trigger mechanism gumming it up. I have taken it apart several times to clean up said trigger, and can confirm that the heater and glue chamber are solid diecast alloy of some sort, wrapped up in Kapton tape and plugs directly into the 240V mains. It must be going on 18 years old and still works well considering I only paid about £10 for it new

 

[MrAl]

Hi,

Consider switching a power resistor in series with it after it heats up to reduce the power a little. You might have to experiment to get the value you need.
I actually do this with a soldering gun i have from good ol' Harbor Freight, which gets so hot it melts the tips so they break in half after only two or three short uses. Using a variac i lower the power to the gun so that it works without hurting the tip, and also overheating the inside guts. Without the adjustment it gets real hot inside and smells bad. About 80 percent of full line voltage seems to work pretty well.

 

[Nigel Goodwin]

As far as I remember, when they first came out (and I still have a pre-trigger early Bostik one) it was said that 'new technology' had made them possible. Essentially a self-regulating heating element - so no thermostat.

So not really 'repairable', as it's just an element and a casing.

 

[Paul_L]

Mine does not even have a switch just a trigger to force the glue stick through the heated nozzle.

 

[Nigel Goodwin]

Mine does not even have a switch just a trigger to force the glue stick through the heated nozzle.

Mine doesn't even have the trigger - you push the glue stick directly with your thumb

 

[dr pepper]

I have a couple, and the silly blurb on the side of one I translate to it having a ptc heater, the heater element also being a thermistor, when cold the resistance is low making it pull more power, then when warm the resistance is higher making it pull less current, making the element sort of self regulating.

By all means clean it up, but if it still doesnt work better chuck it.

Petrol car engines often have a similar arrangement to warm the air entering the engine when cold to avoid performance flat spots.

 

[flat5]

tunedwolf, if it has a switch and just a simple element consider soldering a diode across it and see if you then have a low/high heat gun.
If it does use a transformer then this is not a good idea.

 

[Rich D.]

Never thought to open up my cheap glue gun. I plug it in. It works. The end.
But now that you got the idea in my head I guess I'll have to take it apart and see what's in there.

What I DO notice about hot glue is that at least for me, it always seems to work best when other glues fail.
Better than CA glue.
Better than wood glue.
Better than plastic cement.
Long live hot glue!!!

 

[MrAl]

Hello again,

Rich:
Yes, hot glue is very handy. I've used it so many times that a while back when i went to a store that was having a sale on glue sticks i purchased 100 sticks. I have purchased more after that too.
We were talking about hot glue on another site a long time ago and one member decided to do a test high pot test. It was found that it has very high resistance to electrical current even at 2000 volts. So it works well as in insulator, but unfortunately it cracks over time if there is any flexing and the cracks can hold moisture which with a small amount of air born minerals can then make the cracks conduct, which means it isnt as mechanically stable as we would like for an electrical insulator. It works good as a temporary fix though or if the part never moves. Of course the part can not get too hot either or the glue melts
As a side note, there is also a special kind of plastic that is made that turns to a jelly like state at less than 100 degrees C. Once cool, it acts like a very tough and durable plastic which you can barely cut with a strong sharp knife. Downside is the application temperature can not get too hot or else it gets soft, and that could easily be too low for many application in electronics. I think it was made with the idea it would be used for crafts or mold making, but it does work for long term low temperature stuff too.

 

[flat5]

I built a high voltage arc-er. The voltage jumps about 8mm. To get it to jump at the thread end of two screws consistently and not at the screw head end I put a barrier of hot glue between the screws. This was effective.
The voltage is somewhere between 20,000 volts and maybe a few hundred thousand volts. Driven by two AAA batteries.