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Picture of Make your hot glue gun cooler!
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WHY would you want to make your hot glue gun cooler?

Well, hot glue guns are great. They will stick just about any two materials together with a strong and flexible bond which hardens in less than a minute. But . . .
I occasionally make radio control model planes out of Depron foam and EPP sheets (foamies) and these materials have quite a low melting point. At its normal temperature, hot glue will spread across the surface of the foam and eat into it causing bubbles of gas to blow into the glue and making a very messy joint. The same is true of fanfold foam and Styrofoam (expanded polystyrene) which is much the same thing and melts into nothing at full heat.

Look at the photo. At its normal temperature my gluegun makes a mess of the foam. Turning down the heat reduces the bubbling until the glue is below the foam's melting point, which still gives a solid join much stronger than the foam, but so much neater. With my modified glue-gun I can now make repeatable neat joints in the foam with no distortion due to overheating.

Temperature controlled glue guns are available, but these are still too hot for Depron or EPP. You can also get adjustable guns, but these come in way more expensive than my idea here. There are also cool-melt guns, but I've never found them to have the adhesive power of hot glue.

*** Warning : This project uses potentially lethal mains voltages ***
*** Safety should be the main consideration during construction ***


( Contrary to what appears on the blog sites which have picked this up, I did not ruin
several sheets of depron using too hot a glue gun. I'm not quite that slow a learner #;¬)
 
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Step 1: What you will need

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Unless you have a particularly long mains lead on your glue-gun, you will need a length of mains wire with a mains plug on the end.  You'll find one around the house somewhere, probably attached to a defunct gadget.  It should be no thinner than the lead to the glue-gun.
You will also need a cheap switched light dimmer (£5, $8) which you can get from any DIY shop electrical department.  Get as low a power one as possible; 250W is much more than enough.  My glue-gun is 35W and the dimmer cuts off about 1/5 travel which is probably due to it being below the minimum (60W rating).  Not a problem as this is below the glue melting point.
As I'm in the UK I'm using 3 pin mains plugs and a 240V dimmer but obviously you would use items suited to your local mains.   You will also need a standard single surface mount plastic back-box to mount the dimmer in.  Additionally, you'll need the trusty soldering iron, a couple of lengths of heat-shrink and something to provide strain-relief on the cable; I used a cable tie here.
 

Step 2: Construction

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The wiring of this is really simple :
If you have a permanently wired glue-gun or if it's the removable lead type, cut the mains plug off and cut the additional lead at the equipment end.  This gives you two leads - one which will go to the wall socket and the other to the glue-gun.

Strip back the insulation and connect together the two neutral wires (blue in the UK / Europe, white in the US / Canada) - I twisted and soldered the wires then put an overlong sleeve of heatshrink over. I doubled back the heatshrink and shrunk another piece over it.  Break out one of the openings in the back-box and feed the cables through.  I used larger diameter heatshrink over these to reduce abrasion of the cable insulation.

The live / hot wires (brown in UK / black in US) go to the dimmer switch.  The feed from the plug goes to the AC symbol (~) and the wire to the glue-gun to the other (L2) terminal.  Bare the ends and screw down tightly making sure there are no exposed conductors.  No earth connection is required here as there are no metal parts accessible to the user. 
To stop the wires pulling out of the box I've put a large tie-wrap tightly around the cable, too large to go through the cable hole.

Screw the dimmer plate to the back-box, plug it in, turn it on and you're ready to glue!
 

Step 3: Finishing touches

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Now you've got an operational controllable glue gun, lets just finish things off :

Calibrate the gun with a piece of scrap foam.  Set the dimmer to half way and wait for a few minutes for the temperature to stabilise.   Rest the gun nozzle on the foam and if it fizzes and sinks through, turn the dimmer down a bit, wait and repeat.
The optimum temperature will be the point where the nozzle just marks the foam surface.  Mark this on the dimmer dial.
Depron and EPP have about the same melting point so can use the same setting, but if you're working with other materials you may want to calibrate for these as well.  I find about 1/3 setting gives the best results for the foams I use.

Roughen up the underside of the dimmer box near the corners; I had four handy raised areas on mine.  Put a small blob of hot glue (not too hot) on each one, turn the box over and put it onto a sheet of glass or polished metal.  This will flatten the blobs and level the box.  Wait a minute for things to cool and then twist off the box.  You now have a box with non-scratchy feet.  You could use this idea on many items which need levelling or making non-scratch (e.g. ornaments on varnished shelves).

Dribble a bit of glue around the cable entry.  This will fix the cable in place and stop it abrading.  It will also stop liquid entry if you have one of those unfortunate workbench / coffee cup incidents.
Trike Lover2 years ago
Great idea to use this on a glue gun! No more melted foam! Years ago I made up a similar control to add temp control to an el-cheapo soldering iron.(t never occurred to me to plug the glue gun into it). Cost was less than CAD$10. Two things I did differently: 1) I used a double electrical box, put the dimmer in one side and a regular wall socket in the other side. Double cover plates are available (in North America) with an opening for a switch or dimmer on one side, and a standard 15 Amp double receptacle on the other. I wired the plug to the dimmer, & dimmer to the receptacle (black wire to copper, white wire to silver, green (if present) to earth). Reason was I didn't want to cut the plug off the soldering iron, so it would still fit into a small toolbox. The other thing was to put 4-5 wraps of black electrical tape around the cord where it entered the electrical box as wear protection, as well as a strain-relief. Paranoid, I guess. Anyhow great idea for the hot gluing!
AndyGadget (author)  Trike Lover2 years ago
 
Thanks for the nice words.
I thought of that and seriously considered doing it with a double box but decided to keep it as a dedicated unit as that was what I needed, and also aimed at a beginner level considering it does use mains voltage.  Having a socket would leave the door open to plugging other devices in, in which case you'd have to start considering the current rating of the cable and connecting the earth through as you say.
In the end I went with Keep It Sweet and Simple.
MartijnD1 year ago
Cool idea, Dremel has high- and low-temperature glue guns, and 2 in 1, especially for kids the lower temperature is nice, no more 3rd degree burns. Will also not met your foam projects: http://www.dremeleurope.com/gb/en/ocs/category/6114/glue-sticks
nerd74731 year ago
I noticed your light dimmer and cord have both the same plugs I live in the USA so I don't know what country you are in. What country are you in if you don't mind me asking?
AndyGadget (author)  nerd74731 year ago
I'm in the UK. We use those 3 pin plugs here . . . Live, neural and earth.
If a device is double-insulated (like the glue-gun) then it doesn't need the earth connection.
yeah we use the 3 wire system here too I am currently in a vocational school I am in electrician class
Advar2 years ago
You just proved cool is hot. [now] I can do those other 1001 things bumping around in my head! Thanks! :)
poofrabbit2 years ago
Hey congratulations on being a finalist in the hack it contest! Good luck to you!
AndyGadget (author)  poofrabbit2 years ago
Many thanks - Fingers crossed.
(Lucky rabbit's foot? #:¬)
mweir2 years ago
Nice job but I have a correction. Here in the states the white wire is the common/neutral and black or red are the hot leads. but want to change that to avoid problems with anyone who doesn't know that!
AndyGadget (author)  mweir2 years ago

Yeow!  Many thanks for picking that up - Now changed.
Really, really should have double checked that.

Colour codes: http://www.allaboutcircuits.com/vol_5/chpt_2/2.html
LeoRey2 years ago
Another way to cool the glue gun is cutting half-wave of the AC with a diode. Its works well with soldering iron, lamps, etc. We can put a switch for selecting one of the two temperatures or with 3 points switch we can select: OFF, HALF-POWER and NORMAL POWER. (Sorry for the bad english... I'm Argentinean).
spockofborg2 years ago
Not only does this work well for hot gluing and soldering as mentioned, but also using an iron to melt through plastic without burning, and works great for cauterizing nylon rope/strap/paracord. Some irons come with wood burning tips, including a hot knife, which lend themselves well for these uses.
I have found an easier alternative to using a light dimmer, on eBay you can buy dimmer plugs for around £5, I use those on soldering irons and glue guns

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AndyGadget (author)  nathandance19962 years ago
I hadn't seen one of those before - They could be rather useful.
BRILLIANT! So simple and you can use this for lots of similar operations.
Great idea, my glue turns to a caramel brown colour because my glue gun gets too hot!
What are the chance's of you finding a way to stop the glue strings when you take the glue gun from your project?
Your technique needs some tweaks - try changing the motion you use at the end of the run... don't just pull the nozzle away, use an out/in/out or a wee twirl like a pig's tail.

Or if you have a stringy bit, you use the nozzle to "wipe" it off. Still leaves the string but its in your hand not on the work.
AndyGadget (author)  Green Silver2 years ago
 
Running a cooler temperature does reduce stringing a bit, but not all together.  I've found the glue-sticks make a difference too.  The ones I'm using now string a lot less than my last batch, but the downside is the glue has a bit of a yucky odour when it's melted.  The old ones were almost odourless.
jawasan2 years ago
Nice! I might have to try this...been working with hot glue a lot lately.
Would love to have this! I burned my hand once because my glue gun was so freaking hot..
AndyGadget (author)  MoustacheCat2 years ago
 
The things to note about hot glue are :-
1) It's hot.
2) It's gluey.
3) It still hurts when you get it on your fingers using this mod - after all, it has to melt the glue - but not quite so much, and for not quite so long.
I'm using my glue gun for a while now, and I got alot of hot glue on my hands, wich didn't hurt as much as it did that time. I'm not a doctor but I think it was a second degree burn..
The worst part is that you can't get it off or you'll burn your other fingers, too!
mikeasaurus2 years ago
This is great stuff! I use my glue gun a lot and could use an idea like this.
kondzio292 years ago
I made the same thing with soldering iron to not overheat smd parts
iceng2 years ago
Cool project :-)