Make Your Hot Glue Gun Cooler!

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 #;¬)}

Step 1: What You Will Need

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

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

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.

Comments

[Trike Lover]

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]

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.

[robotlord2004]

nice

[viktor.bozicevic.9]

Hi, nice modification, though I'm not clear about the wattage value of a light dimmer. In my case, I use a 100W glue gun, and will the 250W max. dimmer be enough for this application as well?

[Han_Solo_Order66]

thank you so much im going to use this to make a 3 d printer extruder with variable heat settings because a high temp hot glue gun is at the higher end of the heat requirements thanks so much

[AndyGadget]

This wouldn't be any good for an extruder as it is an open loop system, i.e. the controller just sets the power going to the glue gun but there is no feedback of the gun temperature to adjust the controller and keep the heat constant.

An extruder needs to be a closed loop system to keep the nozzle within a couple of degrees of a set temperature. Just about all printers will use a PID control system to do this. HERE is a super simple explanation of PID control - The principle is the same for a heating element.

[Han_Solo_Order66]

I see how that would be very useful in say a computer controlled extruder but I was just going to control the heat my self and measure that heat so as to correct it my self in essence i would become the PID control system I mean I guess i could rip the pid out of a stove and do that but that's a little to complicated I just need to get within a 20 degree range

[MartijnD]

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

[nerd7473]

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]

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.

[nerd7473]

yeah we use the 3 wire system here too I am currently in a vocational school I am in electrician class

[Advar]

You just proved cool is hot. [now] I can do those other 1001 things bumping around in my head! Thanks! :)

[poofrabbit]

Hey congratulations on being a finalist in the hack it contest! Good luck to you!

[AndyGadget]

Many thanks - Fingers crossed.
(Lucky rabbit's foot? #:¬)

[mweir]

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]

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

[grey_starr]

Colour codes: http://www.allaboutcircuits.com/vol_5/chpt_2/2.html

[LeoRey]

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).

[spockofborg]

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.

[nathandance1996]

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