3D printable plastic welder
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WARNING handle with caution. Keep away from children, pets and anything flammable. USE WITH CARE. I will not be held responsible for injuries or damages from the use of this device

The electronics are the work in progress.

(low duty cycle only)

With the limited build size of most 3D printers I found a need for a better way to assemble multi-piece models and the obvious choice seemed to be a welder.

It based on Gregs hinged accessible extruder (wildseye hotend version).
It uses my revision of Ryhs_jones Herringbone gears.

Universal mount for miscellaneous gear motors or steppers.

Uses 70mm of 1/2" PTFE rod.

The heater barrel is a 1/4" bolt drilled to 3.5mm.
Aluminium heater block with 6.8ohm vitreous enamel resistor heater.
100k thermistor.
1/4" brass acorn nut with .8mm nozzle hole.
Built the same way as geometricobjectdepositiontool.blogspot.com/p/no-lathe-plumstruder.html but with out any support material.
( I did not feel it needed support because it is to be used hotter and slower which equals lower pressures, as well as for shorter durations )

The heater circuit I used is similar to pdf417.blogspot.com/2010/09/problem-with-extruder-heater-solved.html but used components I had lying around.

The gear box I used was from some old toy.
(My_gearbox.stl is a block model of the gearbox I used. I created the model to be sure it would fit. Do NOT print it unless you want to compare it to one you have)

PLEASE use the circuit mentioned earlier pdf417.blogspot.com/2010/09/problem-with-extruder-heater-solved.html unless you are like me and have a lot of low power mosfets.

The Eagle file provided is for my heater circuit and is still undergoing testing.

I have 100 TIP29's around so have made use of them here. They are only rated to 1A continuous 3A peak each so I have used three of them in parallel.

T1 = PNP transistor (to turn off the three NPN's when at set temp)(must be capable of R4's current flow)

T2-T3-T4 = NPN transistors (3A total minimum)

L.E.D. 1 = (turns off when at set temp)

R1 = 100k ntc Thermistor (measures temp)

R2 = 50K pot (sets temperature)

R3 = 1k 1/8w resistor (for L.E.D.)

R4 = based on gain of transistors used (holds T2-T3-T4 high)(I choose 1/2watt 150ohm resistor @ 12V = 80mA * 40 (TIP29 = 40x gain) = 3.2A max output)

R5 = 5K 1/8w resistor (increases adjustability at higher temps)

C1 = Smoothing cap rated higher voltage than 12V and as high of capacity as you have lying around and still fits on the board (8mm dia max)

All modelling done with Blender 2.57 


I printed the entire thing in PLA and the handle does get soft near the end after a few minutes. If you have the ability to print in ABS I highly recommend printing the handle in ABS.

1 main body
1 idler
1 handle
1 large gear and 1 small gear
You can still use Gregs original Gears or the herringbone ones.
The Gear named Plastic Welder Small Gear is designed to it on a 5.5mm hex shaft.

Assemble extruder portion as per Gregs extruder.

If using a small DC motor you may need to use a custom small gear.

If using DC motor drill holes for mounting and screw down.

If using Stepper attach using four holes provided.

Build your favourite hotend using 1/2" PTFE (PTFE 70mm's fits inside the handle and body)

Install prepared PTFE in body using two screws through mounting holes in the body) (groove mount style)

Slide handle over PTFE rod and tab on body. (install bolt through hole provided if necessary)

Install hotend in PTFE.

Wire Hotend to Heater control board.
Or the one I provided
Or your RepRap electronics
Or ?????

Wire DC with a PWM circuit such as dprg.org/tutorials/2005-11a/index.html
Or direct through a switch
Or ?????

Wire Stepper motor using a microcontroller and Stepper driver
Or use your RepRap electronics
or ?????