Hot Plastic Gun





Introduction: Hot Plastic Gun

This is a plastic extruder that's capable of extruding a lot of plastic. It's a work in progress.

here the entire Fusion360 file that has every component of this build.

Here's the current BOM

Not included in the BOM are custom parts that you'll need to fabricate by CNC milling and 3D printing parts.

The basic idea is to take plastic pellets and melt it down and extrude it through a custom shaped die. In order to do this, I used a 1" wood auger driven by a stepper motor to push material forward and heat bands to heat the material. There is also a thermistor to measure the temperature and a PID to close the loop and turn the heat bands on and off as needed. At the tip of the extruder is a mist cooling system that uses compressed air to draw water to the tip and sprays a mist onto the hot plastic so it cools down quickly. To control the flow of plastic, there's a potentiometer, finger trigger, and foot pedal to accommodate different extruding styles.

The current design of the hopper holds approximately 1.5lb of plastic pellets. This could easily be extended with a 1" tube to a larger hopper hosted elsewhere.

Step 1: CNC Mill Shaft Collars and Spider Coupling Housing

These parts make the bulk of the custom parts needed for the extruder. Two extra-wide shaft collars for 1.125" OD tubing to hold the different tubes in place.

The spider coupling housing is used to hold one end of the tube agains the stepper motor while housing the spider coupling (which provides just enough slop to prevent the auger from jamming)

Almost all the components in this build are held together with M6 screws (for easy disassembly and reassembly)

Step 2: Mill Nozzle and Extruder Dies

The nozzle houses the thermistor and an interchangeable die. Lots of dies were made and tested, but in the end the two that were most reliable were the .125" and .5" rod extruding dies.

Step 3: Mill Slot in Pipe

The short aluminum pipe between the thermal break and the spider coupling housing needs a slot for the pellets to flow in.

Step 4: Trim Auger

Ideally we'd want to mill our own auger, but to keep things simple, you can use a 1" wood auger with a few modifications.

First, cut off the small screw at the tip of the auger. Then grid it down. You'll also probably need to run the auger on the lathe since the tip of the auger is usually not perfectly round and won't fit in a 1" ID tube.

The back end of the auger also needs some trimming. We are using the spider coupling to attach to the auger, so you can trim off the hexed area of the auger.

Step 5: Assemble Barrel

This is what the assembly of the custom parts with the tubing should look.

Step 6: Assemble Electronics and Test

The electronics for this build are pretty straight forward. The PID circuit + heat band + thermistor circuit is standard. To control the stepper motor controller, the momentary switches, stomp switch, and potentiometer, are connected to an arduino which then controlls the stepper controller.

Step 7: 3D Print Handle

The grip for the build is two 3D printed halves that get screwed together with M6 screws. Two toggle switches are housed inside to control forward and reverse motion of the auger.

Step 8: Assemble Gun

Here's the basic assembly. Were' still missing insulation around the heat bands (they get crazy hot) and the mist cooling system.

Step 9: Build Parts for Mist Cooling System

The cooling nozzle is made of 2 parts.

The white push-to-connect fitting draws compressed air through the tip, while the black fitting draws water. The smaller aluminum part fits over the black -push-to-connect fitting to decrease the nozzle diameter to 1mm, which is just enough water to break into a mist when it meets the compressed air at the tip.

Step 10: 3D Print Hopper

The hopper could be any size, but for this build, the black hopper was made to fit the maximum build volume of an Ultimaker2.

Step 11: Bend Metal Stand

This machine is heavy! You'll want somewhere to rest this thing. You can put it up-side-down and rest it on the hopper (it's design to stand up-side-down). But if you want to extrude hands-free, you'll want to build a stand. This stand is built out of 3/8" stainless steel and some simple bending using a vise.

Step 12: Extrude!

Ok all done! extrude!

Depending on your plastic you'll need to set your PID to run at the appropriate temperature.

Getting the right feed rates and temperatures takes a lot of practice!


Polypropylene is the most forgiving plastic I could find.

Mist cooling blasts the area with a lot of pressure, thin extrusions can get pushed around. 1/2" round extrusions seem to hit the right balance of stiffness, extrusion speed, and cooling speed (if you're trying to get the plastic to cool fast enough to freeze midair).



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    Nice work!

    Can we use this machine for extrude Rubber beading or Is there any way to upgrade this machine for rubber :)


    amazing work, man!

    I'd like to ask, how do you open this .f3z file? Am I right trying to open it in Fusion360?

    unfortunately i've got stuck with this error message. do you know any way to get rid of it? fusion360 does not open the model because of it :(


    I got it to work by doing this:

    1. Follow the link

    2. Download>Fustion 360 Archive

    3. Enter email address, follow link in email to download file.

    4. Open fusion, open a project folder in the Data Panel, click Upload

    5. drag the fusion archive folder you just downloaded onto the upload window.

    Once built, all someone would need at this point to make filaments is use a multi port die (drilled holes in sizes needed)actual holes size will be dependent on vertical or horizontal setup of the extruder. Then simply extrude into a water bath (tub of water would work). simple really. Just a suggestion to the maker. Cut some cross channels in the tip of your screw(auger)flight. I am assuming your getting a surging in material out the die every time the flight of the auger rotates by. All the pressure needed to extrude should be supplied at the first half (feed section) of your screw(auger). the tip end of the auger/screw should be used for mixing up the flow patterns of your materials.

    Amazing job BTW!

    I would like to offer making one of these with some of my professional experience in extrusion in exchange for a high quality 3D printer for a beginner in 3Der like *me. Any takers? Piece Out!

    DanM6, exposure to water, or even high humidity, is a major no-no for 3D printer filament. Both PLA and ABS absorb moisture/water. When heated in the 3D printer's extruder, the water forms steam bubbles. This destroys the print. There's a reason people who use FDM 3D printers store their filament in air-tight containers with packets of desiccant.

    If you plan to use this device to make 3D printer filament, you need to modify it. First, the filament extrusion size needs to match your printer (usually 1.75mm or 3mm). Printers do not use 1/2" diameter filament. "Surging in material" does not matter. The filament diameter does not change.

    Second, you need to cool your filament with dry air if you ever want to have a successful 3D print from it.

    Finally, if you want a good 3D printer, check out They list designs and details on a wide range of 3D printers. Many of them are open source with links on GitHub or Thingiverse or available in kits. It will help you decide which model is right for you to dip your toes in the pool (NOT YOUR FILAMENT!!!). You can also find several plans for printers here on Instructables.

    What do you use this for?

    :) If you ask, you don't need it. :) So sorry, really. :)

    If you use a 3d printer, this can make the filament for a printer. You can also recycle plastic by grinding bad prints and other plastic into small, BB sized pellets and running it through the extruder.

    You can also use it to make the parts for the extruder....but then again, :) you need a printer and FILAMENT to make the extruder.... :)

    I'm stopping now.

    Outstanding build!

    LarryK4, I don't think so. Every 3D printer I have built, used, or looked at plans for uses either 3mm (less common) or 1.75mm filament. This extruder produces 1/2" (12.7mm) filament. In addition, moisture in 3D printing filament causes MASSIVE problems in printing. It produces steam bubbles in your printer's print head/extruder. Both PLA and ABS absorb moisture on their own. This means a misting system to cool the product is a no-no.

    This is a good jumping off point to create a 3D printer filament extruder, but it would need some major mods to the extrusion nozzle, the speed of the stepper motor, and a completely different cooling system.