Hot glue extruder

[Generic Default]

I've always wanted to have a multi-extruder printer so I can print parts with over-molding. Over-molding is typically a layer of rubbery or elastic material on top of a base plastic. Your toothbrush is probably polypropylene with an elastomer over-molded onto it for an ergonomic grip. There are a few elastomer filaments on the market right now but they're rediculously expensive. My idea is to extrude hot glue sticks from larger individual sticks into a single, continuous filament for 1.75mm or 3mm 3d printers.

In the above cross section render, the glue stick is placed in a PTFE guide where it is pushed through a brass/copper/aluminum heating die to reduce the diameter. It squirts out of the die into another PTFE tube where it cools. The front PTFE piece also prevents diameter inconsistencies that would happen if the hot glue was extruded into open air. The sticks can be fed by hand, or possibly by pinch wheel gears for an automated process. If it works out with individual sticks, a hopper could gravity feed sticks into the PTFE guide where they would be pinch-pushed through the die for continuous extrusion. I only have a basic render right now because the design obviously needs to be improved for thermal efficiency and stuff. I'm considering putting an aluminum heat sink around the front PTFE piece to keep it cool during extended use.


So, what do you guys think about this? Plausible, or is there some reason this wont work at all.






It's just an idea for now, but I'll be getting a lathe and mill in a few weeks. Then I can prototype this.

[Captain Starfish]

It takes a bit of pressure to get glue through a gun, so I don't think the gravity feed will work - but a superfat version of a normal extruder with hobbed wheels would go great.

I'd be kinda tempted actually to jury rig a hot melt gun's nozzle with a modified ez-struder or something on a stepper and throw it on the effector platform to try out before I went down the long path of trying to make perfect hotmelt filament.

If it works off the test rig, and the resultant material does everything it needs to, then great - move onto the filament from there. I also like the idea of combining this with another thread's idea and using it as cheap infill too!

[Eaglezsoar]

I've always wanted to have a multi-extruder printer so I can print parts with over-molding. Over-molding is typically a layer of rubbery or elastic material on top of a base plastic. Your toothbrush is probably polypropylene with an elastomer over-molded onto it for an ergonomic grip. There are a few elastomer filaments on the market right now but they're rediculously expensive. My idea is to extrude hot glue sticks from larger individual sticks into a single, continuous filament for 1.75mm or 3mm 3d printers.

hot glue stick extruder.jpg

In the above cross section render, the glue stick is placed in a PTFE guide where it is pushed through a brass/copper/aluminum heating die to reduce the diameter. It squirts out of the die into another PTFE tube where it cools. The front PTFE piece also prevents diameter inconsistencies that would happen if the hot glue was extruded into open air. The sticks can be fed by hand, or possibly by pinch wheel gears for an automated process. If it works out with individual sticks, a hopper could gravity feed sticks into the PTFE guide where they would be pinch-pushed through the die for continuous extrusion. I only have a basic render right now because the design obviously needs to be improved for thermal efficiency and stuff. I'm considering putting an aluminum heat sink around the front PTFE piece to keep it cool during extended use.


So, what do you guys think about this? Plausible, or is there some reason this wont work at all.






It's just an idea for now, but I'll be getting a lathe and mill in a few weeks. Then I can prototype this.

Very Plausible, the biggest hurdle I see is designing the feed mechanism to push the sticks into the extruder. Everything has a solution and you will
come up with a workable solution. Good job in just thinking of it.

[Generic Default]

It's actually not gravity fed in this model, although it would be if the whole thing was tilted to 90 degrees. I was thinking I would just push each glue stick with another glue stick behind it. You can buy them in packs of like 20 at Walmart and stuff, and I think they average out to around 1 dollar per pound of hot glue. Dirt cheap.

I always thought that hot glue guns were easy to squeeze glue out of, but maybe I just have strong fingers. The viscosity decreases with temperature. Hotter glue flows easier but needs more cooling time. It doesn't stick to PTFE, but it DOES stick to most other plastics, which is what made me consider it as a support material and over-molding material. I think it would be nice as a raft on the first layer. It even sticks to nylon, so that might fix my glue stick addiction.


I think the biggest benefit of this design over something like a Lyman extruder is that it doesn't need a constant feed rate to maintain consistent filament diameter. The PTFE tube on the front end should fix that. It will take a lot of tweaking to get the extrusion temperature just right, and the front end PTFE tube will have to be modified a lot too. By the way, the things sticking out of the middle piece in the render are thermistor and heater cartridge wires.

[Captain Starfish]

They are easy to squeeze but have a look at the lever ratio between the trigger and feed pawl or try just to push it through consistently from the back without the trigger.

If you still find it easy then there's your answer: drill a cheapo heat gun out to 1.75mm, clamp it vertically so the filament drops out from underneath onto the floor (it'll have cooled plenty by the time it gets there) and just smash them through it by hand. Measure with your micrometer and adjust, ie drill out, the nozzle a little more to compensate for the extra draw created by the weight of the filament.

Very cheap and easy way to have a dabble and make sure it's going to work in the printer, before you start getting too invested in the filament extruder side of things.

[Generic Default]

Here are two more renders to clear things up;

The pinch wheel gears would go on both sides of the input rod just before it enters the melt zone. That would push the rod (and everything in front of it) into the melt zone. Inside the melt zone, the separate rods would merge into one continuous flow before going through the die hole. If there is a stop in the feed system, the lack of pressure would keep the molten plastic idle inside the die hole. Since there is no air extrusion where gravity is shearing the unsupported molten plastic from the die hole plastic, the feed rate wouldn't matter too much.

No moving components in this entire design except possibly the feed pinch wheels.

[jesse]

If you can turn the hot glue into pellets, you can run them through a filastruder: http://www.filastruder.com/

Edit: the pellets can be found on ebay by searching "hot glue pellets"

[Batteau62]

If you can turn the hot glue into pellets, you can run them through a filastruder: http://www.filastruder.com/

Edit: the pellets can be found on ebay by searching "hot glue pellets"

Have you tried this with your filastruder Jesse?