The quest for the ultimate extrusion screw

In the plans of the current extrusion machine a basic drill is being used in the barrel to push and melt the plastic to the nozzle. This seems to work, however, in the industry a different type of screw is used which compresses the plastic while it’s melting. These are way less accessible than the drill, for obvious reasons. So Dave had the idea of possibly trying to produce these ourselves. Therefore this topic will be dedicated to the research on trying to design/model/produce this.

I was quickly doing some research on this yesterday and it seems to be a world on its own with different designs of screws, different compression ratios and different “zones”. If there’s anybody that might have some experience or knowledge on this that could help out, let us know here.

I turned the basic idea for the screw design into a quick 3D model, to see if I would be able to model it. Now I need to find the right design requirements to turn that into the eventual 3D model, so we can turn this into a physical prototype.

https://en.wikipedia.org/wiki/Plastics_extrusion#Screw_design

Here’s some images from the 3D model I made of the design concept. What I so far understand is that the distance between the turns of the spiral logarithmically build up towards the end of the barrel, while the diameter decreases. I now need to know what the optimal ratios for these design requirements are.

Hello everyone,
In case extrusion screws run out of stock in the bazar or unavailable in your country, I found a supplier who provides extrusion screws, barrels and other accessories.
They both have 588mm and 790mm sizes.

Here the links :
588mm set (screw+barrel+nozzle or just separately)
https://www.aliexpress.com/item/4001127912035.html?spm=2114.12010612.8148356.18.5dd72f6fJ4QtCC

790mm set (screw+barrel+nozzle or just separately)
https://www.aliexpress.com/item/4000635677820.html?spm=a2g0s.imconversation.0.0.55f43e5f84JmR8

Also a nice post to make your own filament maker :
https://medium.com/endless-filament/make-your-filament-at-home-for-cheap-6c908bb09922

TO precious plastic team : You can delete my message if you think it is not appropriated to send it here. I don’t advertise anything, I just want to help people to find this famous screw so difficult to obtain.

Cheers,

Hello, I am considering making these screws by collaborating with a local makerspace who have a metal-capable CNC machine

My plan is to upgrade the CNC machine with a 4th axis

Can any of you offer any advice?
Thanks

@sanderi
Some claim aluminium is not strong enough but, as far as I know, nobody actually ever tested. I guess it would be possible to cast it but the sandcasting is not super precise as far as I know so I’m uncertain how well the extruding will work. I think you’ll come across problems along the way but it would be very valuable information to share here in case you try it out. So in case you do, please let us know how it goes! 🙂

The easiest way to change the model would probably be to just scale it in 1 direction (this is possible in your slicer). But you’ll end up with thinner threads, so that might not work. Ideally you’d have to model this from scratch with the correct parameters. I don’t know how to get those correct parameters. The model for this screw was based on the expertise of @dustintweir.

Ok, great thread with a lot of info. I want to built myself a large 3d printer which uses granulate or flakes of recycled material. But the auger here is too large for this use. I need a smaller one because the whole extruder needs to be not too heavy/light.

I did not find ready made augers but i had an idea. Maybe it is possible to model the auger with software. Print it in pla and cast it with the lost material method with aluminium. Do you think that would be feasible? Or is alluminium too weak?
Any ideas?

Great site!

Hi Faridah,

Keep checking the bazar, there will be a packaged screw and proper fitting barrel there very soon. 1 / 2nd week of April.

Seems i will have hard time finding a fitting tube. By the way, thanks @jegor-m.

@faridahmadsofizada, that would definitely not be ok. As soon as plastic melts inside it will go anywhere except for the nozzle. I guess it is not that easy to find a proper one, but this combination is not good at all. This question has been asked before in this topic/ forum, you could check it out.

Hi guys, have a question:
I have found a pair of screw and tube. But the diameter of screw is 3mm smaller then the inner diameter of the tube, which means screw will be a little loose.
IS THAT OK? or should i find another tube?

@pe-trhlinka
I think you paid more for redesign and build it than you order one of Precious plastic official.
I look for long time, better price with less transport shipping and the result was to order one at Dave and the crew

Cheers

Hi everyone,
I´ve contacted more than 50 local workshops and everybody told me that they would make the screw I wanted according to the plans I downloaded from the website, so it hot me thinking how to solve that problem, I posted my question to our national machining forum and the answers I got werent very nice 😀 they basically told me that the the blueprint is total trash and that they aren´t surprised nobody wanted to make it for me, they told me I should start over and make a better design, but here is the catch, I´m total amateur, I can´t make new design, but I think that new design is necessary in order to bring the price down so that the screw could be cheaper, which would be really nice right? I can start to study the theory behind the problem but I don´t know how to use any software to make new design. Can someone help us with this? Or what do you think about that? Is that a bad idea?

next machine i will build is the extruder
any update on this?

Has anyone made a closer tolerance barrel for the industrial screw? The closest U.S. size tubing I could find without having to ream has a nominal ID of 1.031 which is 0.019 larger than the 25.7mm screw. This seems like a lot and I’m worried about plastic leaking from around the edges or not building pressure. Ideas here?

Hi! Does anybody still have some screws in stock? And from where do you ship?

Looking good @plasticsurfer. Sell them in our bazar, many request for those screws!

HI everyone.

For those who want one ultimate screw, i have an offer for 180 usd per piece if we buy 3 pieces.

Someone need one ?

Cheers

Gaetan

Can an improved extrusion screw (compared to a wood drill) put more pressure and force on the extruded plastic, to the point that it can be used as an injection machine?

Hi @davehakkens,

Jerry say me in an other post you order 20 screw.

Is still on the pipe ?

Definitly need one and it’s boring if i ordered just one in alibaba.

If they still ordered, you know when they arrived ?

Thank’s a lot

Cheers

I found this link with a quick google search for someone who sells them from alibaba.com:
https://www.alibaba.com/product-detail/screw-and-barrel-extrusion-for-ppr_60693234451.html?spm=a2700.7724838.2017115.2.13e58a03Aj7wFt&s=p
i don’t know if this has already been mentioned, but it would be an option.