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The quest for the ultimate extrusion screw

This topic contains 90 replies, has 26 voices, and was last updated by  Siemen Cuypers 2 months ago.

1
Siemen Cuypers siemenc

The quest for the ultimate extrusion screw

15/02/2017 at 10:48

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

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warrior
10/07/2017 at 12:16
2

Noted 😉 But I’m not going to be mass producing these by this method. Perhaps if there’s enough interest a larger order from Dave’s supplier would bring the price down?

warrior
21/09/2017 at 19:11
3

Hey guys,

Here is a question for those of you who decided to go with an auger wooden drill bit for the screw (photo below).

Do you cut the sharp edges off at the end of the screw (the pointy thing)?

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warrior
25/09/2017 at 22:26
4

So, here is a screenshot of Dave’s video ‘Build the extrusion’..

The question therefore changes to: Isn’t it easier to clean it when it has no sharp end?

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warrior
26/09/2017 at 00:04
3

@jegor-m, yes I always grind of the pointy thing. don’t need it.

dedicated
05/12/2017 at 12:48
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What are the tolerances for the barrel and the screw PLEASE HELP!!!

warrior
05/12/2017 at 13:00
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Barrel: 26mm ID 34 mm OD. Screw (drill): 26mm diameter.

There are no tolerances given. Depending on where you source your tube a 26mm drill may not even fit inside, so you do need a small gap. I think you just have to find what works for you, there doesn’t seem to be a definitive answer to this, but some clearance between screw and barrel is necessary. Too tight and the screw will bind and seize, too loose and it will not extrude with as much pressure, but will probably still work.

warrior
05/12/2017 at 13:38
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For the compression screw siemenc designed, the diameter of the threaded section is 25.7mm. There are drawings in the download kit.

dedicated
05/12/2017 at 23:55
4

@mathijsstroober @andyn @davehakkens
> have you tried extruding a short section, letting it solidify, then extrude more using the first part as a plug to stop the ‘tunnelling’ effect?

Has anyone explored this possibility to extrude beams of an infinite length ?
I think this method will cause the plug to be pushed by molten plastic as the extrusion goes, though I think the operation would need to be repeated if the extrusion goes quicker than the cooling.

We should make sure there will be always an entirely cooled transversal section of the beams inside the metal part attached to the nozzle.

Another idea is to fuse two beams after extrusion by heating an end of each beam then pushing the ends through a metal tubing of the same shape. working with plastic is not like working with wood you can’t fuse lumber as you could using plastic 🙂

starter
06/12/2017 at 03:25
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Dave, do you have contact info for this company (Five Star Machinery), and the cost of the finished screw? @davehakkens

Glenn

dedicated
06/12/2017 at 13:30
1

@armbouhali
I did not had any time to test this (first graduation).
Still I would love to test this. I will update if I found any solutions

warrior
07/12/2017 at 20:14
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@plasticsurfer got them at this company: https://www.alibaba.com/product-detail/Mixing-Type-Screw-plastic-extrusion-screw_60505829299.html?spm=a2700.8443308.0.0.SlLhjl final price depend a lot on the amount and shipping costs.

starter
14/12/2017 at 22:45
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Hello everyone, do you think its a good idea to make the screw out of a soft and easily machined metal, such as aluminum?

helper
15/12/2017 at 11:51
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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

helper
15/12/2017 at 11:59
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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.

helper
15/12/2017 at 15:01
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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

starter
25/12/2017 at 01:35
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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?

helper
08/01/2018 at 14:47
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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

starter
10/01/2018 at 06:04
1

I have a couple of spares for @210USD if someone needs one?

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warrior
10/01/2018 at 10:10
0

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

new
16/01/2018 at 15:45
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Hi! Does anybody still have some screws in stock? And from where do you ship?

starter
18/01/2018 at 01:28
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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?

helper
24/01/2018 at 11:22
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next machine i will build is the extruder
any update on this?

starter
05/03/2018 at 22:27
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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?

helper
06/03/2018 at 23:42
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@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

starter
12/03/2018 at 14:03
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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?

warrior
12/03/2018 at 14:31
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@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.

starter
12/03/2018 at 16:10
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Seems i will have hard time finding a fitting tube. By the way, thanks @jegor-m.

starter
27/03/2018 at 15:48
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Hi Faridah,

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

new
13/08/2018 at 10:56
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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!

dedicated
13/08/2018 at 11:13
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@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.

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