DIY Extruder Screw

OK. After the discussions on this thread about adding compression to a wood auger by welding material into the root of the auger to create the compression zone, I came up with an alternate idea to use the wood auger as the basis for a machine to make an extruder screw from scratch. I thought I would start a new thread rather than taking the existing thread any further off-topic.

 

To recap, the reasoning behind my idea was that the pitch of the wood auger is already acceptable as it has already been proven to work, so instead of trying to use a wood auger itself as the extruder screw, it could be used as the basis for a machine to make an extruder screw instead…

 

Having already looked into making an extruder screw in my machine shop, I realised that that manufacture of an extruder screw is not easily possible without some form of NC machine, which is not something that is accessible to a majority of the wider PP community. Even with the machinery I have at my disposal I could not make a screw without first making some form of machine or machine aid.

 

So if it was possible to make a simple machine, to make a better extruder screw, from widely available materials with hand tools, then it would help to improve the efficiency and quality of extruder output for the wider PP community.

 

The basic proposal is to use the wood auger as the transport mechanism (lead screw) along with a grinder following a profile template to make an extruder screw that has a compression and metering zone. I outlined my ideas on how this might be achieved here. Of course, there are also many other ways to achieve the same, and the purpose of this thread is to explore how this might be made to work and to provide a place to collaborate and document development.

 

I have started to gather materials to make a prototype and should have a basic first-blush together over the next week or so.

 

Please feel free to continue the conversation already started on the previous thread, and also contribute with ideas, critiques and your own creations.

 

/DM

 

Materials I have gathered so far:

>Drawer guides (for table movement)

>Metal Hinge (for angle grinder attachment)
>Auger screw (for table transport)
>Angle grinder (I already have this)

 

Materials I (may) need to get

>Timing pulleys
>Timing Belt

A 1000 – 2000 grid polish is doing alright too though – you can do this with a finger sander or grinding paper – manually –  that’s good enough to send the screw to hard chrome plating / nitrating (recommended, not cheap) 🙂 read more about :
– https://www.ptonline.com/articles/why-bother-to-chrome-plate-your-screws
http://fordhamplastics.com/wp-content/uploads/2016/08/HANDBOOK-REILOY-USA-BARREL-SCREW.pdf.
– https://www.slideshare.net/GlyconCorporation/feed-screw-manufacturing-design-for-injection-extrusion-blowmolding-glycon-corp
– the ultimate intro : https://www.youtube.com/watch?v=GridDLZ56yQ

For garage projects you can get a away with an SDS drill hack 🙂

Interestingly, I came recently along a nice topic – thanks to the incompleteness and exclusivity of v4 😉 : making ‘screw tips’. I am opening another post about this. Looks like that you can compensate screw issues by making a custom tip – or even stack them up. I need 2-3 more lifes just for testing it 😉

Nice design. I think if you were to reduce it to basic functionality the cost would be pretty low. All the 3D prints and bearings are nice but could be done in other ways. Printing the timing pulleys and the grinder mount is convenient. Here the grinders can be bought for $15. You can skip the chuck if you are willing to size the hole in the timing pulley to your part.
The Robodigg parts are nice, but if you need something local.

Do you really need super polish? Isn’t there always going to be shear within the plastic? Of course you could use polishing wheels on the grinder and use a router speed control (<$20) to slow down the grinder.

Interesting, I have SDS concrete bit that is waiting in the project cue.
Thanks

Happy put a cap on a year long topic, somebody did it 🙂

The actual article has been posted in full length and a nice list of research references here (or check hackaday). Unfortunately the files are still incomplete but I keep watching out for the rest and add it to the library.

The build involves several hundreds of dollars, 2-3 times the price of an extrusion screw on Robotdigg.

Be aware that a good screw needs a certain surface polish to prevent plastic from sticking … as mentioned, be prepared to polish it up with 3000 grid paper, all day long 🙂

Yes the RHS frame that the grinder is mounted to slides within the larger RHS mounted to the slide allowing for the grinder position to be adjusted.

The grinder can also pivot a little on its mounting bolt to compensate for any angular deviation between the wheel and workpiece as the grinder frame pivots.

That looks great. Do you have some axial adjustment for the grinder to set the channel width on the screw (presumably wider than the grinder wheel thickness)?

I had some time to mount the grinder today (after I fixed my welder 🙁 ). I ended up having to raise the auger up from in-between the rails of the base as the cutting wheel did not engage deep enough into the workpiece. So I used this opportunity to simplify the ‘nut’ design. It is now a simple round bar sitting across the top of the auger. It works very well. No bearings, no complicated design. Much easier to build. The mechanism also still runs pretty smoothly, not as smoothly as the previous design, but I think that it is not important.

 

So for anyone who was having trouble visualising how the grinder was to be mounted, now it should be clearer to see 😀

 

Next step is to finish off the cam profiles and workholding and then I will be able to make some tests.

 

You can read more info and see some more photos here – https://deeemm.com/index.php/entry/general/diy-extruder-screw-making-machine-part-2-the-grinder

 

There’s also a sketchy video here – https://www.youtube.com/watch?v=kHPv1I7LjN0

Yes, I think that any grinder could be made to work. It’s just a case of presenting the workpiece to the wheel in the correct orientation.

 

I’ll try and make some time this weekend to mount the grinder

I wonder if you could adapt something like this https://www.harborfreight.com/electric-chain-saw-sharpener-63803.html .  It seems to have many of the functions. The wheels are probably too thin and expensive but maybe change out the wheel.

@deeemm, Possibly you addressed this in your design but are your sure about the angle grinder? the discs wear out in no time and you have to continuously correct depth of ‘grind’ which is ok with the xy vise but yet the procedure invites more mistakes… I found today a number of smaller bench grinders and the appropriate grinding discs are also cheap on the net.

then it should be easy to get it on the xy vise slide which you definitely need for all the maneuvers; especially for beginners it’s the only way to deal with mistakes; the cross slide is also key on the lathe; i think my right arm is double strong by now 🙂

My plan is to use an angle grinder – either 4 or 5 inch size – just a small hand held one. These are available everywhere. They also mostly all have screw mounts on the sides for the handle (also usually on both sides for left and right handed people), so it should be possible to make a mount that holds it. I plan to hold it in a vertical orientation.

 

I have also seen 3D printed mounts for similar tools. Worst case scenario is simply to use one or two large worm-drive universal clamps. I have done this before when I mounted a router to my plasma CNC. It works pretty good. Lots of options depending on what people may have available. For me I want to try to avoid using my 3D printer on this build as it is not tech that everyone has access to. Just basic tools.

nah, i just did hold the thing in place to see how much shatter and cleanup work it creates; there aren’t smaller grinders here in the shelf here; i am still puzzled how this can go; more search on amazon may give me some options … vacation is in the door step; best luck to you 🙂
one thing is for sure: the grinder is best on a cross-slide vise (30$) with a way to align the angle to the flights, easy with some set-screws and the arrangement you have already , yep.

Cool. One thing that I was planning when I get the time to make the rest of the device is to angle the grinder wheel so that it aligns with the angle of the flights, and also to choose a wheel that matches the width of the channel (if possible). If the wheel is narrower than the desired channel width then the wheel or workpiece will need to be reset.

Do you have a link to your video?

please check the video; it’s easier than that. besides; I made an bench grinder attachment test for your variant; looks promising.

Is delrin a thermoplastic? could be a good way to create the nut if it can be molded.

great stuff indeed. just some hints, folks use ‘delrin‘ also for mill & lathe lead-screws. it’s self lubricating and has basically no play; that can last for decades; I am considering it for making a screw based injection; anyways, in your case that looks alright; machine build around the job 🙂

s2019 Sorry I missed your comment on making a nut from plastic.
Yes, I think that this could also work. I don’t think ‘drilling’ through the block would work, but I bet you could make the nut in two halves and press them together around the auger – much like the split nut on a screw cutting lathe. These two halves could then be mounted into a casing.
3D printing is another alternative, although some consideration of the design would need to be made.
An issue with trying to make a single design to suit all augers is that I think that no two augers are probably the same. Not only would the size differ (obviously) but I would imagine augers from different manufacturers would all be slightly different too.

Is there a way to embed videos?

https://www.youtube.com/watch?v=3FFFDuHzDP0&feature=youtu.be