Hollow shaft extruder
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@o_lampe I did initially think of the cut alignment as an issue but I think the solution should be easy enough. My initial solution was to mount one roller set, feed filament and then thread the other roller set onto the filament and shaft at the same time for alignment. You may be absolutely right about the back to back design being more efficient though.
I did see discussion about the diameter of the threaded rollers in some places when I was researching this last year. I've got a micro pipe cutter that has a cutting wheel < 10mm, but I'm still trying to source replacement blades. -
@lee-iii-will One thing to watch out for with a large gap between the pusher and puller sets of wheels is when thread compression happens. The larger the distance along the filament between wheels the greater the alignment challenge when the thread pitch changes. On the other hand, with greater misalignment there will also be more force against the side of the groove and potentially more thrust. I think whether it works or not can only really be established by testing.
Hardened steel wheels are interesting. I have assumed (without actually testing it) that sharpened bearing flanges will be chewed up by glass or carbon filled filament. I would hope hardened steel might be able to handle these filaments.
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https://a.aliexpress.com/_mK0e0jY
Anyone seen this yet
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@breed Well that's very interesting. And also confusing: who is this marketed at? It claims to be for a "Funssor rolling screw extruder" but Funssor don't appear to sell those. The image is taken from https://www.thingiverse.com/thing:5447706, which is a re-upload of David Leitner's screw extruder. I wonder how long it's been available on Ali.
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@tombrazier said in Hollow shaft extruder:
It claims to be for a "Funssor rolling screw extruder" but Funssor don't appear to sell those.
Let's play devils advocate: They cloned his design and ordered a few thousand of these screw rollers. But then figured out it dosn't work as expected.
So they sell them seperately (for a surprisingly high price). -
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@tombrazier showed up 9-17-23 according to the funssor new items page. Does anyone know if this design works? I'll order a set and print the parts from that link and give them a shot. That's a pretty little design, I like how he solved the hollow stepper issue.
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@breed I guess it will work somehow, but the NEMA14 will have problems to spin fast enough. Davit Leitner wrote, he'll make a BLDC version, which I've posted (and printed) in this thread.
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@breed Ah I was looking at https://www.funssor3dp.com/ and found nothing. Didn't think to check the Aliexpress store. I wonder whether the two are related at all.
David did post videos on YouTube of a functioning extruder so it definitely works to some degree. One thing I would want to test is whether it retracts and de-retracts without accurately. Another would be whether it grinds up the filament considering how many "teeth" will be contacting the filament. If making one myself I think I would try to arrange for all the threads to fall into just one or (probably) two grooves.
I agree with @o_lampe and @Herve_Smith that these are rather expensive although I note that they are a lot cheaper than buying a metal lathe so maybe that's was in the seller's mind when setting the price. There have been 3 sales so far - I wonder who is planning to make these extruders other than @breed.
I am now beginning to wonder whether we might be able to persuade them to list sharpened flanged bearings. (Maybe for not so great a markup!)
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@tombrazier I'm posting here my drawing of a sharpened MF85ZZ so I can point potential manufacturers to it...
VDE-100_Bearing.pdf -
@Herve_Smith said in Hollow shaft extruder:
M8x1.5mm pitch bolts, i could pop those out in 10 minutes on a lathe for less than a euro each
If the funssor version uses 8mm OD bearings and threaded rod it won't cut at all.
The screw extruder I made uses 6mm OD bearings. At least that would work with 8mm threaded rod ( OD ~7.8mm).
Where can I order your 1€ version?
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@o_lampe The rods are mounted at an angle so the center of the rods will be closer to each other than the bearings.
PS I have sent a message to Funssor.
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@tombrazier Making a bearing-holder to grind three bearings at once doesn't sound too hard? I hought, there was a guy in discord channel working on it?
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@o_lampe Deadlock is working on it. His initial design has too much friction.
I reckon we need lots of ways of getting these bearings as different people will be happy with different solutions. e.g. pretty much anyone can already use my method but most regard it as too fiddly. Some will be happy to use a home-printed jig. Others will just want to buy the part and not be too worried about cost.
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@tombrazier My concern is that the chinese guys will be tempted to use cheap labour child-slaves to grind your bearings by hand. We'd have to buy 10pcs. to find three good ones...
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I ordered a set. I'll take pics and let you know what they measure. If you get someone to commercially make sharpened flange bearings for the vde that would be awesome.
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@o_lampe I remember talking to you about that screw extruder. Are these the right size screws for that design? You had 3d printed the rollers correct to see what the looked like?
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@o_lampe That is a very reasonable concern and a good point.
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@o_lampe did you publish your Stepper-to-BLDC-via-simpleFOC solution somewhere? People are interested in it for other use cases.
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