New extruder design, testers needed.

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gfeliksdal
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New extruder design, testers needed.

Post by gfeliksdal »

I've designed a new extruder, which is simpler in many ways. Before I roll it out officially, I hope some users want to test it out and share there experiences.
Extru_top_side.png
Extru_top_side2.png
Extru_open_door.png
The benefits in my opinion are:
- Simpler design, easier to assemble.
- Less parts
- Easier to exchange, remove hot-end
- Better belt tensioning mechanism, just like y-axis.
- stiffer construction

I've been testing with this for 3 weeks now, without any problems. I sometimes had to slightly increase the tension of the tensioning mechanism.

Please give your critical opinion, you don't have to play nice :)

The print assembly can be downloaded here.
extru_printassy.png
print_assy_extruder_RevF_v1_export.zip
(3.45 MiB) Downloaded 137 times
The manual to assemble it can be downloaded here:
New Extruder concept.pdf
(751.31 KiB) Downloaded 170 times

Kjetilei
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Post by Kjetilei »

Guillaume: as you already know I think the updated extruder design is extremely slick looking :D

I would really love to test it out but doubt I'll have the capacity due to the other project I'm working on.

I really hope many others will help out with the testing! I think it's a no brainer ;)

Do you have photos/videos of the real thing?

Good luck!

dognotdog
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Post by dognotdog »

Could you post the parts separately, as well? I'm doing a print of the parts right now, but there is some curling, and I'll have to redo one or two.

dognotdog
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Post by dognotdog »

Looks like all parts came out usable, after all, if not pretty. However, at the moment, I can't mount this version, as I can't get the extruder gear to move enough on the motor axis, it's quite a tight fit. I'll try to find a bearing puller tomorrow, maybe that'll do.

Kjetilei
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Post by Kjetilei »

dognotdog: I might have misunderstood you but are you saying that you are unable to mount the extruder gear (extruder insert piece) onto the stepper shaft?

I had the same problem but solved it by using a hand drill with a 5mm bit lightly on the extruder insert piece. I pushed and pulled the insert piece against the drill bit and rotated the insert piece 45-degrees several times to expand the insert piece a tiny fraction (enough to get it on to the stepper shaft).

Before I did that I managed to jam the insert piece solid onto the shaft when trying to assemble it and I was just lucky that heating up the part loosened it enough to be able to pull it of without destroying anything.

Good luck.

dognotdog
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Post by dognotdog »

Kjetilei, I indeed pretty much jammed the extruder insert onto the shaft when assembling the original extruder, and now I can't move it without tools to fit the new design, which needs the insert to be a few millimeters further away from the motor.

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Post by dognotdog »

I did manage to mount it, after all, heating the insert a bit allowed me to move it with a bit of leverage :)

Looks like so (you can also see the alternative X idler mount):
Image

I was at first worried that my cabling wouldn't be long enough, but it works, after all, though I can't just swing the "fan door" open without first dismounting the fan, as that cable's too short.

Observations so far:
1. Prints fine, no problems on day one.
2. The alu block of the hot end still wants to twist around when mounting, maybe a proper slot for it would be good?
3. Not sure if this is intentional, but now the extruder is no longer above the bed when homed. Losing precious mm here in X travel.
4. As you can see in the picture, I added a teflon bowden tube, so that the filament wouldn't twist around. I'm sure I'm not the only one annoyed by this, so maybe a mount point on the motor mount, where the filament goes in, would be nice:
Image
5. The new tensioning mechanism is still a bit weird to me. I'm not sure if the springy washers are needed, at all.

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gfeliksdal
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Post by gfeliksdal »

Hi Dognotdog,

Thanks for testing it out! Also the alternative idler and teflon tube look nice.

Comments to your observations:
2. I thought of it, but it was difficult to print a slot, because support material is required. This will create a slightly un-even surface. That's why I didn't try it.
3. The intention was to have the hot-end in the middle of the cart. It sticks out 1mm out of the bed on my printer, so I assumed it wouldn't be an issue. But will move it 2 mm's back :)
4. The teflon tube is a nice addition. Where did you get it? If I know dimensions and specs of the tube I'll design it into the extruder guiding. By the way to prevent filament from twisting I place the filament rolls in the front right or front left of the printer. This is the ideal spot where filament doesn't get stuck.
5. They are theoretically not needed, but they provide a way to dose the force of the bearing onto the filament, that was at least the intention.

dognotdog
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Post by dognotdog »

2. Not sure how to solve this, maybe the nut should be kept for fixing it in place? As it is, the alu block easily twists and moves enough to touch the extruder's idler, though fortunately not when the hot-end bumps into something. Maybe increase the clearance there? On my printout, it's just about 0.2mm clearance between the idler and alu block, when it's positioned right.

3. Maybe the bed of the printer should be moved instead of the hot end? As pictured above, X axis travel is such that the extruder has about 2cm left at the far end, which cannot be used.

4. As for the teflon tube, I got 4x2mm PTFE tubing from ebay, as that's what everyone seems to use for the bowden type extruders. I cut a M4 thread on one end, to attach it to the nut on the frame, but at the extruder it just dangles at the moment, being kept in place by the sitffness of the filament. The threading is probably overkill when the tube is just used as a guide, and its a right pain to cut into the tube in the first place. But, it does allow the tube to be attached firmly, without squeezing it together too much.

Kjetilei
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Post by Kjetilei »

Dognotdog: how is the fit of the alternative x-axis belt mount? Although I uploaded it a long time ago I never actually got around to printing it and I'm still using my first prototype that had some fit issues :)

2) You could design/print a loose adapter that is placed between the sides of the top printed part with a slot/opening for the alu block. Hopefully the friction/press fit would be enough to keep it in place.

4) I really like the PTFE tube solution but since I use the roll holders on top of the printers I think I'll do without. Could you try to come up with a design where threading of the tube is not needed and post it under the "Hacks and printer upgrades"? It could become a popular mod :)

5) I think it is nice to have the wavy washers in case of varying filament dimensions but I think that in 99% of the cases it is not needed :)

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