This engineer claims 100 grams direct extruder. I want one

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ipcalit

Here is another idea inspired by these two:
1) thread the shaft of a tiny stepper (1-2Ncm is probably enough, <50g) with something between an M3-M5
2) make grooves with the corresponding tap (M3-M5) into the outside of a small bearing (e.g, 623, 624)

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etfrench

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ipcalit

Here is another idea inspired by these two:
1) thread the shaft of a tiny stepper (1-2Ncm is probably enough, <50g) with something between an M3-M5
2) make grooves with the corresponding tap (M3-M5) into the outside of a small bearing (e.g, 623, 624)

I doubt you would be able to use a tap as a hob on a bearing. The bearing will probably be harder then the tap You could hob a steel ring, then press the bearing into the ring.

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DjDemonD
I wonder if it would be possible to just stick a small stepper on the top of a flex3drive extruder, with its 40:1 reduction, especially for driving 1.75mm, it should need only a very small and light motor. I wonder if it would have sufficient power for a decent retract.

This motor [www.omc-stepperonline.com] can provide 7Ncm which into 40:1 (with no losses from the flexdrive itself), is only 50g making the complete extruder only 135g. Using a 13 Ncm nema 17 pancake with 3:1 gearing works extremely well on the titan so it should be powerful enough.

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powdermetal

The Cycloidal Extruder Drive has been updated with a 16:1 ratio to engage the proposed lightweight NEMA14 pancake stepper 14HR08-0654S (7Ncm, 50g). This did work fine until the heat from the stepper made the PLA-components start to creep - will be resolved soon...

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o_lampe
The stepper of a flex3drive is already in a remote position. What would the weight gain be good for?

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DjDemonD

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o_lampe
The stepper of a flex3drive is already in a remote position. What would the weight gain be good for?

Cost! It's my understanding that a fair amount of the cost of the flex3drive system is the flexible drive itself. We are talking about making a lightweight direct extruder - flex3drive is that already and is lighter than anything we've discussed here - problem solved. So why the discussion at all, lets all buy flex3drive's and enjoy. I have got one Its really good. But its a little more expensive than any of the other extruders I've made/bought and its more complicated.

My thinking is that the worm gear in the flex3drive is a part you would have to buy, but you can print a housing and attach the 50g motor and you have a 135g direct extruder for a cost of $20-$30. The current flex3drive extruder minus the flexible drive is relatively cheap, already highly geared enabling use of light motors and its known to work.

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o_lampe

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etfrench

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ipcalit

Here is another idea inspired by these two:
1) thread the shaft of a tiny stepper (1-2Ncm is probably enough, <50g) with something between an M3-M5
2) make grooves with the corresponding tap (M3-M5) into the outside of a small bearing (e.g, 623, 624)

I doubt you would be able to use a tap as a hob on a bearing. The bearing will probably be harder then the tap You could hob a steel ring, then press the bearing into the ring.

+1 about threading the bearing.
Also the circumfence of the bearing has to be an exact multiple of the thread pitch to provide smooth extraction.
I'm also in doubt that a thread would be a good filament guide. Wouldn't it push the filament in a diagonal/sideways direction?
There would be a lot of pressure necessary to keep the steppershaft meshed to the threaded bearing. Another idler/support bearing on the opposite side would help.
Like : o!O/_O

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powdermetal

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JamesK

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powdermetal
1. Some docs: Cycloidal Extruder Drive
2. Have indulgence - it's my first wiki...

Many thanks! My nema14 extruder with 5:1 ratio is right on the ragged edge for 3mm pla, so I'm looking for alternatives in the 10:1 ballpark. I may end up trying this

The Cycloidal Extruder Drive has been updated with a 16:1 ratio to engage the proposed lightweight NEMA14 pancake stepper 14HR08-0654S (7Ncm, 50g). This did work fine until the heat from the stepper made the PLA-components start to creep - will be resolved soon...

[attachment 77607 CycloExtruder_v02-2_small.png] [attachment 77608 CycloExtruder_v02-6_small.jpg]

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ipcalit
I agree with the challenge to machine threads into the bearing as it is a strong steel. The idea to add a sleeve out of steel or brass is probably better.

How about turning the flange of a largish bearing directly into a gear with some heavy duty cutting disk? That should be easier I think, and we could use either an M5/M6 to drive it or another smaller gear. If the cuts into the flange reach the outside diameter of the bearing then you get enough grooves to drive the filament. We would still need to find the right bearing diameter to match the screw threads. What do you think?

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o_lampe

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etfrench

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ipcalit

Here is another idea inspired by these two:
1) thread the shaft of a tiny stepper (1-2Ncm is probably enough, <50g) with something between an M3-M5
2) make grooves with the corresponding tap (M3-M5) into the outside of a small bearing (e.g, 623, 624)

I doubt you would be able to use a tap as a hob on a bearing. The bearing will probably be harder then the tap You could hob a steel ring, then press the bearing into the ring.

+1 about threading the bearing.
Also the circumfence of the bearing has to be an exact multiple of the thread pitch to provide smooth extraction.
I'm also in doubt that a thread would be a good filament guide. Wouldn't it push the filament in a diagonal/sideways direction?
There would be a lot of pressure necessary to keep the steppershaft meshed to the threaded bearing. Another idler/support bearing on the opposite side would help.
Like : o!O/_O

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DjDemonD
This looks good but it is more complicated than flex3drive despite doing the same thing. I agree with one of the comments above the fewer gears the better. One worm gear and one gear with a hobbed drive is all it needs.

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DjDemonD
My experience with the flex3drive is that it can do the necessary retraction, it just takes a fraction of a second to do it. I can retract 1.4mm @ 10mm/s with e-acceleration at 250. This does generate a noticeable pause, but no strings/blobs/ooze. I think it might even do better with a smaller motor. I think the 40mm motor I am using might be able to generate a lot of torque, but the extruder is 40:1 geared so it doesn't need to do so, it needs to change direction fast, so a smaller motor with less rotating mass, and lower detent torque to overcome might work better. I might experiment with some smaller motors, like the nema 17 - 20mm pancake.

Perhaps its just our current expectation of what retraction should be, will have to change for the sake of a lightweight extruder.

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MKSA

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powdermetal

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JamesK

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powdermetal
1. Some docs: Cycloidal Extruder Drive
2. Have indulgence - it's my first wiki...

Many thanks! My nema14 extruder with 5:1 ratio is right on the ragged edge for 3mm pla, so I'm looking for alternatives in the 10:1 ballpark. I may end up trying this

The Cycloidal Extruder Drive has been updated with a 16:1 ratio to engage the proposed lightweight NEMA14 pancake stepper 14HR08-0654S (7Ncm, 50g). This did work fine until the heat from the stepper made the PLA-components start to creep - will be resolved soon...

[attachment 77607 CycloExtruder_v02-2_small.png] [attachment 77608 CycloExtruder_v02-6_small.jpg]

I would like to know:
- At start, what torque do you measure at the hobbed gear, filament pulling force and at which intensity ?
- What printing speed can it achieve ?
- What about retraction speed ?

If the PLA softens, the motor may be driven outside of its specification. What t° did you measure ?

I was looking to replace the motor I took from a HP printer for this NEMA14, gaining a further 70g although so far, above 120mm/s the limiting factor I met is the hot end. SO change of priority.

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MKSA

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DjDemonD
This looks good but it is more complicated than flex3drive despite doing the same thing. I agree with one of the comments above the fewer gears the better. One worm gear and one gear with a hobbed drive is all it needs.

My opinion too. I have looked at planetary gears, cycloidal gears too. When you need high reduction, minimal backlash, fine. Then I determined what gears ratio I needed to come to the conclusion that you don't need much in fact and just regular gears could do it. On the extruder, you need torque to drive the filament but rotation inversion, acceleration/speed to retract it ! High reduction will give you the torque but will the stepper be able to provide the required speed in reverse ?
The next real progress is Servo BLDC but not the same cost range.
But then it is the whole 3D printer that has to be revised.

The engineer who designed the printer with this 100gr extruder took the right approach. There is more in it than just the light weight extruder.

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DjDemonD
My experience with the flex3drive is that it can do the necessary retraction, it just takes a fraction of a second to do it. I can retract 1.4mm @ 10mm/s with e-acceleration at 250. This does generate a noticeable pause, but no strings/blobs/ooze. I think it might even do better with a smaller motor. I think the 40mm motor I am using might be able to generate a lot of torque, but the extruder is 40:1 geared so it doesn't need to do so, it needs to change direction fast, so a smaller motor with less rotating mass, and lower detent torque to overcome might work better. I might experiment with some smaller motors, like the nema 17 - 20mm pancake.

Perhaps its just our current expectation of what retraction should be, will have to change for the sake of a lightweight extruder.

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Chri
Wow thats looking awsome

whats the overall weight of the Extruder part with/without hotend ?
What E-Steps do you have with this ?

Chri

Weight_Assembly1.jpg

Weight_Assembly2.jpg

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Curry44
Great project!

Whats with supporting 1,75mm filament?

greets from Germany

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DjDemonD
Yeah I'd say there is a lot to be said for looking at 1.75mm as it does not require as much force to push through the hot end, therefore lowering the bar on making a lightweight extruder. Respect for doing this with 3mm it is a greater challenge but I run my corexy and delta on 1.75mm so I can have a lighter extruder.

Plus 1.75mm runs off the spool better

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realthor
The 12:1 you use now would be more than enough for the 1.75mm filament, what changes are necessary to make it 1.75mm compatible?

CycloExtruder_v03-1.75.png

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asbo
@powdermetal
Are you modelling your CycloidalExtruderDrive in SolidWorks? If so could you upload the native SolidWorks files as both the 3mm step files from the wiki and the 1.75mm ones above throw up all sorts of errors for me.
Thanks

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o_lampe

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asbo
@powdermetal
Are you modelling your CycloidalExtruderDrive in SolidWorks? If so could you upload the native SolidWorks files as both the 3mm step files from the wiki and the 1.75mm ones above throw up all sorts of errors for me.
Thanks

I had the same issue when converting the .stp files to .stl with the ABViewer.
I took netFabb to repair the parts, but stil got errors shown, but now Cura can slice them perfectly.

Printing the excenter is a different story