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billdempsey

Drop-In Herringbone Gear Set?

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I'm having an issue with the wooden gear popping the black clip off on the motor side and then drifting until it isn't making contact with the smaller gear. Ruined a couple of 5 hour prints this way.

Does anyone know of a drop-in herringbone replacement gear set for the filament feeder?

I'd much prefer something that doesn't require recalibration of the filament feed speed, since I don't know how to do that.

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I believe he's referring to the entire bolt assembly sliding out. In which case, I would print off one of these....

http://www.thingiverse.com/thing:31563 (I see you already liked it)

If it's not tight enough to hold the bolt in place, try scaling it down to 95%. If that still doesn't work, I would say there's an alignment issue with the stepper not making a flush contact with the larger gear, thus trying to walk the gear out of the assembly.

But, no, I do not know of a herringbone set that is "drop in ready." Your steps per e should be easy to re calibrate, and should be done for any gear change regardless of "drop in" status by simply re-running the first time wizard of Cura and adjusting slightly as needed.

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Personally what I did when I built the machine was to file off about 1/4 of the thickness of the

black clip where it goes over the shaft to lock it in place.

This was because, when I aligned the knurling where I wanted it, the black plastic clip didnt QUITE

actually snap properly into the groove. Thus meaning that with a tiny amount of force it would easily

ping off.

If the black clip is properly in place there is absolutely NO way that the machine can generate enough shaft

side load to ping it off.

So have a look, because my guess is 90% that your clip is not able to fully seat into the groove in the steel shaft.

Fix that and it will never come off. Modify black clip as shown below if you think this is your problem.

C.

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Sounds like you didn't assemble something properly. The wooden gear should be kept in place because of the 2 nuts (cap nut and normal nut) screwed together, not because of the black clip. As per:

http://wiki.ultimaker.com/File:Bolt_assy_v3bolt.png

 

It is assembled correctly. When the clip is missing, the entire bolt assembly slides right out of the filament feed mechanism. That's my problem.

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I believe he's referring to the entire bolt assembly sliding out. In which case, I would print off one of these....

http://www.thingiverse.com/thing:31563 (I see you already liked it)

If it's not tight enough to hold the bolt in place, try scaling it down to 95%. If that still doesn't work, I would say there's an alignment issue with the stepper not making a flush contact with the larger gear, thus trying to walk the gear out of the assembly.

But, no, I do not know of a herringbone set that is "drop in ready." Your steps per e should be easy to re calibrate, and should be done for any gear change regardless of "drop in" status by simply re-running the first time wizard of Cura and adjusting slightly as needed.

Yes, you are correct. The entire assembly is sliding out. In order to get the knurled bolt to line up with the filament, I had to space it a little toward the nut, which shortened the side with the black clip. My clip is -barely- in the groove as a result and it pops off randomly.

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Personally what I did when I built the machine was to file off about 1/4 of the thickness of the

black clip where it goes over the shaft to lock it in place.

This was because, when I aligned the knurling where I wanted it, the black plastic clip didnt QUITE

actually snap properly into the groove. Thus meaning that with a tiny amount of force it would easily

ping off.

If the black clip is properly in place there is absolutely NO way that the machine can generate enough shaft

side load to ping it off.

So have a look, because my guess is 90% that your clip is not able to fully seat into the groove in the steel shaft.

Fix that and it will never come off. Modify black clip as shown below if you think this is your problem.

C.

Yes, that's exactly my problem and I'll try it. Thanks guys!

EDIT: Here's a photo of the black clip which barely fits into the slot.

Bending.thumb.jpg.0718aa68e427bf015a2ffe08350af18d.jpg

EDIT 2:

I designed and printed a replacement for the black clip which fits perfectly and works like a charm. It's a bit like the one on Thingiverse, but just decided to use my own measurements to make an exact fit.

splitting.thumb.jpg.2971caa412710df073eabb4e0d30aabe.jpg

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Hi Bill,

Helical gears can avoid backlash when ground in steel. Modern gear grinders can grind gears to within

7 decimal places in metric units. Talking fractions of microns....

I dont think that 3D printed gears of any shape will reduce backlash, because the mnaufacturing tolerances are

so colosally above the theoretical shape of the meshing gear pair.

If you want to reduce the backlash, you can do so perfectly adequately with the standard unit by

adjusting the centre distances of the shafts. When you see Kisslicer do a retract motion, it will often

do something like a 1/4 of a full turn of the big gear to do so (90 degrees)

If you were to replace the gears with ground hardened steel helical gears, in a special steel housing, you would

probably eliminate about 1 degree of backlash. So the backlash you have once the extruder is optimally assembled

will equal about one hundredth of the rotation used by a typical retract motion. In other words, by all means do it but I promise it will make absolutely no difference whatsoever to the print performance. Once you consider that the printed gear will be to a lower tolerance than the gears you have now...you will be going backwards.

If there is alot of backlash, just loosten the stepper motor screws in the extruder assembly, and slide it towards the big gear until rotation gives noticable friction. The backlash will then be neglidgable.

Unfortunately, 3D printed gears are about the last thing that will ever be removed from coventional manufacturing in the additive manufacturing revolution.

There are no appreciable side loads on your gears, and so once your black clip is adjusted properly there will be no gain in print performance or reliability by printing your own gears. In fact I almost guarantee the backlash will go UP because the manufacturing tolerances are far worse than the laser cut items you have (even if they are just spur gears).

Sorry I suppose thats not really very useful when you just want a link to a file download. Other than searching

thingiverse I cannot suggest anything - if you really must have them you will probably need to design them

yourself if there is nothing on thingiverse

C.

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Hi Bill,

Helical gears can avoid backlash when ground in steel. Modern gear grinders can grind gears to within

7 decimal places in metric units. Talking fractions of microns....

I dont think that 3D printed gears of any shape will reduce backlash, because the mnaufacturing tolerances are

so colosally above the theoretical shape of the meshing gear pair.

I agree with this, herringbone gears don't have any intrinsic design feature that make them better for backlash. In fact you inherit an issue on reversing rotation of the gear where the main reason they exist (eliminate axial force caused by a helical gear) stops existing.

I have gone over the 'what if' of replacing the gears before, and the most sound conclusion was to replace them with moulded MOD1 gears (example) which are reasonably obtainable and have excellent friction, backlash, noise etc. etc. properties in comparison to printed or otherwise DIY gears.

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Sounds like you didn't assemble something properly. The wooden gear should be kept in place because of the 2 nuts (cap nut and normal nut) screwed together, not because of the black clip. As per:

http://wiki.ultimaker.com/File:Bolt_assy_v3bolt.png

 

I have the same problem... the gears do not line up, and after some printing the whole slides out until the gears start skipping. Looking at the picture you posted above, I have the impression that the my bolt is longer... If i assemble it as in the picture there is a gap between the delrin clip and the bearing of at least 6 mm...

Will post some pics when my print has finished.

EDIT: Reassembled the material feeder, everything is working now ;)

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Since I printed my replacement knurled shaft clip, I haven't had any problem with gear drift on the small gear or the large, which was what I was targeting with herringbone gears, since they self-center. So, I'm following your advice and skipping them. Thanks for the input everyone!

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I printed and mounted those herringbone gears and found that they were easy to mesh with a good bit of tension without binding. In doing so, a majority of the backlash was eliminated. They do seem a little quieter too. Just skip the knob. Mine is still intact but because it is a loose fit it groans as the stepper vibrates the set.

Retracts don't have the loud clunk of the wooden gear.

it's a fun print for a newbie like me.

 

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I believe the argument for herringbone gears reducing backlash is that unlike a normal gear, they are constantly and consistently engaged. This combined with the flexibility of the plastic allows them to be pressed up against each other in a way that would cause problems with normal gears (normal gears tend to bind when pressed tightly together). I have a friend with a Printrbot. While for a variety of reasons the UM is a way better machine, his printed herringbone gears seem to function perfectly (if it matters, they were printed on an older Stratasys system at his school. In general, I have found that our UM can produce better print quality than their Stratasys)

All that said, I don'y have any plans to switch my gears. I don't believe there is any significant room for improvement.

 

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That was my finding. You can press them together pretty hard and not get the chug chug chug of the wooden straight gears. Furthermore, because the plastic is flexible, you get very little backlash and very little binding with the herringbone pattern.

I'm not saying everyone should switch over. I did but it was more just to see if it could be done and how they wear over time.

I will say getting the small gear on the stepper shaft was a pain in the butt! It is also difficult to get them aligned and unlike the straight cut set, they must be aligned due to the centering nature of the herringbone.

 

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