Fine tune your E axis  

Re: Fine tune your E axis

Am I completely wrong in my theories or is this something that Prusa should look at?

I have been looking into this more than the other issues reported as it seems to me to present more significant challenges to fix than most.

I agree with your analysis based on the parts files and the pictures I have seen. The "skew" in the meshing of the teeth seems to have been quite significant in the pictures in the "grinding gears" thread.

But I don't have a printer to look at yet ...

Re: Fine tune your E axis

<r><QUOTE><s></s>Am I completely wrong in my theories or is this something that Prusa should look at?<e></e></QUOTE>

I have been looking at this more than the other issues reported as it seems to me to prevent more significant challenges to fix than most.

I agree with your analysis based on the parts files and the pictures I have seen. The "skew" in the meshing of the teeth seems to have been quite significant in the pictures in the "grinding gears" thread.

But I don't have a printer to look at yet ...

</r>

Re: Fine tune your E axis

Shoot me the files and I'll print and test it!

Re: Fine tune your E axis

I don't think this mod is needed. My extruder idler gears teeth mesh perfectly to the gear on the extruder motor. The screws on the side of the extruder motor pass through the idler and ensures solid contact. It does not look skewed like mockup photo at all.

Re: Fine tune your E axis

I don't think this mod is needed. My extruder idler gears teeth mesh perfectly to the gear on the extruder motor. The screws on the side of the extruder motor pass through the idler and ensures solid contact. It does not look skewed like mockup photo at all.

If so, Prusas SCAD files are not updated. I use Prusas SCAD and STL files when I make my assemblys.

Re: Fine tune your E axis

I don't think this mod is needed. My extruder idler gears teeth mesh perfectly to the gear on the extruder motor. The screws on the side of the extruder motor pass through the idler and ensures solid contact. It does not look skewed like mockup photo at all.

That is right. GitHub models are R1 version, but I got a few days ago kit, where are mostly A9 and B3 versions.

Re: Fine tune your E axis

It's quite serious if I claim there are dimensions errors on MK3 that are already fixed by Prusa.

It is also serious that Prusa has not posted the updated parts for download.
This means that if we need to make a spare part for the printer, then we manufacture a piece that works worse than the original!

Prusa should immediately add the latest versions.

Re: Fine tune your E axis

It's quite serious if I claim there are dimensions errors on MK3 that are already fixed by Prusa.

It is also serious that Prusa has not posted the updated parts for download.
This means that if we need to make a spare part for the printer, then we manufacture a piece that works worse than the original!

Prusa should immediately add the latest versions.

I think you are over-reacting a bit. R1 is just the place holder for the version in SCAD. They tweak the parts on their assembly line (mostly for high volume printing success) and when they are satisfied they eventually push that back to the source, albeit too slowly for my taste. I agree if they solve something critical they should push that out as soon as they validate the fix.

Can you check your measurements? I just looked and in my assembly, with the idler in the neutral position, the axes are in perfect alignment. This is good because you need to allow for variable filament diameter, too thin and too thick, and variable amount of bite of the teeth into different hardness filament. In other words, there will be a large amount of variation and you want to start neutral. You state the idler arm should make contact with the extruder but that is wrong. It needs swing past neutral.

Re: Fine tune your E axis

I'd rather Prusa work on fixing the bugs and getting as many order out the door before they worry about posting up the latest revision of parts for the idea thieves to poach. I understand the need to have the latest 3d parts up and I hope they're available to those who break a part or have one damaged, if you contact support.

OP, I think what you're doing is wonderful. I'm all for tweaking and making things better but perhaps you should wait and get your printer first before you waste so much time on making parts that may or may not be needed.

Re: Fine tune your E axis

Can you check your measurements? I just looked and in my assembly, with the idler in the neutral position, the axes are in perfect alignment.

According to the CAD drawing, the extruder idler cover is not closed when the gears are in the optimal position (cc distance = 9 mm). It leans slightly downwards, it should be vertical. The risk is that the idler cover will twist if you tighten the screws too tight.
But I'll have to wait a while. I should receive delivery messages next week 😮

OP, I think what you're doing is wonderful. I'm all for tweaking and making things better but perhaps you should wait and get your printer first before you waste so much time on making parts that may or may not be needed.

Yes, you are right in what you say. I have to wait until my printer arrives so I can verify my ideas.

Re: Fine tune your E axis

I have previously written about the X, Y and Z axes and have now started looking at the E axis, and I think it also needs fine tuning.

The filament should, according to me, have a completely straight path through the Exrtuder unit. When I check the MK3 extruder, it seems that the extruder engine is seated 0.5 mm laterally.
This means that the filament must be bent slightly to pass the engine's Bondtech pulley.
The center distance between the two Bontech wheels should be 9 mm and the center distance is determined by the two gear wheels (module 0.5).

There is thus no idea to design details (extruder idler) that allow a smaller center distance because the gears can not be pushed together.

On the other hand, you may have a slightly larger center distance if the filament requires it. That is why there are springs against the extruder idler that will allow the a little bit.

I have drawn a modified extruder assembly where the above points are fixed, but I have no printer yet to test my ideas.

So my question to you is:
Am I completely wrong in my theories or is this something that Prusa should look at?

Have you seen this thread? https://shop.prusa3d.com/forum/original-prusa-i3-mk3-f30/bontech-gears-griding--t13627.html

This proves what you have discovered (hope they will publish new part soon)

Re: Fine tune your E axis

Have you seen this thread? https://shop.prusa3d.com/forum/original-prusa-i3-mk3-f30/bontech-gears-griding--t13627.html

This proves what you have discovered (hope they will publish new part soon)

That thread doesn't prove that the gears are out of alignment, it just proves that you should use a small amount of grease on the gears or they will grind. This causes the surface treatment on the gears to wear, and I'm assuming humidity is causing rust.

Re: Fine tune your E axis

Have you seen this thread? https://shop.prusa3d.com/forum/original-prusa-i3-mk3-f30/bontech-gears-griding--t13627.html

This proves what you have discovered (hope they will publish new part soon)

That thread doesn't prove that the gears are out of alignment, it just proves that you should use a small amount of grease on the gears or they will grind. This causes the surface treatment on the gears to wear, and I'm assuming humidity is causing rust.

I say that because we can see on this drawing that the gears are not parallel and so only part of the teeth are touching each other (which correspond to the used part in the other thread). The consequence of this is that they are aging faster and so you need to lubricate more...

Re: Fine tune your E axis

That thread doesn't prove that the gears are out of alignment, it just proves that you should use a small amount of grease on the gears or they will grind. This causes the surface treatment on the gears to wear, and I'm assuming humidity is causing rust.

I say that because we can see on this drawing that the gears are not parallel and so only part of the teeth are touching each other (which correspond to the used part in the other thread). The consequence of this is that they are aging faster and so you need to lubricate more...

Where are the spring tension screws in that drawing? If that drawing was accurate the screws would have to be bent in order to pass through the extruder body and through the idler.

BTW - a very light coating of lithium grease on the gear teeth will not hurt anything.

Re: Fine tune your E axis

To clarify what I meant with the picture:
I created the image to show what can happen if you tighten the screws too much.

If the plastic details in your printer are the same as those available downloadable on the Prusas website, this may happen.
If the gear wheels are angled to each other, lubrication is not a solution to the problem.

Re: Fine tune your E axis

I'd rather Prusa work on fixing the bugs and getting as many order out the door before they worry about posting up the latest revision of parts for the idea thieves to poach.

Fixing stuff and posting fixes doesn't need to be mutually exclusive. If they already use git to store their work, you're just a short git push away from publishing the changes.

Re: Fine tune your E axis

Hi All,

I did some measurements on an extruder made by Bondtech for MK2 printers and they use a gear spacing of 8.5mm. This means a move of 0.25mm from original Prusa extruder. Here is the Bondtech extruder : http://shop.bondtech.se/en/kits/mechkit-extruder-kit-prusa-i3-mk2.html

More details in page 8 and 9 here : https://shop.prusa3d.com/forum/original-prusa-i3-mk3-f30/any-ideas-how-to-get-this-flexable-material-to-pri-t14765-s70.html

Bellow the STL from Bondtech extruder. This 11.25mm value in my measurements corresponds to 11.5mm on original Prusa extruder :

Re: Fine tune your E axis

Have you seen this thread? https://shop.prusa3d.com/forum/original-prusa-i3-mk3-f30/bontech-gears-griding--t13627.html

This proves what you have discovered (hope they will publish new part soon)

That thread doesn't prove that the gears are out of alignment, it just proves that you should use a small amount of grease on the gears or they will grind. This causes the surface treatment on the gears to wear, and I'm assuming humidity is causing rust.

Those gears are meant to be used parallel to one another. Using them off-axis clearly explains this:

Re: Fine tune your E axis

Is it just me or it looks like these bondtech gears are designed for 3mm filament instead of 1.75mm given that setting them parallel would make them work perfectly with 3mm filament?