how much to tighten the extruder idler mounting screws
 
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Ken
 Ken
(@ken-4)
Eminent Member
how much to tighten the extruder idler mounting screws

Step 15 of the E-axis assembly has you insert the screws for mounting the extruder idler. The instructions are only to "Place both screws into the Extruder body and tighten them. The screw's head should be almost aligned with the printed surface." How do you know if you've properly tensioned the screws? Under what conditions would you tighten or loosen them further? Under what conditions would you remove them entirely? Would you be able to remove the filament if it gets stuck during an unload as is the case here: https://shop.prusa3d.com/forum/original-prusa-i3-mk3-f30/how-to-unload-filament-correctly--t12822.html ?

Thanks,
Ken

Napsal : 03/01/2018 1:43 am
AJS
 AJS
(@ajs)
Noble Member
Re: how much to tighten the extruder idler mounting screws

First, I don't own a MK3, only a MK2S with MMU which uses the same configuration. I have helped a friend with a MK3.

I think you really want the screws to barely engage the spring when there is no filament in. The filament then expands the gears and the springs engage.

You want them EVEN looser if you are printing very soft filament (to prevent it from being squashed before entering the heat chamber).

This is counter intuitive to most folks who really want the gears to grab the filament hard. If they are too tight, the filament gets little teeth cuts in it and it flattens. This can cause it to intermittently jam in the extruder making your extrusion non-uniform.

Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage or loss. If you solve your problem, please post the solution…

Napsal : 03/01/2018 2:01 am
Ken
 Ken
(@ken-4)
Eminent Member
Topic starter answered:
Re: how much to tighten the extruder idler mounting screws


First, I don't own a MK3, only a MK2S with MMU which uses the same configuration. I have helped a friend with a MK3.

I think you really want the screws to barely engage the spring when there is no filament in. The filament then expands the gears and the springs engage.

You want them EVEN looser if you are printing very soft filament (to prevent it from being squashed before entering the heat chamber).

This is counter intuitive to most folks who really want the gears to grab the filament hard. If they are too tight, the filament gets little teeth cuts in it and it flattens. This can cause it to intermittently jam in the extruder making your extrusion non-uniform.

I was tempted to ask "how tight is right" but I guess you're saying "if it works then don't worry about it but if you're having trouble consider tightening or loosening the screws as appropriate..."

Thanks,
Ken

Napsal : 08/01/2018 12:11 am
JoanTabb
(@joantabb)
Veteran Member Moderator
Re: how much to tighten the extruder idler mounting screws

Hi Ken...

on my mk3, without filament in the extruder, the pressure screws are literally advanced until the first resistance from the spring, is felt and that has worked perfectly with PLA and PETG.

when fiament is later inserted the bondtech pair, drives well...

i havent yet used tpu on this printer I was going to do that tonight but life got in the way!

Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK

Napsal : 08/01/2018 4:23 am
simon.l4
(@simon-l4)
New Member
Re: how much to tighten the extruder idler mounting screws

The tips of the screws are about 3mm below the surface of the printed part on mine and I have been using this setting for both PLA and TPU successfully. I think It is important the screws should at least past the trapped square nuts.

Napsal : 08/01/2018 5:16 pm
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