User avatar
david.f42
Posts: 695
Joined: Feb 17, 2018 4:53 am
Answers: 6
Contact: Send private message

Extrusion gears grinding black PETG idler part into dust. Probably on yours too.

Jun 11, 2018 6:43 pm

I had reprinted part of my printhead in white. Whenever I've opened the extrusion idler, I've seen a pile of black dust. I actually had already cleaned it off before it dawned on me that I should take a picture, so here it is, which shows a wideshot and then a closeup with some of the traces still left:
wideshot.jpg
wideshot.jpg (455.98 KiB) Viewed 1317 times
closeup.jpg
closeup.jpg (373.36 KiB) Viewed 1317 times
I'm pretty sure it's ground black plastic from the idler (from the original kit):
grinder.jpg
grinder.jpg (492.22 KiB) Viewed 1317 times
That gear piece has nothing to prevent it from grinding against the sides (nylon washers would maybe help if the part were redesigned to make room for them), and so it grinds off the black plastic. Well, why is that a problem, you ask? There are fans moving air around. All it takes is for those plastic bits to land on the filament, or go in the hole which leads to the hotend. Those are PETG bits of plastic. If you're printing PLA, they won't necessarily melt, possibly leading to... a clog. There, I said it.

Since the original kit is all black, you might not even notice this black dust against a black background. So, maybe no one is aware of it. As you can see in the last photo, I am now going to try to mitigate against it by using some sparing amounts of white lithium grease. It's not a good solution, but it will have to do until someone comes up with a better fix (like maybe a redesign with washers on either side or perhaps something better still).

Comments/suggestions welcome.

Best Answer by martin.w15 » Jun 14, 2018 11:36 pm
As I now have spare nylon washers I felt safe enough in removing the idler from my MK3 for a close look.
Image
Image

As well as the expected brown of rust in the lithium grease small amounts of near black plastic can also be seen matching the colour of the printed part. All though it turns freely when not under load I suspect it grinds lightly when under the tension from the springs.

As a result I have added some tolerancing clearance to the part under the gear.
Image
STL of Extruder Idler W2
Autodesk DWG of Extruder Idler W2

Regards,
Martin

GO TO FULL POST ➙

martin.w15
Posts: 375
Joined: Nov 06, 2017 9:51 am
Answers: 9
Location: Hertfordshire, England
Contact: Send private message

Re: Extrusion gears grinding black PETG idler part into dust. Probably on yours too.

Jun 12, 2018 12:06 am

David,

The extruder body needs to be printed in black. The filament sensor requiers this to work.

Regards,
Martin
Last edited by martin.w15 on Jun 12, 2018 2:00 am, edited 1 time in total.

martin.w15
Posts: 375
Joined: Nov 06, 2017 9:51 am
Answers: 9
Location: Hertfordshire, England
Contact: Send private message

Re: Extrusion gears grinding black PETG idler part into dust. Probably on yours too.

Jun 12, 2018 1:32 am

Here is a redesigned extrudler idler with room for nylon washers.
Image
STL of Redesigned Idler
Autoddesk DWG File of Drawing

Regards,
Martin

User avatar
david.f42
Posts: 695
Joined: Feb 17, 2018 4:53 am
Answers: 6
Contact: Send private message

Re: Extrusion gears grinding black PETG idler part into dust. Probably on yours too.

Jun 12, 2018 8:42 am

Wow! Fantastic! You've got amazing talent. And fast too. Thank you!

:D :D :D

martin.w15
Posts: 375
Joined: Nov 06, 2017 9:51 am
Answers: 9
Location: Hertfordshire, England
Contact: Send private message

Re: Extrusion gears grinding black PETG idler part into dust. Probably on yours too.

Jun 14, 2018 7:11 pm

David,

I have just been looking at the extruder Idler again.
extruder-idler W1-A Section.jpg
extruder-idler W1-A Section.jpg (142.53 KiB) Viewed 941 times
The rubbing that is causing your problem may not be from the ends. Does the Idler in the new part spin freely because looking at the section I just added to my drawing (I tend to review my work after a couple of days,) there is no tolerancing between the idler gear and the printed part.

Regards,

Martin

User avatar
david.f42
Posts: 695
Joined: Feb 17, 2018 4:53 am
Answers: 6
Contact: Send private message

Re: Extrusion gears grinding black PETG idler part into dust. Probably on yours too.

Jun 14, 2018 9:59 pm

martin.w15 wrote:
Jun 14, 2018 7:11 pm
Does the Idler in the new part spin freely...
I don't know. I'm waiting for the next time I disassemble my print-head to try out your new part. Not sure when that will be.

martin.w15
Posts: 375
Joined: Nov 06, 2017 9:51 am
Answers: 9
Location: Hertfordshire, England
Contact: Send private message

Re: Extrusion gears grinding black PETG idler part into dust. Probably on yours too.

Jun 14, 2018 11:36 pm

As I now have spare nylon washers I felt safe enough in removing the idler from my MK3 for a close look.
Image
Image

As well as the expected brown of rust in the lithium grease small amounts of near black plastic can also be seen matching the colour of the printed part. All though it turns freely when not under load I suspect it grinds lightly when under the tension from the springs.

As a result I have added some tolerancing clearance to the part under the gear.
Image
STL of Extruder Idler W2
Autodesk DWG of Extruder Idler W2

Regards,
Martin

martin.w15
Posts: 375
Joined: Nov 06, 2017 9:51 am
Answers: 9
Location: Hertfordshire, England
Contact: Send private message

Re: Extrusion gears grinding black PETG idler part into dust. Probably on yours too.

Jun 22, 2018 9:03 pm

I have now fitted the redesigned part to my printer. So far no issues.

Regards,
Martin

User avatar
david.f42
Posts: 695
Joined: Feb 17, 2018 4:53 am
Answers: 6
Contact: Send private message

Re: Extrusion gears grinding black PETG idler part into dust. Probably on yours too.

Jun 28, 2018 12:31 pm

I installed it this morning:
fixed.jpg
fixed.jpg (397.63 KiB) Viewed 474 times
I had to ream the holes a little bit to make the axil fit, but aside from that it looks like it will work just fine. :D

User avatar
david.f42
Posts: 695
Joined: Feb 17, 2018 4:53 am
Answers: 6
Contact: Send private message

Re: Extrusion gears grinding black PETG idler part into dust. Probably on yours too.

Jun 28, 2018 2:37 pm

martin.w15 wrote:
Jun 14, 2018 11:36 pm
As I now have spare nylon washers I felt safe enough in removing the idler from my MK3 for a close look.
Image
Image

As well as the expected brown of rust in the lithium grease small amounts of near black plastic can also be seen matching the colour of the printed part. All though it turns freely when not under load I suspect it grinds lightly when under the tension from the springs.

As a result I have added some tolerancing clearance to the part under the gear.
Image
STL of Extruder Idler W2
Autodesk DWG of Extruder Idler W2

Regards,
Martin
Actually, there is a problem, which is the axil is not long enough to guarantee that it won't fall out on one side or the other. This has happened to me twice now. I'll try gluing it into place, but if that doesn't work, I'll have to revert to the original idler that came with the kit. :cry:

Return to “Hardware, firmware and software help”

Who is online

Users browsing this forum: No registered users and 2 guests