Strange poblem: dimension accuracy depends on the X position
 
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the_master_1
(@the_master_1)
Active Member
Strange poblem: dimension accuracy depends on the X position

Hi all,

I have a problem, and I was not able to find anything regarding users having the same problem or potential solution. May be one of you can point me in the right direction:

I've been building i3 clone over years, starting with parts from Anet A6 and subsequently replacing the components. Currently only the motors and the rods are from Anet, the rest has been replaced: metal frame, STM processor based board, MK3S bed, MK3S+ extruder, Bear X axis, driven by Marlin 2. The printer provides good quality, but has an issue with dimension accuracy depending on the X position. In the middle of the bed it's 100%, on the left site it's let's say 105%, on the right site 98%. As you can imagine, changing the steps per mm stepping wouldn't solve this problem. Has anyone an idea, what might be the root cause?

As I said, the X axis is from the bear project, the belt is tight enough and parallel to the rods.

Posted : 01/06/2023 10:39 am
Stefan
(@stefan-3)
Estimable Member
RE: Strange poblem: dimension accuracy depends on the X position

MK3S+ extruder, Bear X axis

See here: https://github.com/gregsaun/bear_extruder_and_x_axis/blob/master/README.md#compatibility  

The Bear X-ends cannot be used together with the original Prusa Mk3S+ extruder. You should use the two original MK3S+ X-end parts, too.

Posted : 02/06/2023 11:33 am
the_master_1
(@the_master_1)
Active Member
Topic starter answered:
RE: Strange poblem: dimension accuracy depends on the X position

Hello Stefan,

thanks for your reply. I red this, but I thought, it's only about compatibility to the original Prusa frame and firmware. As I never intended to be that close to the original, I just ignored it.

But could the "different belt path" be really the root cause for that problem? Why?

Posted : 02/06/2023 11:59 am
Stefan
(@stefan-3)
Estimable Member
RE: Strange poblem: dimension accuracy depends on the X position

yes, the belt path is the reason.

If the belt does not pull exactly parallel to the X-rods, the X-movement will not be the exact amount as it is intended.

Think about it as a exaggerated triangle  with C as the extruder.  In the middle the error is quite small, but the more the extruder "C" moves to the stepper "A" the bigger the error will be.

 

Posted : 02/06/2023 3:15 pm
the_master_1
(@the_master_1)
Active Member
Topic starter answered:
RE:

I've spent some time with the printer. The first thing I did was to replace the stock prusa extruder with the Bear extruder, but unfortunatly it didn't solve the problem. Then I measured a special thing printed some time ago using the Prusa stock extruder, but it was fully ok -> the problem couldn't be the Prusa stock extruder even if it is claimed to be incompatible with the Bear x-axis.

The next thing I did was to replace the x-axis belt by a new one, because the old one looked strange, I was not able to pull it straight. This was indeed the solution. In the picture you can see the misformed end. I have no idea what could cause the problem that suddenly, I have used this belt for years, without any issues.

This post was modified 12 months ago by the_master_1
Posted : 16/06/2023 7:30 pm
_rob_
(@_rob_)
Eminent Member
RE: Strange poblem: dimension accuracy depends on the X position

Looks like a cheap belt. What brand is it? I only use gates belts. They cost a bit more but worth it. Trianglelab has them on aliexpress... https://www.aliexpress.us/item/2251832667244886.html

Posted : 17/06/2023 2:08 am
Stefan
(@stefan-3)
Estimable Member
RE: Strange poblem: dimension accuracy depends on the X position

the problem couldn't be the Prusa stock extruder even if it is claimed to be incompatible with the Bear x-axis.

Let me clarify:

i never did this "Bear Exxa" Mod myself. I only looked at the documentation they provide.

There was said, that they made a change so that you have 5 mm more Z-build volume. 

This was achieved also by a different belt path and therefor the Bear Extruder and the X-axis ends can only be used as one entire set.

Maybe there are also versions of the Bear Exxa X-ends that do not sacrifice the MK3S+ compatibility for gaining 5 mm more Z.

Regarding belts: They have a fiber reinforcement inside that can break or tear apart, if overtightened or bent in a too small radius.
Of course this will affect dimensional accuracy.

Posted : 17/06/2023 9:36 am
3Delight
(@3delight)
Moderator Moderator
RE: Strange poblem: dimension accuracy depends on the X position

Hi, Please bear in mind that this is a forum for owners of Prusa Research made printers not clones.  You will likely find better help for self builds on sites such as Reddit, etc.

Posted : 17/06/2023 9:35 pm
Stefan liked
Stefan
(@stefan-3)
Estimable Member
RE: Strange poblem: dimension accuracy depends on the X position

a forum for owners of Prusa Research made printers not clones

I provided my very limited knowledge, because i printed original MK3S+ X-end parts
for somebody who had bought a MK3S printer with this Bear X-axis mod second hand.
He wanted to change it back to a standard machine. 

There are original Prusa printers where this modification has been made.

I do own a original MK3S and have a order for a MK4 kit from day one.

I do not support and would not encourage anyone to build clones. 

It is not a good idea to build this printer with parts of unknown quality and struggle with problems later on.

If you ever decide to sell your printer: Nobody wants a second hand clone printer.

For me: As little money as possible for China economy. 

No chinese 3D printing technology or filaments as far as possible...

No Geetech Sunlu Eryone Anycubic Jayo Creality AmazonBasics whatever Chinese filaments or printer for me. 

 

 

 

Posted : 18/06/2023 9:45 am
_rob_
(@_rob_)
Eminent Member
RE: Strange poblem: dimension accuracy depends on the X position
Posted by: @stefan-3

...

I do not support and would not encourage anyone to build clones. 

It is not a good idea to build this printer with parts of unknown quality and struggle with problems later on.

If you ever decide to sell your printer: Nobody wants a second hand clone printer.

...

Hard to even call something a clone when it's an open source project. Of course people are going to build their own and other companies are going to sell their own kits. That's the nature of open source. There's nothing at all wrong with it.

Posted : 18/06/2023 1:15 pm
_rob_
(@_rob_)
Eminent Member
RE: Strange poblem: dimension accuracy depends on the X position
Posted by: @stefan-3

For me: As little money as possible for China economy. 

Where do you think most prusa parts come from?

Posted : 18/06/2023 1:24 pm
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