Bending Correction - A solution for bending during printing?

Scottty

Hi, my printer is a self made CoreXY with moving bed, which is rail guided at the backside.

With BLTouch I perform autolevel (3 points , close to 3 adjusting screws) as well as distortion correction, which works well except one issue:

Printing test lines (Layer height 0,3, extrusion width 0,6mm) I found, that the resulting line thickness is 0,3 at the front side of the bed, and 0,2mm at the back side.

Probably bed bending during printing causes this issue.

So I tried to set bendingCorrection_A and _B to 0.1mm in EEPROM setting. No more G32 or G33 or reboot.

The result was: no effect of bending correction.

My question: Is BendingCorrection a good way to solve this issue and , if yes, do I need to more steps to activate bending correction or should it be enought just to change EEPROM settings and reprinting my test lines.

Thanks in advance for your help!

Repetier

First update to latest 1.0.4dev - there was a problem that it did not always go to start height so it could accumulate an error. If that happened here it explains the error in correction.

Bending correction is not the way to go here. That is if you need a good potion of force to trigger z probe so bed bends. And I know BLtouch needs nearly no force.

Scottty

Thanks for your reply!

• Updating to V1.0.4 would be a big job for me since I did several changes, most of them for BLTouch implementation, which are working really fine now. And in V1.0.4 there are a lot of just format changes like line feeds, which make it complicate to search for differences.
  I'm no software engineer, so I invested a lot of time to reach this. So I tend to wait for V2.
  Maybe I try to find the fix you are talking about and try tp copy it to my 1.0.3.
  Where do I find it? Bedlevelling.cpp?
• Since I felt so close I tested to fix my 0,1mm difference from bed backside to front side I gave bendingCorrection a chance - and it worked!
  In this link there is a screenshot from heightmaps showing
  - bed without correction
  - bed with G32 and G33
  - including bendingCorrection, again G32
  https://1drv.ms/u/s!Akv1JUPvfLrzhKQP2SCJG3Txd7_VoQ?e=QISXO6
  
• by the way: I want to donate for your really fast and excellent support. How to?
  

Repetier

Yes, fix would be in Bedleveling.cpp in the last few month. Guess the commit headline on github would give a hint.

For donation you can go here: https://www.repetier.com/download-software/
Meant for donating to support host but money comes to us same way:-)