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I'm working on designing a 3d printer with a team. The team is using marlin open source software and I started half way into project trying to make sense of things.

Apparently there is an issue with the wheels moving the print head and it always moves a few mm short in the of the desired position. Can some one tell me which part of the marlin code interprets the G-code file and controls movement? I'm thinking of increasing the distance in the x and y axis to correct this (seemingly) minor problem.

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    $\begingroup$ What does "arc" in the title refer to? It seems like you have more of a mechanical problem, because no amount of software compensation is going to fix "a few mm" of backlash. Marlin has no support for backlash compensation, and adding it in is going to be complicated. $\endgroup$
    – Tom van der Zanden
    Oct 18, 2016 at 7:05
  • $\begingroup$ Does it always cut off a certain distance, or does the distance vary? If you see a constant error rate per distance moved, it could be possible to adjust some stepper motor movement settings. For instance, if your motors always move 20% too short (20mm for a 100mm move, but only 10mm for a 50mm moved, etc...), you could increase the overall stepper motor movement by 20%. $\endgroup$
    – Tormod Haugene
    Oct 18, 2016 at 10:34
  • $\begingroup$ @TomvanderZanden I mean the movement pattern $\endgroup$
    – Jay
    Oct 18, 2016 at 17:40
  • $\begingroup$ @TormodHaugene it is always a fixed distance in both the x and y axis. I was wondering where in the code do I edit stepper motor movement $\endgroup$
    – Jay
    Oct 18, 2016 at 17:43
  • $\begingroup$ I'd suggest you change your title to "Adjusting X and Y axis configuration settings in Marlin Firmware" or something similar to more accurately describe your question. I figure you mentioned "arc" because you know you're translating rotational to linear movement, but my first impression from the title was that you were asking something about moving the print head in an arc. $\endgroup$
    – Chris Thompson
    Oct 19, 2016 at 2:01

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Since your team is designing a printer, you'll have to do some basic calculations to figure out your x and y axis steps per millimeter and then set them in your firmware.

For a decent primer in the basic idea, this video is a good start. For another decent getting started summary check this blog post

Also, since you're using Marlin, become very familiar with the Marlin Firmware and how to configure it. The setting you want to change exists in the configuration.h file. Documentation is included in the file, but you can find good information here in the Marlin Configuration instructions within the Marlin Firmware Github repo.

I hope this helps! :-)

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    $\begingroup$ Note that this answer is correct IF your issue is in the firmware configuration and not a mechanical problem that is causing you to loose steps or experience significant backlash in both the x and y. I suspect that's not the case, but if you nail down your steps per mm setting and are still not getting the expected movement, be sure to spend some time to rule out mechanical issues as your root cause. :-) $\endgroup$
    – Chris Thompson
    Oct 19, 2016 at 1:53

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