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Author Topic: Help with X Axis Error offset  (Read 125 times)

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Help with X Axis Error offset
« on: June 12, 2020, 04:59:24 PM »
Dear All,

First, forgive me if this is not the correct place to post this question. I simply could not find another one. After struggling for a while I decided to ask you guys for help. Here is the deal:

I´ve built my DYI CNC from scratch using aluminum profiles and parts that were machined somewhere else. Everything fit perfectly (or with minor adjustments).

I am using Mach4 software and HSMExpress to generate the G-code from the SolidWorks model. I am using a Trapezoidal Screw and stepper motors to move the axis around.

After the first attempt to create a part, I realized that my bed was not flat ( I am using MDF and it came warped). So, I decided to face the surface of the MDF to creat a flat surface with regards to my spindle.

The problem I am facing is that every line it started has some offset from the previous line. Let me try to explain:
  • It starts the first line on X287mm and cuts all the way to X-0.4mm;
  • When in X-0.4mm, it retracts Z to 5mm and goes all the way to X287mm to start cutting again;
  • When it gets back to X-0.4 I can see that it´s not the exact same spot as before. It was slightly to the right;
  • The cycle reapeats and every beggining of a new line we can see it is shifted to the right from the previous one. Also, it´s going further than X287mm;
  • I stop the operation and sit in contemplation;

Trying to find out where the problem is, I created a marking line and jogged the X axis back and forth from 50mm to 270mm. At the end, the carriage was exactly where it started.

Additionally, I cut a square to see if the mill would end at exactly the same spot as it started and it did.

I´ve also switched X and Y motors to see if the error would change axis but it persisted on the X Axis. After doing this, I could see that the offset between the lines was smaller but was there and still increasing. I tried to play around with the backlash compensation but it didn´t change anything.

Have any of you guys ever faced anything like that?

Please forgive my english.

Regards,

marcus