Not straight angel

nerdegutta

Not straight angel
February 10, 2015 07:48AM

Registered: 9 years ago
Posts: 41

Hi,

What is causing this?

The angles are not 90 degrees, as it should be. The X- and Y- axis are the same, and both are calibrated correct. They run 100mm when told to.
Could it be that the axis are not 90deg on eachother?

- nerdegutta

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the_digital_dentist

Re: Not straight angel
February 10, 2015 08:22AM

Registered: 11 years ago
Posts: 5,780

What are we looking at here?

You can test the orthogonality of the axes by printing a rectangular object and measuring the diagonals. If the axes are orthogonal, the diagonals will be the same length. That works for checking the Z axis orthogonality to Y and X axes also. Print a rectangular solid and measure diagonals in the YZ and XZ planes.

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Ohmarinus

Re: Not straight angel
February 10, 2015 08:32AM

Admin
Registered: 11 years ago
Posts: 3,096

Question one should be: Is your frame square?

I think printing rectangular objects is what the poster shows us in the first picture against an angle hook.

http://www.marinusdebeer.nl/

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nerdegutta

Re: Not straight angel
February 10, 2015 11:03AM

Registered: 9 years ago
Posts: 41

Quote
Ohmarinus
Question one should be: Is your frame square?

I think printing rectangular objects is what the poster shows us in the first picture against an angle hook.

That is correct.

My caliper measure 95.80mm one way, and 98.26 the other way.

I recon the Y is not excactly 90deg on the X.

- nerdegutta

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IMBoring25

Re: Not straight angel
February 10, 2015 11:04AM

Registered: 9 years ago
Posts: 351

Questions can be better addressed with more details. If this is a Cartesian bot it almost has to be a mechanical issue with your X and Y axes not traveling orthogonally to each other.

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nerdegutta

Re: Not straight angel
February 10, 2015 11:17AM

Registered: 9 years ago
Posts: 41

This is a homemade Reprap Prusa.

I printed the parts on my first 3d printer, and then I bought some smooth- and threaded rods. Along with some linear ball barings.

I'll guess I have to double and triple check the alignment.

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nerdegutta

Re: Not straight angel
February 10, 2015 01:07PM

Registered: 9 years ago
Posts: 41

Found the error. smiling smiley

The X and Y is not in perfect 90 deg on each other. I placed a piece of paper on the hotbed and hold a pencil on the extrudermount. While holding the pencil I marked a square with the X and Y axis. It turns out one way is 187mm and the other is 192. That is 5mm, out of course. angry smiley

- nerdegutta

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dc42

Re: Not straight angel
February 10, 2015 02:33PM

Registered: 10 years ago
Posts: 14,672

Best solution is to correct the mechanical error in the angle between the axes. However, if your firmware supports axis compensation, you can correct for it in firmware, either by changing the configuration file or by sending appropriate gcodes.

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

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nerdegutta

Re: Not straight angel
February 10, 2015 02:45PM

Registered: 9 years ago
Posts: 41

I changed the mechanical part. I don't think
Marlin Prusa i3 supports corrections.

- nerdegutta

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nerdegutta

Re: Not straight angel
February 10, 2015 03:36PM

Registered: 9 years ago
Posts: 41

I've adjusted the Y-axis, and now the print looks like it's good.

- nerdegutta

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the_digital_dentist

Re: Not straight angel
February 10, 2015 07:12PM

Registered: 11 years ago
Posts: 5,780

I made a spreadsheet for calculating the amount of error and the required correction based on the length of your printer's axes. You can DL the spreadsheet here:
[mark.rehorst.com]

You tell it the size of the rectangle you're printing, then give it the length of the long diagonal and it will tell you the error (how far from 90 degrees the axes are apart), and tell you how much you have to move one end of one axis to correct the problem.

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Ohmarinus

Re: Not straight angel
February 11, 2015 01:19PM

Admin
Registered: 11 years ago
Posts: 3,096

Overly complicated dentist, however, I like the effort winking smiley

A Prusa i3 can be corrected in a few ways. The threaded rods on the bottom can be corrected a little bit to get the frame more square.

http://www.marinusdebeer.nl/

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nerdegutta

Re: Not straight angel
February 12, 2015 02:20AM

Registered: 9 years ago
Posts: 41

Quote
the_digital_dentist
I made a spreadsheet for calculating the amount of error and the required correction based on the length of your printer's axes. You can DL the spreadsheet here:
[mark.rehorst.com]

You tell it the size of the rectangle you're printing, then give it the length of the long diagonal and it will tell you the error (how far from 90 degrees the axes are apart), and tell you how much you have to move one end of one axis to correct the problem.

Sweet!

Thanks a lot!

- nerdegutta

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