X-Carriage replacement and problem

Hello all

Yesterday I replaced the X-carriage part on my Mendel90. All was ok, the assembly was done as the manual rules, the x-axis moves smoothly and the printer prints. But, the final dimensions of the printed parts in the X axis are smaller than the STL file. The test parts were some plates of 25mm and 90mm of width and final dimensions were of 24mm and 88mm respectively.

Any ideas about that?

Can it be that the belt isn't running in a straight line and therefor moving a different length as it gets closer or further away from the belt pulley or motor pulley? Do you have a photo? Did you upgrade anything in the firmware? Did any of the belt pulleys get replaced by a bigger pulley by any chance?

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http://www.marinusdebeer.nl/

Other than perhaps the belts being very slack, I can't think what would reduce the size by so much in both x and y.

Tighter belts stretch slightly so will have a slightly bigger pitch but I don't think it normally makes so much difference.

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[www.hydraraptor.blogspot.com]

Hello all

Thanks for your answers.
These gave me something to think about. I adjusted the tension of the belt.
I made a test to check any mechanical issue and it was ok. I manually moved the head to signal different positions on the bed and it moved to the correct coordinates. See the white spots on the paper in the attached image.
Now I am printing one part to test the final dimensions.