Horizontal lines take on a parabolic arc (similar issues but different)

I have read the issues about the similar issues with a horizontal cut near the top of the work space, and wanted to start a new thread as my issue is slightly different.

My top horizontal cuts are RAISING at the center of the work. The apex of the parabola is at the Y axis. The far left and right edges of the cut are slightly off- which is an issue, but tolerable for my purposes. What makes this different is two fold:

  1. The left and right edges are at the correct location within the workspace- and at the center of the workspace the cut is elevated 1” above where it should be.

  2. I do not have the “peak” at the left and right edges of the cut as others have experienced.

My apologies for the dark picture. I placed an uncut piece of ply so you can see the difference in the cut behind. Stitch was a test cut that my kids painted- but cut spot on as well.

My sled weighs 11.8kg.
I am using the ring set up.
Chains off the top, And calibration done/ done again/ and redone.

Any help is appreciated!

How much is your beam deflecting when it is cutting in the top center? I have a display hanging from my beam and I don’t think I would have noticed it moving it it hadn’t been for that. Is your ring centered and your router centered? Did you use holey calibration?

This just means that calibration is not correct, the direction of the curve just
indicates what direction the net errors end up being. There are a LOT of errors
that can contribute to this result. There is a thread with a topic like sources
of error where we attempted to enumerate all the possible causes.

In practice the care of the rigidity of the frame and measurement in calibration
(and calibration type) matter a lot

the stock calibation routine is pretty poor, it was an improvement over the
first version, but when I suggested it, we really didn’t understand the way the
maslow works.

holey calibration is a big improvement, and there is another new calibration
routine (that requires calculations not in GC/WC) that is supposed to be a big
improvement. I haven’t had the time to dig into it yet.

David Lang

Thank you @Orob:

I haven’t noticed any deflection either, but will look for that. The Holey calibration will be the next step.

@dlang thank you for your reply. I will try the Holey calibration- I did have a thought about the way I have the chains setup, and if it could be the culprit.

My chains come off the top, and hang under the motor in a loop. At the turn in the loop I have added a 2 lb weight rather than using an elastic cord. I did this because of skip in the chain when first set up. Could this counter weight be the cause?

picture please, I’m not sure I’m understanding this. But a weight instead of the
elastic cord is much more likely to help than hurt, but the difference ould be
something you se more towards the bottom corners than the top center.

David Lang

That was my thought- that the weights would provide a counterbalance, and lessen the work on the motors.

I will post a picture ASAP as I am traveling today.

1 Like

Here is the image of how the chains are weighted.

Setting up web control and will run Hoely after I figure out why it is greyed out…!


you have to flash with the holey firmware to use holey clibration

make sure you save your existing settings before switching

David Lang

Thank you David,

I had to take a break and run through it mentally before I came up with the same conclusion.