# Non-Symmetrical Errors **URL:** \ **Category:** Technical Details\ **Created:** [July 23, 2017, 10:40pm UTC](https://forums.maslowcnc.com/t/non-symmetrical-errors/232 "2017-07-23T22:40:57Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![krkeegan](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/krkeegan/32/17443_2.png) [@krkeegan](https://forums.maslowcnc.com/u/krkeegan)\ **Post date:** [July 23, 2017, 10:40pm UTC](https://forums.maslowcnc.com/t/non-symmetrical-errors/232/1 "2017-07-23T22:40:57Z")
I am noticing what appears to be errors that are not mirrored about the central axis of the machine in some of my cuts. To flush it out, I cut a 4 foot long 1 inch tall blank which was centered on the machine horizontally, it was probably about 8-10 inches above the center line vertically. The result was that the right hand side was about .15 inches thinner in height than the left hand side. The difference in height seems to be close to a straight line from one side to the other. Any ideas what might cause this? ---
**Author:** ![blurfl](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/blurfl/32/9_2.png) [@blurfl](https://forums.maslowcnc.com/u/blurfl)\ **Post date:** [July 23, 2017, 11:06pm UTC](https://forums.maslowcnc.com/t/non-symmetrical-errors/232/2 "2017-07-23T23:06:23Z")
No idea, but some questions - Are both the horizontals skewed with respect to the top edge of the workarea sheet or is just one of them skewed? If they are different, is the difference in the right-to-left cut direction, or left-to-right? is one end correctly cut 1” tall, the other off, or are both ends wrong? Looking for some asymmetry in the machine here that might give a clue. ---
**Author:** ![dlang](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/dlang/32/859_2.png) [@dlang](https://forums.maslowcnc.com/u/dlang)\ **Post date:** [July 24, 2017, 1:08am UTC](https://forums.maslowcnc.com/t/non-symmetrical-errors/232/3 "2017-07-24T01:08:29Z")
> Any ideas what might cause this? As a matter of looking at the code, it makes all it’s calculations on the left side and then just switches the chain lengths for the right side, so errors that are not symmetric from one side to the other indicate some sort of mechanical problem, not software problem. Are you sure you start off with the chain lengths the same? ---
**Author:** ![krkeegan](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/krkeegan/32/17443_2.png) [@krkeegan](https://forums.maslowcnc.com/u/krkeegan)\ **Post date:** [July 24, 2017, 2:00am UTC](https://forums.maslowcnc.com/t/non-symmetrical-errors/232/4 "2017-07-24T02:00:43Z")
> [@blurfl](#): > > Are both the horizontals skewed with respect to the top edge of the workarea sheet or is just one of them skewed? They are both skewed by about the same amount. The top cut on the left side is 1/16 higher than the right and the bottom cut is 1/16 lower than the right. > [@dlang](#): > > indicate some sort of mechanical problem, not software problem. I figured as much. > [@dlang](#): > > Are you sure you start off with the chain lengths the same? I certainly thought so, but I guess that is worth recalibrating the chain lengths. ---
**Author:** ![blurfl](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/blurfl/32/9_2.png) [@blurfl](https://forums.maslowcnc.com/u/blurfl)\ **Post date:** [July 24, 2017, 2:05am UTC](https://forums.maslowcnc.com/t/non-symmetrical-errors/232/5 "2017-07-24T02:05:44Z")
You might want to mark the chain link at the top of each sprocket when the calibration finishes. I used a white paint marker, nail polish would work too. This way you can quickly check to see if the changes are “right“ in the future. ---
**Author:** ![dlang](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/dlang/32/859_2.png) [@dlang](https://forums.maslowcnc.com/u/dlang)\ **Post date:** [July 24, 2017, 3:22am UTC](https://forums.maslowcnc.com/t/non-symmetrical-errors/232/6 "2017-07-24T03:22:04Z")
someone should add this suggestion to the assembly wiki (I don’t have time right now, I’ll try to do it later if someone else doesn’t do it first) ---
**Author:** ![jwolter](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/jwolter/32/30787_2.png) [@jwolter](https://forums.maslowcnc.com/u/jwolter)\ **Post date:** [July 25, 2017, 11:30am UTC](https://forums.maslowcnc.com/t/non-symmetrical-errors/232/7 "2017-07-25T11:30:22Z")
I don’t even see a reference to calibration in the assembly wiki. I think we need a step 8. ---
**Author:** ![blurfl](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/blurfl/32/9_2.png) [@blurfl](https://forums.maslowcnc.com/u/blurfl)\ **Post date:** [July 25, 2017, 1:33pm UTC](https://forums.maslowcnc.com/t/non-symmetrical-errors/232/8 "2017-07-25T13:33:18Z")
@krkeegan, I see you’ve written a [PR#374](https://github.com/MaslowCNC/GroundControl/pull/374) in GroundControl to simulate a slipped chain - was this the cause of the distortion you wrote about? If not have you narrowed it down? ---
**Author:** ![krkeegan](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/krkeegan/32/17443_2.png) [@krkeegan](https://forums.maslowcnc.com/u/krkeegan)\ **Post date:** [July 25, 2017, 5:13pm UTC](https://forums.maslowcnc.com/t/non-symmetrical-errors/232/9 "2017-07-25T17:13:21Z")
> [@blurfl](#): > > was this the cause of the distortion you wrote about? Based on what the distortion showed, I don’t think so. I need to center the sled, mark the chains and then rerun the chain calibration, but I bet I will see that it has not changed. I am confident I am seeing some dimensional distortion, inches are smaller in certain areas of the workspace. But I need to spend a little more time characterizing it. I think I can borrow a laser grid projector which might allow me to do the simulation presentation in real life. ---
**Author:** ![krkeegan](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/krkeegan/32/17443_2.png) [@krkeegan](https://forums.maslowcnc.com/u/krkeegan)\ **Post date:** [July 27, 2017, 5:06am UTC](https://forums.maslowcnc.com/t/non-symmetrical-errors/232/10 "2017-07-27T05:06:32Z")
I redid the chain calibration tonight. It turned out exactly the same. I think the next thing I am going to do is confirm that this is happening buy cutting a 1 inch square block in multiple locations on the work piece and then comparing their dimensions.