# Calibration Issues, maybe scaling? **URL:** \ **Category:** Troubleshooting\ **Created:** [September 30, 2018, 1:53pm UTC](https://forums.maslowcnc.com/t/calibration-issues-maybe-scaling/7006 "2018-09-30T13:53:42Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![AHancock](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/ahancock/32/9450_2.png) [@AHancock](https://forums.maslowcnc.com/u/AHancock)\ **Post date:** [September 30, 2018, 1:53pm UTC](https://forums.maslowcnc.com/t/calibration-issues-maybe-scaling/7006/1 "2018-09-30T13:53:42Z")
I have calibrated and recalibrated several times and have just performed the calibration benchmark test (which I will post the results to soon). My question is, what would usually cause improper scaling of coordinates? My system thinks it is at the top of the cut surface when it is actually 3.5 inches shy, and it thinks it is at the bottom surface when it is an inch past. ---
**Author:** ![Bee](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/bee/32/2160_2.png) [@Bee](https://forums.maslowcnc.com/u/Bee)\ **Post date:** [September 30, 2018, 3:53pm UTC](https://forums.maslowcnc.com/t/calibration-issues-maybe-scaling/7006/2 "2018-09-30T15:53:11Z")
@AHancock welcome to the group. When I do calibration I’m working in MM. You could try offsetting the distance from the top beam when entered. I suspect @dlang or others will have a better answer. Thank you ---
**Author:** ![Gero](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/gero/32/17487_2.png) [@Gero](https://forums.maslowcnc.com/u/Gero)\ **Post date:** [September 30, 2018, 4:53pm UTC](https://forums.maslowcnc.com/t/calibration-issues-maybe-scaling/7006/3 "2018-09-30T16:53:25Z")
Sadly being off on Y seems common. Do a sanity check and compare your groundcontrol.ini settings with hand measured values. Values that will change Y are: [Maslow Settings] motoroffsety = 333 motorspacingx = 3505 [Advanced Settings] rotationradius = 140.0 Use with caution as this values go into further calculations and getting X0/Y0 in the centre of your sheet, could throw off coordinates on other parts of the sheet. ![image](https://canada1.discourse-cdn.com/flex031/uploads/maslowcnc/original/2X/c/c16f5a029d492f7261f9badf545dd7f44b348065.png) ---
**Author:** ![madgrizzle](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/madgrizzle/32/1372_2.png) [@madgrizzle](https://forums.maslowcnc.com/u/madgrizzle)\ **Post date:** [September 30, 2018, 6:21pm UTC](https://forums.maslowcnc.com/t/calibration-issues-maybe-scaling/7006/4 "2018-09-30T18:21:19Z")
> [@AHancock](#): > > My question is, what would usually cause improper scaling of coordinates? My system thinks it is at the top of the cut surface when it is actually 3.5 inches shy, and it thinks it is at the bottom surface when it is an inch past The current calibration model adjusts three parameters, the rotational radius, height of motor above worksurface, and chain sag correction factor to match, to the greatest extent possible, the three measurements you entered. There are certain assumptions made by the calibration process and if those assumptions are bad, then the calibration will be bad. For instance, if your top beam is tilted, that will introduce error. if your chains are worn unevenly (or even constructed improperly), that will introduce error. If your router is not perfectly aligned with the center of rotation of your linkage kit, that will introduce error. The problem with those potential errors is that the program is still trying to adjust those three parameters to make it work. So, it looks like it probably raised the height of the motors above the worksurface and increased the rotational radius to overcome some issue. what values for those do it arrive at? ---
**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:** [September 30, 2018, 8:53pm UTC](https://forums.maslowcnc.com/t/calibration-issues-maybe-scaling/7006/5 "2018-09-30T20:53:37Z")
> Sadly being off on Y seems common. small errors in chain length translate into large vertical errors in the center (as much as 2x the chain length error) > Do a sanity check and compare your groundcontrol.ini settings with hand measured values. > > Values that will change Y are: > [Maslow Settings] > motoroffsety = 333 > motorspacingx = 3505 > [Advanced Settings] > rotationradius = 140.0 This is the first thing to do, it’s very common for the current calibration routine to change things to incorrect values. the fact that it’s high on the top and low on the bottom means it’s not the motoroffsety,but is probably either motor spacing, rotation radius, or your chains are stretched. David Lang ---
**Author:** ![AHancock](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/ahancock/32/9450_2.png) [@AHancock](https://forums.maslowcnc.com/u/AHancock)\ **Post date:** [September 30, 2018, 11:04pm UTC](https://forums.maslowcnc.com/t/calibration-issues-maybe-scaling/7006/6 "2018-09-30T23:04:23Z")
I plan to remeasure the three variables prompted in manual calibration (rotation radius, motor spacing, vertical gap). Do you recommend measuring true chain length and putting that in advanced settings? ---
**Author:** ![AHancock](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/ahancock/32/9450_2.png) [@AHancock](https://forums.maslowcnc.com/u/AHancock)\ **Post date:** [September 30, 2018, 11:05pm UTC](https://forums.maslowcnc.com/t/calibration-issues-maybe-scaling/7006/7 "2018-09-30T23:05:36Z")
I’ll get those values to you when I get the chance, with the work week starting it might be a few days.