# Dimensional Accuracy Biased Too Big XY

**URL:** <https://forum.lulzbot.com/t/dimensional-accuracy-biased-too-big-xy/6792>\
**Category:** LulzBot Mini\
**Created:** [July 10, 2019, 5:47am UTC](https://forum.lulzbot.com/t/dimensional-accuracy-biased-too-big-xy/6792 "2019-07-10T05:47:58Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Maxparker72](https://avatars.discourse-cdn.com/v4/letter/m/e8c25b/32.png) [@Maxparker72](https://forum.lulzbot.com/u/Maxparker72)\
**Post date:** [July 10, 2019, 5:47am UTC](https://forum.lulzbot.com/t/dimensional-accuracy-biased-too-big-xy/6792/1 "2019-07-10T05:47:58Z")

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Hey Guys!

So, I have a second hand Lulzbot mini and I am still trying to get familiar with the printer. First, I do want to ask opinions on calibration/what to check since it’s second hand. Secondly, I am puzzled by a recent experiment I performed. I printed 12 20mm test cubes and recorded their actual dimensions with calipers in excel. My goal was to find an average dimensional error so I could determine my printer’s accuracy (eg: my printer can print to +/- 0.15mm). Instead, I found that my printer was pretty consistent but not accurate. My X axis was biased too large while my Z is biased too small. It might be easier to take a look at the screenshot I attached to see what’s going on. I’m curious if this is normal, just my printer, all lulzbot minis, or if there is something I can tweak physically or in software.

I appreciate the help. Thanks!

 ![Screen Shot 2019-07-09 at 10.49.54 PM.png](https://us1.discourse-cdn.com/flex020/uploads/lulzbot/original/2X/6/62f37ac024a3ab16dc0c9333139a0d7aee1a1eb9.png)

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**Author:** ![nopick](https://avatars.discourse-cdn.com/v4/letter/n/7bcc69/32.png) [@nopick](https://forum.lulzbot.com/u/nopick)\
**Post date:** [July 10, 2019, 12:48pm UTC](https://forum.lulzbot.com/t/dimensional-accuracy-biased-too-big-xy/6792/2 "2019-07-10T12:48:57Z")

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For the X and Y, I would start with an extruder calibration. Over extrusion will produce a part larger that the design size. Make sure you are actually extruding 100mm when you command a 100mm extrusion. Adjust your ESTEPS value to correct over or under extrusion. If the extruder is moving the correct amount of filament, you can tweak the flow rate for a given filament in the slicer. Here is an info page about adjusting steps per mm from terminal commands if you don’t have an LCD display on the Mini. [http://marlinfw.org/docs/gcode/M092.html](http://marlinfw.org/docs/gcode/M092.html)

Your Z measurements look pretty good. For my purposes, I wouldn’t worry about it. If you want to try to dial that better than what it is, I would suggest getting X and Y corrected and see what happens to Z. Z steps per mm can also be tweaked with M092 but you might find yourself chasing the mechanical limits of the machine.

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**Author:** ![Keebie81](https://avatars.discourse-cdn.com/v4/letter/k/858c86/32.png) [@Keebie81](https://forum.lulzbot.com/u/Keebie81)\
**Post date:** [July 12, 2019, 10:48pm UTC](https://forum.lulzbot.com/t/dimensional-accuracy-biased-too-big-xy/6792/3 "2019-07-12T22:48:33Z")

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The issue is the mini 1 and taz6 and lower all use 100.5 steps/mm on x and y. It should be 100, the mini2 uses 100 now.