Calibration Cube XYZ is off, how to adjust Axis length

duetino

Hi,
I have a Tevo Little monster and printed the testcube (https://www.thingiverse.com/thing:2145703), because all of my prints where not really fitting together. I know why now, since I never paid attention on how the WCS was aligned (on a delta it does not matter I thought)
As i measured all the sides and get the following reading:

X: 20.2
Y: 19.99
Z: 20.01

As you can see the Y and Z Axis have an acceptable deviation, but X is far off limits.

My Question is where and how can I feed some correction factors into the machine? gcode?

dc42

The easy way is https://duet3d.com/wiki/G-code#M579:_Scale_Cartesian_axes. But I suggest you measure a print larger than 20mm.

duetino

Thank you I will print a upscaled hiphop uptodate cube to get accurate settings. Do you think that 100x100x100 is the right dimension?
all the best

duetino

Hi, thanks for the response and which leads me to the following questions:

@dc42:

The easy way is https://duet3d.com/wiki/G-code#M579:_Scale_Cartesian_axes. But I suggest you measure a print larger than 20mm.

… that that does not so directly apply on deltas or am I unright and the wiki does not know the duet3d controller?

https://duet3d.com/wiki/G-code#M579:_Scale_Cartesian_axes here is says …

But this does not work so easily for Delta and other RepRaps for which there is cross-talk between the axe

please let me know before I print a monster cube

fma

I also noticed such deviation on X axis. I didn't dig yet, but is changing the scale the right answer?

I mean, it can be an extrusion problem, so tuning scale on a 100x100 square won't fix the problem on a 20x20 square.

So, I suggest you first try to see if it is really a scale problem, by printing a 100x100 square (100x100x2 cube, as you don't need to calibrate Z; even a 100x2x2 should be ok, if you only want to check X), and see if you get something like 101x100x2 (10% more on X).

fma

In fact, you can first try to measure the head move with a good ruler, without extruding. 10% of 200mm is 2mm, so easy to see.

duetino

Hi, I'm talking about a tenth of a millimeter on X, which is way off, since Y and Z only have a hundredth deviation

dc42

M579 can be used to correct axis scaling on any type of printer. The "this does not work so well for a delta printer" bit refers to adjusting the tower steps/mm instead as described in the preceding sentence.

You should also check that the X and Y sides of a large cube or square are straight, not bowed inwards or outwards.

fma

Duetino, if your problem is really a scaling problem, when moving 200mm you should measure 202mm, which is easy to see. If you still have 0.2mm more, this means this is not a scaling problem! In this case, if you correct the scale for 20mm, a 200mm print will be something to 198.2mm…

So, first, move your axes as far as you can (200mm), and measure with a ruler.