[solved] My Z scale is wrong. Any idea ?

Hi there.

My Techzone Huxley is finally somewhat working now that I replaced it hot end for a mendel-parts V5. Still sometimes got problems with the clamping of the bowden tube, but I'll find a solution.

Now everything I print looks somewhat crushed. I know you all love seeing printed parts so here is one (forget the blob, it was printed with my original leaky hotend) :

So this is supposed to be 1 cm high, but ended up a bit above 7mm. The other dimensions are good.

I also tried to measure the height when manually moving with repsnapper and got that : asked moving up 40 mm ; actually moved 33.33...

The first strange thing is how "round" that error is. This looks like I need exactly to multiply the height by 1.2 to get it fixed.

Now the thing that puzzles me : I changed my Z steps per mm in the firmware and... it did not change the result ! I'm still getting the same height move ratio.

Any idea is welcome for fixing it or getting a workaround in skeinforge (although I doubt that last is the best idea).

Asm me for any details I omitted of course.

Edited 1 time(s). Last edit at 09/29/2011 12:24PM by DeuxVis.

If moving it 40mm only moves 33.33mm then either your STEPS_PER_MM_Z is wrong in the firmware, OR you are losing steps because you are moving the Z axis too fast. How fast is your Z axis moving? It should not generally be faster than 1mm/s (or 60mm/m).

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Thanks,

I thought about skipping, so already tried to avoid that :
- Skeinforge has limit enabled with max z feed rate = 0.2mm/s
- I'll check for repsnapper settings - not at home right now - but I think I lowered Z speed (something like half the default from my bad memory) there too.


Just had another idea, about the firmware not changing anything : Do I need to specify to rebuild after modifying configuration.h, or does arduino software automatically do it before uploading firmware ?

You must of course compile and upload after changing configuration.h.
Nothing is done automatically.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

I did upload, but I assumed the rebuild is automatic before upload. Meeehhh.

Thanks, I'll retry tonite.

Make sure you'd changed the correct Z_STEPS_PER_MM in configuration.h, there are several, but only one has effect.

Ooh, right. Mine is probably the one in the MOTHERBOARD == 3 section. Thanks !

That worked ! Changing the right #define solved it - thanks DetaFlight !

Also had to lower Z_Slow_speed a bit in firmware, so it starts acceleration earlier. Now I have only a 5% error left on the Z sizes, a little more tweaking in the Z_steps_by_mm should do it.