1 Topic by Claghorn

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Topic: with M3 Z rod, 0.1mm layers thicker than 0.1mm?

I obviously need to do more investigation, but having switched to a M3 Z screw everything seemed to print well till I tried printing at 0.1mm layer height last night, and the printed object seemed to grow in Z by about 10%. Before I do a lot of investigation and test prints at different layer heights, I just thought I'd ask if this strikes a familiar note with anyone? (Like maybe a known firmware arithmetic bug when Z steps/mm is a bigger number like 6400?)

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2 Reply by wardjr

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Re: with M3 Z rod, 0.1mm layers thicker than 0.1mm?

Is it possible that you are just over on your steps per mm and therefor for every mm the distance compounds.

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3 Reply by Claghorn

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Re: with M3 Z rod, 0.1mm layers thicker than 0.1mm?

wardjr wrote:

Is it possible that you are just over on your steps per mm and therefor for every mm the distance compounds.

Yea, but you'd think that in Z the calculation that leads to 6400 would be exact, and I've printed 3mm layer height objects that needed to match the physical dimensions exactly, and they came out perfect (as near as I can tell).

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4 Reply by IronMan

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Re: with M3 Z rod, 0.1mm layers thicker than 0.1mm?

Could you be losing steps because of the increased speed? Try slowing it down...since it is Z, it does not need to move that quickly.

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5 Reply by Claghorn

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Re: with M3 Z rod, 0.1mm layers thicker than 0.1mm?

IronMan wrote:

Could you be losing steps because of the increased speed? Try slowing it down...since it is Z, it does not need to move that quickly.

If I was losing steps, I'd expect things to be shorter not taller :-).

But I have wondered if there are any recommendations for changes to make to Z acceleration and speed settings after switching to M3.

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6 Reply by wardjr

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Re: with M3 Z rod, 0.1mm layers thicker than 0.1mm?

Claghorn wrote:
wardjr wrote:

Is it possible that you are just over on your steps per mm and therefor for every mm the distance compounds.

Yea, but you'd think that in Z the calculation that leads to 6400 would be exact, and I've printed 3mm layer height objects that needed to match the physical dimensions exactly, and they came out perfect (as near as I can tell).

Are you sure you are using the correct pitch in your calculation though?

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7 Reply by Claghorn

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Re: with M3 Z rod, 0.1mm layers thicker than 0.1mm?

wardjr wrote:

Are you sure you are using the correct pitch in your calculation though?

Can't say I'm sure of anything at this point :-). Back over in the original post about switching to M3, it says the stepper is 1.8 degree per step, which is 200 steps for a full rotation, and M3 is .5mm pitch, so thats 400 steps per 1 mm, but the printrboard drivers use 16x microstepping so that 16*400 == 6400.

Anyway, I definitely need to do some test prints (when I get home later today) and see if this really does only happen when the layer height is set to 0.1mm. I'm certainly confused right now.

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8 Reply by wardjr

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Re: with M3 Z rod, 0.1mm layers thicker than 0.1mm?

I don't see any problems in your calculations.  I am curious to see what you come up with.

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9 Reply by IronMan

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Re: with M3 Z rod, 0.1mm layers thicker than 0.1mm?

Claghorn wrote:

If I was losing steps, I'd expect things to be shorter not taller :-).

Yep...I glossed over the the "Growing" part big_smile

It is strange that 0.3 resolution comes out correct.  How many layers are the pcs you are measuring?

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10 Reply by Claghorn

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Re: with M3 Z rod, 0.1mm layers thicker than 0.1mm?

IronMan wrote:

It is strange that 0.3 resolution comes out correct.  How many layers are the pcs you are measuring?

The 0.1mm part I printed last night was quite tall - the model says it is 90.11 mm, but the printed part came out real close to 100mm (and looked very well printed with nice uniform layers, each one of which must have been slightly too thick :-). Maybe I'll print the same part at .2 and .3 to see if it really is different with different layer heights.

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11 Reply by IronMan

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Re: with M3 Z rod, 0.1mm layers thicker than 0.1mm?

That sounds like a good test...

Was the .3 print sliced from the same .stl?  Just wondering if it got accidentally scaled for some reason...

Also, note how many layers are created/called out after the slices...see if that calculated height is in line with your original CAD model height.

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12 Reply by jagowilson (edited by jagowilson 2014-12-19 03:15:53)

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Re: with M3 Z rod, 0.1mm layers thicker than 0.1mm?

Id say grab a dial indicator. Does 0.1mm of movement with manual controls result in 0.1mm of difference on the dial?

13 Reply by tealvince

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Re: with M3 Z rod, 0.1mm layers thicker than 0.1mm?

Claghorn wrote:

The 0.1mm part I printed last night was quite tall - the model says it is 90.11 mm, but the printed part came out real close to 100mm (and looked very well printed with nice uniform layers, each one of which must have been slightly too thick :-). Maybe I'll print the same part at .2 and .3 to see if it really is different with different layer heights.

I'd check the z-code for the .1mm print in a text editor to see where the z-level was supposed to end up.  Maybe it didn't slice correctly.

14 Reply by accusedmonk

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Re: with M3 Z rod, 0.1mm layers thicker than 0.1mm?

My m3 seems to give me shorter prints.  I have the same 6400 steps per mm.   I attributed mine to the squished first layer.  I want to add a second hot end just to at least print a layer of dissolvable raft support.

I recommend the dial indicator as well.  I made a mount for mine to go on the rails.

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15 Reply by Claghorn

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Re: with M3 Z rod, 0.1mm layers thicker than 0.1mm?

Well, I finally got a chance to get back to this after spending a couple of weeks finishing a vast array of mods to the printer, and it doesn't seem to be a problem any more :-). This will forever remain a mystery, but if I had to guess, I'd guess that somehow (completely without noticing) I managed to set the Z axis scale factor when loading the model.

In case anyone is interested, these are parts for a sonic screwdriver, and the printer works so much better after all my mods, I now need to reprint all the rest of the parts before painting and assembling it.

http://home.comcast.net/~tomhorsley/har … sonic.html

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