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Moving bellow 0.1mm

Posted by serandre 
Moving bellow 0.1mm
February 10, 2018 05:41AM
I have an issue trying to move the steppers bellow 0.1mm. My Delta printer is using 1/8o stepper motors with pulleys with 20t and 1/16 microstep drivers, so all steppers are using 80mm steps/unit in Marlin.

If I try to move for example (I have tested with a dial indicator):

G1 Zx.x5

It doesn't move.

G1 Zx.x7

It moves, but for some reason it rounds to x.x+1

The command M114 shows the axis right numbers (without rouding);

I didn't found in Marlin any settings to fix this. Anyone knows how to fix this ?

So If I need layers at 0.25mm in fact they are been printed at 0.25mm

Edited 3 time(s). Last edit at 02/10/2018 05:44AM by serandre.
Re: Moving bellow 0.1mm
February 11, 2018 11:23PM
Higher levels of Microstepping is BS, It doesnt move 1 position per step, it ignore some steps and then jumps to correct position when it can on the 4 or so step... all it does it reduce noise

reduce micro stepping to 1/4 and then it will move as expected (and even then between pole positions the stepper may not be uniform positions)

it will of course reduce steps to 20 steps mm and your limit is 1/20 0.05mm

If you need more real physical resolution you need 0.9 degree steppers and or geared steppers.
VDX
Re: Moving bellow 0.1mm
February 12, 2018 05:04AM
... if higher microstepping is "effective" or not, depends mainly on the mechanical setup.

With the common RepRap-style setup and relative weak direct drive steppers it's an "ineffective" relation between friction, stip-slick and torque.

With much stronger steppers (2Nm or more torque, instead of some ten mNm as with the typical 3D-printers) and optional gearing, micrsotepping will propagate "stepwise" without stalling or "jumping" (as long it isn't blocked by too high loads).

I have IMS drivers with 1/256 microstepping and 3A current (4A peak), what's pretty good/precise even with highest microstepping with the used NEMA-36 steppers.

Have some other (pretty expensive) linear drives with 5:1 gearing and 2Nm- NEMA-23 steppers, which are wired 3-polar and driven with 325 Volts, where the 10x microstepping is totally accurate "stepwise" too ...


Viktor
Re: Moving bellow 0.1mm
February 13, 2018 06:11PM
Hi.

Just discovered an option in configuration_adv.h:

// Moves (or segments) with fewer steps than this will be joined with the next move
#define MIN_STEPS_PER_SEGMENT 6

Changed it to:
#define MIN_STEPS_PER_SEGMENT 1

Wow, now I got it to work.

Thanks
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