Scaling factors in Duet?

Apologies, but this is another of those dumb questions...

I've been setting up the '.g' files for Duet, ready for the time when I install it in my new CoreXY printer. Going through each step I think I can understand what each line is trying to achieve, but I have one puzzle - in Marlin you use the following configuration.h line to define how many steps each motor must take to move one unit:

#define DEFAULT_AXIS_STEPS_PER_UNIT {80.0,80.0,4000.0,789.48}

This is, in order, the steps for x, y, z and extruder (taken from the Marlin setup for my Prusa i3).

I was wondering if there should be an equivalent statement in Duet's config.g file? If not, how is scaling handled?

Hi David,

I have setup the step of my printer using the gcode M92.

I using 1/32 stepper, you have a duet then you must use 1/16.
The calculation for your printer:

Steps per mm for belt (X and Y axes)
= ( motor steps per revolution * microstepping ) / ( number of pulley teeth * belt tooth pitch )
= ( 200 * 16 ) / ( 20 * 2.032 ) = 88.583

Steps for leadscrew (Z axis)
= ( motor steps per revolution * microstepping ) / thread pitch
= (200 x 16) / 2
= 1600

Extruder using an mk8 -> 144
for the extruder do not simply use this value, you need to test your extruder. try to find an value that allow to retract 10 cm of filament.

add the next line to config.g
M92 X88.583 Y88.583 Z1600 E144

Edited 3 time(s). Last edit at 10/20/2015 12:34PM by filipeCampos.

Thank you, Filipe!

The M92 command wasn't shown in the example config.g code in the RepRap wiki - although I admit that it is in the list of G codes the wiki shows elsewhere.

I can cope with setting the extruder feed rate - I've done that quite a few times in Marlin, and this doesn't look a lot different in principle. Initially I will be using a geared Wade-style extruder for bowden, so I will do those tests when everything is set up.

David

Quote
David J
The M92 command wasn't shown in the example config.g code in the RepRap wiki - although I admit that it is in the list of G codes the wiki shows elsewhere.

Thanks for pointing this out. I have just added it to [reprap.org].

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I have made an error, for the Z axis.

If you are using the same i have, each complete rotation the z screw move 8mm, them:

Steps for leadscrew (Z axis)
= ( motor steps per revolution * microstepping ) / thread pitch
= (200 x 16) / 8
= 400

M92 X88.583 Y88.583 Z400 E144

Edited 1 time(s). Last edit at 10/20/2015 02:31PM by filipeCampos.

I thought that was a lot of steps per millimetre! That Z screw has quite a steep pitch on the thread...

I'll make the amendment right away...

Edited 1 time(s). Last edit at 10/20/2015 03:12PM by David J.

Quote

= ( 200 * 16 ) / ( 20 * 2.032 ) = 88.583

Is it common sense that a GT2 belt has 2.032 pitch? I always calculate with 2.0mm..
-Olaf

very good question...
I found these formulas in the online help of the reprap, but i was thinking is was the value for the GT2 belt.

I googleled about 2.032mm Vs 2mm and found that the GT2 was an 2.0mm pitch and them the MXL belt was 2.032mm.
The formula is for MXL belts.
I do not now why there is an MXL and GT2 belts, there have almost the same value and same aplication. Some smart guy remember one day that will be an good idea to create a new one with plus 0.032mm...

In my case i have GT2 belt and i was using the wrong values.

calculator

Edited 1 time(s). Last edit at 10/21/2015 12:42PM by filipeCampos.

I keep forgetting about that calculator page.

Filipe - I guess that the value for X and Y should be 80 for GT2 belts.

Quote
David J
Filipe - I guess that the value for X and Y should be 80 for GT2 belts.

correct.


By the way, this week i printed an arm to install an tablet in the g&c printer using reprapfirmware and these wrong values of x and y.
After i checked theirs dimension i have noticed there off some millimeters, but i not make an big deal of it.