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Offset from HomingOrigin

Posted by Sompy 
Offset from HomingOrigin
June 12, 2016 02:06PM
Hallo

I just have bought the smartrapcore alu kit.
The assembling of the mechanic parts was pretty easy and well documented.
Its my first printer and now i have some questions about the calibration.

First questions is about the Calibration of the printing bed.
In the Documentation of the Kit is one picture that shows the Offset from the Homing-Position to the Start (Left Cornor ) of the Printbed.


How i can tell the Printer that my Printbed starts with the Offset 20/30 from HomingOrigin ( x/y Endstops ) ?
In the Documentation they only use the M500 Command

I hope you can help me with that

Sompy
Re: Offset from HomingOrigin
June 14, 2016 06:05AM
If you are using the firmware that comes with the printer (which is Marlin 1.0.0 unless they have changed it) the best way IMO is to change this section in configuration.h

// The position of the homing switches
//#define MANUAL_HOME_POSITIONS  // If defined, MANUAL_*_HOME_POS below will be used
//#define BED_CENTER_AT_0_0  // If defined, the center of the bed is at (X=0, Y=0)

//Manual homing switch locations:
// For deltabots this means top and center of the Cartesian print volume.
#define MANUAL_X_HOME_POS 0
#define MANUAL_Y_HOME_POS 0
#define MANUAL_Z_HOME_POS 0
//#define MANUAL_Z_HOME_POS 402 // For delta: Distance between nozzle and print surface after homing.

So uncomment define manual_home_positions
then enter the x and y values you have above, they should be negative so it would read
#define MANUAL_X_HOME_POS -20
#define MANUAL_Y_HOME_POS -30

Then upload the firmware to the board using Arduino IDE.

What will then happen when you home, is x and y move to their physical endstop switch positions, but the firmware considers the coordinates to be -20,-30 (x,y), then on the next move command (often to go to bed centre to home z) Marlin moves these distances then begins at 0,0 which is physically at 20,30 from the endstops.

If you have travel limits defined, which you do by default these are also called software endstops
// Travel limits after homing
#define X_MAX_POS 190
#define X_MIN_POS 0
#define Y_MAX_POS 180
#define Y_MIN_POS 0
#define Z_MAX_POS 160
#define Z_MIN_POS 0
then it will not move below 0,0 unless it receives a home command.

I have copied these sections from Smartfriendz github for SmartrapCore Alu which you can get here:
[github.com]

Once you have a handle on how it all works (in a few months time probably) I'd consider configuring a later marlin version for your printer and tweaking a lot of the default settings, I binned the default firmware after about 20 minutes. Let me know when you want to do it I have some versions that should work with a few tweaks.

Edited 2 time(s). Last edit at 06/14/2016 06:08AM by DjDemonD.


Simon.

[www.precisionpiezo.co.uk] Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters. PT1000 cartridge sensors plug straight into duet boards and others.
Published:Inventions
Re: Offset from HomingOrigin
June 23, 2016 12:13PM
Hallo DJDemond

Im Sorry for my late reply i was busy alot.
Thank you for all the Information ! It was a good point to start.
I have downloaded the File from ....
[github.com]

The Configuration of the new Homing was quit easy because of your information.
But it seems to be that i have overwrite some other configurations because my printer now just run the half way on both axis.
When i tell the Printer to run 10 cm on the X-Axis it just run 5 cm ... the same on all axis.
Can you tell me the Values for the Axis ? I thought they have all the major Values allready changed for the Printer but it seems to be that i have to calibrate it from scratch after uploading the Marlin Firmware

Edited 1 time(s). Last edit at 06/23/2016 12:15PM by Sompy.
Re: Offset from HomingOrigin
June 23, 2016 12:51PM
Your steps are probably off in the configuration.h file. The kit I received included (4) DRV8825 boards instead of the (4) A4988 boards. This means your microstepping is 1/32 and not 1/16, so your X and Y should be 160 and not 80 with the GT2 belt and pulley setup.

One thing to note that I noticed with my kit build, if you offset your home to something besides 0,0, your print area won't be 200x200 anymore and will be less. The only workaround I've seen is to move the heatbed so the 0,0 is under the hotend when your sitting on the endstops.
Re: Offset from HomingOrigin
June 23, 2016 01:05PM
@sompy - Hi that's cool. I think PDBeal has it nailed on the steps/mm.
@pdbeal setting a home offset like this and then making sure your travel limits are correct will not limit your travel across the bed unless that's a limitation in marlin 1.0.x in all 1.1.0 RC versions it works just fine
My offsets are x-7 y-39 and my travel limits are x0-280 y0-200 z-3 - 170 on my enlarged machine.

Edited 1 time(s). Last edit at 06/23/2016 01:06PM by DjDemonD.


Simon.

[www.precisionpiezo.co.uk] Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters. PT1000 cartridge sensors plug straight into duet boards and others.
Published:Inventions
Re: Offset from HomingOrigin
June 23, 2016 01:13PM
Hallo

Thank you for the Tip !
I have changed the Steps to 160 and now it runs perfekt.

What im worried about is the shaking and vibrating ! The Frame looks very good and tight but the printer starts to virbrate alot when it moves !
I would love to run a stresstest or a small test programm that moves the printer in x and y ! Anyone knows a GCode Programm for that ?
Re: Offset from HomingOrigin
June 23, 2016 01:19PM
Quote
DjDemonD
@pdbeal setting a home offset like this and then making sure your travel limits are correct will not limit your travel across the bed unless that's a limitation in marlin 1.0.x in all 1.1.0 RC versions it works just fine
My offsets are x-7 y-39 and my travel limits are x0-280 y0-200 z-3 - 170 on my enlarged machine.

What I've noticed, on the Smartrapcore ALU kit I received it was designed for 200x200, and on the X axis from endstop to full travel was only like 203-206ish, meaning when I offset my bed beyond the 6-8mm, I was now stuck only being able to travel 198 or so before it ran into the y-slide piece. The y travel distance was much greater like 0-220ish, but the X travel was much shorter in the kit, still doing 200x200 but not being able to do much of an offset for the x and 0,0.

This being a mechanical limit and not related to the controller configuration beyond the offset start.

Edited 1 time(s). Last edit at 06/23/2016 01:19PM by PDBeal.
Re: Offset from HomingOrigin
June 23, 2016 02:49PM
Ah fair enough.


Simon.

[www.precisionpiezo.co.uk] Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters. PT1000 cartridge sensors plug straight into duet boards and others.
Published:Inventions
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