XY Printing offset

[My1 1]

Hello I have a little issue with Cura and the Ender-3.

 

the Auto-Home Position is outside the print bed and beyond that there are clips on 2 sides of the bed holding it in place meaning there needs to be an offset for proper printing when you need larger models. I have read this can be done with custom G-Code and yet that doesnt seem to work in 2 attempts so far:

 

Attempt 1:

at the G28 auto-home I added a G92 to set the position so it knows it's out of bounds

G28 ; Home all axes
g92 X-4 Y-16 Z0; custom offset

 

Attempt 2:

in the off chance it doesnt like negative values for G92 I tried this where I moved it to the Zero-Point I use and looking at the printer the initial command seems to work

G28 ; Home all axes
G1 X4 Y16; move to zero
g92 X0 Y0; custom offset
G1 X-4 Y-16; move back to edge to make the preparation line from the default custom code

 

however in both cases it goes right to the y-edge of the bed and rams into these clips which is obviously what I want to avoid considering the offsets I made.

 

is there something in the G-code that I might have missed that makes the coordinates not work?

the only G92s I can find are Extruder resets and the custom I added and there is also no other G28 to auto-home and I am kinda not sure what I can try to get that working.

[gr5 2,071]

First of all I think it's case sensitive so your "g92" need to be changed to "G92".  I could be wrong but it doesn't hurt to capitalize.

 

Secondly I think Marlin (the firmware on the Ender) has soft limits at 0 such that X can't go negative so your attempt #2 is better.  Also in attempt #2 it looks like it will hit the clips so move the Z up first.

 

G28

G0 Z 5 ; move z up

G0 X4 Y14

G92 X0 Y0

 

Now I don't think the G1 X-4 will work as again I think you have soft limits at X=0 - this I suspect will cause an "out of bounds" error.

[gr5 2,071]

But a better solution would be to tell cura where the clips are.  There is a way to do that in the printer definition file.  The printer definition files are json files somewhere in a folder called "machines".  Something like ender3.json.  However these get written over when you upgrade cura.  I'm not sure exactly what the proper procedure is.  Anyway you could look at the S5 file to see if you can figure out how they made the clips a keep away zone.  It's called "9051.json".

[gr5 2,071]

@GregValiant - I assume there is a better ender3 machine file somewhere?

[My1 1]

regarding the Z move

the clips are not exactly in the corners so that is not a worry.

 

 

also I have been feeding the printer the first attempt's commands manually in the monitor section before sending out the moves for when I need to position bed leveling already so it seems weird.

 

but I'll try capitalizing it all.

(also kinda frustrating when you extrude the wall sections of inner holes first before doing the part that actually matters, which takes time and filament)

 

here's a bad mspaint image of the way it should be

forgot to label then but the clips are orange, so they generally arent in the way as long as the offset works

Edited January 19, 2021 by My1

[GregValiant 1,112]

The Ender 3 Pro has disallowed areas for the clips.  They make the available area smaller in Cura but don't really help as far as the printer goes.

The firmware only understands uppercase letters.  Any lowercase command will be ignored.

 

The Auto-Home position will likely be off the build surface.  It's just a function of where the end stop switches are located.

 

Auto-Home the print head.  Use the LCD to move the nozzle 5mm in from the left edge of the build surface and 5mm in from the front of the build surface.  With the Z at 0 select "Set Home Offsets" on the LCD.  That let's the printer know where to put the Gcode 0,0,0.  In Cura, in the Machine Settings, make your build surface 225 x 225 in the XY.  That will make the center of the Cura model area the same as your printer center point.

 

Negative X and Y moves beyond the Home Offset 0,0,0 may be possible but you shouldn't need or want to do that.  Better to move the Z up to 15 or something and then let the Gcode file move the print head to the start of the print.

 

If you put a skirt around your models you really don't need the purge lines that are in the Ender 3 and Ender 3 Pro Cura definition files.  You can put semi-colons in front of those lines and they will be ignored.  I like that because from say X0 Y0 Z15 Cura will make a straight line move to the start of the skirt and likely miss the clips.  I use a single clip in the middle of the front and two in the back.  That keeps my print head from shooting the clip into my eye.

[My1 1]

the custom G code that was in at the beginning already has an auto home in so if I set a custom home before the print that would be removed.

 

the purge line currently is pretty useful as I dont have room for a skirt on the model I am currently trying.

 

also regarding disallowed areas, it's an ender-3 not a pro as far as I can see.

 

also 5mm in on both might be a little tight. I measured out the XY print size and start coords with the printer itself before already which is where I got my G92 values from as well as the 226x214 for max print size

Edited January 20, 2021 by My1

[GregValiant 1,112]

Not in the gcode.  It's part of setting up the printer.

The LCD has an Auto-Home command and a Set Home Offsets command.  That's what I was talking about using.  You really need to do that.  It insures that Cura and your printer are on the same page.  It has nothing to do with the start-up gcode.

 

The purge line is fine to use.  Regarding the skirt, the default in Cura is 10mm from the print.  If you change the skirt distance to 2 you can fit larger models in.

[My1 1]

yes I am aware of the LCD command for home and offsets, however in the G-Code there is due to the machine settings (even the default) a G28 (auto home) already and as far as I am aware that also resets any custom home offsets you have made.

[GregValiant 1,112]

No.  The G28 sends the print head to the end stop switches.  M206 sets the home offsets.

[My1 1]

at least whenever I told the printer to autohome it automatically set the coords it arrived to zero rather than knowing the offsets

[GregValiant 1,112]

Using the LCD

Auto-Home the print head.

Move the nozzle 5mm in from the left edge of the build surface and 5mm in from the front of the build surface.

With the Z at 0 select "Set Home Offsets" on the LCD.

Select "Save Settings".

[My1 1]

1 hour ago, GregValiant said:

Select "Save Settings".

Oh I wasnt aware that you have saved the settings in another menu, now the homer actually sees the offsets