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Change position of purge line

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Posted · Change position of purge line


I am using Cura 4.13.1 and my printer is Geetech Mizar S build is  255x255 on the bed.  Home is front left.  Actual size of the bed is 260x260.


My Start Gcode :


G28 ; Auto home

G1 Z15 F300 ;Move up slightly

M107 ;Off fans

G90 ;Switch to absolute positioning

M82 ;Extruder absolute mode

G92 E0 ;Set position of extruder to 0

G0 X10 Y20 F1500 ;Move to X10 Y20 at 1500mms

G1 Z0.8 ;Move Z to 0.8

G1 F300 X180 E40 ;Extrude a line of filament

G1 F1200 Z2 ;Raise Z

G92 E0 ;Set extruder position to zero

G28 ;Auto home


I know the G1 is move in straight line.  As the Gcode reads the purge line is on X axis too far away from the edge of the print   Maybe 20mm or so.


What I want to do is move that purge line to the left side with the line on Y axis 10 mm fro the edge off the build plate.  5mm would bring it away from the edge and the other 5mm would be safe and not interfere with the print.


My recent printer Kywoo Max did this.  That start code is;

G92 E0 ; Reset Extruder

G28 ; Home all axes

G1 Z2.0 F3000 ; Move Z Axis up little to prevent scratching of Heat Bed

G1 X0.1 Y20 Z0.3 F5000.0 ; Move to start position

G1 X0.1 Y200.0 Z0.3 F1500.0 E15 ; Draw the first line

G1 X0.4 Y200.0 Z0.3 F5000.0 ; Move to side a little

G1 X0.4 Y20 Z0.3 F1500.0 E30 ; Draw the second line

G92 E0 ; Reset Extruder

G1 Z2.0 F3000 ; Move Z Axis up little to prevent scratching of Heat Bed

G1 X5 Y20 Z0.3 F5000.0 ; Move over to prevent blob squish



The big difference is the Kywoo bed is 300x300  Print area.  I a bit scared moving Kywoo's G1 to my Geeetech.  Can someone help? You can see what U mean in the photo.




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    Posted (edited) · Change position of purge line

    Have you set the Home Offsets in the printer?  If you have not then use a decent ruler and:

    Auto-Home the printer.

    Using the LCD controls:

    Move the nozzle up 3mm

    Move the nozzle in the X to a point 2.5mm in from the LEFT edge of the build plate.

    Move the nozzle in the Y to a point 2.5mm in from the FRONT edge of the build plate.

    Drop the Z to "0".

    Select "Set Home Offsets" on the LCD.

    Select "Save Settings" on the LCD.

    Move the nozzle up 3mm again and move the nozzle to X=127.5 and Y=127.5.  The nozzle should be at the mid point of the build plate.


    The snippet below will work for your startup.  The purge line will go along the bottom 12.5mm from the edge PROVIDED you have set the Home Offsets correctly.


    ;Begin StartUp

    M106 S0 ;Layer cooling fan off

    G90 ;Switch to absolute positioning

    M82 ;Extruder absolute mode

    G21 ;metric units

    G28 ;Auto-Home all axes

    G1 Z15 F600 ;Move up

    M140 S{material_bed_temperature_layer_0} ;start to heat the bed

    M109 S{material_print_temperature_layer_0} ;heat the hot end and wait for it

    M190 S{material_bed_temperature_layer_0} ;wait for the bed just in case it's not up to temp yet

    G92 E0 ;Set position of extruder to 0

    G0 X5 Y10 F1500 ;Move to start of purge

    G0 F600 Z0.3 ;Move Z to 0.3

    G1 F1500 X180 E15 ;Extrude a line of filament at 25mm/sec

    G1 F1200 Z2 ;Raise Z

    G92 E0 ;Set extruder position to zero

    G1 F3000 X0 Y0 Z10 ; move back to the left front corner for start of print in case the nozzle oozes

    ;End of Startup



    Edited by GregValiant
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    Posted · Change position of purge line

    Hi Greg

    sorry I didn't see this until today.  I thought I'd get n email notification when someone replied.


    I didn't actually set the home location. I added the new printed endpoint area.


    Also now I just installed Cura 5.

    I do notice that in Home position the nozzle is off the bed front left side.


    Thank you very much for your reply.


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    Posted (edited) · Change position of purge line

    Auto-Home location might be off the bed.  Mine is.  That's why you need to set the Home Offsets.

    The printer takes the coordinates from a gcode file and puts the origin at the Home Offset 0,0,0 location.  If you don't define the Home Offsets then the printer puts the gcode origin at the Auto-Home location which as you found out is off the bed.  That means some prints will be off the bed and no prints will be centered on the bed.


    So you must set the Home Offset location in order for the 0,0,0 origin of the virtual build plate in Cura to match the 0,0,0 origin of the real build plate on the printer.


    I think you can change the "Notification" settings here on the forum so you do get emails regarding your posts.


    Edited by GregValiant
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    Posted · Change position of purge line

    OMG I actually never knew that.  Thank you very much.  I suspected something wasn't right because that's why I did my original post.  Nozzle was front left off the bed and that purge line did not seem right to me.Of all the printers I had I always thought the home was set in the Gcode script.  Tht's why I asked about how to change it.


    I copied your original 'how-to' and I'll follow the instructions.  


    Thanks again


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