# Is there a placeHolder for Max_y_Size

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Posted · Is there a placeHolder for Max_y_Size

I am trying to work on my startup code

I currently print a stripe down the Left side before I begin to prime the extruder

I was wondering if there is a Variable/PlaceHolder for the Y_Bed Size I could use in my start up so I could "G1 X10 Y(Y_Bed_Size * .75) E15 so it would print the stripe to 75% of the bed.  As I have several different printers, with different bed sizes, and TRYING to standardize my startup code...

PS... for a .40 wide line, what do I need my E value to be, E15 draws a very thin line, the E30 on the way back does the same, pretty thin... not sure what the value should be vs. distance...

Thanks...

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Posted · Is there a placeHolder for Max_y_Size

{machine_depth}

The page with all the Cura Keywords is HERE and we can thank @ahoeben (FieldofView) for that.

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Posted · Is there a placeHolder for Max_y_Size

Note that Cura does not support math operations on the replacement patterns.

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Posted · Is there a placeHolder for Max_y_Size

The formula for an extrusion at 100% flow is "Volume of Filament In = Volume of Extrusion Out".

((FilDia/2)² x PI) x FilamentLength = LineWidth x LayerHeight x ExtrLength

so

Filament Length(Enumber) = (LineWidth x LayerHeight x ExtrLength) / ((FilDia/2)² x PI)

The FeedRate then dictates the FlowRate of material through the hot end as:

FlowRate in mm³/sec = Volume of Extrusion / (ExtrusionLength/PrintSpeed in mm/sec)

If you don't know which printer will get the Gcode file then it is best to have a StartUp Gcode that is suitable for all your printers.  That would mean your purge lines must work on the printer with the smallest build plate "Y".

Ahoeben also brings up a point.  There is no way to calculate an E value (within the StartUp Gcode) that is dependent on the bed size/length of extrusion.

Things become more complicated when one printer has 1.75 filament and the other has 2.85 filament.  If that is a possibility then you would need to change ALL the printers, AND Cura, to Volumetric extrusion.

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