Custom built IDEX, 2 gantries, nozzles 355mm apart in y direction. I can print ok but need to understand Cura machine size settings.

[ljbeng 0]

I took 2 ender 3 printers and combined the frames into one to make an IDEX printer. I replaced the Y direction Extrusion with a 700mm long piece so there are 2 hotend X direction gantries.  The bed can now move between nozzles in the y direction.  I have made my calibrations and 3 successful multi color prints.  To "fool" cura into slicing for my situation, I did all the following.  If I don't make the Y direction in Cura 900mm as soon as I assign a piece to Extruder 2, the entire build plate turns gray and I cannot slice.  When I make it 900mm then the middle stay white and I can slice.  When I sliced  a project, I looked at the gcode and all the Y direction values seemed reasonable so I did all my calibration by changing the Extruder 2 Offset values.  The prints came out fine.  I just need to know if there is a way to make the y direction be smaller and if I am doing this correctly.  The beds are standard Ender and measure 235mm x 235mm.  The nozzles are offset by ~353mm in Y.  The x offset came out close and was -.6mm.

 

New FFF printer

 

[GregValiant 1,409]

For what you've built I think you have it right.

Because the back extruder cannot reach the front of the machine, and the front extruder can't reach the back, you need to make the build plate that big in the Y.

Currently your Machine Width(X) in Cura is 220.  That is the Creality standard even though the bed is physically 235 x 235.  It leaves a safety margin of 7.5mm around the periphery of the bed.

220 + 353 + 220 = 793 which would be a minimum "Machine Depth(Y)".

 

You can increase the Machine Width(X) to 230 in Cura.  You would need to change the Home Offset to manage that on the printer, but it would give you 10mm more in the X and Y.  That would make the minimum machine depth:

230 + 353 + 230 = 813 which is still smaller than your 900.  At 230 you only get a 2.5mm safety margin but that works for me on my Ender 3 Pro.

 

Ya know, you don't have a "true" IDEX machine because the bed can only be under one nozzle at a time.  That means no "Mirror" or "Duplicate" mode which a true IDEX would have.

 

How are you handling the extra X axis?  Is it simply tied to the stepper of the primary X(?) or is it handling the additional axis (A or V) in the firmware?

 

One thing for sure...there won't be a problem with the unused nozzle drooling on a print.

 

 

 

[ljbeng 0]

Thanks and your correct,  it's not a true IDEX but I couldn't come up with a term for it.  I did tie the X axis' together with a stiff rod and a flex coupler.  That was only because the BTT board I used had only 5 stepper drivers.    If I get a different board, then I could make the X axis 2 independent steppers and home switches.  The Z it a single driver and 2 outputs and I only leveled the bed under the E0 gantry then moved the bed to the E1 and I made a special piece to slightly adjust the z-rod up or down to set the gap there.  In Marlin there is nothing special other than 2 extruders and the 580 mm of y travel to go from home to the end of the run.

[GregValiant 1,409]

I was playing with the machine settings.  It looks like for a 230 x 230 bed then Machine Depth(Y) setting needs to be 940 for both nozzles to access the entire Y of the build plate.

 

Cura always assumes (because of UM machines) that neither nozzle can reach the extents of the bed.  That is typically true in the case where both print heads are on the X axis.  On your machine it's the Y axis and there may be some oddities in the Cura code because it wasn't set up to consider that.

At any rate, with the Machine Depth at 930 the entire 220 x 220 printable area of your build plate is accessible by both extruders.  For my 230 x 230 printable area the Machine Width would need to be 940 to push the disallowed areas off the build plate and just leave the Printable Area.

As an aside - Cura doesn't actually support IDEX printers as Cura has no capability to handle the AB (or UV) axis.  Any interpretation must take place in the firmware.  That brings me to Raise3D printers.  They use M605 S0 for normal prints, M605 S1 for Mirror prints, and M605 S2 for Duplicate prints.  I've always thought that was a very nice way to handle it.