dual extruder, setting up offsets, print area, homing



  • I managed to get most of the stuff working with RRF3 and Duet2Eth (modified ender5 printer) but now I'm stuck with the dual extruders, in a way, no clue where to begin ๐Ÿ˜„ so I'm maybe (probably) going to be too long but I kinda believe better to overshare than to withhold info that might help someone help me ๐Ÿ™‚

    I modded ender5 so it's head holds a dual flex3drive + bltouch

    The new head one extruder is left from where original extruder was, other extruder is bit right from where original one was and bltouch is more right from there

    I moved X endstop so that it home X at ~ -3cm compared to original Z home

    so at home position (printer think is on 0,0,0)

    • 3mm extruder X is roughly at bed edge +10
    • 1.75mm extruder X is roughly at bed edge -16
    • BLTouch is roughtly at bed edge -45

    all three devices are more / less at same Y and Y0 is more less edge of the bed so Y axis is not a problem

    So, the question ... finally ... how to go about all this?

    What offsets should I set up to have this all make sense?



  • Hi,

    With your current position for X=0 can you move over the entire Y range without any problems?

    Frederick



  • @smece Basically, this is a 2-dimensional problem - if you can eliminate the Y-axis, you are even down to one dimension. I suggest you to simplify the topic by reducing the print head (with two nozzles and the Z-probe) to a single point in space: either by defining the preferred nozzle (if there is one) or the exact middle between the two nozzles as X=0, Y=0. RRF takes this point as the location of the entire print head.

    Second, you measure the X/Y offsets of each nozzle and the BLTouch to this point. You will need them for your slicer and for bed-levelling.

    Having the print head (mentally) out of the way, you still have to deal with two 2-dimensional spaces: the physical limits of X/Y movement and the printable area - the latter one being limited by the print bed, by the physical capabilities of your X- and Y-axis, and by the nozzle offsets - in your case Y-only: each nozzle must be able to reach every point of the printable area. Note that this must not be true for the BLTouch.

    First step, then, is to set up the end stops of X and Y so that you can home both axes. In a second step, you define the origin of your coordinate system - I strongly suggest to follow Mark Rehorstโ€™s excellent guides:

    Setting Up the Printer's Origin
    Setting Up a 3D Printer's Origins in Firmware and Slicers

    To simplify this task, itโ€™s a good advice to fix some sheet of paper on your print bed so you can mark positions and attach some notes. This is especially valuable when you want to take the tool offsets (of your dual print head) into account.

    If you have followed these guides, you will have a thorough understanding of your printerโ€™s geometry - this will help you with the final steps: converting the measurements into gcodes and parameters for your slicer. Good luck!



  • @fcwilt said in dual extruder, setting up offsets, print area, homing:

    Hi,

    With your current position for X=0 can you move over the entire Y range without any problems?

    Yes, why ?



  • @smece said in dual extruder, setting up offsets, print area, homing:

    @fcwilt said in dual extruder, setting up offsets, print area, homing:

    Hi,

    With your current position for X=0 can you move over the entire Y range without any problems?

    Yes, why ?

    When I was setting the X & Y min/max values on my printer I failed to noticed that a small part of the frame extended a bit in the direction of the printing area. With my initial X max setting the part cooling nozzle would strike this part of the frame when at Y max. So I had to reduce my X max setting by 10mm to prevent the strike.

    Just thought I would ask since you were talking about offsets, clearances and such.

    Frederick



  • @fcwilt well, checking it now with extruders, I do have full range of motion in Y as I had before but not accessing bed in whole Y direction .. I'm overshooting bed by 27mm in front of the printer and I can't access 27mm in back of the printer, so if I slide the glass 27mm towards the front I will have full original Y size, otherwise I'm missing first (back) 27mm (and can use front 27mm for purge and similar stuff ๐Ÿ™‚ ) ... I'll probly be switching this dual flex3drive for new dual G5 flex3drive system so that will require a new holder so I'll see then what's going to happen with Y... but for now I have "full range of motion in Y" but the extruders are moved bit to forward ๐Ÿ˜„ .. X is more confusing for me attm



  • @infiniteloop said in dual extruder, setting up offsets, print area, homing:

    @smece Basically, this is a 2-dimensional problem - if you can eliminate the Y-axis, you are even down to one dimension.

    yup, I know, kinda, what I need to do, issue is - I never done it before with dual extruder and bltouch, now for bltouch I kinda assume it's irrelevant, I just give it an offset from "whatever point I decide represents the head position" and that's it.. but the thing is with 2 extruders... should I only look at one of them and arrange everything around the one or .. again, one see, on one side more then bed, on other side less then bed, other similar but on other side ๐Ÿ˜„ so .. read the links you sent "diagonally" only (will go now read them properly) and I see that moving the 0,0 to center of the bed makes sense .. then I can just mark the physical movement range of the head (irrelevant if bed is under it or not) and I know how big my bed is (in slicer) and that should work.. thanks for the clues, I'll probbly have more questions after I read properly the both shared documents



  • @smece

    bltouch I kinda assume it's irrelevant, I just give it an offset from "whatever point I decide represents the head position" and that's it..

    Just so.

    but the thing is with 2 extruders... should I only look at one of them and arrange everything around the one or ..

    Well, that depends on which imagination of the geometry you feel most comfortable with. In my case, I took the center between both nozzles because this fits nicely with my centered bed origin - on each side, I have to take the same offsets into account.

    This makes life a bit easier when you want to determine your printable area - remember, each nozzle must be able to reach every point of that region. If the origins of head and bed are both centered, they collapse (in my imagination) to a single point which is the root of all X/Y coordinates in four quadrants. Really simple.



  • @infiniteloop thanks once more, set everything up those 2 posts are a jewel :D. I also changed the "orientation" of the printer, on Ender5 normally 0,0 is back right so the normal orientation of the plate is if you look at it from behind the printer (X increases to the left and Y to the front), so I switched the XY motor directions and set back right home position to be maxx, maxy and the 0,0 to be at the center of the bed and .. and.. it's awesome ๐Ÿ˜„ ...

    I centered my "main" (1.75mm) nozzle as most of the 3mm filament I have is either PLA or ABS and I doubt I'll be printing much of either on Ender5.



  • If anyone can find the useful ... the config for RRF3 is here..

    deployprobe.g homez.g bed.g config.g homex.g homey.g homeall.g



  • @smece

    Hi,

    I think you will find, if you have not already, that having 0,0 at the center of the bed is a good idea.

    Frederick



  • @smece Congrats!

    I centered my "main" (1.75mm) nozzle as most of the 3mm filament I have is either PLA or ABS and I doubt I'll be printing much of either on Ender5

    As you tell it, this decision sounds absolutely reasonable. And just to add this: Thanks to @mrehorstdmd for his great tutorials.



  • I'm printing for 10+ years and I never had the idea to put 0,0 to the center of the bed ๐Ÿ˜„ ... it makes so much sense when someone opens your eyes ๐Ÿ˜„ .. thanks!!


  • administrators

    To clarify: on a single-carriage multiple nozzle machine, you need to decide where the head reference point (HRP) will be. Common choices are either at one of the nozzles, or at the geometric centre of the nozzles. It doesn't make much difference where you decide to make it. However, the following items are all relative to that HRP:

    • Tool offsets
    • Z probe offset
    • M208 lower and upper axis limits (i.e. these defined the allowed limits of the HRP).

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