Ideas for Z probing. Real hot build chamber



  • My new printer will be constructed specifically to print Ultem (with Duet electronics of course) which means the build chamber will operate up to 200c. This is a Cartesian machine with x and y above and the bed moving up and down for z. The bed is made from stainless steel with a sheet of PEI vacuumed down for the build surface. Dual extruders squirting through a .1 mm orifice. First layer may need to be as low as .08 with subsequent layers in the .05-.08 range . Any ideas on the best approach for Z probing in this environment at this level of accuracy?


  • administrators

    PEI and Ultem are the same thing, so how are you going to prevent the print fusing to the bed?



  • It'll likely need to fuse to the bed because with a 0.08mm layer height and around 0.1mm width, it most likely won't stick any other way. 🙂



  • Electrical contact to specified points on (around) the bed would work well. You could probe with the hotend itself, as long as the nozzle is exposed and electrically conductive.



  • Perhaps they're working on a vacuum chuck like idea. Keep vacuum on to hold sheet and print in place then release vacuum to release sheet and cut parts free. Something similar was considered on the metals machines when I was working on them but residual tension in the build was considered likely to overcome the vacuum.



  • DC42-
    Understood Sir, I only stated it that way because the material for the filament I am using is from Sabic. Trademarked "Ultem" and the bed sheet is not. Just regular old PEI from China
    deckingman-
    Correct.
    bot-
    Simple. So I would need to figure out a repeatable, retractable metal contactor. I could set up a test fixture to see if the nozzle will be consistent. Maybe write a subprogram to move it in a small pattern to ensure it wipes away any plastic .
    DocTrucker-
    yes. I'm essentially duplicating the way Stratasys' handles the material on there Fortus 900's. If you saw what their hotend looked like your jaw would hit the floor



  • Interesting project. I've got something in the back of my mind about a UK Additive Manufacturing University group that I've visited being equipped with Material Extrusion Deposition systems that can handle PEEK, if the Fortus is indeed that machine then I'm not surprised it's note worthy. One thing I've learnt from my limited exposure to small scale (upto 30mm screw diameter ish) single screw pellet extrusion is one size doesn't fit all and different zone lengths in sections of the screw have significant effects on the output quality. I think the development of that sort of knowledge within our community is in it's infancy.

    Regarding temperature I had been tempted to go towards carbon fibre sheet to get something that was dimensionally stable with regard to thermal expansion but think 200C is probably pushing it for that. Current issues that I'm having are pushing me towards an enclosure and a thermally controlled enclosure is the gold standard, but I do hope to get away without that!



  • @3DPMicro:

    bot-
    Simple. So I would need to figure out a repeatable, retractable metal contactor. I could set up a test fixture to see if the nozzle will be consistent. Maybe write a subprogram to move it in a small pattern to ensure it wipes away any plastic .

    I think using the nozzle to contact, if possible, would be more reliable. Like this: https://www.youtube.com/watch?v=-QorlypTFr0



  • If using a sprung loaded bed for levelling could you just use a contact behind each bolt to the bed and a simple electrical three or four way fast AND circuit?



  • @bot:

    I think using the nozzle to contact, if possible, would be more reliable. Like this: https://www.youtube.com/watch?v=-QorlypTFr0

    Makes sense. pretty straight forward idea there in the video.

    @DocTrucker:

    Interesting project. I've got something in the back of my mind about a UK Additive Manufacturing University group that I've visited being equipped with Material Extrusion Deposition systems that can handle PEEK, if the Fortus is indeed that machine then I'm not surprised it's note worthy. One thing I've learnt from my limited exposure to small scale (upto 30mm screw diameter ish) single screw pellet extrusion is one size doesn't fit all and different zone lengths in sections of the screw have significant effects on the output quality. I think the development of that sort of knowledge within our community is in it's infancy.

    Regarding temperature I had been tempted to go towards carbon fibre sheet to get something that was dimensionally stable with regard to thermal expansion but think 200C is probably pushing it for that. Current issues that I'm having are pushing me towards an enclosure and a thermally controlled enclosure is the gold standard, but I do hope to get away without that!

    I wonder what the advantages are for a screw extruder? The Fortus uses conventional 1.75 mm filament driven by DC motors with encoders (dual extrusion) close to the hot end and the hot end being no more than a 75 mm long tube with a heater block clamped to it. No well defined heat break and no cooling above other than a 20 mm hose blowing some air on the motors. It appears they are using well developed pressure advance/tool path planning with no retraction. With pressure advance coming along nicely here . I would like to see our slicers offer more in tool path options.
    Im not 100% sure but I dont think PEEK would need a real high chamber temp since its Tg is only 143c. The Tg of Ultem 1010 is 217 so printing it in a chamber just below the Tg not only aids in layer bonding but also eliminates most of the printed in stresses eliminating the need for post print stress relieving.



  • Well you know I like a good z probe but in a 200 deg C chamber Id settled for just making it mechanically flat and level manually.



  • thats how ive been doing it on my existing machine. it works but I want to take the operator out of the equation as much as possible on this new build. At these extrusion widths and part sizes the first layer is quite a bit more sensitive than what we are used to


  • administrators

    You could perhaps use a strain gauge sensor like the Smart Effector, but you would need to use shielded twisted pair wiring to connect the strain gauge elements inside the heated chamber to the electronics outside it.



  • I really like the idea of using force. The strain measuring elements are integrated in to your board/effector?


  • administrators

    Yes they are. The design files are at https://github.com/T3P3/SmartEffector. The PCB uses 0.5oz copper instead of the usual 1oz.



  • Thanks for all the input folks. I am going to try using the nozzle to make the circuit. If that isnt reliable I will integrate a strain gauge


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