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Flexible shaft - the best of both worlds?


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Posted · Flexible shaft - the best of both worlds?

Did you already try running a print file with the extruder motor separated from shaft, just to see what it does?

If not, I might do that and then try running the motor at different filament feed rates to see what it does.

Also, IIRC, the acceleration for the extruder motor is set very high. You could try turning that down some.

 

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    Posted · Flexible shaft - the best of both worlds?

    I tried running without the shaft. Same problems.

    The problem is if I run it with microsteps the fastest extrusion is 3,5mm/s which is not fast enough for retraction. But at least it works.

    If I remove mircostepping the fastest extrusion should be 56mm/s but if I go faster then 1,6mm/s the motor just vibrates.

    If I lower the acceleration from 3000 to 50 the motor is able to run with 25mm/s but the acceleration is set for all motors so X and Y accelerate extremely slow if I do that :(

     

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    Posted · Flexible shaft - the best of both worlds?

    Its hard to put the UM2 in any other mode then 16 microstepps or full step mode. At 16 microstepps the motor works fine but the steps/mm are way to high.

    In full step mode the steps/mm would be fine but the motor doesn't work because it skips.

    At 3000 acceleration the motor is able to move at max 5mm/s

    To be able to move at 25mm/s I have to lower the acceleration to 75 to get any movement instead of vibration.

    It seems the only way is to lower the gear ratio so I can use the 16 microstepps :/

    What I don't understand is that full step mode is much worse then microstepping. I would have thought that full step is easy but noisy while miicrostepping is more difficult but quieter.

     

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    Posted · Flexible shaft - the best of both worlds?

    Is acceleration of 50 not high enough?

    @gr5, BTW, is acceleration in steps/s/s or mm/s/s?

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    Posted · Flexible shaft - the best of both worlds?

    accel is in mm/sec/sec

     

    Its hard to put the UM2 in any other mode then 16 microstepps or full step mode

     

    Oh! Of course. On the UMO there are jumpers and it's easy. UM2 isn't for tinkerers.

     

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    Posted · Flexible shaft - the best of both worlds?

    There is an UM2 Flex3Drive design by Erik van der Zalm on Youmagine and Bas van Deursen made several postings here. So some people at Ultimaker should have an answer to your problem ...

     

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    Posted · Flexible shaft - the best of both worlds?

    yes indeed!

    Sorry for the late reply! It's awfully busy here...

    I think that the problem is that the printer can't handle the enormously high steps per unit that you would need because of the high gear reduction in the Flex3Drive worm gear set. I also noticed that you will run into trouble when using a UM2 extruder motor because it has 400 steps / rev and is on 16 microsteps.

    Erik van der Zalm also had this problem when he installed it on his UM2 so he adapted the firmware to do "double stepping". However because Erik has a very early version of the UM2 he has a 200 steps/rev extruder motor. Because of this it works just fine on his UM2 but not on other UM2s.

    The solution would be to install a 200 steps/rev extruder motor. I think we still have a bunch of them here at UM HQ. I'll check out and if we still have some lying around I'll send you one, that should solve your problem.

    cheers,

    -Bas

     

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    Posted · Flexible shaft - the best of both worlds?

    That's what I call service! :)

     

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    Posted · Flexible shaft - the best of both worlds?

    I can't find them but a 200 steps/rev stepper should do the trick. I think you could probably do with a nema14 because you won't need a high torque because of the worm gear reduction.

    -Bas

     

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    Posted · Flexible shaft - the best of both worlds?

    BTW: Any insights you can share?

    I liked the flexdrive because it realizes direct extrusion with almost no additional weight. However, I had some extrusion issues with short paths and frequent retractions in between. Perhaps some torsional flex, perhaps my setup wasn't dialed in perfectly. So I went ahead for my NEMA8 direct extruder.

     

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    Posted · Flexible shaft - the best of both worlds?

    I did not do an awful lot of printing with the Flex3Drive yet but during the first bunch of prints I noticed that there was some stick-slip between the gears. I put some grease on the gears and that solved the problem.

    -Bas

     

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    Posted · Flexible shaft - the best of both worlds?

    Thanks for the info. Yes I was talking to Erik over at youmagine about his design. Unfortunately I can't use his hex file.

    I think I'll get another stepper. All options I have tried are not able to retract with the right speed.

    I'll do a write-up about my setup as soon as everything works.

     

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    Posted · Flexible shaft - the best of both worlds?

    But you are building it onto a UM2?

     

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    Posted · Flexible shaft - the best of both worlds?

    And restinpieces - what country do you live in? Please update your profile, thanks.

     

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    Posted · Flexible shaft - the best of both worlds?

    Hello Guys, thanks for all the help. I learned a lot.

    For the moment I have returned to the bowden extruder. I wasn't satisfied with the solution I had. I could print just fine without retraction, but for retraction the movement was to slow.

    I'm not done jet, but I have to take a brake.

    The problem is the flex shaft is high speed low torque. And high speed doesn't work well with the arduino based boards.

    Here is the calculation:

    40000 steps/s is max for the electronic

    If one wants to retract at 25mm/s this turns out to a maximum of 1600steps/mm

    The UM2 has a 400 steps/360° Motor and is fixed at 16 microsteps. I reused the knurled sleeve so the 1:1 steps/mm are 282.

    This combined with the 1:40 worm gear, I bought, ends up at 11280 steps/mm or a max speed of 3,5mm/s

    Leaving the UM2 as it is I could use a 1:5 gear at maximum. This would not work well with the flex shaft I have.

    Replacing the motor with a 200 steps/turn one and modding the board for 8 microstepps would get me to a 1:20 gear ratio. Replacing the knurled sleeve with one with twice the radius would then get me 1:40.

    But I don't know if I want tor try that and atm I'm out of time. I'll think about it, maybe there is a better solution.

     

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    Posted · Flexible shaft - the best of both worlds?

    So, quick recap just to sum up who has and what we know about using the Flex3Drive (or other flex shaft projects) on UMO and UM2:

    foehnsturm - Flex3Drive working on UMO, original design for Merlin hotend mounting here.

    Bas van Deursen - Flex3Drive working on UM2, older version with 200 step/rev feeder?, required custom shaft for hobbed wheel.

    restinpieces - Custom flex setup, not working correctly with 400 step/rev UM2 feeder.

    Erik van der Zalm - Created UM2 Flex3Drive carriage here also includes custom firmware for UM2 for 200 step/rev feeder, installed and working?, hasn't commented here yet?

    CCW1984 (me) - Purchased Flex3Drive, installing soon with Erik's design and apparently can "use the attached firmware and change the E steps with M92 xxx." for the 400 step/rev stepper motor, if that's what I have.

    So I actually have no idea which kind of feeder stepper motor I have on the UM2 I received (long story short I purchased in late Dec 2014 but believe I got an older stocked printer), if anyone knows an easy way to find out please do tell.

     

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    Posted · Flexible shaft - the best of both worlds?

    Remove Filament

    Use pronterface to send Gcode

    Connect and save the

    M92 line for safety

    Type:

    M92 E320

    and

    G1 E10 F100

    If the Motor rotates 1 turn its a 200 if it rotates 1/2 turn its a 400. Values should be back to normal after On/off

    You can check when connecting with pronterface the M92 line should be the same as befor.

     

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    Posted · Flexible shaft - the best of both worlds?

    As far as I know all UM2's have 400 steps/rev motors. It might be that Erik did not use his stock UM2 feeder motor for his Flex3Drive setup. I should ask him about that next time I see him.

    Another comment that Erik made to me the other day: make sure that your retraction length is set to 1.5mm or something in that range. The drive wheel is so close to the nozzle that you won't have to compensate for any slack in the Bowden tube so you can use a low setting on your retraction length.

    -Bas

     

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    Posted · Flexible shaft - the best of both worlds?

    Remove Filament

    Use pronterface to send Gcode

    Connect and save the

    M92 line for safety

    Type:

    M92 E320

    and

    G1 E10 F100

    If the Motor rotates 1 turn its a 200 if it rotates 1/2 turn its a 400. Values should be back to normal after On/off

    You can check when connecting with pronterface the M92 line should be the same as befor.

     

    So I started learning the G-Code and if I interpret it correctly that would:

    M92: Set the steps per unit of axis for the extruder (E) to 320 steps/mm

    G1: Move (nowhere) and extrude (E) 10 mm at a feed rate (F) of 100 mm/min

    So the UM2 has 1/16 micro-stepping AFAIK. Extruding 10mm means the motor should attempt to make 3200 'steps' at 1/16 micro-stepping this means 200 physical steps! Cool, need to try that when I get home.

     

    As far as I know all UM2's have 400 steps/rev motors. It might be that Erik did not use his stock UM2 feeder motor for his Flex3Drive setup. I should ask him about that next time I see him.

     

    Please do! Or point him to this discussion. Hopefully this weekend I can print and test the design and firmware he has on Youmagine for the Flex3Drive. I wonder if he'll be updating it since Cura 15.01 firmware is out now though.

     

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    Posted · Flexible shaft - the best of both worlds?

    So I started learning the G-Code and if I interpret it correctly that would:

    M92: Set the steps per unit of axis for the extruder (E) to 320 steps/mm

    G1: Move (nowhere) and extrude (E) 10 mm at a feed rate (F) of 100 mm/min

    So the UM2 has 1/16 micro-stepping AFAIK. Extruding 10mm means the motor should attempt to make 3200 'steps' at 1/16 micro-stepping this means 200 physical steps! Cool, need to try that when I get home.

     

    Thats correct :)

     

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    Posted · Flexible shaft - the best of both worlds?

    So from what I've heard there will be an updated version of the UM2 housing coming soon, and the new plans and parts should be available soon.

     

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    Posted · Flexible shaft - the best of both worlds?

    Hi Everybody!

     

    So from what I've heard there will be an updated version of the UM2 housing coming soon, and the new plans and parts should be available soon.

     

    We are indeed working together with Mutley3D to make an upgrade kit that would fit the UM2. This kit would be aimed at people who are not afraid to do some tinkering on their machines.

    However, at the moment we are still in the prototyping phase, so it might take a while before this kit will become available. So "should be available soon" might be a bit too optimistic.

    Kind regards!

    Bas

     

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    Posted · Flexible shaft - the best of both worlds?

    @CCW - some clarifications (are you going to order a heater block by the way? I was hoping to send you one today or tomorrow and combine my trip to the post office):

     

    G1: Move (nowhere) and extrude (E) 10 mm at a feed rate (F) of 100 mm/min

     

    G0 and G1 do the same thing on the UMO and UM2 - move axes. They have six axes: X,Y,Z,E where E is extruder. All moves are linear meaning if one axis has to move slow, the other axes move correspondingly slow and accelerate in a corresponding maner so that the head always moves linear in all 4 dimensions (all 4 axes).

    If you only command one axis to move it of course can use max acceleration and speed.

    If you leave out an axis it doesn't move that axis:

    G1 X0 Y0 Z0 E0

    followed by

    G1 X1 Y0 Z0 E0

    is the same as

    G1 X1

    F is feedrate and is goal speed in mm/sec for all 4 axes but on the UM machines if X or Y is moving this limits the speed because they always move the most in a particular move.

    For example a typical move might for extruding a wall of a 10mm wide box might be 10mm in X, 0mm in Y, 0mm in Z and .4mm in E. Since the E move has to take the same amount of time and since it moves so little it is the X move that will be at the feedrate and E will be of course linearly slower.

    Feedrate is an old term for milling machines and implies this is how fast the cutting bit can go through the stock that you are cutting. Obviously cutting moves (or extruding moves) are slower than non cutting moves.

     

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