Moving mass / torque requirements

  • Hi

    I´m planning a large Duet 2 xycore with a print volume of 550 x 1000 x 50mm (x,y,z) It is for a specific project an I will exclusively use PLA with print speed as main objective (200mm/s) at the expense of quality.

    my concern is that even with bowden the moving mass will be between 700-900gr and that at these speeds a nema 23 will not be sufficient. If that turns out to be the case, would servos for the x/y axis be feasible?

    ps, can you also tell me the most reliable method of calculating the torque requirements of this system?

    best regards

  • Moderator

    @gisli Not totally sure about how your machine will look but from what you have told I don't even see the need for NEMA23.

    In my i3-style Cartesian I use only NEMA17 with running at just 52% of the rated current. This still allows my bed that is moving in Y and weighing in at around 1kg (probably even a bit more) to be accelerated at 2,000mm/s and reach 250mm/s speed very easily.

    So torque will more or less only limit your acceleration capabilities (see my Maximum Acceleration Calculator). Top speed rarely is an issue in terms of motor power. If at all it is a question of system voltage. You should definitely use 24V in this case.

  • @gisli said in Moving mass / torque requirements:

    my concern is that even with bowden the moving mass will be between 700-900gr and that at these speeds a nema 23 will not be sufficient..............................................

    Your concerns are unfounded. I have a moving mass of around 3Kgs although that is spread between two separate gantries on my CoreXYUV. However, the moving mass per gantry is about 1.5Kgs and I use Nema 17s to print at up to 300mm/sec using multiple melt chambers. Even with a single melt chamber, my default non-print seed is 350mm/sec.

    Read about here

    Or watch the video here

  • @wilriker Hi Manuel, Thank you for taking the time to help me with my project.

    I see from your calculator that going beyond nema 17 is unnecessary.

    What width of (GT2) belt would you use, the Y axis belt will be very long and 5mm seems narrow for a 3800mm long belt?

  • @deckingman Ian, your setup is very interesting, I have never seen counterweights used in this way,

    I also have a melt efficiency concern as I will run 200mm/s, 0.4mm nozzle, 0.3mm layer height will a normal e3d hotend manage that throughput?

    ps. I´m working on a welding robot that will weld printed pla components using a hotend and extruder. The problem is that I need to get into 90 degree corners with the nozzle and pump filament into them, it needs to be close enough to the material to bond to it before it cools. Most heating blocks and nozzles are not shaped for this and will not fit into corners, do you know if there are any more compact nozzles and hotends out there that might work for this job?

  • Moderator

    Not sure if 5mm belts even exist. Usually they are 6mm wide. In terms of mass to move they should suffice. You could also use 9mm but certainly not wider. What I actually don't know is if a 6mm belt will stretch less compared to the 9mm one if all other parameters are the same. My guess is that they will behave the same and based on that I think 6mm will be OK. But I am not absolutely certain here.

    Ref melt capabilities: this is easy to calculate. A regular E3D V6 is capable of melting around 10mm³/s. An E3D Volcano can manage around 30mm³/s.

    Your requirement is 200mm/s, 0.4mm nozzle (I just assume extrusion width to be 0.45mm here) and 0.3mm layer height. This is a simple multiplication:

    200mm/s * 0.45mm * 0.3mm = 27mm³/s

    It follows that you definitely need a Volcano or another hotend with comparable melting capabilities. You could increase the capability of the V6 by printing hotter but there is only so much you can do there.

  • @gisli said in Moving mass / torque requirements:

    @deckingman Ian, your setup is very interesting, I have never seen counterweights used in this way,

    Forget the counter weight / dynamic load balancing thing - it makes no difference (although it might if the frame flexed rather than the entire printer "rocking"). The point was that you can print at 300mm/sec (if your hot end can melt filament that fast) with a mass of 1.5kgs using Nema 17s.

    I don't know of any long, thin, nozzles that would accomplish what you want to do.

    6mm belts will be fine - it's what I use. Timing belts are designed not to stretch (although some cheap Chinese ones might).

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