Stupid question of the day for DC: How big?

  • What math limit would prevent going any larger on a printer from the Duet's perspective? How big would it be?

  • Without being directly involved in the firmware, I can say that it uses 32-bit floating point values ("float" for C/C++ programmers) and those have 6-7 digits precision. So at 1m for each axis you have at least 1micron precision. Larger printer will imply worse precision, with the precision being somewhere between 10E-6 and 10E-7 (that is 0.000001 and 0.0000001) of the maximum travel. Still, even with a 10m axis travel you have at least 10 micron precision and even that is way beyond the capabilities of most hobby grade mechanics.

  • administrators

    There are some other limitations:

    • No axis can be more than 2^31 microsteps long. At 1000 microsteps/mm this corresponds to about 2km, so you are not likely to hit it.

    • On deltas there is a further limitation that you could hit on a large delta with high microstepping. AFAIK nobody has hit this limit yet, but in firmware 2.01 I plan to increase it anyway. AFAIR it would kick in at somewhere above 10m if using x16 microstepping.

  • Cool stuff. I know from being a PLC programmer years ago that there had to be a something that would limit an axis but wasn't sure what.

    Thanks for indulging the question.

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