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Archive for April 24th, 2011

Thing-O-Matic: Useful Numbers

Various numbers that I’ve either measured or collected, scraped into one untidy heap, with the intent of figuring out the stepper motor torques. One significant figure will be entirely enough for what we’re doing; kg & g are really kg-force and g-force; you know what I mean.

Weights

  • X stage wood structure = 120 g
  • Aluminum build plate = 100 g
  • XY stage with plates & c =1.1 kg

Forces

  • Guide rod in two bushings = nil
  • X stage with four bushings = 0.8 lb = 0.4 kg
  • X stage with X rod follower = nil
  • X stage with X follower and motor = 1 lb = 0.5 kg
  • Y stage = 2 ounces = nil
  • Y stage with motor = 1.5 kg static, 1 kg moving

Distances

The ReplicatorG/machines/thingomatic.xml file lists the X and Y pulleys as 10.82 mm diameter. I measure 12.5 mm over the belt and the belt is 0.78 mm thick, sooo that makes it 10.9 at the pulley surface (which I can’t get to without taking everything apart again). Let’s call them 11 mm.

  • X and Y = 47.069852 step/mm. Let’s call that 47 step/mm → 0.021 mm/step
  • Z = 200 step/mm → 0.005 mm/step

[Update: see nophead’s comment for the right way to compute the X & Y distances. The answer is 47.0588 step/mm = 0.02125 mm/step, which is 0.1% off what I’d been using.]

The XML file lists the MK6 extruder at 50.235478806907409 step/mm. Measuring the results on my geared extruder, using the same filament drive doodad as they do, works out to 48.2 step/mm and 1456 step/rev.

  • Extrusion thickness = 0.33 mm

Speeds

  • Extrusion feed = 40 mm/s
  • Extrusion flow = 2 rpm
  • Traverse speed = 50 mm/s
  • First layer = 25% of normal
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