Darwin/BOM Notes

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BOM Notes


Cartesian Robot

  • The 8mm smooth rods supplied by McMaster are 3' long, not 1000mm. You will need 16 instead of 9.
  • The MXL belts supplied by McMaster are not compatible with the RP'd pulleys. You will need to either use belts from RS with the RP'd pulleys or use the McMaster belt with the McMaster pulleys.
  • The toothed pulleys supplied by McMaster fit a 1/4" shaft. For the Y and Z axes, these need to be bored out to 8mm. The X pulley should be fine as-is.
  • The BOM lists enough 8mm studding for the Z axis and 6 diagonals. This is sufficient to build a Darwin but it's possible to have 10 diagonals, in which case, you'll require 4 more.
  • The anti-backlash springs supplied by McMaster are not the correct size.

Thermoplastic Extruder

  • The stated thermistor is sufficient for low-temperature thermoplastics but may cause problems at higher temperatures. A 100k thermistor is recommended for high-temperature work.
  • On the generation 1 extruder board, the value of C3 should be 100nF for normal operation. Also verifythat the host settings match the value of C3. Raising the value of C3 will increase resolution at higher temperatures. A value of 220nF in combination with a 100k thermistor appears to work well up to about 250C.


  • No notes yet.

-- Main.SteveDeGroof - 11 Mar 2008