Design parameters 3d print models

[last updated: 2020-06-14]
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This page needs editing... see also 277
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(Also see: FreeCAD)

• Misc Drawing Tips (below):
• Insert screws into 3d printed parts:
• general concept for screw holes:
• options to make a hole:
• print a solid block, and hand-drill a hole of required size
• print a hole for the screw, in correct size for desired thread depth
• options to cut threads:
• use a tap (for machine thread screws)
• use self-tapping screws (for sheet metal screws)
• heat up the screw and "melt" to cut threads into the part as you screw it in. This has not been necessary for PLA & PET that I've used so far.
• use nut inserts, "nutserts"
• create a structure to "capture" a nut, like is done in so many places on the Prusa build.
• model and print the threads in your 3d part
• screw hole dimensions (worked for PLA & PETG):
• #1 sheet metal:
  shaft incl threads: 1.75 mm diam
  hole to thread: 0.75 mm rad worked well
  head: 3.378 mm diam (1.69 mm rad) x 1.27 mm
• #2 sheet metal:
  shaft incl threads: 2.15mm diam mm
  hole to clear: 2.1mm diam (5/64th in)
  hole to thread: 1.6mm diam (0.80 mm rad) worked well
      however would still thread snuggly into 1.5mm diam (0.75mm rad) hole
  head: 4.115 mm diam (2.06 mm rad) x 1.575 mm
• #4 sheet metal:
  shaft incl threads: 2.8 mm OD
  shank (minus threads) measures 2.0 mm OD
  thread depth = 2.7 - 2.0 /2 = 0.35 mm radius
  hole to thread: 2.5 mm diam. (1.25 mm rad)
      (~3/32" diam)
  hole to clear: 2.95 mm diam (~ 1.5mm radius)
      (~1/8" diam)
  head: 5.35 mm diam x 1.9 mm
  counterbore: 5.60 mm diam (2.8mm radius) x 2.05 mm
• #6 sheet metal:
  hole to thread:
      1.75 rad easy
      1.60 rad best?
      1.50 rad doable but very snug
  hole to clear:
      2.00 rad difficult
      2.05 rad workable
      2.10 rad easy
  pan head: 6.8mm diam x 2.1mm (est) deep
  pan head counterbore: ...?
  oval head countersink: 7mm diam (3.5mm rad) w/ 0.7mm counterbore
• #8 sheet metal:
  shaft OD: 4.2 mm
  hole to clear: 4.6 mm diam (2.3 mm rad) (confirmed)
  head: 7.9 mm diam (4 mm rad)
• #10 sheet metal:
  OD incl. threads: 4.6 mm
  hole to thread: 2.1 mm rad
  hole to clear: 5.4 mm diam (2.7 mm rad) (confirmed)
  head: 9.3 mm diam (4.65 mm rad) x 3.5mm high

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• M2.5:
  OD incl threads: 2.42mm (1.21mm rad)
  hole to clear: 1.35mm rad (1.45mm rad?)
  head: 4.45mm diam (2.225mm rad) x 1.66mm high
• other screw parameters...
• for 75% thread depth:
  4/40 taps need 3/32 (closest fractional) or #43 drill bit (0.890")
  2-56 needs #50 bit (0.700")
• Dimensions for other parts:
• PIR mini:
  frame holding head: 2.5 mm thick
  hole for head: 5.55 mm rad = 11.1 diam
• LED's:
  • 5 mm LED:
    hole to fit: 2.625 mm rad fit, easy slide, no snugness
  • 3 mm:
    hole to fit: 1.6mm radius fit snugly, should hold without glue...
• tactile metal ball PB (6mm) Adafruit 3347
  3.2mm radius? 0.75mm 45deg chamfer for 3.32mm thick panel
  but profile of ledge on PB where it seats against the underside of the panel is not fully planar
  ... will try to adjust model to accomodate...
• Misc drawing tips:
• Scale a model in SU:
• select guide tool
  click at start of dimension to be scaled
  click at end of dimension
  note prompt below: "Enter value to resize model"
  enter new value, press enter
  note my version of SU does not seem to have the option of scaling just the active group, but does the entire model.

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