📝 NOTE

• refresh this page each time you resume working on the homework
• do NOT use green plastic
• make sure "Use Support" is turned on in Bambu Studio
• do NOT measure anything except the screws, nuts, and servos (do NOT measure my example parts)
• you should use the full number of screws for your parts (i'm only including 1 or 2 in the examples so they're easier to take apart)

TODO

• A-

  • 30x30x10mm box matching mine (mine is in green)
    • do NOT use green plastic
    • do NOT measure my box
    • counterbore the holes for the socket heads
    • use captive nuts in the lid
    • add alignment geometry to the lid (see example)
  • 30x30x??mm box with two plates and standoffs matching mine
  • T-junction matching mine (my example is in orange)
    • nuts pressed in sideways
    • teardrop clearance holes going all the way through
    • (counterbored holes for the screw heads)
  • servo bolted to a 2mm thick plate using "nut holder" plate (my example is in pink)
    • clearance for the servo's ribs
    • nuts captive in the second thicker plate
  • (Due with next week's homework) 30x30x30mm metal-plastic box
    • one tapped plate
    • one plate with clearance holes
    • one prismatic piece of plastic with clearance holes

• A

  • Choose 1
    • lithophane of not-Jeannie
      • NOTE: you must create this "from scratch" in code (do NOT use a lithophane generator from Google)
      • NOTE: you may use whatever programming language you like (hints are below)
      • HINT: see hints below
    • 1:4 scale pantograph
      • NOTE: it must actually work (you need to be able to draw with it), though doesn't have to work perfectly (i will use it to draw a heart)
      • HINT: see hints below

• A+

  • Do both of the above

✨ HINT

Lithophane

First, make sure you understand the rules for a triangle mesh (review the hw00 writeup very carefully).

• All triangles need to be facing the right way (out).
• Triangle corners can only touch other corners (NOT the middles of edges.)
• ...

Next, make sure you have a triangle mesh visualizer you really like (I recommend my new and improved viewer, formerly dxfviewer, which can now also visualize STL's, and draws the backs of triangles in red).

Next, get ready to write a bunch of for loops

The name of the game is incremental development (break the problem down into a bunch of simple steps).

• First make just a single triangle.
• Then a square.
• Then a grid.
• Then a height field.
• Then a height field based on a picture.
• Then add the sides (probably one side at a time).
• Then add the back.

Pantograph

There are probably a lot of ways to make a revolute joint (pin joint) with the tools we have. None are amazing (a correct solution is to use rotary bearing, which we don't have yet). Nevertheless, here are some ideas:

• Plastic cylinder rotating freely in plastic hole. In order to keep it from falling out, you can make the pin out of two pieces that you screw together so it has "caps," and looks kind of like an I from the side. Big cylinder is probably better.
• Screw rotating freely in plastic hole (some sort of jam nut approach can serve as the "cap" but still permit free rotation about the pin (screw). (You don't want to bolt the links together, or they won't be able to spin.)

Dimension Cheatsheet (for our printers)

• M3 screws

  • tap drill: 2.5mm
  • through-hole: 3.4mm
  • clearance for head of socket head cap screw: 6mm

• M3 hex nut captive in PLA -- exact width of nut (height maybe a little deeper)

• General

  • min wall thickness: 2.0mm
  • offset for slip fit 0.1mm