Level 2Unit E · Session 26
26

Unit E · Designing a part that fits

The stand

What we are making: the finished design for a stand that holds your ultrasonic sensor upright, aimed straight ahead, at a height you choose.

What it has to do

  • Hold the sensor square to the front — not tilted up, down or sideways.
  • Hold it at a fixed height above the desk, the same every time.
  • Leave room behind the board for the pins and the wires.
  • Stand up on its own without falling over when the wires are plugged in.
  • Print in under 45 minutes. There are many teams and one machine.
💡 Tip
Write those five down as your spec, before you draw. Then you can check the finished design against them rather than deciding afterwards whether you like it.

The shape most teams arrive at

An L. A flat base that sits on the desk, and a vertical face with the sensor in it. Simple, stable, and printable lying on its back with no overhangs.

What you drewWhat the slicer made of it16 layers0.2 mm eachThe printer cannot make a solid shape. It can only put down one thin line of melted plastic at a time,then move up 0.2 mm and do it again. A 20 mm tall object is a hundred layers.
Printed lying on its back, an L has no overhang at all. Printed upright, it does.
📷
images/l2-e2-tinkercad-orient.png
Screenshot: the same stand shown in both orientations on the workplane, side by side
⚠ Careful
Orientation matters more than shape. The same part printed two ways can be strong or snap in your fingers, because layers peel apart much more easily than they break. Print so the force pushes layers together, not apart.

Do it — build it

  1. Start with the base: a flat box wide enough not to topple, 3–4 mm thick.
  2. Add the vertical face, at least 2 mm thick, tall enough to cover the sensor board.
  3. Cut the two barrel holes as Hole cylinders, 0.4 mm oversize, at your measured spacing.
  4. Leave a gap behind the face for the pins — use the number you measured.
  5. Group it all. Spin it. Check nothing floats and nothing is under 2 mm.
  6. Take a screenshot of your design from an angle and put it in your notebook.
  7. Save as team-N-sensor-stand-v1. The v1 matters — there will be a v2.
📷
images/l2-e2-tinkercad-stand.png
Screenshot: the finished L-shaped stand in Tinkercad, seen from an angle, holes visible

Check it against the spec

Before you hand it in, go back to your five lines and tick each one. Then have another team check it too — they will spot the floating bit you stopped seeing an hour ago.

What you seeWhyWhat to do
Something floats in mid-airNo support beneath it.Add a fillet, a rib, or rotate the part.
A wall is 1 mm thickIt will snap.Nothing under 2 mm anywhere.
The holes are the measured sizeIt will not fit.Add 0.4 mm.
It is 90 minutes of printingToo big, or solid all the way through.Hollow it out, or make it smaller. 45 minutes is the budget.
The pins are crushed against the faceNo clearance behind the board.Leave the gap you measured, plus a millimetre.
⚠ Careful
Hand your file in at the end of the session with the exact filename asked for. Your teacher is queueing sixteen prints and a file called Untitled does not get printed.
Challenge optional — only if you finish early
  • Design a second version of your stand that uses less plastic but is just as strong.
25. Measuring, and designing to fit