3D printing lesson plan: design and print a functional part in one class period
A 45 to 60 minute lesson plan: measure a real object, design a part that fits it, check it and send it to the printer, with timings, prompts and what to grade.Most 3D printing lessons end with a keychain nobody needed. The part works as a first print, but it teaches dragging shapes, not design. A better first lesson takes the same 45 to 60 minutes and ends with a part that fits something real: a clip that holds a cable on the edge of the student's own desk, a tag sized to a backpack zip, a bracket for a sensor the robotics team already owns. The skill it teaches is the one that matters in every later project: measure, describe, check, print.
This plan works on school Chromebooks, iPads and phones, because the editor runs in the browser.
Before the lesson (10 minutes, once)
- Apply for the class in SpeakCAD a few days ahead (each class is approved before it pays), then pick the seats and copy the join link. Students sign up with any e-mail address.
- Put a digital calliper or two on each table, or rulers if that is what you have.
- Pick the object everyone designs for. A desk edge works because every student has one in front of them, and the clip prints in under half an hour.
- Slice one sample clip yourself in the online slicer so you know the print time on your printer.
The timeline
| Minutes | What students do | What you check |
|---|---|---|
| 0 to 5 | Look at a clip that does not fit (too loose, too tight). Ask: what number was wrong? | Everyone has an account open |
| 5 to 15 | Measure the desk edge thickness three times, write the smallest. Measure the cable. | Numbers in millimetres, written down |
| 15 to 25 | Describe the part in one or two sentences with every number, or start from a box and shape it by hand | Each sentence names the fit and the size |
| 25 to 35 | Read the part back: dimensions panel, two taps with Measure across the gap | The gap equals the measurement plus clearance |
| 35 to 45 | Change one thing by hand (a hole, a rounded corner, their initials with Text), download | One deliberate change, saved |
| 45 to 55 | Slice for the class printer, read the print time and grams, add to the queue | Print time under your limit |
| 55 to 60 | Exit ticket: which number decided the fit, and how much gap did you leave? | Written answer |
On a 45-minute period, merge the last two rows and print the queue after class. The parts are small enough that a class set prints in an afternoon on one or two printers.
The three ideas the lesson teaches
A part is defined by the thing it fits. The desk is 18 mm thick, not "about 2 cm". The clip's opening is that number plus a gap. Students who start from the measurement design differently from students who start from a shape.
Clearance is a design decision. Printed openings come out a little smaller than drawn. A clip that must slide on wants about 0.3 mm per side; one that must grip wants almost none. how much clearance to leave has the table you can hand out.
Read it back before printing. The dimensions panel lists the sizes the model was built with, and Measure gives the distance between any two points. A student who checks the gap before printing saves a 20-minute print and a reprint.
Two routes, same lesson
Students can type the part into the AI as a sentence with numbers, or shape it from a starter box with the hand tools: tap a face, add a cut 18.3 mm wide, round the corners, type their initials. Both routes end with the same check and the same file. Let students choose; the ones who describe it tend to finish first and then change it by hand, which is the point.
The hand tools (hole, cut, add, extrude, text, round, fillet, shell and measure) are free on any account, and so is downloading what you shape with them. With the AI, a new part spends 4 credits on a plan with its first 3 small changes free, a design change 3, a small change 2, a quick edit 1, so a seat's 25 credits cover 5 or 6 new AI parts a month with their small changes. A clip from a sentence is one new part; most students in a first lesson use one or two.
What to grade
- The measurement sheet: three readings, the one used, and why.
- The gap they chose, in millimetres, and the fit they wanted (snug, sliding, loose).
- The print: does it fit the desk? If not, what number would they change, and by how much?
The last question is the best one. A clip that is 0.4 mm too tight is a better lesson than one that fits by luck, because the student can name the fix. On a seat, that fix is a small change on the same part, and the first 3 small changes of each part spend nothing.
Next lessons
After the clip, move to a part with two fits: a holder for a phone or a calculator (outside size plus clearance, and an angle), then a part with a hole pattern, such as a bracket for a sensor or a board. Ten functional projects for high school students has the dimensions for each.
An Education seat is $3 a month, or $30 a year (2 months free), taxes included. Each seat puts 25 credits a month on the student's own account, with every STL, 3MF and sliced G-code download included and the online slicer up to 60 files a day. The teacher applies for the class in SpeakCAD with the school, its website and their role; once it is approved (usually within a day) they pick the number of seats (from 2 to 300, your own seat included) and pays through Stripe; the invoice carries the school's name, address and tax ID. Students join with the class link you put on the board, in the LMS or in the class chat, or with an e-mailed invitation, and they sign up with any e-mail address: no school e-mail needed. The teachers' page has the details.
Prompts to start from
Open one in the builder, change the numbers to yours, and the model renders in your browser, usually within a minute or two. Keep adjusting in the chat before you print.A clip that slides onto an 18 mm thick desk edge and holds a 6 mm round cable underneath, 15 mm wide, 2.5 mm walls, 0.3 mm clearance on the desk, the cable snaps in through a 5 mm opening
A tag 60 x 20 x 3 mm with rounded corners, a 5 mm hole 5 mm from one end, my initials engraved 0.6 mm deep
A bracket for an HC-SR04 ultrasonic sensor board 45 x 20 mm, two 16 mm round openings for the transducers 26 mm apart centre to centre, two M3 holes to screw it to a 3 mm robot chassis plate
Questions
Yes, if the part is small. A cable clip or a tag takes 15 to 25 minutes to design from a measurement and 15 to 30 minutes to print. Design and slice in the period, and print the queue during or after class.
A part that fits something every student has in front of them, such as a clip for the desk edge. It teaches measuring and clearance, prints fast, and the student can test the fit the next day.