CAD Practice Exercises
Use these exercises to practice the skills introduced in Module 5. Each one adds a new constraint and includes measurements you can check without waiting for a mentor to review the file.
They are tool agnostic. The wording assumes Onshape because it is free for FTC teams and runs in a browser, but every exercise works in Fusion, SolidWorks, or Inventor.
Work through Lesson 5.2 first. The exercises assume you can create and recognize a fully defined sketch.
Check your file before you ask anyone to look at it
Export the part and drop it below. The check reads the file in your browser, measures what is actually in it, and tells you which of the exercise's stated numbers it matched.
Two formats, two different answers. STEP carries exact geometry, so hole diameters are read as modelled and a 3.0 mm hole where a 3.2 mm clearance hole belongs is caught immediately. STL is triangles, so it can measure volume, mass, and whether the solid closes, but every curve in it is a polygon and reads slightly small. Send STEP for sizes, STL for mass and watertightness, and both when you want the full picture.
CAD File Check
Export a part, drop it here, and see which numbers match what the exercise asked for.
Drop a .step, .stp, or .stl file here
- Reports what the file says about itself, with no expected answer to compare against.
Send STEP when you want hole sizes checked exactly, and STL when you want volume, mass, and whether the solid closes. Onshape, Fusion, and SolidWorks all export both. Nothing leaves your browser.
The check measures the submitted geometry. It can confirm that a plate is 80 mm long and that its holes have the required diameter, but it cannot decide whether the plate is appropriate for your robot. Review function and fit separately.
- Community design guides for the mechanisms these exercises are drawn from: Game Manual 0: Design Skills
When an exercise names a fastener or bearing, use dimensions from the vendor's current drawing. The model should match the part the team can buy and measure.
Stage 1: Sketching and single parts
Fully defined mounting plate
Model a flat aluminum plate with a pattern of mounting holes. The goal is not the plate. The goal is finishing with a sketch that has no free geometry left in it.
Requirements
- Plate is 80 mm wide, 40 mm tall, 3 mm thick.
- Four M3 clearance holes at 3.2 mm diameter, one in each corner, inset 6 mm from both edges.
- One 8 mm bore centered in the plate.
- All external corners filleted at 3 mm radius.
Check your own work
0 of 4 checks passed
What this exercise is really testing: Four separate hole positions can produce the correct first version but fail when the plate width changes. Use symmetry and equal constraints so the sketch records the intended relationship and keeps the holes aligned after an edit.
Adapter plate between two hole patterns
Model the one custom part that lets a component with an awkward bolt pattern mount to a build system rail. This is the part that saves a team from making a custom robot.
Requirements
- One face carries a 4 hole pattern on a 32 mm square, for M3 clearance.
- The opposite face carries a 2 hole pattern spaced 48 mm apart, matching a rail, also M3 clearance.
- Plate thickness 4 mm. Overall size no larger than 70 mm by 70 mm.
- At least one of the rail holes is a slot with 4 mm of adjustment.
Check your own work
0 of 4 checks passed
What this exercise is really testing: Use the slot to provide intentional adjustment. Two fixed hole patterns can be difficult to align when part and assembly tolerances accumulate, while a short slot lets you set the final position without modifying the finished plate.
Stage 2: Assemblies and motion
Dead axle wheel assembly
Assemble a wheel on a non-rotating axle supported by two bearings. This is the assembly that teaches why Lesson 4.3 insists on two supports.
Requirements
- An 8 mm axle, two 8 mm bore bearings, one wheel, and two side plates.
- Bearings are pressed into the side plates, spaced at least 30 mm apart.
- The wheel sits between the bearings, not outboard of them.
- Spacers set the wheel position so it is centered between the plates.
Check your own work
0 of 4 checks passed
What this exercise is really testing: Calculate the spacer stack before adding mates. If its total does not match the plate spacing, the assembly will contain either a gap or interference even when the wheel has the correct revolute mate.
Arm with a range of motion check
Build a pivoting arm on a chassis and drive it through its full travel to find where it collides. Finding the collision is the deliverable, not avoiding it.
Requirements
- A chassis block roughly 400 mm by 350 mm by 100 mm as a stand-in.
- An arm 450 mm long on a pivot mounted to the chassis.
- A simple end effector block at the far end, 60 mm by 60 mm.
- Arm travel from 0 to 120 degrees measured from horizontal.
Check your own work
0 of 4 checks passed
What this exercise is really testing: Do not check only the endpoints. An arm can clear at 0 and 120 degrees but strike the chassis at an intermediate angle. Step through the range and run interference checks at several positions.
Two stage linear slide
Model a two stage slide and mate it so the stages extend together in the correct proportion. This is where slider mates and their relationships get real.
Requirements
- A fixed base stage and two moving stages.
- Total extension of at least 500 mm from the retracted length.
- Stage overlap of at least 60 mm at full extension.
- A spool of your chosen diameter mounted at the base.
Check your own work
0 of 4 checks passed
What this exercise is really testing: Overlap at full extension. It is easy to hit a travel target by letting the stages nearly separate, which produces a slide that binds and deflects badly under load. The overlap requirement is the real constraint, and it is what forces the retracted length to be longer than you first want.
Stage 3: Design intent under change
Survive the requirement change
Take your Exercise 2.1 wheel assembly and change the wheel diameter and the plate spacing. A well built model absorbs this in two edits. A poorly built one has to be rebuilt.
Requirements
- Change the wheel diameter from its original value to 96 mm.
- Change the plate spacing by 12 mm.
- Do not delete and remodel any part.
Check your own work
0 of 4 checks passed
What this exercise is really testing: This exercise tests how the earlier model responds to change. If the edit requires extensive repair, inspect where the model recorded fixed positions instead of relationships and revise those features.
Drawing someone else can build from
Produce a fabrication drawing for the adapter plate from Exercise 1.2 and hand it to a teammate who has not seen the model.
Requirements
- Every hole is marked as either clearance or tapped, with its size.
- Material and thickness are stated.
- Tolerances are given only where they matter, not on every dimension.
- At least one view shows the slot with its travel dimensioned.
Check your own work
0 of 4 checks passed
What this exercise is really testing: Tolerancing everything. Putting a tight tolerance on every dimension tells the fabricator that nothing matters more than anything else, so they either spend the effort everywhere or guess. Lesson 11.1 covers choosing tolerance from function, and this drawing is where that becomes concrete.
Where to go next
Once you can finish Stage 3 comfortably, model your team's actual robot. Start with the drivetrain, add each mechanism as it is designed, and keep the master assembly current. Module 5.3 covers checking the starting envelope before parts are fabricated.
Stuck on this lesson?
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