Design Reviews
Every mechanism should go through at least one design review before manufacturing begins. The goal is to catch problems when they're cheap to fix (in CAD) rather than expensive to fix (in fabricated parts, or worse, at competition).
When to review
There are three natural points in the design cycle where a review adds value, and each one serves a different purpose.
Concept review (post-prototype, pre-CAD)
The mechanism has been prototyped and it works. Before starting detailed CAD, walk through the concept with the team: what the prototype showed, what the plan is for the real version, and what the known risks are. This should be a 10 to 15 minute conversation, not a formal presentation.
Design review (CAD complete, pre-manufacture)
The mechanism is fully designed in CAD. This is the big one. Go through the full checklist below and verify everything before cutting any material. The designer walks through the CAD, explains the mechanism, and reviewers check it against the criteria.
Post-build review (after assembly)
The mechanism is built and on the robot. Does it work as designed? What's different from the CAD? What would you change? These notes go into the Lessons Learned Archive so future teams don't repeat the same mistakes.
Design review checklist
Walk through each category and check whether each item applies to the mechanism being reviewed. Not everything will be relevant every time, but skipping a category entirely is how things get missed.
Running the review
Who should be there
The designer(s)
The mech lead
At least one person not involved in the design (fresh eyes catch things the designer has been staring at for days)
A mentor, if available
What comes out of it
A short list of specific action items. "Add a bearing support on the left side of the intake shaft" is useful. "Fix the shaft" is not.
Separate items into things that must be fixed before manufacturing and things that can be addressed later.
Design reviews work best when they feel normal and non-threatening. The goal is catching problems, not criticizing people. If someone found an issue, that's a win because it means you caught it before it cost time and material.
Commonly missed
These are the things most likely to slip through if you're not actively looking for them.
Wiring and cable routes
Mechanism works in CAD but there's no space for wires to reach the motor or sensor
Trace the wire path from every motor and sensor back to the electronics board
Range of motion conflicts
Two mechanisms don't conflict in their home positions, but they do when one is extended and the other is moving
Animate or manually move every mechanism through its full range in CAD while other mechanisms are also in various positions
Fastener access
A bolt is easy to place during assembly but impossible to reach with a wrench once surrounding parts are installed
Mentally walk through assembly order and check tool clearance around every fastener
Weight creep
Each part is light individually, but the mechanism as a whole is heavier than expected because hardware, fasteners, and wiring weren't accounted for
Add 10 to 15% to CAD weight estimates as a buffer for hardware and wiring
Assuming perfect parts
CAD has zero tolerance, real parts don't
If the design requires two things to be perfectly aligned, then there might be an issue... add space.
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