The Machine That Was Built Before the Design Review: Why Reviews Matter
A machine built by a small team. They skipped the design review (they were behind schedule). They built it. During commissioning, they found three major errors: a guard that blocked the operator’s access, a valve that was mounted where maintenance couldn’t reach it, and a sensor that was placed where the operator’s hand hit it. All three should have been caught in a review. This is about design review process, not about the engineers being incompetent.
What a design review catches
| Issue | Caught in review? | Cost to fix after build |
|---|---|---|
| Guard blocks access | Yes (layout drawing) | $2,000 (rework guard) |
| Valve unreachable for maintenance | Yes (3D model walkthrough) | $1,500 (relocate valve) |
| Sensor in operator’s path | Yes (3D model, human factors) | $500 (relocate sensor) |
| Wire color wrong | Yes (electrical drawing review) | $300 (re-label) |
| Bolt wrong size | Yes (BOM review) | $100 (replace bolts) |
The review process
A design review is a 2-hour meeting where the engineering team (mechanical, electrical, controls) walks through the design with manufacturing, maintenance, and the customer. The group looks at:
- 3D model: Walk through the machine. Can the operator reach everything? Is there clearance for maintenance?
- Electrical drawing: Is the I/O correct? Are the safety circuits right? Is the wire labeling consistent?
- BOM: Are the parts available? Are the ratings correct? Is there redundancy?
- Cycle time: Does the design meet the takt time? Are the motions reasonable?
- Safety: Are the guards adequate? Is the e-stop reachable? Are the interlocks correct?
What we did
After the commissioning failures, we ran a design review on the next machine. It was a 2-hour meeting. We found 12 issues on the drawings. None of them required rework — they were all changes before build. The next machine commissioned in 2 weeks (vs 6 weeks for the first). The review saved 4 weeks of rework.
The cost of skipping review
The first machine (no review) took 6 weeks to commission (4 weeks of rework). The second machine (with review) took 2 weeks. The review was 2 hours. The ROI was 4 weeks of engineering time. The machine that was built before the review wasn’t badly designed — it was designed in a rush. The review would have caught the issues on paper. Paper changes are free. Machined changes cost thousands.
The design review rule: Don’t skip the review. A 2-hour meeting catches issues on paper. Paper changes are free. Machined changes cost thousands. The machine that was built before the review had three major rework items. All three were visible in the 3D model. The review isn’t a formality — it’s the cheapest rework prevention you’ll do.
