Drawing Reviews — The Key to Productive Product Engineering

Our research has shown that as much as 40% of a product development cost and 60% of product development time is related to errors in the drawings. For every mistake on a drawing, parts have to be re-made and tests have to be done again. Further, often a mistake in one drawing percolates through the assembly causing mistakes in other drawings as well.

One way to prevent drawing errors is to conduct a formal drawing review before the drawings are released for pilot production. Studies show that having a proven drawing review process can save as much as 35% of the product development cost.

Here are some tips to conduct better drawings reviews:

1. Use Checklists for Each Type of Drawing: No one would get on an airplane if the pilot did not use a checklist and no part should be made before the drawings have gone through a checklist. We will make the same mistakes over and over again unless we document them on a checklist and use the checklist to prevent them. You can find our checklist here.
2. Co-Pilot Reviews: Have at least one other person review the drawing and formally sign off the checklist. The primary reason for the co-pilot is to check the pilot. It is easy for one person to make a mistake; two people making the same mistake at the same time is unlikely.
3. Above and Below Reviews: Review the drawing tree to find out which drawings (if any) feed into the assembly under review, and what drawings use this drawing — so called “above and below” because they are directly above and below on the drawing tree. Make sure the part under review is still compatible with other assemblies.
4. Drawing Control System: Part of a design review should be to make sure all drawing control procedures have been followed. It’s amazing how much money and time is wasted simply because someone used the wrong version of the drawing.