customer had a bracket that needed assembly. The unit used four self-tapping screws to hold it in position. The wrong disk washer bolt type was used, but that's only part of the problem. With hand assembly everything went together and the simple assembly fixture worked pretty well.Then the production rate went up and the demand rose to about 90,000 units per month. It was time to automate, and instead of starting the screws with an operator, four automatic drivers (on fixed centers) were attempted. After many "machine caused" rejects, the parts were inspected.
Stamped parts with tolerances hole to hole mate quite nicely, but not when located on the part profile. The interference in the holes caused the screws not to start through the holes and jam in the self-feeder drivers.
Part of the problem is the way the parts were drawn and the way the holes were referenced. But a big part of the problem is a supplier that used up all the tolerance in the drawing to make up for differences in bend radius, material changes, spring-back, and take up. Selecting a supplier that was ISO qualified and could certify all the parts would be a help, but part of the issue is poor drawings and no Cpk spec on the incoming product. These are the manufacturer's problems.
The drive to lower cost parts delivered faster and with higher quality is not going to stop. The first step to being the manufacturer that can deliver better, faster, cheaper is under
standing that good parts start with good drawing and solid specifications. Responsibility for this issue falls on both the consciencious manufacturer and the qualified supplier.
We welcome your comments and criticisms, so PLEASE tell us what you think.
No comments:
Post a Comment