What’s happening here? A manufacturer of engineered hinges, precision tubes and spacers, custom stampings and assemblies for the automotive industry is not being considered for future business by a customer dissatisfied with the inconsistent quality and poor delivery of an ongoing order for bracket assemblies. The cycle of late deliveries and broken promises began almost three years ago at the very start of production for this product. Can the manufacturer repair its reputation and ever be considered for new business again?
The Situation as observed on the shop floor:
The bracket assembly consists of three metal pieces in a line. They are connected by two shouldered rivets, which allow each end piece to rotate. The current process requires three steps to create these bracket assemblies: Step 1 presses a bushing into one of the end pieces. Step 2 hammers in the rivet connecting the other end piece to the center piece. Step 3 hammers in the rivet connecting the end piece with the bushing to the center piece. One operator completes Step 1, a second operator completes Step 2, and together they create quantities of parts to pass on to a third operator who completes step 3 and also inspects them and packs them in boxes. The required rate is 120 perfect pieces per hour. The production rate hovers around 60, but with many of those 60 defective.
The Findings
The manufacturer’s process requires the machine stroke (distance the machine advances) to be adjusted every few pieces. The need to adjust the stroke begins at the start of production, resulting in an immediate slowdown. The parts need to be snug, but not too tight and cannot touch each other when rotating. If the parts are not parallel before the rivet is set, the pieces hit each other when rotated and have to be sorted and removed as defective parts. Production slows again. No employee assigned to Step 2 can achieve the expected output for those two reasons: He must spend extra time adjusting for correct stroke depth for each assembly, and secondly he is at high risk for creating defective assemblies because the components are not held securely in place and can shift when being hammered together.
The Solution
The process was changed from hammering or peening the rivet to compressing it in a single stroke. All pieces are now held securely in a fixture to prevent the movement in Step 2. All three steps are connected in a one-piece flow wherein a single operator loads and cycles the three steps together. He simply monitors the process air pressure, not stroke length, to control the rivet tightness.
The Results
One operator instead of three now produces 120 flawless pieces per hour. Not only are the defects eliminated but the wasted labor inspecting 100% of the assemblies is also gone. Furthermore, the output is consistent and meets the customer’s expectations in all respects. Earning back lost confidence can be a long road, but the manufacturer is now traveling it confidently, visibly and hopefully.
Comments