The plant has a custom-built, multi-stage production machine. Each stage is a modified machine that formerly served some other purpose; “recycling” made this system affordable.
Some stages require operator input, others do not. For example, the operator loads metal blocks into a multi-position drilling/chamfering machine but a robotic arm moves the drilled/chamfered parts to a multi-position buffing machine. A programmable logic controller (PLC) controls the flow of plastic pellets into another stage.
Lately, the scrap rate has been unacceptably high (finished parts don’t meet specs). Three different techs have run through the manufacturer’s maintenance and calibration procedure and no adjustments were needed. How might you address this?
A good first step is to audit the operators. Identify where in the process the out of spec operations are occurring and observe the operators at (and upstream of) each “where.” Are they following the manufacturer’s procedure? Make videos of each operator and each station.
Characterize the failure modes (give each one a name, for example “over-chamfer”) and compile a spreadsheet showing the number of instances of each. Submit this information, along with scrap part photos and the videos taken earlier, to the manufacturer for technical and troubleshooting assistance.
A machine problem could be caused by any of several factors, such as:
- Inadequate vibration protection. Install vibration sensors.
- Power quality problems. Conduct a power quality audit.
- Improper bonding, including mechanical integrity issues with the equipment grounding conductor (EGC). Conduct a bonding inspection.
