Fixing a machine problem can sometimes take minutes. Finding it can take hours, sometimes days. One of my clients recently told me of a problem with a leaflet feeder. They struggled for several days with erratic operation, unable to find the cause. In the end, it turned out to be a loose terminal that took about a minute to tighten. Effective troubleshooting skills are among the most valuable a technician can possess. There are some ways to help improve these skills. One is by use of the Ishikawa or “Fishbone” chart.
These are often used after the fact to figure out what happened. They can be even more valuable when used prospectively as a troubleshooting tool. By serving as a checklist or roadmap they can improve the speed and accuracy of the diagnosis. The Ishekawa chart can turn the technician into a troubleshooting shark.
An Ishikawa chart identifies a specific problem at its head. Causes are located along the fishbones. One approach is to sort all potential causes into one of 4 generic causes.
Man groups all causes that are the result of operator or other human error.
Machine groups all causes that result from issues with the machine such as erratic sensors.
Material groups problems caused by the materials which are to be run in the machine. These materials include packaging materials such as bottles, caps and film, the product itself, and ancillary materials such as glue or tape.
Method groups problems caused operating the machine outside of its capabilities.
The concept can be better shown than described:
The example shows a chart developed for a chuck style capper for the specific problem of inconsistent cap torque.
A method problem in this example is that an unsuitable torque tester is being used. The tester is being used according to design so it is not an operator problem.
Material issues potentially include over/undersized bottles and caps as well as deformed bottles or caps. Other potential issues might include flashing or excess mold release or loose or missing liners.
Potential machine issues include adjustment and maintenance. A machine with excessive wear will never be consistent in its end results. Another potential issue is the tester. If this is out of calibration, it may well show out of limits torqe even though it is really in specification.
Man is shorthand for operator error. If they are operating the capper incorrectly such as failing to maintain a proper level of caps in the hopper this could cause problems in operation. Perhaps the operator is testing improperly, snapping the cap loose in the tester instead of twisting slowly. Perhaps they are clamping too tightly and causing deformation.
Ishikawa charts can be prepared in advance. Develop a template and then begin to fill them in for potential problems in each machine such as the example shown for the capper. Other sheets in the capper set might be for crossthreading, missing caps, chute jams and other recurring issues.
It will usually be possible to fill in some of the initial potential causes of each. Then put the sets of templates in the hands of the technicians. As problems occur, they can serve as a handy guide to what to look for. As additional causes are discovered, they can be added.
The Ishikawa chart is a powerful trouble shooting tool. It can turn a troubleshooting fish into a troubleshooting shark.
