Testing control performance
Check the performance of the hold-to-run controls using the following tests:
- Inch movement - mark the cylinder and machine frame, inch and measure
- Crawl speed - count the number of revolutions per minute and multiply by the cylinder circumference.
Check performance of trip nip devices at regular intervals, particularly where slow crawl cleaning has been identified as appropriate. Deterioration of the trip nip performance will lead to a significant risk to the operator during cleaning on slow crawl. On tripping, the length of movement of the trip bar should be greater than the stopping distance of the cylinder, ie cylinder movement ceases within the deflection travel distance of the bar.
To test trip nip performance:
When press is stationary, measure the total deflection of the trip nip bar (t). Mark the cylinder and machine frame. Operate the crawl control. Push the trip nip with a cardboard tube when the two reference marks are in line. Measure the distance moved by the cylinder (c) and compare measurements (t) and (c); (t) should be greater.