| Every brush leaves a track mark on the metal it touches. It allows us to understand how the abrasive material has made contact with the metal strip. The track marks give a visual picture of whether adjustments need to be made to change the brushes’ point of contact. If you're reading this post, you likely HAVE unwanted tracks (also called footprints or nips) on your strip. Let's take this step-by-step. 1. Analyze the footprint. What do they tell us about what's going on in the machine? This image to the right can give us the information we need |  |
2. Make adjustments based of what you see.
- Just Right: In the diagram above, the first image illustrates the footprint we want to see. Here the brushes are balanced, the shaft is aligned, and the load is calibrated correctly. Our strip will be cleaned consistently across the entire surface. In general, we achieve the desired results if our brush is calibrated to a load that compresses the brush no more than 9mm.
- Too Light: In the second example, the brush pressure is too light to clean adequately. The footprint will be uniform and consistent, but it won't clean the surface of the metal adequately. This machine needs to have its load recalibrated so there is more pressure on the brush. (Suggested: read our "Bigger is Better" post to learn the rule of thumb for optimum foot print width/per diameter of your scrubber brush.)
- Misaligned: Example three illustrates what happens when the brush shaft is misaligned. Another indication of misalignment is "Surface Chatter." In general, if the chatter marks are far apart, it's a brush issue. If chatter marks are close together, it's usually a problem in the back-up roll. Often, the response to misalignment is to increase load pressure to try to force the raised part of the brush to scrub the strip. That will never happen without causing damage to the brush. Instead, fix the alignment and recalibrate the pressure.
- Uneven wear: The fourth example shows what happens when a brush has uneven wear. The sides of the brushes will touch and clean the sheet, but the center never makes contact unless you smash the brush into the strip. We call this an Apple Core effect, and what it means is that the brush needs to be redressed. (DO NOT increase the pressure on the load thinking this will solve your problems. At the very early stages, this situation may be resolved through recalibration, but it's likely by the time you're seeing the Apple Core Effect, the brush needs to be repaired.) Also, consider this: in this situation, the brush is making contact with the back-up roll and creating a parasitic load. So, if you are using Amps or kW as a measuring device, the read you receive on the measuring device won't be a true representation of what is happening on the surface of the strip.
We can't stress enough the importance of correct calibration. Incorrect calibration is the cause of an extraordinary loss of time and money. It's essential to adjust your machine for the job. We can find the sweet spot of the brush on the sheet when we calculate the kW measurement at three or more different points in the load:
- no load
- point of friction
- at points with varying amounts of compression
If you find you're having problems processing strip with consistent quality, or if you're frustrated with how quickly your brushes wear out, please contact APT. We're available to help you discover what needs attention in your machines, on your line, or with your brushes. We have developed innovative scrubber brushes and brush-dressing tools that allow us to offer solutions that wouldn't have been possible in the past.
We also have machines that automatically calculate all the pressure measuring and footprint analysis for you--without ever having to change the brush.
Please give us a call to discuss ways we can help.
We also have machines that automatically calculate all the pressure measuring and footprint analysis for you--without ever having to change the brush.
Please give us a call to discuss ways we can help.
