Sanding quality requires a slower approach

The biggest operating problem that I witnessed during countless plant visits was the use of excessive feed speeds. This resulted in abrasive belt loading, burning, streaking and shortened belt life, along with poor sanding quality. There were no guidelines provided by abrasive belt or machinery manufacturers.

In last month’s column, I provided a chart listing the approximate depth of scratch imparted by various grit belts using different sanding head characteristics. The next information that you must have in order to sand intelligently is: What is the maximum amount of material that can be removed at the required feed speed?

I have developed six matrices that provide the approximate maximum material removal capabilities of various grit belts at various feed speeds for various groups of material. Please note the material removal values given are based on contact drum type sanding heads. Use 60 percent of the listed values for platen type sanding heads.

It is important to understand that the cutting capability of any abrasive belt is dramatically affected by a sander’s feed speed. If you double the feed speed, the cutting capability of any given grit belt is cut in half. If you reduce the feed speed by 50 percent, the cutting capability of any given grit belt is doubled. Therefore, if possible, slow the feed speed down and maintain production rate by feeding multiple rows of parts across the entire width of the machine. Slower feed speeds will allow each belt to remove more material, while minimizing belt loading and streaking and maximizing belt life and sanding quality.

If you are experiencing streaking and belt burning, you are trying to remove too much material at too fast of a feed speed and with too fine of a grit belt.

Almost every plant I have visited did not have material removal targets established for each individual sanding head. They knew approximately how thick parts were coming to the sander and what thickness they wanted coming out of the sander, but had not established individual sanding-head target removals.

They had no idea as to what each sanding was removing and, in many cases, the middle sanding heads were not cutting anything at all. It is essential to establish and maintain correct target removals for each sanding head in order to optimize sanding quality and belt life. This technique will be covered in my next article.

For help with sanding problems, contact: Howard Grivna, Sanding Systems Consulting Inc. Tel: 218-678-2929. www.sandingsystemsinc.com

This article originally appeared in the June 2012 issue.