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3M Offers Tech Tips on Abrasives

3M has released new technical tips on how to get the most out of your abrasives during the body repair process.

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3M has released new technical tips on how to get the most out of your abrasives during the body repair process.

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It all starts with the tool. There are many things to consider when choosing abrasive pads for random orbital sanders (ROS) such as tool orbit, backup pad, tool speed, down pressure and approach angle.

Branden Loesch, application engineering specialist at 3M automotive aftermarket division, recommends using a 5/16” (8 mm) with a firm backup pad for the body department and 3/16” (5 mm) with a soft backup pad/interface pad combo for the paint department that enhance the life of the pad while reducing risk of burn-through in the paint shop with 3/16” tools.  Loesch said the use of 3/32” orbits is no longer advised due to the negative impacts it can have on your abrasive performance, as low tool orbit contributes to low cutting power. 

Loesch also recommends that technicians use a controllable medium tool speed with reasonable down force and low approach angle to the substrate.  Sanding with a high angle can lead to difficulties, creating flat surfaces while also contributing to the premature wear of an abrasive which translates to high consumption rates. To ensure technicians are using proper settings and techniques, Loesch said they use a visual training aid. (Figure 1). He said they draw two to three lines on the backup pad with a permanent marker: if the operator is using too high a speed or not enough down force, the lines will be difficult to see and will track around the tool quickly like old-fashioned sanders locked into a grinding mode. This will lead to abrasives wearing prematurely and burn-through along the panel edge. 

When tool speed and down force are set appropriately, it allows the ROS to engage in its sanding pattern, and Loesh said that’s when you’ll see the lines tracking slowly around the pad. The tool will be doing more orbiting than rotating. This will lead to more effective sanding, longevity in abrasive life, enhanced control and improved surface finish.

Best Practices for Dent Repair Finishing and Blend Panel Prep

Loesh also addressed two common concerns of techs in the paint shop: inline scratches from incomplete featheredge, and burn-through on blend panels from novice preppers. He said for the body man, it is of paramount importance to the final quality of the repair that they properly featheredge any damage repairs in an appropriate grade to remove all inline scratches before sending the vehicle to the paint department. Inline scratches are the number-one cause of what is called “repair mapping,” which is the ability to see the repaired area post-delivery of the vehicle. (See Figures 1 and 2 below). Proper feather-edging would remove these inline scratches and produce a repair of significantly higher quality, leading to improved CSI, body shop reputation and customer satisfaction.

Loesh added that to prevent aggressive preppers from burning through the edge of the panel, you should focus on perfecting their hand sanding techniques. Frequently, technicians sand the panel with a ROS first, then come back by hand to sand the “picture frame” around panel edges and hard-to-reach areas. Instead, he said to take a flexible abrasive sheet, or whatever product is preferred for use on blends, and start with this on the next job. Anticipate and sand the hard-to-reach areas and panel edges completely to remove the sheen prior to sanding the larger areas by machine. This will allow the prepper to get a proper preparation of the edges and hard-to-reach areas without burning through, and it will also allow them to remove adjacent inline scratches from the larger panel surface by finishing with the ROS.

For more information, shops can contact their local 3M collision repair specialist or visit 3Mcollision.com.

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