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Streaking Workpiece

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Ask Tech - Streaking Workpiece

In our continuing effort to create a reference for our customers on troubleshooting information, below please find our problems for this issue. If you clip this section or just keep this page in a file, it will build a troubleshooting reference for your use in the future.  These check lists are good regardless of what type of material you are sanding, as they are problem oriented in regard to the abrasive/machinery as opposed to workpiece based.

IX.       Streaking of workpiece

            1.  Belt loaded or dull.

            2.  Contact roll too aggressive or hard. 

            3.  Sanding pressure too high. On platens, excessive pressure will cause streaking which is shiny and 

               wide (1/2” or more).  Normally the streaking is straight.  Wavy streaking (longitudinally) is caused by belt

                oscillation (snakemarks).

            4.  Belt tension too low. 

            5.  Contamination of platen surface or contact roll.

                        - felt layer on platen may be compacted.

            6.  Contact roll face damaged or worn.

                        - often caused by feeding the workpieces unequally across the width of the belt causing uneven

                            wear. Always process the widest pieces first.

                        - grooves worn in surface of the contact roll can cause raised areas on the workpiece. 

            7.  Sanding dust or loose graphite between belt and contact roll or platen.

            8.  Damaged abrasive belt. i.e. inclusions of loose grit, resin or other foreign matter.

            9.  Excessive out-feed hold-down shoe pressure, normally seen as straight streaks.  

         10.  Damaged graphite cover on platen (hand sand cover with 100/120 material to re-establish a smooth surface).

         11.  Defective abrasive material.

         12.  Oscillation mechanisms out of adjustment.

         13.  Needle-shaped streaks or hairlines are often caused by inclusions of sand, resin, grit or minerals in the workpiece.  These inclusions can damage the grit or backing sides of the belt.

         14.  Dust on the workpiece or resin spots in wood.

         15.  Static electricity buildup, machine improperly grounded or low

                 humidity. Streaking of this nature is normally very narrow in

                 width (1/16” or less) and is intermittent.

         16.  Overloading due to glue lines, pitch or tramp material on workpiece. Causes belt burning.

         17.  Improper belt mounting can cause slight creasing (check  handling procedures!)

X.        Scratching of workpiece

            1.  Grit too coarse for application.                           

            2.  Platen surface uneven or tilted.  High or low platen surface.  

            3.  Abrasive belt too narrow for pressure shoe.

            4.  Improper grit sequence. Previous grit scratch not being removed.

            5.  Loose grit from another operation getting into sanding area.

            6.  Contamination on abrasive belt surface.


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