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How to find particleboard defects.


Laminators of particleboard require a smooth, even surface, especially when applying thin papers or foils to the substrate. Undetected defects in the substrate surface can lead to poorly laminated finishes.

Some main causes of these surface defects arise from improper sanding techniques. However, Cliff MacDaniels, sales engineer at Willamette's Lillie Division and consultant to this guide, said, "Even though many of these sanding defects are hard to detect to the untrained eye, they usually won't be seen in the field because of quality control at the manufacturing plant."

The pictures and descriptions in this guide can be helpful in spotting particleboard surface defects, but MacDaniels added, "There's nothing better than chalking or examining the board by touch to detect defects."

PHOTO : Streaks Description: Uneven sanding. Usually a variation in panel smoothness or sheen, not thickness Probable cause: Loaded or worn sanding belts Troubleshooting: Replace sanding belt or smoothing bar

PHOTO : Sand Through Description: Removal of fine surface material, causing the large material of the core layer to show through Probable cause: Panel is too thick when it enters the sander, or an unequal amount is sanded off one side Troubleshooting: Adjust sanding press

PHOTO : Scratch Description: The panel appears to have scratch marks down its length Probable cause: Inconsistent abrasive grain dispersion on sander belts or finishing heads not working properly Troubleshooting: Replace sanding belts or adjust finishing heads

PHOTO : Hesitation Description: Dip in surface caused by idling sanding head when a panel stops or hesitates in the sander Probable cause: Feeder belt slippage, or an extra thick panel disrupts the feed rate Troubleshooting: Reject the board

PHOTO : Thin Description: Yellowish areas on the panel surface Probable cause: The pre-cured layer has not been sanded off because the panel is too think for the sander. Troubleshooting: Panel production problem; reject board

PHOTO : Chicken Scratch Description: Raised or gouged area on surface Probable cause: Decreased amount of abrasive concentration on sander belt Troubleshooting: Replace sanding belts

PHOTO : Ridges & Grooves Description: Thickness variations on panel surface. May appear in a straight line (smoothing bar related) or back and forth across the panel (sanding belt related) Probable cause: Caused by poor sanding belts or smoothing bar Troubleshooting: Replace smoothing bar or sanding belts

PHOTO : Snipe & Rollover Description: Snipe: tapering off at about an inch from the end of the panel Rollover: tapering along length of panel Probable cause: Improper panel feeding into the sander, or too much pressure is applied along the panel edges Troubleshooting: Snipe: Butt panels together and keep straight when feeding Rollover: Adjust smoothing bar pressure by angle-cutting or tapering the felt on the ends

PHOTO : Chatter Description: Pattern of marks appearing across the board, usually appearing within 12 inches of the edge of the panel Probable cause: In most situations, the problem is caused by not enough pressure on the smoothing bar. Out-of-balance rolls and bearings or an abnormally thick belt splice may also cause chatter Troubleshooting: readjust pressure on smoothing bar
COPYRIGHT 1991 Vance Publishing Corp.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1991, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

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Author:Derning, Sean
Publication:Wood & Wood Products
Date:Apr 1, 1991
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