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Abrasive Troubleshooting Chart

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Manybelt sandingproblemscanbealleviatedbyobservingtheproper belt speeds, tensions, andfeedratesaslistedbelow.

   MACHINE 
  
APPLICATION  
 BELT SPEED  
 (sfpm)   
 BELT TENSION 
 (psi)   
 FEED RATE 
  (
fpm)  

HORSE POWER 
per inches of
be
lt width

 MACHINE

                          

Rough Lumber Sanding and Planing 6000 + 70-80 30-125 3 to 5

 

 

 

AEM, Anthon, Boere, Bogma Bridgewood, Burlington, Butfering, Cemco, Costa, DMC Heesemann, Jet, Powermatic Ramco, Sandingmaster, SCMI, Steinemann, Stemac, Tannewitz Timesavers, Viet, Weber

Abrasive Finish Planing 3800-7500
5000 (common)
65-75 45-50

1 to 3

 

Intermediate
Wide Belt Sandin
3000-600 75-90 (poly/coarse grits) 55-70 (cloth)
45
-55 (paper)
20-70

1 to 2

 

Man-Made
Board Sandin
6000-700 75-90 (poly/coarse grits) 55-70 (cloth)
45
-55 (paper)
 80-20

100 to 250

 

Cross Belt Polishers 4000-8000 N/A 20-60

15 to 30

 

Mold Sandin 1800-4500
most common
3000-4500 
30-40   20-5

N/A

 

   

Anderson, Bouligny, Critz, Crouch, Delle, Diehl, Fletcher-Tolbert, Oakley, Taglibue, Timesaver

 

Problem / Solutions

I. Loading up or clogging of the abrasive
1.       Switch to open coat product.

2.       Excessive sanding pressure.

3.       Excessive infeed pressure.

4.       Inadequate dust exhaust.

5.       Excessive belt speed.

6.       Moisture content of wood too high.

7.       Grit too fine.

II. Shedding (stripping) of abrasive grain

  1.       Excessive product flex; specify stiffer backing.

  2.       Depth of cut too heavy.

  3.       Excessive infeed speed.

  4.       Belt speed too low.

  5.       Contact roll too aggressive for application (smaller groove-to-land ratio needed).

  6.       Sanding in one area of belt only.  Oscillate the belt if possible or stagger the workpieces across the

            width of the belt.

  7.       Contact roll worn. Re-dress the roll.

 

III. Abrasives dulling prematurely

  1.       Grit too fine.

  2.       Excessive sanding pressure.

  3.       Belt too stiff for application.

  4.       Wrong product for application.

  5.       Excessive belt speed.

  6.       Contact roll not aggressive enough (greater groove-to-land ratio needed). 

  7.       Excessive wheel speed (flapwheel or brush wheel).

 

IV. Belts creasing

  1.       Belt too flexible.

  2.       Grit too fine.

  3.       Contact roll is tapered (cone-shaped).

  4.       Contact roll and idler roll not parallel.

  5.       Contact roll or idler roll worn in the center portion.

  6.       Belt tension too low (or less commonly, too high)

  7.       Dirt on the contact roll or idler roll.

  8.       Tracking mechanism damaged or defective.

  9.       Worn bearings on the contact roll or idler roll.

 10.      Uneven belt stretch due to improper feeding of workpieces.

 11.      Belt not installed on machine straight.

 12.      Moisture imbalance across the belt.  Check humidity!

            - Hang belts on proper storage rack for at least 24 hrs prior to use.

            -Paper belts are more susceptible than cloth belts.

            -Belts should be removed from machine, or at the least have the tension released during        shut-down periods if belt is on machine.

 13.      Belt improperly joined.

 14.      Drop in air line pressure affecting tracking or tensioning mechanisms.

 

 

V. Belt slippage

  1.       Belt tension too low.

  2.       Contact roll is excessively worn.

  3.       Shock load on belt due to big variation in workpiece thickness.

  4.       Dirt or dust between belt and contact roll.

  5.       Plain steel contact roll not providing enough traction for belt.  Try serrated roll or knurl surface of roll.

 

VI. Belts splitting

  1.       Belt too flexible for application.

  2.       Burr on the contact roll or platen.

  3.       Contamination on workpiece (nail, staple, etc.)

  4.       Excessive depth of cut or sanding pressure.

  5.       Contact roll and idler roll not parallel.

  6.       Abrasive material not heavy enough for application.

  7.       Variation in workpiece thickness.

  8.       Sanding in only one area of the belt.  Stagger workpieces across the width of a wide belt.

 

VII. Belts not tracking

  1.       Belt tension too low.

  2.       Sanding pressure too high or too low.

  3.       Uneven sanding pressure.

  4.       Contact roll or idler roll worn.

  5.       Dust between belt and contact roll.

  6.       Variation in workpiece thickness.

  7.       Alignment between contact roll and idler roll incorrect.

  8.       Belt stretched due to improper work feeding.

  9.       Platen out of position.

 10.      Damaged belt edge interfering with tracking mechanism.  Check for humidity imbalance.  Increase belt tension.

 11.      Belt tension overriding the tracking cylinder.

 12.      Tracking mechanism defective or out of adjustment.

            -electronic eye photo cell defective or dusty (clean the eye regularly).

            -microswitch failure or damage.

            -air jet controlled tracking mechanism may fail due to drop in line pressure.  Check air jets for blockage.

 13.      Contact roll tapered.

 14.      Belt joined or cut incorrectly.

 15.      Idler crown area worn (narrow belts only).

 

VIII. Chatter marks on workpiece

  1.       Worn bearings or bearing journals on contact roll or idler roll.  Normally shows up chatter on one     side of                                    panel only.

            -check bearing temperature if possible.

            -“listen” to the bearings using a mechanic’s stethoscope.

  2.       Sanding pressure too low.  Marks normally show up in spots.  Increase pressure.

  3.       Contact roll or idler roll out of balance.

            -Chatter marks caused by vibration are regularly spaced and clearly defined.

  4.       Contact roll too hard.

  5.       Belt splice defective or incorrect for application.

            -Chatter marks caused by belt joints are normally narrow, regular and clearly defined.

            -Try a different belt on the machine to compare.

  6.       Grit too fine.

  7.       Machine vibration.

  8.       Belt tension too low.

  9.       Hesitation in feed or drive mechanisms.

            -Chatter marks are irregularly spaced.

 10.      Drive belts too tight or too loose.

            -Check V-belts.

 11.      Abrasive belt too stiff for application.

 12.      Glazed conveyor belt.

 13.      Hold-down rolls or pressure shoes incorrectly set up.

 14.      Dust build-up on conveyor rollers or underneath conveyor belt.

 15.      Loose motor coupling, guards, cover plates or machine anchoring.

 

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 and stagger pieces when loading.

            -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.  Inclusions of loose grit, resin or other foreign matter.

  9.       Excessive out-feed hold-down shoe pressure.  Normally see as straight streaks.

 10.      Damaged graphite cover on platen (hand sand cover with 100 or 120 grit 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 side or the backing side 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 with (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’s scratch not being removed.

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

  6.       Contamination on abrasive belt surface.

 

XI. Burnished surface of workpiece

A condition identified by a wood surface that is too dense to properly accept stain or color. Often is glossy in appearance.

  1.       Abrasive belt is worn out.

  2.       Grit too fine for step.

  3.       Workpiece surface uneven in spots.

 

XII. Excessive fuzz on workpiece

Usually occurs when sanding wood of less dense species.

  1.       Use a finer grit.

  2.       Reverse belt or workpiece on successive passes.

  3.       Moisture content of wood should be less than 12%.  6% to 8% is ideal.

  4.       Try a glue sizing operation:  16 parts warm water to one part white glue is applied lightly over the    work                            piece.  Allow to dry fully and then sand.

  5.       Sanding pressure is too high.

  6.       Feed speed too high.

 

XIII. Belts or Workpiece Burning

  1.       Lack of graphite-covered cloth or other friction-reducing material on the platen.  IMPORTANT!

  2.       Lack of air or water cooled platens.

  3.       Lack of graphite stick applied to belt backing.

  4.       Sanding pressure too high.

  5.       Dust accumulation due to lack of exhaust.

  6.       Switch to open coat material.

  7.       Excessive belt speed.

  8.       Grit is too fine.

  9.       Burn streak on belt caused by excessive glue or pitch on the workpiece.

 

XIV. Soft grain being sanding out excessively

  1.       Contact roll too soft.

  2.       Excessive sanding pressure.

  3.       Grit is too fine.

  4.       Excessive feed speed.

 

XV. Belts breaking

  1.       Belt tension too high or too low.

  2.       Excessive sanding pressure.

  3.       Belts damaged in handling or mounting.

  4.       Belt splices defective.

  5.       Belt splice or belt material wrong for application.

  6.       Lap splice installed in wrong direction.  Check directional arrows on the back of the belt!

  7.       Inadequate storage procedures.

  8.       Belt tracking defective.

  9.       Heavy sanding residue at sanding area.

 10.      Frictional heat too high.

 11.      Excessive chatter or vibration.

 12.      Workpiece too thick (wide belts).

 

XVI. Belt flutter (in center of belt)

  1.       Belt tension too low.

  2.       Belt tension fluctuates.

  3.       Contact roll or idler roll dirty.

  4.       Contact roll or idler roll worn excessively.

  5.       Variations in workpiece thickness cause belt stretching.

  6.       Defective belt splice or dimension.

  7.       Inadequate storage procedures or moisture imbalance within belt.

 

XVII. Belt flutter (at one edge)

  1.       Belt tension too low.

  2.       Belt tension fluctuating.

  3.       Belt tension too great on one side only.

  4.       Tracking mechanism defective.

  5.       Contact roll and idler roll not parallel.

  6.       Contact roll and idler roll dirty.

  7.       Belt material stretched.

  8.       Belt material dimension wrong.

  9.       Damaged belt splice.

 10.      Defective belt splice.

 11.      Inadequate storage procedures, moisture imbalance within belt.

 

XVIII. Swirl marks from orbital disc sanding

  1.       Dirty muffler or exhaust on air sander.

  2.       Insufficient air supply or too small an air hose (air-powered sanders should have an air supply of 15           to 18 cfm at 90 p.s.i.).

  3.       Operator using too high an angle with the sander.

  4.       Grit too coarse.

  5.       Sanding pad too aggressive or worn in spots.

  6.       Worn bearing in sander.

  7.       Hold disc sander flat against workpiece before switching machine on or off.

 



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