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Troubleshooting Guide: Abrasive Belts

Common Sanding Belt Problems and Possible Solutions

As a knifemaker, you may be experiencing some common problems such as breakage, tracking, or chatter when working with abrasive belts. Outlined below are possible causes and remedies to those problems, along with a few other troubleshooting tips to help your belts work at optimum efficiency. 

Why is my sanding belt breaking?

 Possible Cause: Remedy/Correction:
Heat build-up due to friction Reduce belt speed or depth of cut, increase/redirect cooling flow
Belts are creased/damaged Belt edges are damaged or stretched Practice proper belt handling and storage, replace belt if necessary
Accumulation of chips/swarf in grinding area Check machine exhaust system, increase/redirect coolant flow
Improper product specification Ensure belts and machine are appropriate for application
Improper belt storage Belt edges are damaged or stretched Practice proper belt handling and storage, replace belt if necessary
Improper belt tension Adjust belt tension accordingly
Belt is installed backwards Use directional arrows on backside of belt and install in accordance with operating direction of the contact wheel
Excessive rate of cut Reduce belt feed rate or depth of cut
Unpredictable belt tracking Replace belt if damaged, check belt tracking mechanism on machine

 

Why is my sanding belt slipping?

Possible Cause Remedy/Correction
Contact roll is worn Resurface/redress contact roll to ensure proper contact
Coolant between belt and contact roll Increase belt tension or redirect coolant
Belt tension is too low Tighten belt/increase belt tension

 

Why is my sanding belt tracking?

Possible Cause: Remedy/Correction:
Improper belt geometry Check belt length and edges - belt may be improperly cut
Tracking mechanism on machine is out of adjustment Adjust/repair belt tracking mechanism
Belt edges are damaged or stretched Practice proper belt handling and storage, replace belt if necessary
Contact roll is out of alignment Re-align contact roll 
Worn pulley Reduce belt tension or replace pulley
Contact roll is uneven/tapered/concave Replace or true contact roller
Improper belt fit Check belt length
Uneven grinding pressure/wear/stretching Use full belt width to grind
Insufficient or excessive pressure on belt Adjust grinding pressure
Insufficient or excessive belt tension Correct/adjust belt tension

 

Why is my sanding belt creasing/folding?

Possible Cause:  Remedy/Correction:
Belt is cone-shaped Replace the belt, as its side-to-side length is different
Belt shows moisture imbalance Replace belt and follow proper belt storage practices
Improper belt installation or size Adjust belt placement or replace with appropriately-sized belt
Uneven belt stretch Use the full width of the belt while grinding to ensure even wear
Uneven belt tracking Adjust or repair belt tracking mechanism
Contact roll and idler are not parallel Properly align components to parallel each other
Low belt tension Tighten belt/increase belt tension
Contact roll is concaved or tapered Replace or true contact roller

 

What causes sanding belt chatter?

Possible Cause: Remedy/Correction:
Improper wear, lubrication, or maintenance of machine Practice regular maintenance on machine
Improper product specification Ensure belts and machine are appropriate for application
Contact wheel is too hard/aggressive Replace with less aggressive contact wheel
Low belt tension Tighten belt/increase belt tension
Contact wheel is out of balance or shape Replace or true contact roller
Excessive grinding pressure Reduce grinding pressure
Improper belt speed settings Adjust belt speed accordingly

 

Why is my sanding belt loading/clogging?

Possible Cause: Remedy/Correction:

Insufficient dust collection

Check dust collection system for efficiency/effectiveness
Insufficient cooling Redirect or increase coolant flow
Excessive grinding pressure Reduce grinding pressure
Improper product specification Ensure belts and machine are appropriate for application
Excessive belt speed Reduce sanding belt speed

 

Why is my sanding belt glazing/dulling?

Possible Cause: Remedy/Correction:
Insufficient lubrication/cooling Increase/redirect lubrication or coolant flow
Improper product specification Ensure belts and machine are appropriate for application
Low belt infeed pressure Increase belt infeed pressure
Machine contact wheel is not aggressive enough Replace contact wheel with one of appropriate hardness/design
Improper grinding pressure Adjust grinding pressure accordingly
Excessive belt speed Reduce sanding belt speed

 

Why is my sanding belt shedding grit?

Possible Cause: Remedy/Correction:
Excessive belt infeed speed Reduce belt infeed speed
Improper product specification Ensure belts and machine are appropriate for application
Excessive cutting depth Reduce the cutting depth of the belt
Machine contact wheel is too aggressive Replace contact wheel with one of appropriate hardness/design
Not using the entire area of the sanding belt Use the entire surface of the belt while working
Machine contact wheel is improperly dressed or worn Re-dress or replace contact wheel

 

Why is my sanding belt resulting in a poor surface finish?

Possible Cause:  Remedy/Correction:
Uneven belt wear Use entire surface of belt when grinding/sanding
Difficulty removing previous grind lines Use different grit sequence
Belt is loading/dulling Replace belt or adjust grinding pressure
Insufficient cooling Redirect or increase coolant flow
Low belt tension Increase sanding belt tension
Overly-worn belt Replace belt
Machine contact wheel is improperly dressed or worn Replace or re-dress machine contact wheel
Coolant is contaminated Drain/replace coolant, check coolant filtering system if necessary
Machine contact wheel is too aggressive Use less-aggressive machine contact wheel design
Belt oscillation/movement Ensure that belt tracking mechanism is in good repair, check belt tension
Excessive grinding pressure Reduce grinding pressure

 

Why is my sanding belt causing poor workpiece tolerance?

Possible Cause: Remedy/Correction:
Excessive belt speed  Reduce belt speed
Improper product specification Ensure belts and machine are appropriate for application
Insufficient cooling Redirect or increase coolant flow
Improper belt tension Increase/decrease belt tension accordingly
Loose fixtures, conveyors, table, etc. Determine which part is loose, correct appropriately

 

Finding the Source of Chatter on Your Workpiece

Make 11 evenly-spaced marks on a sanding belt. Measure the distance between the 11 marks and divide by 10 to determine the spacing between the consecutive marks.
Determine which of the formulas below matches the distance between the adjacent marks you created.

 

Main Drive Transmission Belt:

Chatter Speed = Work Feed Speed (inches/minute) / RPM of Drive Belt

RPM of Drive Belt =  (Pitch Diameter of Motor Pulley or Sheave (inches) x Motor RPM) / Pitch Length of Drive Belt (Inches)

 

To Determine unknown belt speed:

Belt Speed (FPM) = (Roll Diameter (inches) x 3.14 x Roll RPM) / 12

RPM of Contact Roll = (Motor RPM x Pulley Diameter of Motor) / Pulley Diameter of Contact Roll 

 

Joints:

Chatter Spacing = Work Feed Speed (inches/minute) / (RPM of belts x Number of Joints)

RPM of belt = Belt Speed (FPM) x 12 / Belt length (inches)

 

Main Drive Motor

Chatter Spacing = Work Feed Speed (inches/minute) / RPM of Motor

 

Machine Idler or Contact Roll

Chatter Spacing = Work Feed Speed (inches/minute) / RPM of Idler or Contact Roll

RPM of Belt = Belt Speed (FPM) x 12 / Belt length (inches)

 

Main Drive Motor

Chatter Spacing = Work Feed Speed (inches/minute) / RPM of Motor

 

Oscillating/Automatic Tracking Contact Roll

Chatter Spacing = Work Feed Speed (inches/minute) / RPM of Motor