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