Common Polishing Defects on Double Edgers and Their Root Causes

Double-sided edging machines offer speed but are sensitive to misalignment and wear. Here are the most frequent post-polish problems.

Uneven Polish (One Edge Glossy, Other Hazy)

Cause: Spindle speed or wheel wear differs between left and right sides. Also, the conveyor belt might be worn more on one side, causing uneven glass pressure.
Solution: Measure spindle RPM on both sides – they should be within 2%. Replace polishing wheels in pairs (both sides simultaneously). Check belt thickness variation: replace if difference exceeds 0.5 mm across width.

Chipping or Shelling at the Edge Corners

Cause: The rough grinding wheels are too aggressive (too coarse a grit) or the pressure on the intake rollers is too high. Also, the glass might be entering the machine slightly skewed.
Solution: Reduce feed rate to 70% and inspect chipping location. If chips are on the leading corner, reduce entry roller pressure. Change to a finer rough wheel (e.g., 120# instead of 80#). Align the glass guide rails to be exactly parallel to the conveyor.

White, Translucent Edge Instead of Clear Mirror

Cause: Inadequate polishing sequence – skipping grit steps or using worn polishing wheels. Insufficient coolant flow to the last two polishing spindles.
Solution: Verify that the polishing sequence includes at least 600#, 1200#, and 2000# wheels. Replace the 2000# wheels if they have processed more than 15,000 linear meters. Increase coolant flow to 12 liters/minute per wheel and use a 0.5 micron filter to remove glass sludge that can scratch the edge.

Calibration and Setup Solutions for Double Edgers

Setting the Correct Distance Between Spindles

If the spindles are too close, the wheels will dig into the glass surface; too far, they won't contact the edge. Use a calibration glass of known thickness. Run the machine and measure edge material removal. Adjust until each side removes exactly 0.8–1.2 mm per pass.

H3: Parallelism of Left and Right Spindle Axes

Non-parallel spindles will produce a tapered edge (wider at the top than bottom). Use a dial indicator mounted on the spindle housing. Traverse the indicator along the spindle length – variation should be <0.03 mm over 200 mm. Realign the spindle support bearings if necessary.

Coolant and Maintenance Fixes

Coolant Contamination

Old coolant with glass fines acts as a lapping compound, scratching the edge during final polish. Change coolant every 200 operating hours or when pH drops below 7.5. Install a magnetic separator and a paper band filter to remove ferrous particles (from worn bearings) and glass dust.

Worn Conveyor Belts

A glazed or hard conveyor belt allows glass to slip, causing variable edge pressure and uneven polish. Replace the belt every 12 months for single-shift operation. Use a belt with a Shore hardness of 60A–70A for double edgers.

Step-by-Step Troubleshooting Checklist for Operators

1. Visual inspection of wheels – Look for glazing, cracks, or uneven wear. Dress metal-bond wheels with a silicon carbide stick. Replace resin-bond wheels if the surface is shiny.

2. Check coolant nozzles – Each polishing wheel must have a jet pointing at the contact zone. Nozzles clog often; clean daily.

3. Measure edge gloss – Use a gloss meter (60° angle). Acceptable value >90 gloss units for interior glass, >95 for automotive.

4. Run a test piece after any adjustment – Keep records of settings that produced defect-free edges.