Studer CNC Universal Grinders presents Grinding Errors Detection and Repair

1. 1
The most frequent grinding errors
Optically detectable grinding errors
Grinding with comma sign
Cause: Abrasive grains in the coolant.
Remedy: Better filtering of the coolant, clean the
grinding wheel guard.
Grinding with dull grinding wheel
Cause: Grinding wheel too fine or dressed with
dull dressing tool.
Remedy: Increase dressing feed speed or renew
the dressing tool.
Grinding with source of interference
Cause: From a source of interference inside or
outside the machine. Errors like those in the
picture can be caused by a press, a passing
pallet stacker inside the building or a heavy
vehicle outside the building. Where the source of
interference is a fan or centrifuge, the bevels are
spread over the entire workpiece.
Remedy: Place the machine in a disturbance-free
area. Isolate the disturbance.
Grinding with chatter marks
Cause: Vibrations in the machine and workpiece
caused by an imbalanced grinding wheel or the
grinding process itself.
Remedy: Never let coolant run over a stationary
grinding wheel. Re-balance the wheel. Check
that the set-up is rigid and the centers clean.
Eventually use a steady rest.
Grinding with angular marks
Cause: A spiral, non-circular wheel caused by a
faulty dressing process which copies the error
onto the workpiece. (Rough patterns can also be
caused by interfering vibrations.)
Remedy: The wheel must always be dressed in
the same direction. It is often sufficient to change
the workpiece speed slightly.
Grinding with burning marks
Cause: This very dangerous error can cause local
structural alterations and the forming of cracks
through overheating during the grinding process.
Remedy: Choose a cooler grinding wheel or
increase the dressing feed speed. Better cooling
of the process, increase the coolant amount.
Reduce the material removel rate (Qw).
Grinding with feed marks
Cause: The centre line of the grinding wheel is
not parallel to the table. This can be caused by
the dressing tool shifting during the dressing
process, through thermal influence or through
wear.
Remedy: Monitor temperature situation by modi-
fying the dressing tool or dressing conditions.
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2. The most frequent grinding errors
Geometrical grinding errors
Dimension error in the diameter
Cause Remedy
– Substantial grinding wheel wear Harder grinding wheel
– Dressing amount is smaller than wheel wear Increase dressing amount or dressing interval
– Dull grinding wheel Dress / check dressing tool
Tapered workpieces
Cause Remedy
– Unfavourable workpiece (long and thin)
Coolant pressing on the workpiece
As little coolant as possible
– Unfavourable workpiece (long and thin)
Grinding wheel pressing on the workpiece
Use narrower wheel / relocate wheel
– Thermal growth of the dressing tool Better cooling of the dressing tool
– Dressing tool wear New dressing tool
– Dressing axis not parallel to the grinding axis Set
– Unstable clamping Adjust clamping / less infeed
– Tailstock and WSS not aligned Correct
Roundness errors
Cause Remedy
– Non-circular workpiece centres (A) Regrind workpiece centres
– Deformation of workpiece centres Regrind workpiece centres
– Non-circular centres (B) Regrind/replace centres
– Lateral force on driver Re-form driver
– Workpiece centres not aligned (C) Grind centres (axis)
– Workpiece centre too short,
centre standing out in the base (D)
Re-bore centre base
– Unstable clamping Adapt clamping / less infeed
Form errors
Cause Remedy
– Insufficient spark-out time Increase spark-out time
– Incorrect grain (form; edge holding
capability capacity not guaranteed)
Finer wheel
– Substantial wheel wear Harder wheel
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