The fine polishing of steel balls
reach to the standard requires of steel ball by
customer, G28, G10, G5
Fine grinding and ultra-fine
grinding of steel balls are the final processing
procedures of steel balls. For steel balls above G40,
ultra-fine machining process is generally adopted. The
final dimensional deviation, geometric accuracy, surface
roughness, surface quality and burn of the steel ball
shall meet the technical requirements of precision or
ultra precision machining process.
When checking the diameter deviation and geometric
accuracy of steel ball, it must be measured on the
specified special instrument. After finishing, the
workpiece surface roughness and surface quality are
tested, which is generally used for visual inspection
under spotlight. In case of dispute, the 90x magnifying
glass can be inspected and compared with the
corresponding standard photos. In order to inspect the
surface quality and roughness of workpieces after
superfinishing, a certain number of workpieces must be
sampled 90 times with a magnifying glass and inspected
with standard photos. When there is visual doubt about
the surface roughness, it can be tested on the surface
Burn examination was performed by random sampling. The
quantity and quality standard of sample inspection shall
meet the requirements of burn standard.
The reasons for poor surface roughness are as follows:
1. The processing quantity is too small and the
processing time is too short.
2. The groove of the grinding disc is too shallow and
the contact surface between the groove and the workpiece
is too small.
3. The hardness of the grinding disc is too high or
uneven, as well as trachoma and porosity.
4. Excessive addition of abrasive paste or
5. The groove of the grinding panel is too dirty, with
iron filings or other sundries.
The main reasons for the poor local surface roughness
are: the groove of the rotary grinding disc is too
shallow, the contact area of the workpiece is too small,
the groove angle of the grinding disc is too small, and
the rotation of the workpiece is not flexible. The
on the upper grinding panel is very small, resulting in
sliding between the workpiece and the grinding panel.
Surface wear is also a common defect in circular
machining. In severe cases,
there are obvious pits under the astigmatism lamp. Only
one black or yellow can be seen in the light. However,
the pit can be seen at 90 times magnification. The lower
part of the pit is rough and the scratches are uneven.
The reason is: the groove depth of the grinding disc is
different. The workpiece in the deep groove sometimes
stays and sometimes slides due to low pressure,
resulting in grinding at the contact between the
workpiece and the grinding disc; The groove wall of the
grinding disc drops and grinds.