6 Common Grinding Problems and How to Solve Them
Most grinding problems affect one of two categories: either appearance of the workpiece or productivity and return on investment. After verifying that the grinding machine isn’t at fault, there is one likely culprit causing your grinding problems: your grinding wheel.
Poor surface finish, chatter, and burning all affect the appearance of your product. Productivity issues like short wheel life, slow or inefficient cutting, or the wheel not cutting at all are also costly problems to have.
Let’s take these one at a time to see how a fix to your grinding wheel can solve some of your most challenging grinding issues.
1) Poor surface finish
Why your grinding wheel may be at fault:
In the appearance category, poor finish is a common complaint when your grinding wheel isn’t optimized. Grinding is a multi-point cutting process, but broken down to the microscopic level, it has similarities to a single point operation like turning. Viewed this way, it’s easy to see how surface finish is affected by the same factors: the more material removed by each grinding point, the bigger the individual chips and the rougher the surface.
Solutions:
Select a grinding wheel with a finer grit size
Reduce the relative speed between the wheel and workpiece
Other possibilities:
If grinding wet, the coolant may not be efficiently removing chips from the workpiece or wheel interface.
It's also possible that the wheel is being dressed excessively, creating grinding points that are standing too proud of the wheel surface.
2) Chatter
Why your grinding wheel may be at fault:
Recognizable by a distinct, often audible, pattern on the workpiece, chatter has many causes. Wheel-induced chatter occurs when an out-of-true grinding wheel acts as an excitation source.
Solutions:
In this case the wheel should be trued carefully.
Also check that it isn’t slipping on its mount.
Other possibilities:
If the problem is tracked down to a vibration in the machine — possibly some kind of resonance — the solution is to vary the grinding speed. Try going 10% faster or slower to remove the forcing excitation.
A detailed discussion of chatter is available at the Abrasive Engineering Society website.
3) Burning
Why your grinding wheel may be at fault:
Machinists use the term “burning” to describe thermal damage. It can show up as cosmetic discoloration, changes in workpiece hardness, and possibly distortion-inducing internal tensile stresses. Burning can occur if the wheel is glazed or loaded, causing more rubbing and friction. This often occurs if the machinist is trying to push the wheel through the workpiece too quickly or using a wheel that’s too durable.
Solutions:
Dress the wheel with the correct dressing tool
Reduce the feed rate or the relative velocity between wheel and workpiece.
Other possibilities:
Burning is far more common when grinding dry, although can still be experienced in wet grinding if there isn't enough coolant flow to carry away the heat.
See “Burn Awareness”, originally published in Cutting Tool Engineering, December 2000, for more information.
4) Wheel life too short
Why your grinding wheel may be at fault:
This costly issue can be caused by a wheel that's either too hard or too soft for the workpiece. When this is the case, the grinding wheel loads up or wears away too quickly.
Solutions:
Try a grinding wheel manufactured with a different material that is better suited for your grinding operation.
Other possibilities:
Insufficient coolant
Dressing your grinding wheel too frequently
Wheel speed too low
5) Wheel cutting slowly
Why your grinding wheel may be at fault:
This productivity issue is usually caused by feeds and/or wheel speeds that are too low. If you are using the wrong type of grinding wheel, you may be forced to cut slowly to avoid burning, but ultimately that’s not efficient for your process.
Solution:
The solution is to find a wheel that can grind as fast as possible without burning. A grinding wheel specialists can suggest alternatives that will increase speed for your specific operation.
6) Wheel not cutting at all
Why your grinding wheel may be at fault:
Most likely, this happen when the grinding wheel is glazed by truing.
Solution:
The solution is to dress the wheel lightly until the grit opens up. For dressing advice, consult with a grinding specialist.
OUR BEST ADVICE: THINK LOGICALLY
Most grinding problems can be solved by tracing the fault back to basic principles. With all grinding applications, imagine your material being removed by individual cutting points. Thinking from this perspective, a solution usually emerges.
Also, use your resources. The grinding experts at CDT are happy to discuss your cutting and grinding issues and offer solutions that will set your manufacturing operations on track to success.