Dan Goad, Application Engineer III, Norton Abrasives
hen calculating the material removal rate (MRR) for a roll grinding process, many may read and understand some of what they are looking at, but it quickly turns into a science class with formulas typically not used in roll grinding. Ultimately, the important information to determine is how does it affect the operating budget?
In a previous article, we explained how an operator can measure to see if the grinding wheel is being used efficiently by following some easy test parameters. This helps us to understand how the wheel is really being used without wasting valuable wheels to get the required stock removal and determine the money saved during the process.
Now we want to go a step further and look at the MRR of the wheel and compare MRR rates between two roll grinding wheels. There are a few items to take into consideration.
1. The Roll Grinder: A roll grinder has limitations such as the horsepower to the spindle and the stiffness of the grinder. Most operators know these limits, and in determining the best grinding wheel to purchase, these machine limits will need to be considered.
2. The Setup: The focus of this article is directed at hot and cold mill roll grinding. When grinding on centers or journals, the test would be conducted differently with respect to power used during the operation.
3. The Roll Type: The same type of roll must be used for MRR testing; material removal rates will vary due to material. For example, iron rolls will have higher removal rates than a material such as HSS, which will have lower values during testing. Testing should be performed with a roll that has been ground after mill use to ensure the “mill hard” surface has been removed prior to the grinding process.
4. Consideration should be taken to perform the grind test that best fits your situation, time availability, test wheels, and test roll.
|Calculate Q’w (Q prime)||Definition of MRR||Material Removal Rate|
Depth of cut in millimeters times feed rate in mm/s.
The calculated Q prime value will be in mm2/sec.
Ratio of volume of material removed to the grinding time (Minutes/Seconds).
Better known as Q’w (Q prime).
This is typically measured in cubic centimeters per minute (cm3/min).
When you're ready to perform the grind test, follow these steps:
|CYCLE 1||CYCLE 2||CYCLE 3|
|G Ratio (Test)||3.49||3.60||1.83|
|MRR' (Q'w) Average||in^3/min||4.7138||3.8536||3.8048|
At the end of the day, you can determine what your grinder's MRR is for any given test wheel. To have a Norton Application Engineer support your testing, feel free to contact us or reach out directly to your Norton salesperson to request help with a MRR test.
For more roll grinding resources, check out our articles on determining if your roll grinding wheel is being used efficiently and how to best optimize coolant parameters.