Defining Truing Parameters with The Grinding Doc
Dr. Jeffrey Badger, an independent expert in precision grinding and known as The Grinding Doc, collaborated with Rush Machinery to define scientific truing parameters. In a three-part video series, we discuss truing parameter considerations as well as the testing process and outcomes. This blog post will explain the testing process and results that we cover in the video series, as well as Rush Machinery’s truing and dressing capabilities.
Parameters to Consider When Truing
Defining truing parameters for each application is crucial for achieving the greatest possible efficiency and improved cycle times. By taking a scientific approach to truing parameters using systematic testing, a lot of trial and error can be eliminated from the dressing process. Our tests measured wheel wear and grinding power. Additionally, more valuable information was received by collecting the grits to inspect for bonding material removal and diamond grit fracturing at a microscopic level.
By changing only a few factors, such as the speed ratios and relative aggressiveness, material removal speed can be increased up to four times. By establishing scientific truing parameters, we learned how to obtain the highest removal rate with low forces. Some key considerations for truing a diamond wheel using silicon carbide or aluminum oxide dressing wheels include:
- Wheel Wear (G-ratio): The G-ratio is the length of time the grinding wheel spends grinding the material relative to the amount of subsequent wear it inflicts on the dressing wheel. For example, a durable grinding wheel can grind materials for extended periods with minimal wear.
- Wheel Rotation Directions: The two directions in truing are unidirectional and anti-directional. Unidirectional rotation rotates the wheels in the same direction to crush the substrate, while anti-directional rotation spins the wheels in opposite directions at the point of surface contact. Antidirectional rotation produces more dust by throwing dust in both directions, rather than in one direction.
- Traverse Speed: Traverse speed is determined by the amount of surface area on the diamond wheel that an individual grit on the perimeter of the dressing wheel contacts the diamond wheel area as it rotates around the axis of the wheel.
- Dressing Wheel Infeed: Infeed is the distance the dressing wheel is moved into the diamond wheel for a given traverse stroke.
- RPM: The ideal RPM will be determined by the unique characteristics and shape of the material to be ground. Generally, it falls in the range of 30-60 m/min.
- Surface Speed Ratio: Surface speed ratio refers to the speed of the grinding wheel in relation to the speed of the dressing wheel. It is important to find the proper ratio because an incorrect ratio will result in chatter.
Taking these factors into account develops a good set of starting parameters to obtain significantly faster and more efficient truing results.
The Truing Testing Process
The truing testing process involved the use of a Grindometer device to measure the power in the grinding wheel spindle. The Grindometer measures spindle power in horsepower or kilowatts and is used to compare grinding wheels, eliminate grinding burn, reduce cycle times, and troubleshoot any grinding problems that are occurring.
By attaching a Grindometer to a truing machine, a significant amount of process data is generated. This information allows us to understand which parameters get the most power, which forces are most likely to produce chatter, how the grinding wheel is behaving, and much more. Using the data generated through the Grindometer, truing processes can be evaluated and improved.
When it comes to diamond wheel dressing and truing, some factors to test include:
- Bond material removal
- Grit fracturing and grits coming off the wheel
- Whether the dressing of the wheel works positively or negatively with the truing
- How quickly material is removed by dressing
- Risk of chatter
After the testing process was completed, the data collected was used in several ways. For example, the traverse was measured on time vs. power. The amount of chatter can be converted into specific energy used to chip off pieces of the grit and bond material. This equals the productivity of the truing and dressing process. The specific energy results showed which part of the cycle took up the most time. Then, the most effective process improvements can be made.
To achieve the best truing results quickly, there are several factors to take into account:
- Uni-directional or anti-directional: For unidirectional, speed ratio = surface velocity of the diamond wheel (rpm*diameter)/ velocity of the truing wheel (rpm*diameter). For anti-directional, the best speed ratio should be 0.5. This is the best option to use for truing quickly.
- Size of the grit: The diamond grit should be three times the size of the truing wheel grit. Finer grit requires a finer dressing wheel. For quick truing, stick to the I-M hardness wheel range of dressing wheel grit hardness.
- What material to use: We tested both silicon carbide and aluminum oxide for wheel truing and found that there was no noticeable difference in performance.
Why Choose Rush Machinery for Your Grinding Needs?
Rush Machinery’s wheel dressers are highly accurate, cost-effective, simple to operate, and designed for dressing and truing of angles, flats, and radii on diamond and CBN single and multiple wheel packs. Our team of experts provides training and parts servicing at your facility or ours. Our user-friendly products deliver increased efficiency and improved accuracy in truing or dressing diamond grinding wheel applications. Rush Machinery is a proud provider of grinding and truing wheels, dressing machines, and other manufacturing services. We are committed to quality, innovation, and service.
For more information on improving the truing process with Rush Machinery, visit our truing parameters calculator. Contact our team with any questions or to get started on a solution for your application.