Today, the editor will talk to you about how to choose the rotational speed of the grinding disc? Keywords: Grinding disc diameter, rotation direction, particle size, practical application.

1、 Grinding disc diameter

     Formula: Linear velocity=angular velocity× radius

     Metallographic grinding and polishing machines generally use angular velocity to indicate the working speed of the grinding plate, expressed in Revolutions per minute, but the angular velocity is not the actual relative speed, so the size of the grinding plate must be taken into account.

     Common grinding disc diameters are 8 inches, 10 inches, and 12 inches. It is obvious that the actual relative speed of an 8-inch grinding disc is much lower than that of a 12-inch grinding disc at the same rotational speed. Therefore, when using a small diameter grinding disc, some rotational speed can be increased.

2、 Rotation direction

     If automatic polishing equipment is used, the sample is placed on the fixture. You can choose to rotate the power head with the fixture and the sample in the same direction, in the opposite direction, or without rotation.

     If the power head rotates in the same direction as the specimen with the fixture, it is equivalent to reducing the speed of the metallographic polishing machine. Similarly, if it rotates in the opposite direction, it is equivalent to increasing the speed of the polishing machine.

3、 Particle size

     When we use coarse sandpaper for grinding and polishing, the grinding amount is inevitably large. At this time, we can consider lowering the speed, shortening the time, or reducing the force (load, loading force), all based on the removal of areas on the surface that cannot be tested.

     It should be noted that, contrary to intuition, as the surface of the sample becomes finer and the sandpaper polishing cloth becomes finer, the friction force of the sample at the same speed and pressure load may increase. Because of this, it is necessary to reduce one or several of the parameters.

4、 Actual operating speed of metallographic polishing machine

     Generally speaking, the speed of metallographic preparation refers to the angular velocity of the rotating disc (grinding disc), but due to the different sizes of the rotating disc, the speed of the small rotating disc can be adjusted higher, but the high speed should not exceed 600 revolutions per minute.

     A 12 inch rotary table with a typical angular speed range of 150-300rpm. If the speed is too high, it will affect the stability and service life of the equipment, and also have adverse effects on personnel. In addition, as the polishing steps proceed, it is necessary to reduce the speed.

5、 Loading force (load, force)

     As the surface of the sample becomes finer and the sandpaper polishing cloth becomes finer, the friction force of the sample with the same rotational speed and pressure load may increase. Because of this, it is necessary to reduce the grinding and polishing force.

If it is manual polishing, the downward pressure can be appropriately reduced based on personal experience. If an automatic polishing machine is used, the load on a single sample should not exceed 20N, preferably 15N.

6、 Summary

     As mentioned above, the rotational speed of the grinding disc is basically within the range of 150-300rpm, and the diameter, direction of rotation, particle size, loading force, and polishing time of the grinding disc all affect this parameter.

     At the same time, it is necessary to reduce the rotational speed, loading force, and polishing time of the metallographic polishing machine during fine grinding and polishing, one or more of these three parameters. Of course, the experimenters should seek truth from facts, explore better sample preparation plans, and find more suitable grinding and polishing speeds, which is a good choice.

     Welcome to the official website www.qmaxis.cn for technical exchange with QMAXIS engineers, or visit the QMAXIS testing laboratory in Nanjing for on-site testing.