The operation of a CNC Grinding Machine is based on a basic principle similar to other types of CNC machines, namely using a computer system for control, but focusing on the grinding process , which is removing material from the workpiece in very small amounts using a rough grinding wheel (Abrasive Wheel) to produce a fine, smooth, shiny surface with highly accurate dimensions (Tight Tolerances).
The main working process focuses on controlling the movement of the grinding wheel and/or workpiece with the utmost precision.
1. Basic principles of CNC grinding machines
Abrasive Removal: A grinding wheel made of a hard material, such as corundum or diamond, is attached to a spindle and rotates at high speed. As the grinding wheel contacts the workpiece, countless tiny abrasive grains on the wheel scrape away very little material.
Computer Control (CNC Control): The computer system uses a set of G-code instructions to control the movement of different axes (e.g. X, Y, Z) to determine:
Contact position between the grinding wheel and the workpiece
The depth of cut (Depth of Cut) is very small.
Feed Rate or speed of movement of the grinding wheel
Wheel Speed and/or Workpiece Speed
High Accuracy: CNC grinders provide dimensional accuracy and surface finish that exceed machining with conventional milling machines or lathes.
2. Detailed working procedures
1. Programming & Setup
Design and generate G-code: Use CAD/CAM software to design the desired shape and convert it into G-code, which is a complete set of motion control instructions.
Tool and workpiece setting: Install the appropriate grinding wheel for the material and grinding task (e.g., surface grinding, cylindrical grinding) and securely clamp the workpiece on the worktable or chuck.
Offset Coordinate Setting: Set the center position of the workpiece and grinding wheel in the machine control system.
2. Grinding Cycle Execution
Start operation: The operator enters a command to start the machine according to the G-code program.
Motion Control: The CNC system controls the servo motors to move the grinding wheel and/or workpiece to precise positions according to coordinates specified in the program.
For example, in a surface grinder: the grinding wheel rotates and moves along the plane (X, Y) while the grinding wheel is fed down the Z axis in very small increments.
For example, in a cylindrical grinder: the workpiece rotates on its axis and the grinding wheel gradually moves closer to the workpiece to reduce its diameter.
Grinding: The grinding wheel rotates at high speed and begins continuous contact with the workpiece to remove material until the desired size and surface finish is achieved.
Coolant System Application: Since the grinding process generates very high heat, a coolant system is constantly supplied to the cutting point to reduce heat and flush out grinding swarf.
3. Inspection and Compensation
Some CNC grinders have built-in gauging systems/probes to measure the dimensions of the workpiece in real time and send the data back to the control system.
If the size is not as required, the control system can automatically make compensation for the grinding wheel movement to obtain the most accurate size.
3. Examples of types of CNC grinders and their operation
| Grinding machine type | Main usage | The main movement that controls |
| Surface Grinding | Make the surface of the workpiece smooth and flat. | The workpiece moves back and forth (X, Y) and the grinding wheel feeds down (Z). |
| Cylindrical Grinding | Make the outer surface of cylindrical workpieces have precise dimensions. | The workpiece rotates around itself (Rotation) and the grinding wheel moves in and out (X). |
| Internal Grinding | Grinding the inner walls of cylindrical holes or gaps | A small grinding wheel rotates at high speed and moves into the hole. |
| Centerless Grinding | Grinding a large number of cylindrical workpieces without centering | The workpiece is supported between the grinding wheel and the regulating wheel. |
In short, CNC grinders use the computer's ability to control the movement of a grinding wheel and workpiece in multiple axes to remove material in a precise and consistent manner, resulting in parts with very high dimensional resolution and surface finish (at the micrometer level) required for high-precision parts such as bearings, shafts or molds.
