What Is a Surface Grinder?
A surface grinder is a machine tool that grinds the flat surface of workpieces. It is predominantly utilized in machine shops, employing a method that improves workpiece flatness by moving the piece against a rotating grinding wheel. This method stands out for its versatility across different product types.
Uses of Surface Grinders
Surface grinders are primarily used for finishing flat surfaces on workpieces, like hardened steel. Compared to milling machines, which also perform flat cutting, surface grinders remove significantly less material. In horizontal-axis, square-table surface grinders, the table moves back and forth, inverting to make cuts ranging from 0.01 to 0.2 mm during rough grinding and up to 0.01 mm, typically around 0.005 mm, during finish grinding. This precision is achievable through grinding wheel use, which finely finishes machined surfaces.
Principle of Surface Grinders
Surface grinders remove surface irregularities and foreign matter from workpieces through a rotating grinding wheel contact. The quality of surface grinding depends on several conditions:
1. Rotation Speed of the Grinding Wheel
The grinding wheel’s rotation speed, dictated by peripheral speed, should achieve 1,200 to 1,800 m/min in surface grinders. Various Industrial Safety and Health Laws specifiy the maximum safe operating speed, which must not be exceeded to ensure safety. Wheel speed impacts grinding efficiency, wheel wear, and the temperature of the wheel surface.
2. Workpiece Feed Rate
The feed rate of the table, or workpiece feed rate, is adjusted based on the workpiece’s material and hardness and the desired surface roughness. For finish grinding, it typically ranges from 30,000 to 50,000 mm/min.
3. Depth of Cut of Grinding Wheel
The grinding wheel’s depth of cut affects the amount of material removed per operation. A smaller depth of cut results in lower grinding resistance and less wheel wear, producing a finer finish. Conversely, a larger depth of cut increases material removal but may roughen the finish and decrease the wheel’s lifespan.
Types of Surface Grinders
Surface grinders vary by the workpiece table’s shape and the grinding wheel spindle’s configuration:
1. Classification by Table Shape
Grinding tables are either square or rotary. The square table type, with a smaller contact area between the grinding wheel and workpiece, allows for precision grinding but at lower efficiency. The rotary table type, offering a larger contact area, enhances grinding efficiency but may result in a slightly inferior finish due to variable grinding speeds. The selection of the grinding method depends on the workpiece’s size relative to the wheel width and the required finish quality.
2. Classification by Wheel Axis Direction
The square table type is further divided by the grinding wheel axis’s orientation: horizontal, vertical, or gantry. The horizontal-axis type performs high-precision grinding using the wheel’s outer circumference. Available grinding methods include plunge-cut, traverse-cut, and bias grinding, depending on table movement relative to the wheel axis. The vertical-axis type, suitable for large workpiece areas, provides a broad contact surface between the grinding wheel and workpiece, facilitating efficient grinding.