Surface grinding is commonly used for semi-finishing and finishing operations on various planes that require high surface quality. The primary machine tool used for this process is the surface grinder, which utilizes either the peripheral or end face of the grinding wheel to perform the operation.
There are several major types of surface grinders, each designed for specific applications. When using the peripheral grinding method, the grinding wheel's main shaft is arranged horizontally. In contrast, when the end face of the grinding wheel is used, the main shaft is positioned vertically. Workpieces can be mounted on either a rectangular table that moves in a reciprocating linear motion or a circular table that rotates in a circular motion.
Surface grinders can be classified into four main categories based on the arrangement of the spindle and the shape of the table:
1. **Horizontal-axis rectangular table surface grinder**: In this type, the workpiece is held on an electromagnetic rectangular table. The grinding wheel rotates as the main motion, while the table performs longitudinal reciprocating movement. The grinding wheel frame also makes intermittent vertical and transverse movements.
2. **Vertical-axis rectangular table surface grinder**: Here, the grinding wheel rotates as the main motion, and the rectangular table moves longitudinally. The grinding wheel frame performs intermittent vertical cutting.
3. **Vertical-axis circular table surface grinder**: This type uses a circular table that rotates continuously, allowing the grinding wheel to move vertically for cutting.
4. **Horizontal-axis circular table surface grinder**: In this configuration, the grinding wheel rotates as the main motion, and the circular table provides circumferential feed. The grinding wheel frame moves radially and vertically for cutting. This type is also capable of grinding conical surfaces by adjusting the table’s angle.
Compared to rim grinding, end-face grinding allows for a larger grinding wheel diameter, enabling full-width grinding and higher productivity. However, due to the larger contact area, cooling and chip removal can be more challenging, leading to slightly lower surface finish and accuracy. Circular tables offer continuous feeding, making them more efficient for small or ring-shaped parts, but they are not suitable for long components. Rectangular tables, on the other hand, are more versatile and can handle a wider range of workpieces.
Currently, horizontal-axis rectangular table grinders and vertical-axis circular table grinders are widely used in industrial settings.
**Horizontal-Axis Surface Grinder**
The horizontal-axis surface grinder (as shown in Figure 2) features a spindle directly driven by an internal asynchronous motor. The motor shaft serves as the main spindle, with the stator mounted inside the grinding wheel frame. The wheel frame can move transversely along dovetail guides, while the carriage and wheel frame move vertically along the column’s guide rail. The worktable reciprocates longitudinally along the bed.
This machine can achieve high machining precision, with parallelism of up to 0.015 mm per 1000 mm and surface roughness ranging from 0.32 to 0.63 μm for standard-grade finishes. For high-precision applications, the parallelism can be as tight as 0.005 mm/1000 mm, with surface roughness as low as 0.01–0.04 μm.
**Vertical-Axis Surface Grinder**
The vertical-axis surface grinder (shown in Figure 3) also uses a motor-driven grinding wheel. The wheel frame moves vertically along the column’s guide rail, while the circular table rotates for continuous circumferential feed. The table can also move longitudinally for easier workpiece loading. Due to the large grinding wheel size, insert wheels are often used, which help improve cooling and reduce clogging. This design enhances productivity, making it ideal for mass production.
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