Surface grinding is commonly used for semi-finishing and finishing operations on various planes that require high surface quality. The primary machine tool used in this process is the surface grinder, which can utilize either the circumferential surface or the end face of the grinding wheel for material removal.
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 positioned horizontally. In contrast, when the end face is used for grinding, the main shaft is arranged 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, depending on the type of operation required.
Based on the combination of spindle orientation and table shape, standard surface grinders can be categorized into four types:
1. **Horizontal-axis rectangular table surface grinder**: This machine uses a rectangular electromagnetic table to hold the workpiece. The grinding wheel rotates as the main motion, while the table moves longitudinally. The grinding wheel frame performs vertical cutting and transverse feed movements.
2. **Vertical-axis rectangular table surface grinder**: Here, the grinding wheel rotates, the table moves longitudinally, and the grinding wheel frame makes intermittent vertical cuts.
3. **Vertical-axis circular table surface grinder**: In this configuration, the circular table rotates for circumferential feed, and the grinding wheel frame performs vertical cuts.
4. **Horizontal-axis circular table surface grinder**: This type allows continuous radial feed and intermittent vertical cutting. It can also be adjusted to grind conical surfaces.
Compared to rim grinding, end-face grinding typically uses larger-diameter wheels, allowing for full-width grinding and higher productivity. However, it may result in slightly lower surface finish due to increased contact area and chip accumulation. Circular tables offer better productivity for small or ring-shaped parts but are not suitable for long components. Rectangular tables, on the other hand, provide more flexibility for a variety of part geometries.
Currently, horizontal-axis rectangular table and vertical-axis circular table surface grinders are widely used in industry. These machines are known for their precision and efficiency, with modern models achieving high levels of accuracy.
**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, while the stator is mounted inside the grinding wheel frame. The wheel frame moves transversely along dovetail guides, and together with the carriage, it performs vertical cutting motions. The worktable moves longitudinally along the bed, enabling precise material removal.
Modern horizontal-axis surface grinders in China can achieve the following machining qualities:
- **Ordinary precision level**: Parallelism of 0.015 mm per 1000 mm, with surface roughness Ra between 0.32–0.63 μm.
- **High-accuracy grade**: Parallelism of 0.005 mm per 1000 mm, with surface roughness Ra ranging from 0.04–0.01 μm.
**Vertical-Axis Surface Grinder**
The vertical-axis surface grinder, illustrated in Figure 3, uses a similar motor-driven setup. The grinding wheel frame moves vertically along the column’s guide rail, while the circular table rotates for circumferential feed. The circular table can also move longitudinally for easier workpiece loading. Due to the large grinding wheel diameter, insert wheels are often used, which help prevent clogging and improve cooling. This design is ideal for mass production and offers high productivity.
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