Semi-finishing and finishing of all kinds of planes with high surface quality requirements often use surface grinding methods. The commonly used machine tool for surface grinding is a surface grinder. The working surface of the grinding wheel can be either a circumferential surface or an end surface.
1. Major types and sports
When the grinding wheel peripheral grinding method is adopted, the grinding machine main shaft is arranged horizontally; when the grinding wheel end surface grinding method is adopted, the grinding machine main shaft is arranged in a vertical manner. In the case of surface grinding, the workpiece can be mounted on a rectangular table for reciprocating rectilinear motion, or it can be mounted on a circular table for circular motion.
Fig.1 Schematic diagram of surface grinder
According to the combination of spindle layout and table shape, ordinary surface grinders can be divided into the following four categories:
(1) Horizontal-Axis Moment Desktop Surface Grinding Machine (Fig. 1a) In this machine tool, the workpiece is attracted by a rectangular electromagnetic table. The grinding wheel is used for main rotating motion n, the table is for longitudinal reciprocating motion f1, the grinding wheel frame is for intermittent vertical cutting motion f3 and transverse feeding motion f2.
(2) Vertical-axis-positioned table-surface grinder (Fig. 1b) In this type of machine, the grinding wheel performs the main rotating motion n, the rectangular table reciprocates longitudinally f1, and the grinding wheel frame makes intermittent vertical cutting-in motion f2.
(3) Vertical axis circular table surface grinder (Fig. 1c) In this type of machine, the grinding wheel rotates as the main rotating circular worktable to make a circular feed motion f1, and the grinding wheel frame makes intermittent vertical cut-in motion f2.
(4) Horizontal axis circular table surface grinder (Fig. 1d) In this type of machine, the grinding wheel rotates as the main motion n, the circular table rotates as the circumferential feed motion f1, and the grinding wheel frame performs continuous radial feed motion f2 and intermittent The vertical cut-in motion f3. In addition, the rotary centerline of the table can be adjusted to an inclined position to grind the conical surface.
Among the above four kinds of surface grinders, the surface grinding machine using the grinding wheel end face has a larger grinding wheel diameter than the surface grinding machine using the rim grinding machine, and can grind the full width of the workpiece at the same time. Larger, so higher productivity. However, when the end face is ground, the surface of the grinding wheel and the workpiece is in contact with a curved line or surface, the contact area is large, cooling is difficult, and the chips are not easily eliminated. Therefore, the machining accuracy and the surface roughness are slightly inferior. The productivity of the circular table is slightly higher for the round table surface grinder compared to the table grinder. This is due to the fact that the circular table feeds continuously, and the table top has a loss of commutation time. However, the circular table is only suitable for grinding the end face of small parts and large-diameter ring parts, and it cannot grind long parts. The moment table can easily grind various common parts, including ring parts with a diameter less than the width of the table.
At present, the horizontal axis moment table surface grinder and the vertical shaft round table surface grinder are used more frequently.
2. Horizontal shaft surface grinder
Horizontal axis moment table surface grinder shown in Figure 2. The spindle of this type of machine tool is usually directly driven by an internal asynchronous motor. The motor shaft is usually the main shaft and the electric stator is mounted in the body frame of the grinding wheel frame 3 . The wheel frame 3 can perform an intermittent transverse infeed movement (manual or hydraulic) along the dovetail guides of the carriage 4 . The carriage 4 and the wheel frame 3 together perform intermittent vertical cutting movements (manually) along the guide rail of the column 5 . The table 2 longitudinally reciprocates along the guide rail of the bed 1 (hydraulic transmission).
Figure 2 Surface grinding machine
1— Bed 2—Workbench 3—Grind Frame 4—Slide 5—Post
At present, the machining quality that can be achieved by the horizontal-axis surface grinder in China is:
Ordinary precision level: After the test piece is ground, the degree of parallelism of the processing surface facing the base surface is 0.015mm/1000mm, and the surface roughness Ra is 0.32 to 0.63um;
High-accuracy grade: After the test piece is ground, the parallelism of the machined surface is 0.005mm/1000mm, and the surface roughness Ra is 0.04~0.01um.
3. Vertical axis table grinder
Vertical axis round table surface grinder shown in Figure 3. The main shaft of the grinding wheel frame 1 is also directly driven by an internal coupling type asynchronous motor. The grinding wheel frame 1 can make intermittent vertical cutting movement along the guide rail of the column 2 . The circular table 4 is rotated for circumferential feed motion. In order to facilitate the loading and unloading of the workpiece, the circular table 4 can also move longitudinally along the bed rails. Due to the large diameter of the grinding wheel, insert grinding wheels are often used. This type of grinding wheel makes it easy for the cold liquid to rush into the cut so that the grindstone does not easily clog. This machine has high productivity and is suitable for mass production.
Fig. 3 Vertical shaft surface grinder
1—Drum frame 2—Post 3—Plinth
4—Workbench 5— Bed
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