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Comparison of five-axis machine tools with spindle oscillation and table oscillation

The five axes of a five-axis machine tool are usually composed of three linear axes plus two rotary axes, but their structures are very different. Different structural forms will cause some differences in machine tools’ rigidity, dynamic performance, accuracy and stability. This article mainly analyzes and compares two different structures of five-axis machine tools: vertical spindle swing and vertical spindle fixed workbench swing (cradle type), so that users can fully understand their structural forms, which will help them adapt to the characteristics of their own products. Choose the right machine tool according to your financial ability.

Figure. Cradle type rotary table Figure. Spindle rotation and swing

1. Comparison of machine tool spindle rigidity

During the machining process of the head-swing machine tool, due to the swing of the spindle, the rigidity of the spindle is relatively poor; while for the swing-table machine tool, because the worktable swings, it will not have any impact on the rigidity of the spindle.

2. Comparison of efficiency of machine tool processing

Due to the different rotation points, when the tool tip achieves the same displacement, the spindle of the oscillating machine tool needs to swing at a larger angle (similar to the lever principle), so the efficiency of the oscillating machine tool is lower when processing the same parts.

3. The influence of tool length on machine tool machining accuracy

Swing error = swing arm × swing angle

For head-swing machine tools, the tool length is part of the swing arm.

In other words, in the case of head swing, the length of the tool affects the length of the swing arm, amplifying the error. That is, the error will increase with the length of the tool. For cradle table swing machines, the tool length is independent of the length of the swing arm.

4. With the swing, both machine tools will produce position errors, but the head-swing machine will also produce shape errors, while the table swing will not produce shape errors.

The head-swing machine tool tool rotates, resulting in position error. At the same time, the feed direction of the machined hole deviates from the rotation center of the tool, so not only the position error of the machined hole is generated, but also the shape error is generated, resulting in a wedge-shaped hole.

The position error of the table swing machine tool is caused by the table swing. The feed direction of the spindle and the rotation center of the tool always coincide, so there will be no additional shape error. This is another clear advantage of a cradle table swing over a head swing.

5. Comparison of five-axis machining size ranges

As the spindle of the head-swing machine tool swings, the processing range in the diameter direction of the workpiece will be reduced. That is to say, the stroke will be eaten up when the spindle swings, resulting in the diameter range of the largest workpiece that can be processed by five-axis machining than that of three-axis machining. The worktable swing of the worktable swing machine tool will not have any impact on the horizontal size of the workpiece. In this sense, the workpiece size range during five-axis machining and three-axis machining is the same. However, the maximum range of five-axis machining of workpieces still needs to consider the interference caused by the machine tool structure. Users should ask machine tool suppliers to provide five-axis machining interference diagrams for analysis and comparison. Usually, for the same stroke, the five-axis processing range of a machine tool with a cradle-type worktable swing structure will be larger than that of a head-swing type machine tool.

Therefore, the spindle of the cradle-type worktable swing machine tool has good rigidity and high processing efficiency; the tool length will not affect the processing accuracy; the processing will not produce shape errors; for the same stroke, the five-axis processing range of the machine tool will be wider than that of the head-swing type machine tool. big.

The rigidity of the spindle of the head-swing machine tool is relatively poor, and the processing efficiency is relatively low; the processing accuracy will decrease with the growth of the tool length; the processing will produce shape errors; the stroke will be eaten up when the spindle swings angle, resulting in the maximum workpiece size that can be processed become smaller.

In addition, it should be added that the worktable swing machine tool needs to overcome the self-weight of the workpiece. If the workpiece is heavy, it has higher requirements for the fixture; also, when processing large and heavy parts, the machine tool cannot realize the worktable swing, so it can only use The way your head swings.

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