Adjustment of machining center rotary table
In modern machining centers, a rotary table is commonly integrated (as illustrated in Fig. 1d), enabling the machining of multiple surfaces without repositioning the workpiece. Accurately determining the center of rotation of the rotary table is crucial for ensuring high-quality part manufacturing. This article provides an example using a horizontal machining center to demonstrate how to measure the rotational center of the worktable.
The center of rotation of the table lies at the center point of its upper surface, as shown in Figure 1. There are various methods to measure this center, but one widely used technique involves a standard mandrel, a dial indicator, and gauge blocks.
To measure the X-axis center of rotation:
The principle is based on aligning the spindle's centerline with the table's rotational center. The X-coordinate displayed on the machine’s CRT indicates the distance from the table's rotational center to the machine’s X-axis origin. To perform the measurement:
1. Mount the standard mandrel on the spindle.
2. Fix the dial indicator on the worktable and adjust it so that the pointer points to the top of the mandrel.
3. Move the mandrel upward along the Z-axis.
4. Rotate the table 180 degrees and bring the mandrel back down.
5. Observe the dial indicator and adjust the X-axis until the readings at 0° and 180° match. The X value on the CRT will then represent the position of the rotational center in the X direction.
This measurement directly affects the concentricity of holes machined in U-shaped parts.
For the Y-axis center of rotation:
The goal is to determine the vertical distance from the worktable's upper surface to the machine's Y-axis origin. The process involves:
1. Moving the spindle along the Y-axis to a near position.
2. Gently inserting a gauge block and adjusting the Y-axis until the block fits snugly.
3. Calculating the Y-direction center of rotation using:
**Y = CRT Y coordinate (negative) – Gauge height – Mandrel radius**
This ensures precise positioning of holes on the workpiece.
For the Z-axis center of rotation:
The principle involves measuring the vertical distance between the worktable's rotational center and the machine's Z-axis origin. The method includes:
1. Rotating the table to 0° and 180°.
2. Adjusting the Z-axis so that the dial indicator shows the same reading in both positions.
3. Using the CRT's Z-axis value to determine the Z-center of rotation.
Accurate Z-axis center measurement is essential for maintaining dimensional accuracy during boring operations. However, the rotational center can shift due to mechanical wear or damage, such as a spindle nut loosening or a collision. Therefore, it's important to recalibrate regularly, especially before machining high-precision components. Regular checks ensure consistent performance and reduce errors in the final product.
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