Precautions for acceptance of CNC machine tool processing center

The acceptance of CNC machining center is a complex inspection technology work. It includes the comprehensive performance testing of the mechanical, electrical, hydraulic and pneumatic parts of the machine tool and the testing of the static and dynamic accuracy of the machine tool. There is a special organization in our country, namely the National Machine Tool Product Quality Inspection Center. The user's acceptance work can be carried out in accordance with the acceptance method of the institution, or the above-mentioned institution can be invited to conduct the acceptance. Mainly focus on two aspects:

1. Machining center geometric accuracy inspection

The geometric accuracy of the machining center is the geometric shape error after assembly. The inspection contents are as follows:

The flatness of the worktable

The mutual perpendicularity of each coordinate direction movement

The parallelism of the moving table in the X-axis direction

The parallelism of the worktable in the Y-axis direction

The parallelism of the movement in the X-axis direction to the side of the upper and lower grooves of the worktable

Axial movement of spindle

Radial runout of spindle hole

The parallelism of the spindle box moving along the Z coordinate direction to the spindle axis

The perpendicularity of the rotation axis of the spindle to the worktable

Straightness of headstock movement in Z coordinate direction

The commonly used testing tools are: precision level, square, precision square box, flat ruler, collimator, dial indicator or micrometer, high precision spindle mandrel and rigid dial indicator rod. Each geometric accuracy is tested in accordance with the acceptance conditions of the machining center. Note: The grade of the inspection tool must be one grade higher than the measured geometric accuracy. At the same time, it must be carried out with the machine tool slightly warmed up. After the machine tool is energized, the spindle rotates at a medium speed for 15 minutes before checking.

2. Machine tool performance acceptance (Guide: Commissioning of CNC machine tool processing center)

The test items specified in the 'General Rules of Metal Cutting Machine Test Specifications' are as follows:

Test items

Reliability Dry running vibration thermal deformation static stiffness

Vibration resistance, cutting noise excitation vibration positioning accuracy

Spindle rotation accuracy, linear motion unevenness, machining accuracy

A high-precision testing instrument is necessary for comprehensive performance testing of machine tools. In the specific acceptance of machine tools, the content of each acceptance can be carried out in accordance with machine tool factory standards and industry standards.

Key Points of Machining Center Operation

As a skilled operator, he must understand the requirements of the processed parts, the process route, and the characteristics of the machine tool before he can manipulate the machine tool to complete various processing tasks. Therefore, a few operating points are organized for reference:

In order to simplify the positioning and installation, each positioning surface of the fixture should have an accurate coordinate size relative to the machining origin of the machining center.

In order to ensure the consistency of the part installation position with the selected workpiece coordinate system and machine tool coordinate system direction in programming, and directional installation.

It can be changed into a fixture suitable for new workpieces after a short time of disassembly. Since the auxiliary time of the machining center has been compressed to a very short time, the loading and unloading of the supporting fixtures cannot take much time.

The fixture should have as few components as possible and high rigidity.

The fixture should be as open as possible, the space position of the clamping element can be as low as possible, and the installation fixture should not interfere with the tool path of the work step.

Ensure that all the processing content of the workpiece is completed within the stroke range of the spindle.

For machining centers with interactive worktables, the fixture design must prevent the space interference between fixtures and machine tools due to the movement of the worktable, lifting, lowering, and rotation.

Try to complete all processing content in one setup. When it is necessary to replace the clamping point, pay special attention not to damage the positioning accuracy due to the replacement of the clamping point, and specify it in the process file if necessary.

For the contact between the bottom surface of the fixture and the worktable, the flatness of the bottom surface of the fixture must be within 0.01-0.02mm, and the surface roughness should not be greater than Ra3.2μm.

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