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Inventory vertical machining center processing precision out of tolerance reasons and countermeasures

The biggest processing attribute of the vertical machining center is that the consistency of the batch workpiece size is very high. We know that the traditional processing of the original workpiece from one process to another process, have to go through the clamping process, this process depends on artificial It is difficult to achieve that the processing size of each part is exactly the same. Of course, this does not mean that the workpiece is out of tolerance. As long as the workpiece is within the tolerance band of all qualified parts, it appears that some workpiece sizes may be large. The workpiece is in the middle difference, and some workpieces may be in the small difference. It is difficult to ensure the consistency of the size of the workpiece.

Therefore, at present, the utilization rate of vertical machining centers is the highest among small and medium-sized processing enterprises. Of course, vertical machining centers are also the most cost-effective machine tools among CNC machine tools. He has high processing efficiency and high processing accuracy. From these two aspects, it has solved the problem of maintaining workpieces. The problem of size consistency. Of course, if the CNC parameters are improperly set or improperly operated, the vertical machining center will also appear from time to time in the actual processing. This article briefly introduces the causes and solutions of the common processing tolerances of vertical machining centers:

The machining accuracy of the vertical machining center is mainly manifested as follows: the surface roughness value of the inner hole machining is high, the reamed inner hole is not round, the accuracy of the position of the reamed hole is super poor, the inner surface of the hole has obvious facets, reamed holes The centerline of the rear hole is not straight, the hole diameter increases, and the hole diameter decreases.

1. The accuracy of the position of the reamed hole is too poor

Cause: It may be caused by the wear of the guide sleeve of the vertical machining center, the bottom end of the guide sleeve is too far from the workpiece, the length of the guide sleeve is short, the accuracy is poor, and the spindle bearing is loose.

Solution: If the position accuracy of the hole is too poor when reaming the vertical machining center, you can perform the following maintenance according to the above-mentioned problems. Regularly replace the guide sleeve and extend the guide sleeve to improve the precision of the gap between the guide sleeve and the reamer, and repair the machine in time 3. Adjust the spindle bearing clearance.

2. High surface roughness value of inner hole

Causes: The surface roughness of the inner hole of the vertical machining center is high, and there are many reasons, which may be due to too high cutting speed, inappropriate selection of cutting fluid, excessive main angle of the reamer, and too much reaming hole. The reaming allowance is uneven or too small, the cutting edge is not sharp, the reaming cutting edge is too wide, the chip removal is not smooth when reaming, the reamer is excessively worn, and it may be the reason why the selected milling tool and part material do not match. .

Solution: There are many reasons for the high processing roughness, so the solution is more complicated. You can start from the following aspects: reduce the cutting speed, choose the cutting fluid according to the processing material, appropriately reduce the reaming allowance, and increase the reaming front The accuracy and quality of the bottom hole position or increase the reaming allowance, increase the space of the chip flute, or use a reamer with a blade inclination angle to make chip removal smooth, regularly replace the reamer, choose the tool reasonably, such as when processing steel Measures such as cutting tools for steel parts.

3. Increased processing aperture

Causes: The hole diameter gradually increases during vertical machining center processing. The reasons may be: the design value of the outer diameter of the reamer is too large or the burr edge has burrs, the cutting speed is too high, the feed rate is inappropriate, or the machining allowance is too large 1. The main angle of the reamer is too large, the reamer is bent, the built-up edge is adhered to the edge of the reamer, the edge deflection of the reamer is too poor during sharpening, the choice of cutting fluid is inappropriate, and it may be a problem of the CNC machine tool itself. If the spindle is bent or the spindle bearing is too loose or damaged, the above problems may also occur.

Solution: According to the actual inspection situation, the following countermeasures can be taken: appropriately reduce the outer diameter of the reamer, reduce the cutting speed, adjust the feed or reduce the machining allowance, reduce the main declination, straighten or scrap Unusable curved reamer, choose cutting fluid with better cooling performance, adjust or replace the spindle bearing, or replace the entire spindle.

4. The reamed inner hole is not round

Causes: The processing of the inner hole is not round and the roundness is not enough due to the following factors: the reamer is too long, the rigidity is insufficient, the vibration occurs during reaming, the main deflection angle of the reamer is too small, and the reaming hole margin is deviated Small, there are gaps on the surface of the inner hole, cross holes, especially the surface of the hole has trachoma, air holes, or the machine tool spindle bearing may be loose.

Solution: You can start from the following aspects: the installation of the reamer should use rigid connection, choose a qualified reamer, control the hole position tolerance of the pre-machining process, use unequal pitch reamer, choose a qualified blank, and timely adjust the machine tool spindle Adjust the gap, etc.

5. The center line of the hole after reaming is not straight

Cause: It appears when the vertical machining center processes the hole, and the centerline is not straight. The possible reasons may be: the hole is inclined when drilling, especially when the hole diameter is small, because the rigidity of the reamer is poor, the original curvature, The main angle of the reamer is too large and the guidance is poor, so that the reamer is easy to deviate from the direction during reaming, the inverted cone of the cutting part is too large, and the reamer is intermittently displaced in the middle of the hole.

Solution: increase the correction hole of the reaming or boring process, reduce the main declination angle, adjust the appropriate reamer, exchange the reamer with the guide part or the extended cutting part, and pay attention to correct operation.

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