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Reasons for processing accuracy and countermeasures

The biggest processing property of the vertical machining center is that the consistency of the batch workpiece size is very high. We know that the traditional machining of the original workpiece is carried out from one process to another, and the process of clamping is experienced. It is difficult to achieve the same processing size of each component. Of course, this does not mean that the workpiece is out of tolerance. As long as it is a qualified part within the tolerance band of the workpiece, some workpiece sizes may be in the wrong position. The workpiece is in the middle difference, and some workpieces may be on the small difference, and it is difficult to ensure the dimensional consistency of the workpiece.

Therefore, the current use rate of vertical machining centers is the highest in small and medium-sized processing enterprises. Of course, the vertical machining center is also the most cost-effective machine tool in CNC machine tools. It has high processing efficiency and high machining precision. The issue of dimensional consistency. Of course, if the numerical control parameters are set improperly or improperly operated, the vertical machining center may also appear in the actual processing from time to time. This article briefly introduces the common causes of machining and the solution to the vertical machining center:
The machining accuracy of the vertical machining center is mainly due to the fact that the surface roughness of the inner hole is high, the inner hole of the hinge is not round, the position of the hinged hole is out of precision, and the inner surface of the hole has obvious facet and reaming. The center line of the rear hole is not straight, the aperture is enlarged, the aperture is reduced, and the like.

First, the position of the hinged hole is too poor.
Cause: It may be caused by the wear of the guide sleeve of the vertical machining center, the distal end of the guide sleeve is too far from the workpiece, the length of the guide sleeve is short, the precision is poor, and the spindle bearing is loose.
Remedy: If the position accuracy of the hole in the vertical machining center is too poor, the following problems can be made according to the above-mentioned problems. The following adjustments are made to replace the guide sleeve and the extension guide sleeve regularly, improve the matching precision between the guide sleeve and the reamer gap, and timely repair the machine tool. Adjust the spindle bearing clearance.

Second, the internal surface roughness value is high
Cause: The surface roughness of the inner hole of the vertical machining center is high, which is caused by many reasons. The cutting speed is too high, the cutting fluid is not properly selected, the main reaper angle of the reamer is too large, and the reaming margin is too large. The reaming allowance is uneven or too small, the cutting edge is not sharp, the hinge cutting edge is too wide, the chip removal is not smooth when reaming, the reamer is excessively worn, and the milling tool and the part material may not be selected. .
Solution: Due to the high processing roughness, there are many reasons, so the solution is more complicated. You can start from the following aspects: reduce the cutting speed, select the cutting fluid according to the processing material, appropriately reduce the reaming allowance, and improve the reaming. Bottom hole position accuracy and quality or increase the reaming allowance, increase the chip flute space or use the reamer with the blade inclination angle to make the chip removal smooth, regularly change the reamer, and select the tool reasonably, such as when processing steel parts. Measures such as cutting tools for steel parts.

Third, the processing aperture is increased
Cause: The reason why the aperture is gradually increased during processing in the vertical machining center may be: the design value of the reamer outer diameter is too large or the reamer edge has burrs, the cutting speed is too high, the feed rate is improper or the machining allowance is too large. The main angle of the reamer is too large, the reamer is bent, the built-up edge of the reamer is adhered to the edge of the reamer, the slanting edge of the reamer is too poor, the cutting fluid is not properly selected, and the problem of the CNC machine itself may be The above problems may occur if the spindle is bent or the spindle bearing is too loose or damaged.
Remedy: According to the actual inspection situation, the following countermeasures can be made: according to the specific circumstances, reduce the outer diameter of the reamer, reduce the cutting speed, adjust the feed amount or reduce the machining allowance, reduce the lead angle, straighten or scrap Bent unusable reamer, select cutting fluid with good cooling performance, adjust or replace the spindle bearing, or replace the entire spindle.

4. The inner hole of the hinge is not round
Causes: 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 angle of the reamer is too small, and the reaming allowance is biased. Small, the surface of the inner hole has notches, intersecting holes, especially the surface of the hole has blisters, pores, and possibly the looseness of the spindle of the machine tool.
Solution: It can be started from the following aspects: the installation of the reamer should be rigid connection, the qualified reamer should be selected, the hole position tolerance of the pre-processing process should be controlled, the unequal pitch reamer should be used, the qualified blank should be selected, and the machine tool spindle should be timely. Adjust the gap, etc.

5. The center line of the hole after reaming is not straight
Cause: The vertical machining center occurs when machining holes, and the center line may not be straight. The reasons may be: hole inclination during drilling, especially when the hole diameter is small, because the rigidity of the reamer is poor, the original bending degree cannot be corrected. The main yaw angle of the reamer is too large, and the guiding is poor, which makes the reamer easy to deviate in the direction of reaming, the inverted cone of the cutting part is too large, and the reamer is intermittently displaced at the gap in the middle of the hole.
Solution: Increase the hole reaming or boring procedure to correct the hole, reduce the lead angle, adjust the appropriate reamer, change the reamer with the guiding part or lengthen the cutting part, and pay attention to the correct operation.