Deep hole processing information about CNC machining

- Apr 08, 2019-

In the process of deep hole machining of CNC machine tools, there are often problems such as dimensional accuracy, surface quality and tool life of the machined parts. How to reduce or even avoid these problems is a problem that we need to solve now. 10 kinds of problems and solutions commonly used in machining deep hole machining of CNC machine tools.


A. Increased aperture and large error


1) Cause


The reamer outer diameter size design value is too large or the hinge cutting edge has burrs; the cutting speed is too high; the feed rate is improper or the machining allowance is too large; the reamer main angle is too large; the reamer is bent; the hinge cutting edge is sticky Attached to the cutting edge; the sharpening of the cutting edge of the cutting edge is too poor; the cutting fluid is not suitable for selection; when the reamer is installed, the oil on the surface of the taper shank is not wiped clean or the cone is bumped; the flat tail of the taper shank is loaded The rear taper shank of the machine tool spindle has interference; the spindle is bent or the spindle bearing is too loose or damaged; the reamer is not flexible; when the shaft is different from the workpiece and the hand is reamed, the force of the two hands is uneven, so that the reamer shakes left and right.


2) Solution


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; properly reduce the lead angle; straighten or scrap the curved reamer; carefully repair with the oil stone Qualified; control the swing within the allowable range; select the cutting fluid with better cooling performance; before installing the reamer, the reamer taper shank and the oil splash inside the taper hole of the machine tool must be cleaned, and the cone surface is bumped with oil stone; Grind the reamer flat tail; adjust or replace the spindle bearing; re-adjust the floating chuck and adjust the coaxiality; pay attention to correct operation.


B. Aperture reduction


1) Cause


The design value of the outer diameter of the reamer is too small; the cutting speed is too low; the feed rate is too large; the main yaw angle of the reamer is too small; the cutting fluid is not properly selected; the wear of the reamer is not worn off during sharpening, and the elastic recovery makes the aperture Reducing; when reaming steel, the margin is too large or the reamer is not sharp, it is easy to produce elastic recovery, the aperture is reduced and the inner hole is not round, and the aperture is unqualified.


2) Solution


Replace the outer diameter of the reamer; appropriately increase the cutting speed; appropriately reduce the feed rate; appropriately increase the lead angle; select the oily cutting fluid with good lubrication performance; regularly exchange the reamer, correctly sharpen the cutting part of the reamer; design the hinge When the size of the knife is used, the above factors should be considered, or the value should be taken according to the actual situation; for the experimental cutting, take the appropriate margin and sharpen the reamer.


C. The hinged inner hole is not round


1) Cause


The reamer is too long, the rigidity is insufficient, and the vibration occurs when reaming; the main yaw angle of the reamer is too small; the hinge cutting edge is narrow; the reaming margin is biased; the inner hole surface has notches and intersecting holes; the hole surface has blisters and air holes; The spindle bearing is loose, there is no guide sleeve, or the clearance between the reamer and the guide sleeve is too large, and the workpiece is deformed due to the tight clamping of the thin-walled workpiece.



2) Solution


The reamer with insufficient rigidity can adopt the reamer with unequal pitch. The reamer should be installed with rigid connection to increase the lead angle. The qualified reamer is used to control the hole position tolerance of the pre-processing. The unequal pitch is adopted. Reamer, use longer, more precise guide sleeve; use qualified blank; when reaming more precise holes with equal pitch reamer, adjust the machine shaft clearance, the matching clearance of guide sleeve should be higher or appropriate The clamping method reduces the clamping force.


4. The inner surface of the hole has a distinct facet


1) Cause


The reaming allowance is too large; the back angle of the reamer cutting part is too large; the reaming cutting edge is too wide; the surface of the workpiece has pores, blisters, and the spindle pitch is too large.


2) Solution


Reduce the reaming allowance; reduce the back angle of the cutting part; trim the width of the cutting edge; select the qualified blank; adjust the machine tool spindle.


5. The surface roughness of the inner hole is high.


1) Cause


Cutting speed is too high; cutting fluid selection is not suitable; reamer main deflection angle is too large, hinge cutting edge is not on the same circumference; reaming allowance is too large; reaming allowance is uneven or too small, local surface is not hinged The reamer cutting part has poor balance, the edge is not sharp, the surface is rough; the hinge cutting edge is too wide; the chip removal is not smooth when reaming; the reamer is excessively worn; the reamer is bumped, the edge is left with burrs or collapse Blade; edge has built-up edge; due to material relationship, it is not suitable for zero degree front angle or negative front angle reamer.


2) Solution


Reduce the cutting speed; select the cutting fluid according to the processing material; appropriately reduce the main declination, correctly sharpen the cutting edge; properly reduce the reaming allowance; improve the position accuracy and quality of the reaming bottom hole or increase the reaming margin Use qualified reamer; repair the width of the blade; reduce the number of teeth of the reamer according to the specific situation, increase the space of the chip pocket or use the reamer with the angle of the blade to make the chip removal smooth; replace the reamer regularly, and grind the blade The sharpening zone is ground; the reamer should take protective measures during the sharpening, use and transportation process to avoid bumps; for the reamer that has been bruised, apply the special whetstone to fix the reamer, or replace the hinge Knife; trimmed with oil stone to pass, using a reamer with a rake angle of 5°-10°.


6. Reamer has a low service life


1) Cause


The reamer material is not suitable; the reamer burns during sharpening; the cutting fluid is not properly selected, the cutting fluid does not flow smoothly, and the surface roughness value at the cutting point and the reaming cutting edge is too high.


2) Solution


According to the processing material, the reamer material can be selected, and the hard alloy reamer or coating reamer can be used; the cutting grinding amount is strictly controlled to avoid burns; the cutting fluid is often selected according to the processing materials; the chips in the chip flute are often removed, enough The pressure cutting fluid is refined or ground to meet the requirements.


7. The position of the hinged hole is out of precision


1) Cause


The guide sleeve is worn; the bottom 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.


2) Solution


Regularly change the guide sleeve; lengthen the guide sleeve to improve the matching precision between the guide sleeve and the reamer gap; repair the machine tool in time and adjust the bearing clearance of the spindle.


8. Reamer blade


1) Cause


The reaming allowance is too large; the hardness of the workpiece material is too high; the cutting edge is too large, the cutting load is not uniform; the main angle of the reamer is too small, so the cutting width is increased; the hinge cnc machining CNC machine tool processing deep hole or blind hole When the chips are too much, they are not removed in time and the teeth have been sharpened during sharpening.


2) Solution


Modify the pre-machined hole size; reduce the material hardness or use a negative rake angle reamer or carbide reamer; control the swing within the acceptable range; increase the lead angle; pay attention to timely removal of chips or use a blade angle reamer Pay attention to the quality of the sharpening.


9. Reamer handle break


1) Cause

The reaming allowance is too large; when the reaming hole is used, the coarse and fine reaming allowance and the cutting amount are not suitable; the reamer has a small space for chipping and the chip is clogged.


2) Solution


Modify the pre-machined hole size; modify the margin distribution, reasonably select the cutting amount; reduce the number of reamer teeth, increase the chip space or grind the tooth gap.


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