In the process of deep hole machining, problems such as dimensional accuracy, surface quality and tool life often occur. How to reduce or even avoid these problems is an urgent problem to be solved.
◆ Problem ①: The aperture increases and the error is large
Causes: The design value of the reamer outer diameter is too large or the reaming cutting edge has burrs; Cutting speed is too high; Improper feed rate or excessive machining allowance; The main deflection angle of reamer is too large; Reamer bending; Chip beading is adhered to the reaming cutting edge; The runout of reaming cutting edge is out of tolerance during grinding; The cutting fluid is not suitable; When installing the reamer, the oil stain on the surface of the taper shank is not wiped clean or the cone surface is bruised; The taper interference of the taper shank after the offset of the flat tail of the taper shank is installed into the machine tool spindle; The main shaft is bent or the main shaft bearing is too loose or damaged; Reamer floating is not flexible; When reaming holes with different axes from the workpiece and hands, the force of both hands is uneven, causing the reamer to shake left and right.
Solution: appropriately reduce the external diameter of the reamer according to the specific situation; Reduce cutting speed; Properly adjust the feed rate or reduce the machining allowance; Reduce the main deflection angle appropriately; Straighten or scrap the bent and unusable reamer; Carefully trim with an oilstone until it is qualified; Control the swing error within the allowable range; Select cutting fluid with good cooling performance; Before installing the reamer, the internal oil stain of the reamer taper handle and the taper hole of the machine tool spindle must be wiped off, and the cone surface with bumps shall be polished with an oilstone; Repair and grind the flat end of reamer; Adjust or replace the main shaft bearing; Readjust the floating clip and adjust the coaxiality; Pay attention to correct operation.
◆ Problem ②: Hole diameter reduction
Cause: the design value of the external diameter of the reamer is too small; Cutting speed is too low; Excessive feed rate; The main deflection angle of reamer is too small; The cutting fluid is not suitable; When sharpening, the worn part of the reamer is not worn off, and the elastic recovery reduces the aperture; When reaming steel parts, if the allowance is too large or the reamer is not sharp, it is easy to produce elastic recovery, which will reduce the hole diameter, make the inner hole out of round, and make the hole diameter unqualified.
Solution: Replace the external diameter of the reamer; Properly increase the cutting speed; Properly reduce the feed rate; Increase the main deflection angle appropriately; Select oily cutting fluid with good lubricating performance; Exchange reamers regularly, and grind the cutting part of reamers correctly; When designing the reamer size, the above factors shall be taken into account, or the value shall be taken according to the actual situation; Make experimental cutting, take appropriate allowance, and sharpen the reamer.
◆ Problem ③: The reamed inner hole is not round
Causes: The reamer is too long, the rigidity is insufficient, and vibration occurs during reaming; The main deflection angle of reamer is too small; Narrow hinge cutting edge band; Reaming allowance deviation; There are notches and cross holes on the inner hole surface; There are sand holes and air holes on the hole surface; The main shaft bearing is loose and there is no guide sleeve, or the fitting clearance between the reamer and the guide sleeve is too large, and the thin-walled workpiece is clamped too tightly, so the workpiece is deformed after removal.
Solution: The reamer with insufficient rigidity can adopt the reamer with unequal pitch, and the installation of the reamer should adopt rigid connection to increase the main deflection angle; Select qualified reamers and control the hole position tolerance of the pre processing process; Unequal pitch reamer and longer and more precise guide sleeve are adopted; Select qualified blank; When reaming more precise holes with equal pitch reamers, the machine tool spindle clearance shall be adjusted. The fitting clearance of the guide sleeve shall be higher or appropriate clamping method shall be adopted to reduce the clamping force.
◆ Problem ④: The inner surface of the hole has obvious edges
Cause: excessive reaming allowance; The rear angle of reamer cutting part is too large; The reaming cutting edge belt is too wide; There are air holes and sand holes on the workpiece surface and the spindle runout is too large.
Solution: reduce reaming allowance; Reduce the back angle of the cutting part; Width of grinding blade belt; Select qualified blank; Adjust the machine spindle.
◆ Problem ⑤: The surface roughness of the inner hole is high
Cause: too high cutting speed; The cutting fluid is not suitable; The main deflection angle of the reamer is too large, and the reaming cutting edge is not on the same circumference; Reaming allowance is too large; The reaming allowance is uneven or too small, and the local surface is not reamed; The runout of the reamer cutting part is out of tolerance, the cutting edge is not sharp, and the surface is rough; The reaming cutting edge belt is too wide; Poor chip removal during reaming; The reamer is excessively worn; The reamer is bumped, and the cutting edge is left with burrs or broken edges; The cutting edge has chip accretion; It is not applicable to zero or negative rake reamers due to material relationship.
Solution: reduce cutting speed; Select cutting fluid according to processing materials; Properly reduce the main deflection angle, and correctly grind and ream the cutting edge; Reduce reaming allowance appropriately; Improve the position accuracy and quality of the bottom hole before reaming or increase the reaming allowance; Select qualified reamers; Width of grinding blade belt; According to the specific situation, reduce the number of reamer teeth, increase the chip holding slot space or use the reamer with edge inclination angle to ensure smooth chip removal; Replace the reamer regularly, and remove the grinding area when grinding; Protective measures shall be taken for reamers during grinding, use and transportation to avoid bumping; For the damaged reamer, the damaged reamer shall be repaired with extra fine oilstone, or the reamer shall be replaced; The reamer with a front angle of 5 °~10 ° shall be used when the trimming is qualified with an oilstone.
◆ Problem ⑥: The service life of the reamer is low
Cause: unsuitable reamer material; The reamer is burnt during grinding; The cutting fluid is not properly selected, the cutting fluid fails to flow smoothly, and the surface roughness value at the cutting point and after grinding the hinge cutting edge is too high.
Solution: The reamer material can be selected according to the processing material, and the carbide reamer or coated reamer can be used; Strictly control the grinding and cutting parameters to avoid burns; Always select the cutting fluid correctly according to the processing materials; The chips in the chip groove shall be removed frequently, and the cutting fluid with sufficient pressure shall be used to meet the requirements after fine grinding or grinding.
◆ Problem ⑦: The position accuracy of reamed hole is out of tolerance
Cause: wear of guide sleeve; The bottom of the guide sleeve is too far from the workpiece; The length of the guide sleeve is short, the precision is poor, and the main shaft bearing is loose.
Solution: Replace the guide sleeve regularly; Lengthen the guide sleeve to improve the fitting accuracy of the clearance between the guide sleeve and the reamer; Timely maintain the machine tool and adjust the spindle bearing clearance.
◆ Problem ⑧: reamer tooth breakage
Cause: excessive reaming allowance; The hardness of workpiece material is too high; The swing difference of cutting edge is too large, and the cutting load is uneven; The main deflection angle of reamer is too small, which increases the cutting width; When reaming deep holes or blind holes, there are too many chips, which have not been removed in time, and the cutter teeth have been worn and cracked when sharpening.
Solution: Modify the pre processed hole size; Reduce material hardness or change to negative rake angle reamer or carbide reamer; Control the runout within the acceptable range; Increase the main deflection angle; Pay attention to the timely removal of chips or the use of reamers with edge inclination; Pay attention to the grinding quality.
◆ Problem ⑨: The reamer shank is broken
Cause: excessive reaming allowance; When reaming tapered holes, the allocation of rough and fine reaming allowance and the selection of cutting parameters are inappropriate; Reamer teeth have small chip space and chip is blocked.
Solution: Modify the pre processed hole size; Modify the allowance allocation and reasonably select the cutting parameters; Reduce the number of reamer teeth, increase the chip space or grind off one tooth of the cutter tooth clearance.
◆ Problem ⑩: The centerline of the reamed hole is not straight
Cause: The original bending degree cannot be corrected due to the poor rigidity of the reamer when the drilling hole is deflected before reaming, especially when the hole diameter is small; The main deflection angle of reamer is too large; Poor guidance makes the reamer easy to deviate from the direction during reaming; The chamfer of the cutting part is too large; The reamer moves at the middle clearance of the intermittent hole; During hand reaming, excessive force is exerted in one direction, forcing the reamer to deflect towards one end, which destroys the verticality of the reamed hole.
