October 27, 2021
FAQ of CNC machining center
We know that in the process of deep hole machining in CNC machining center, 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. The following summarizes several common problems and solutions in deep hole machining.
1. The aperture increases and the error is large
1) Cause
The design value of the outer diameter of the reamer is too large or the reaming cutting edge has burrs; Cutting speed is too high; Improper feed or excessive machining allowance; The main deflection angle of reamer is too large; Reamer bending; The cutting edge of reaming is adhered with a chip tumor; When grinding, the swing error of reaming cutting edge exceeds the tolerance; Improper selection of cutting fluid; When installing the reamer, the oil stain on the surface of the taper shank is not cleaned or the conical surface is bumped; After the flat tail of the taper handle is offset and installed into the machine tool spindle, the taper handle interferes with the taper; The spindle is bent or the spindle bearing is too loose or damaged; Reamer floating is not flexible; Different from the workpiece, the force of both hands is uneven when reaming the shaft and hand, which makes the reamer shake left and right.
2) Solutions
Properly reduce the outer diameter of reamer according to specific conditions; Reduce cutting speed; Properly adjust the feed rate or reduce the machining allowance; Properly reduce the main deflection angle; Straighten or discard the bent and unusable reamer; Carefully trim with oilstone to be qualified; Control the swing error within the allowable range; Select cutting fluid with good cooling performance; Before installing the reamer, the oil stain inside the taper shank of the reamer and the taper hole of the machine tool spindle must be wiped off, and the bump on the conical surface shall be polished with an oilstone; Grinding flat tail of reamer; Adjust or replace the main shaft bearing; Readjust the floating chuck and adjust the coaxiality; Pay attention to correct operation.
CNC machining center
2. Aperture reduction
1) Cause
The design value of reamer outer diameter is too small; The cutting speed is too low; Excessive feed rate; The main deflection angle of reamer is too small; Improper selection of cutting fluid; When sharpening, the worn part of the reamer is not worn off, and the elastic recovery reduces the aperture; When reaming steel parts, the allowance is too large or the reamer is not sharp, which is easy to produce elastic recovery, so that the hole diameter is reduced, the inner hole is not round, and the hole diameter is unqualified.
2) Solutions
Replace the outer diameter of reamer; Properly increase the cutting speed; Properly reduce the feed rate; Properly increase the main deflection angle; Select oil-based cutting fluid with good lubrication performance; Exchange reamers regularly and grind the cutting part of the reamer correctly; When designing the reamer size, the above factors shall be considered or the value shall be taken according to the actual situation; Make experimental cutting, take appropriate allowance and sharpen the reamer.
3. The reamed inner hole is not round
1) Cause
The reamer is too long and the rigidity is insufficient, resulting in vibration during reaming; The main deflection angle of reamer is too small; Narrow cutting edge band; Deviation of reaming allowance; There are missing and fork holes on the surface of the inner hole; There are sand holes and pores on the hole surface; The spindle bearing is loose, there is no guide sleeve, or the matching clearance between reamer and guide sleeve is too large, and the workpiece is deformed after removal due to tight clamping of thin-wall workpiece.
2) Solutions
Reamers with unequal tooth pitch can be used for reamers with insufficient rigidity, and the installation of reamers shall adopt rigid connection to increase the main deflection angle; Select qualified reamers and control the hole position tolerance in the pre machining process; Unequal pitch reamer and longer and more precise guide sleeve are adopted; Select qualified blank; When using equal pitch reamers to ream more precise holes, the spindle clearance of the machine tool shall be adjusted, and the matching clearance of the guide sleeve shall be higher, or appropriate clamping methods shall be adopted to reduce the clamping force.
