Operation rules of milling machine faults and troubleshooting of common milling machines

In milling, the accuracy of milling machine itself directly affects the size and shape position accuracy of machined parts. Therefore, in addition to the regular accuracy inspection of the milling machine, the faults of the milling machine should be found and eliminated in time. For the common fault phenomena and causes of milling machines, the solutions are also different.
1. Great vibration during milling
It cannot be processed according to the conventional milling amount, and it is easy to cut during milling, and the surface roughness value of parts is large, so forward milling cannot be used. There are two main factors causing large vibration: one is the looseness of the spindle and the poor rigidity of the cutter shaft system; The other is the looseness of the workbench and the poor rigidity of the workpiece fixture system.
(1) Loose spindle: whether the spindle is loose can be determined by checking the radial circular runout and axial runout of the spindle. The main reasons for the loosening of the main shaft are the excessive clearance of the main shaft bearing and the pitting of the raceway of the main shaft bearing. For the solution of spindle looseness, the former can readjust the clearance of spindle bearing to make it meet the specified requirements, while the latter needs to replace the bearing.
(2) Worktable looseness: the main reason for worktable looseness is that the gap between the guide rails of the worktable is too large. The solution is to readjust the guide rail clearance. In addition, if the clearance is too small, there will be crawling when the workbench moves at low speed. The guide rail inlay is not straight, which will also cause the workbench to move unsteadily, so it is necessary to repair or replace the inlay with a new one.

(3) The clearance between the lead screw and nut of the workbench is large: the solution is to readjust the clearance and tighten the relative position between the fastening screw and the fastening worm and the adjustable nut.
(4) Other factors: the taper of the milling cutter head is not consistent with the taper hole or the milling cutter head is not tightened. The solution is to check and repair the taper; Tighten the milling cutter head. The foundation of the machine tool is poor, and the solution is to rebuild the foundation as required. The vibration of the main motor is large, and measures are taken to dynamically balance the motor rotor. The main drive gear is noisy. The solution is to check and replace the unqualified gear.

2. The tension is uneven when the workbench is moved longitudinally by hand in the whole process
The main causes are bending of the table lead screw, local wear, or the axis of the lead screw is not parallel to the longitudinal guide rail. Solution: for the bending or local wear of the lead screw, the lead screw should be straightened, repaired or replaced; If the axis of the lead screw is not parallel to the longitudinal guide rail, the lead screw shall be re installed and the locating pin hole shall be reamed.
3. The lifting table crawls when lifting at low speed
The reason is that the pressing iron of the column guide rail is not loosened and the lubrication is poor. The solution is to loosen and adjust the pressure iron and good lubrication.
4. Worktable rapid feed cannot be disengaged
In the actual operation process, it is often used to quickly return or move the feed (fast forward) with a large empty distance to shorten the non cutting time. When starting the slow working feed after the rapid feed, the fault that is still the rapid feed is regarded as the rapid feed cannot be disengaged. Although the probability of this kind of failure is very small, it is very dangerous and should be paid special attention. The main reasons are that the remanence of the electromagnet is too large or the spring force of the slow return is insufficient. Repair and adjustment should be carried out by electricians and mechanics.

5. Feed system safety clutch failure
When the feeding system of the machine tool is overloaded, the feeding movement cannot stop automatically. The reason for the failure of the safety clutch is that the torque regulated by the clutch is too large. The solution is to readjust the safety clutch.