What are the common faults of milling machines? How to troubleshoot them? Below is a summary of several common faults and their solutions.
Generally speaking, the common faults are as follows.
Fault 1: Uneven surface at the tool joint on the machined surface.
Solution: Check the parallelism of the worktable, the parallelism of the spindle axis relative to the worktable surface, and the perpendicularity of the knee relative to the worktable surface.
Fault 2: The operating handle of the spindle gearbox automatically disengages.
Solution: Replace the spring or add shims.
Fault 3: The operating handle of the spindle gearbox cannot be operated.
Solution: If the vertical shaft handle is stuck with the hole connection, disassemble it for repair; if the sector gear is stuck with the rack, adjust the clearance to approximately 0.15 mm; if the shifting fork shaft is bent or deformed, straighten it; if the rack shaft is misaligned with the hole on the hole cover, change to other speed levels, move the speed change disc, and adjust the spring of the positioner.
In addition to the above faults, there is another major fault that cannot be ignored: abnormal machining accuracy. This fault is highly concealed and difficult to diagnose. So how should we solve it?
According to experts, there are mainly five causes for this fault:
First, the feed unit of the milling machine has been modified or changed;
Second, the zero offset of each axis of the milling machine is abnormal;
Third, the backlash of the axes is abnormal;
Fourth, the motor operating status is abnormal, that is, the electrical and control parts are abnormal;
Fifth, mechanical faults, such as faults in components like the lead screw, bearings, and shaft couplings.
In addition to the above five aspects, factors such as the programming of the machining program, the selection of cutting tools, or human factors can also cause abnormal machining accuracy of the milling machine. Below is an analysis of some of these points.
(1) System parameters have changed or been modified
What are system parameters? System parameters mainly include the feed unit, zero offset, and backlash of the milling machine. Certain operations during the repair of the milling machine may affect the zero offset and backlash, so after the repair is completed, appropriate adjustments or modifications should be made. In addition, severe equipment wear or loose connections may also cause the measured values of the parameters to change, so the parameters should be modified accordingly.
(2) Mechanical faults
There are several possible causes, including abnormal motor conditions, clearance in the lead screw, and mechanical faults, so they should be checked one by one.
(3) Unoptimized electrical parameters of the milling machine and abnormal motor operation
There are two reasons for this: large backlash in the lead screw and abnormal operation of the X-axis motor. The solutions are: compensate for the existing clearance, adjust the servo gain parameters, and eliminate the vibration of the X-axis motor.
