The mechanical transmission system of a CNC precision gantry milling machine is the core that connects the power source and the executing components, covering key components such as ball screws, gearboxes, couplings, and guide rails. Its operating status directly affects the positioning accuracy and machining stability of the machine tool. Long term high load processing or improper maintenance can easily cause transmission failures, such as feed lag, precision deviation, abnormal noise, etc. The following is a breakdown of typical transmission component failures, their causes, and practical handling techniques.
1、 Ball screw malfunction: Focus clearance and lubrication issues
As the core of feed transmission, ball screw commonly experiences faults such as excessive clearance, abnormal noise, or jamming, which are often caused by wear, lubrication failure, or installation deviation.
If there is a deviation in feed positioning, first check the clearance between the screw and nut: after stopping the machine, manually push the worktable to feel if there is any obvious clearance, or use a dial gauge to check the reverse clearance. If it exceeds the tolerance, adjust the screw pre tightening nut (such as the double nut pre tightening structure) to reduce the clearance. If it is severe, replace the worn screw or nut; If the operation of the screw rod is accompanied by abnormal noise and jamming, it is mostly due to insufficient lubrication or the invasion of impurities. It is necessary to remove the screw rod protective cover, clean the surface oil and chips of the screw rod, supplement the special screw rod lubricating grease (avoid using ordinary lubricating oil to prevent grease from deteriorating and clumping), and check whether the protective cover is damaged, and repair it in a timely manner to prevent impurities from entering again.
Installation deviation can also exacerbate screw failure. When dealing with it, it is necessary to recalibrate the parallelism between the screw and the guide rail to ensure that the axis of the screw is consistent with the direction of movement of the worktable, and to avoid accelerated wear of the screw due to radial force.
2、 Gearbox malfunction: troubleshooting meshing and bearing status
The gearbox is responsible for power transmission and speed change functions, and faults often manifest as abnormal noise and decreased transmission efficiency, with the root cause being poor gear meshing or bearing wear.
If there is high-frequency noise during the operation of the gearbox, first stop the machine and remove the gearbox cover to observe whether there is wear, pitting, or tooth bonding on the gear meshing surface. Mild wear can be repaired by grinding the tooth surface, and in severe cases, the gear needs to be replaced; At the same time, check the gear mesh clearance. If the clearance is too large, it can be restored to the appropriate clearance by adjusting the gear shaft position or replacing the thickened gasket.
If the vibration of the gearbox intensifies, it is mostly due to bearing damage. It is necessary to disassemble the gear shaft, check whether there are scratches or peeling on the bearing raceway, replace with high-precision bearings of the same model, and pay attention to the pre tightening force of the bearings during installation (too tight is prone to heating, too loose is prone to vibration) to ensure a tight fit between the bearings and the shaft neck. In addition, it is necessary to regularly replace the gearbox lubricating oil to avoid lubrication failure caused by oil deterioration.
3、 Coupling failure: solving connection and coaxiality issues
Couplings connect motors and transmission components (such as screw rods and gear shafts), and faults often manifest as transmission slippage and abnormal noise, often caused by loose connections or coaxial deviation.
If the coupling slips, first check whether the connecting bolts are loose, and use a torque wrench to tighten diagonally according to the specified torque (to avoid deformation of the coupling caused by one-way tightening). If the bolts are worn or slip, high-strength bolts need to be replaced; If the coupling operation is accompanied by periodic abnormal noise, it is mostly due to the coaxiality deviation between the motor and the transmission shaft. It is necessary to loosen the coupling bolts, use a dial gauge to detect radial and end face runout, adjust the position of the motor base, ensure that the coaxiality error is controlled within the allowable range, and then tighten the bolts again.
For elastic couplings, it is necessary to regularly check whether the elastic parts (such as rubber pads and nylon columns) are aging or damaged, and replace them in a timely manner to cushion vibration and avoid damage to transmission components caused by rigid impact.
4、 General processing principle: Diagnosis before repair, with emphasis on subsequent maintenance
When dealing with transmission component faults, it is necessary to follow the principle of "static inspection first, dynamic testing later": first stop the machine to observe the appearance of the components (such as whether there is oil leakage, deformation, or loose connections), then start the machine for trial operation, locate the fault point by listening to sound, measuring accuracy, and checking the load, and avoid blind disassembly. After the fault is repaired, it is necessary to conduct trial machining verification to check whether the machining accuracy has been restored. At the same time, a component maintenance ledger should be established to record the type of fault and the handling plan. Regular preventive maintenance (such as regular lubrication and gap detection) should be carried out to reduce the recurrence of faults from the source.