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Common Mechanical Faults and Precautionary Measures of CNC Machine Tools

Common Mechanical Faults and Precautionary Measures of CNC Machine Tools

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As the use of speed motors, CNC machine tool spindle box structure is relatively simple, prone to failure of the spindle within the tool is automatic clamping
First, the spindle component failure .
As the use of speed motors, CNC machine tool spindle box structure is relatively simple, prone to failure of the spindle within the tool is automatic clamping mechanism, automatic speed control devices. To ensure that during the work or power outages will not be self-loose knife, tool clamping mechanism using automatic spring clamping, and with the trip switch to issue clamping or relaxation signal. If the tool can not be loosened after clamping, consider adjusting the pressure of the hydraulic cylinder and the limit switch or adjust the disc spring on the nut, reducing the spring pressure on the amount. In addition, the spindle heating and the spindle box noise, can not be ignored, this time the main consideration cleaning the spindle box, adjust the amount of lubricating oil, to ensure the cleanliness of the spindle box and replace the spindle bearings, repair or replacement of spindle box gears .
Second, the feed drive chain failure.

In the CNC machine tool feed drive system, commonly used ball screw, static pressure screw nut pair, rolling rails, hydrostatic rails and plastic rails. So the feed chain is faulty, mainly reflecting the decline in quality of movement. Such as: mechanical parts are not moving to the specified location, running interruption, positioning accuracy, increased backlash, crawling, bearing noise (crash) and so on.

For such failure can be prevented by the following measures: (1) to improve the transmission accuracy adjustment of the movement of the pre-tightening force, adjust the loose link, to eliminate transmission gap, shorten the transmission chain and set in the transmission chain reduction gears can also improve transmission accuracy. (2) to improve the transmission stiffness. It is an effective measure to improve the transmission rigidity by adjusting the pretightening force of the screw nut and the supporting part and the size of the screw itself. Insufficient stiffness can also cause creep and vibration of the workbench or pallet, as well as a reverse dead zone, affecting drive accuracy. (3) to improve motion accuracy. In the premise of satisfying strength and rigidity of components, the quality of moving parts is reduced as much as possible, and the diameter and quality of rotating parts are reduced to reduce the inertia of moving parts and improve the movement precision. (4) rail guide rails on the stolen goods are more sensitive, there must be a good protective device, and the rolling rail preload to select the appropriate, over the General Assembly to a significant increase in traction. Hydrostatic guide rail should have a good filtering effect of the fuel supply system .
Third, the automatic tool changer breakdown
Automatic tool changer failure is mainly manifested in: knife library movement failure, positioning error is too large, manipulator holding knife handle instability, robot movement error and so on. If the fault is serious, the tool change will be stuck and the machine will stop working.
1. Tool magazine movement fault
If the coupling of the motor shaft and the worm shaft shaft coupling loose or mechanical connection too tight and other mechanical reasons, will cause the magazine can not turn, this time must be tightened on the coupling screw. If the magazine rotation is not in place, it belongs to the motor rotation failure or transmission error caused. If the tool holder can not be clamped, adjust the adjusting screw on the tool case, press the spring and tighten the clamping pin. When the tool cover is not in place, check the position of the fork or the limit switch And adjustment of the situation.
2. Replacement robot failure
If the tool clip does not tighten, the knife, then adjust the clamping claw spring, so that the pressure increases, or replace the robot clamping pin if the tool is not loose after clamping, should adjust the loose lock spring nut, the maximum load Over rated. If the tool exchange knife, it belongs to the tool changer does not return to the tool change point or tool changer point drift caused, should re-operate the spindle box, to return to the tool change position, re-set the tool change point.
Fourth, the movement of the axis position switch stroke crimping failure
In CNC machine tools, in order to ensure the reliability of automation, the use of a large number of movement detection position switch machine. After long-term operation, the motion characteristics of moving parts change, the reliability of stroke switch press device and the quality characteristics of stroke switch itself have a great impact on the performance of the whole machine. General to timely check and replace the trip switch, can eliminate such a switch on the impact of poor machine.
5, supporting auxiliary device failure
Hydraulic system
Hydraulic pump should be used variable pump to reduce the hydraulic system of the heating tank installed in the filter should be regularly cleaned with gasoline or ultrasonic vibration. Common failures are mainly pump wear, cracks and mechanical damage at this time generally have to overhaul or replacement parts.
2. Pneumatic system
For the tool or workpiece clamping, security door switch and the spindle cone hole blowing air pressure system, the water divider should regularly drain, regular cleaning to ensure that the moving parts of pneumatic components in the sensitivity. Valve heart failure, air leakage, pneumatic components, such as damage and malfunction failure caused by poor lubrication, so the oil mist should be cleaned regularly. In addition, the pneumatic system should always check the sealing.
3. Lubrication system
Including the machine guide, transmission gear, ball screw, spindle box lubrication. Lubrication of the filter inside the pump need regular cleaning, replacement, the general should be replaced once a year.
4. Cooling system
It cools and debris acts on the tool and the workpiece. Coolant nozzles should be cleaned regularly.
5. Chip removal device
Chip removal device is an independent function of the annex, the main guarantee for automatic cutting and smooth and reduce the heat of CNC machine tools. So chip removal device should be able to automatically chip removal in time, its installation should generally be as close to the cutting tool cutting area.
VI Conclusion
CNC machine tools is the use of computer-controlled, mechanical and electrical integration of automated processing equipment, the use of CNC machine tools is a technology application engineering. Correct prevention and effective maintenance is to improve the use of CNC machine tools to ensure the basic efficiency. For the common mechanical failure, although there are few opportunities, but should not be overlooked should be a comprehensive analysis and determine the root causes of failure, as short as possible downtime, in order to facilitate the efficient performance of CNC machine tools
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