General handling of mechanical part failure of CNC machine tools
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Repair of the mechanical part of the CNC machine tool, where the same fault as the mechanical part of the conventional machine tool can be treated with the conventional machine tool mechanical fault handling regulations. However, due to the use of electrical control in CNC machine tools, the mechanical structure is simplified, so the mechanical failure rate is significantly reduced.
1. Deal with the failure of the feed chain:
As the drive chains of CNC machine tools mostly use rolling friction pairs, most of the faults in this area are caused by the deterioration of the sports quality. If the backlash increases, positioning accuracy does not meet requirements, mechanical crawling, bearing noise becomes large (especially after a mechanical hard collision). This part of the maintenance is often closely related to the pre-tightening force of the sports team, the loosening ring and the adjustment of the compensation link.
2. Spindle component fault handling:
This part of the failure and the handle of the automatic tensioning device, automatic shifting device and spindle movement accuracy and so on. Because the CNC machine tool has eliminated the mechanical gearbox device after adopting the electric automatic speed control, sometimes the gearbox is very simple, and the structure is simplified to greatly reduce the failure.
3. ATC tool automatic exchange device fault processing:
According to statistics, the ATC tool automatic exchange device accounted for more than half of the mechanical failures of CNC machine tools. The main symptoms are:
·Knife magazine movement error ·Positioning error error ·Inaccurate gripping of the gripper ·Inaccurate movement of the robot
All these failure phenomena will cause the emergency of the tool changer to stop, and the machine will stop because of the failure of ATC tool automatic exchange.
4. Position check with stroke switch pressing failure processing:
CNC machine tools are equipped with a lot of limit movement limit switch, use a period of time, the moving parts of the movement characteristics have changed and the mechanical reliability of the compression stroke switch and the quality and characteristics of the trip switch itself will affect the whole machine movement. This requires a good inspection, replacement or adjustment.
5. The fall of the reliability of the accessory accessory causes the fault to be dealt with:
Supporting accessories for CNC machine tools include:
Cooling device, chip removal device, protective device (including coolant shield, guide rail cover, etc.)
Spindle cooling thermostats, hydraulic tanks, pneumatic pumps, constant pressure gas cabinets, etc.
Failure or malfunction of these parts can cause malfunction and stop the movement of the machine. Therefore, the inspection of these parts should not be ignored. If the power of tool change in the machining center depends on the compressed air, if the air pump supply pressure is not enough, or the air leakage from the air tank will reduce the air pressure, the tool change will be suspended and the machine tool will move. Unsatisfactory constraints also cause an alarm and stop. As long as these factors are eliminated and the machine constraints are satisfied, the alarm will be canceled and transferred to normal operation.
6. ATC troubleshooting example Toshiba Corporation's TOSNAC BMC125 horizontal CNC machining center is a CNC machine tool manufactured in the early 1980s. Its automatic tool changer ATC control circuit schematic block diagram as shown. 
When the tool is exchanged, it is divided into 19 steps and is required to complete the above steps in 15s. When a failure occurs, any one of the above-mentioned steps in the action will make a mistake and will cause the ATC device tool exchange time to be extended, resulting in an alarm. .
The tool change of the BMC125 machining center belongs to the form of automatic exchange of the feed tool of the robot, so it is a relatively complicated one in terms of structure and action.
Most of the users of the BMC125 CNC machining center in use reflect that the reason for the failure of the ATC tool automatic exchange device is that most of the reasons for the limit switch malfunction are that the method of troubleshooting can be performed after manual reset. For limit switch elements, they should be strictly tested after the occurrence of a fault and replaced when necessary.