Common mechanical faults in grinder processing and preventive measures
1、 Main shaft parts fault
The spindle is one of the core parts of the large grinder machining center. Most of the machining surface accuracy is related to the spindle, so the quality of the spindle is very important. Because of the use of adjustable speed motor, the spindle box structure of CNC machine tool is relatively simple, and the parts that are easy to show faults are the active clamping mechanism of the cutter inside the spindle, the active adjustable speed equipment, etc. In order to ensure that the tool holder will not loosen itself during work or power failure, the tension spring clamp is selected as the active clamping mechanism of the tool. If the tool can't be loosened after clamping, consider adjusting the pressure of the hydraulic cylinder and the travel switch device or adjusting the nut on the Belleville tension spring to reduce the compression amount of the tension spring. In addition, the problem of spindle heating and spindle box noise should not be ignored. At this moment, the main consideration is to clean the spindle box, adjust the amount of smooth oil, ensure the cleanliness of the spindle box and replace the spindle bearing, repair or replace the spindle box gear, etc.
Two. Feed transmission chain fault
In the feed transmission system of large grinder machining center, ball screw pair, hydrostatic screw nut pair, rolling guide rail, hydrostatic guide rail and plastic guide rail are generally selected. So there is a problem with the feed transmission chain, the main reflection is the decline of the movement quality. For example: the mechanical parts do not move to the specified direction, the operation stops, the positioning accuracy decreases, the reverse clearance increases, the creeping, the bearing noise increases (after the crash), etc.
Such defects can be prevented by the following methods:
(1) It can also improve the transmission accuracy by improving the transmission accuracy, adjusting the preload of each motion pair, adjusting the loose link, eliminating the transmission gap, shortening the transmission chain and setting the reduction gear in the transmission chain.
(2) Improve drive stiffness. It is an effective way to improve the transmission stiffness by adjusting the preload of the screw nut pair and supporting parts and selecting the screw size reasonably. The lack of stiffness will also lead to creeping and oscillation of the worktable or the carriage, as well as the formation of reverse dead zone, which will affect the transmission accuracy.
(3) Improve motion accuracy. On the premise of satisfying the strength and rigidity of the moving parts, the mass of the moving parts and the diameter and mass of the rotating parts should be reduced as much as possible, so as to reduce the inertia of the moving parts and improve the motion accuracy.
(4) The guide rail rolling guide rail is sensitive to stolen goods, so it is necessary to have outstanding protective equipment, and the pre tightening force of the rolling guide rail should be properly selected, so that the traction force will be significantly increased if it is too large. Hydrostatic guide rail shall have a set of oil supply system with excellent filtering effect.
3、 Fault of active tool change equipment
The main faults of the active tool changing equipment are: the movement fault of the tool magazine, the large missing of the positioning difference, the instability of the manipulator's clamping handle, the large movement error of the manipulator, etc. If the problem is serious, the tool change will be stuck and the machine tool will be forced to stop working.
1. Magazine movement fault
If the coupling connecting the motor shaft and the worm shaft is loose or the mechanical connection is too tight and other mechanical reasons, the magazine will not roll. At this moment, it is necessary to tighten the screws on the coupling. If the magazine does not roll in place, it is caused by motor rolling fault or transmission error. If the tool sleeve cannot clamp the tool, adjust the adjusting screw on the tool sleeve, compress the tension spring, and tighten the clamping pin. When the upper / lower part of the tool sleeve is not in place, check the equipment and adjustment status of the fork orientation or limit switch.
2. Tool change manipulator fault
If the tool is not clamped tightly and the tool falls off, adjust the tension spring of the clamping claw to increase its pressure, or replace the clamping pin of the manipulator. If the tool cannot be loosened after clamping, adjust the nut after loosening the tension spring to make the maximum load not exceed the rated value. If the tool is dropped during tool exchange, if the spindle box does not return to the tool change point or the tool change point drifts, the spindle box shall be operated again to return to the tool change position and reset the tool change point.
4、 Auxiliary equipment failure
1. Hydraulic system
The variable displacement pump shall be selected for the hydraulic pump to reduce the heating of the hydraulic system, and the filter of the equipment in the oil tank shall be cleaned timely with gasoline or ultrasonic vibration. The most common problems are the wear, crack and mechanical damage of the pump body. At this moment, it is generally necessary to overhaul or replace parts.
2. Air pressure system
It is used in the air pressure system of tool or workpiece clamping, safety door switch and spindle cone hole blowing chips. The water separator and air filter shall be punctually drained and cleaned to ensure the sensitivity of moving parts in pneumatic components. The failure of valve core action, air leakage, damage of pneumatic components and action failure are all caused by poor smoothness, so the oil mist device should be cleaned on time. In addition, the tightness of the pneumatic system should always be checked.
3. Smooth system
Including the smoothness of machine tool guide rail, transmission gear, ball screw, spindle box, etc. The filter in the smooth pump shall be cleaned and replaced on time, generally once a year.
4. Cooling system
It has the function of cooling and chip punching for tools and workpieces. The coolant nozzle should be cleaned on time.
5. Chip removal equipment
Chip removal equipment is an independent function of accessories, the first to ensure active cutting plus smooth progress and reduce the heating of CNC machine tools. Therefore, chip removal equipment should be able to actively remove chips in time, and its orientation should be as close to the cutting area as possible.
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