Maintenance and maintenance of mechanical parts and auxiliary devices of CNC machine tools

Mechanical parts and auxiliary devices are an important part of CNC machine tools. Among them, the mechanical part mainly includes: machine tool spindle parts, ball screw nut pairs, guide rails and the like. The auxiliary device mainly includes: a numerical control indexing head, an automatic tool changing device, a hydraulic air pressure system and a cooling lubricating device. Therefore, their daily maintenance and maintenance is one of the whole maintenance and maintenance work of CNC machine tools.

First, the maintenance and maintenance of the mechanical part

The maintenance and maintenance of the mechanical part of the CNC machine tool mainly includes the maintenance and maintenance of the spindle parts of the machine tool, the feed transmission mechanism and the guide rail.

1. Maintenance and maintenance of spindle components

The spindle component is an important component in the mechanical part of the CNC machine tool. It is mainly composed of the spindle, bearing, spindle quasi-stop device, automatic clamping and chip removal device. Lubrication, cooling and sealing of CNC machine tool spindle components are several issues worthy of attention during machine tool use and maintenance.

First of all, good lubrication effect can reduce the working temperature of the bearing and prolong the service life. For this reason, it should be noted during operation and use: grease lubrication and oil circulation lubrication are used at low speed; oil mist and oil lubrication are adopted at high speed. However, when grease lubrication is used, the amount of seal of the spindle bearing is usually 10% of the bearing space volume. Do not fill it at will, because too much grease will increase the spindle heat. For oil circulation lubrication, in the operation and use, it is necessary to check the spindle lubrication constant temperature tank every day to see if the oil quantity is sufficient. If the oil quantity is not enough, the lubricating oil should be added in time; at the same time, check the temperature range of the lubricating oil.

In order to ensure good lubrication of the main shaft, reduce friction and heat, and at the same time take away the heat of the spindle assembly, a circulating lubrication system is usually used, which is lubricated by a hydraulic pump, and the oil temperature controller is used to control the temperature of the oil tank. The high-end CNC machine tool spindle bearings are lubricated with advanced grease storage methods, which can be used for 7 to 10 years. The new lubrication cooling method not only reduces the bearing temperature rise, but also reduces the temperature difference between the inner and outer rings of the bearing to ensure that the thermal deformation of the main shaft is small.

There are two common lubrication methods for the main shaft. The oil and gas lubrication method is similar to the oil mist lubrication method. However, the oil mist lubrication method is to continuously supply the oil mist, and the oil and gas lubrication is to regularly and quantitatively feed the oil mist into the bearing gap. The oil mist is lubricated, which avoids too much oil mist and pollutes the surrounding air. The injection lubrication method is to inject a large amount of constant temperature oil (3 to 4 L/min per bearing) into the spindle bearing to achieve lubrication and cooling. Here, the oil injected at a larger flow rate must be forced to drain by the oil discharge pump instead of naturally returning. At the same time, it is also necessary to use a dedicated high-capacity high-precision constant temperature fuel tank, and the oil temperature variation is controlled at ±0.5 °C.

Second, the cooling of the main shaft components is mainly to reduce bearing heat and effectively control the heat source.
Third, the sealing of the main shaft components not only prevents dust, debris and cutting fluid from entering the main shaft components, but also prevents leakage of lubricating oil. The seals of the spindle components are contact and non-contact. For contact seals with linoleum rings and oil-resistant rubber seals, pay attention to check the aging and damage; for non-contact seals, in order to prevent leakage, it is important to ensure that the oil return can be drained as soon as possible, to ensure the smooth return hole . In summary, in the use and maintenance of CNC machine tools, the lubrication, cooling and sealing of the spindle components must be highly valued, and this work should be done carefully.

2. Maintenance and maintenance of the feed transmission

The electromechanical components of the feed transmission mechanism mainly include: servo motor and detection component, speed reduction mechanism, ball screw nut pair, screw bearing, moving parts (workbench, headstock, column, etc.). Here we mainly explain the maintenance and maintenance of the ball screw nut pair.

(1) Adjustment of the axial clearance of the ball screw nut

In addition to the accuracy of the feed motion in a single direction, the ball screw nut pair also has strict requirements on the axial clearance to ensure the reverse transmission accuracy. Therefore, in operation and use, it should be noted that the axial clearance caused by the wear of the screw nut pair is eliminated by the adjustment method.

Double nut gasket type backlash

Cylindrical external gears are respectively formed on the flanges of the two nuts, respectively meshing with the inner ring gears fastened at both ends of the sleeve, and the number of teeth is respectively Z1 and Z2, and one tooth is different. When adjusting, first remove the inner ring gear, let the two nuts rotate one tooth in the same direction with respect to the sleeve, and then insert the inner ring gear, then the two nuts will produce relative angular displacement, and the axial displacement is:

In the formula, Z1 and Z2 are the number of teeth of the gear, and Ph is the lead of the ball screw.
(2) Daily inspection of sealing and lubrication of ball screw nut pair

The daily inspection of the sealing and lubrication of the ball screw nut pair is a problem we should pay attention to during operation. For the sealing of the screw nut, it is necessary to check the sealing ring and the protective cover to prevent dust and impurities from entering the ball screw nut pair. For the lubrication of the screw nut, if grease is used, it should be lubricated regularly; if lubricating oil is used, it should be noted that oil is often injected through the oil hole.

3. Maintenance and maintenance of machine guides

The maintenance and maintenance of the machine guide rail is mainly the lubrication of the guide rail and the protection of the guide rail.

(1), lubrication of the guide rail

The purpose of rail lubrication is to reduce frictional resistance and frictional wear to avoid creeping at low speeds and lowering the temperature rise at high temperatures. Therefore, the lubrication of the guide rail is very important. Lubricating oil is used for the sliding guide rails, and lubricating oil or grease is available for the rolling guide. The grades of lubricants commonly used in CNC machine tools are: L-AN10, 15, 32, 42, 68. The oil lubrication of the guide rail is generally automatic lubrication. We should pay attention to check the diverter valve in the automatic lubrication system during operation. If it fails, the guide rail will not be automatically lubricated. In addition, it must be done every day

Check the oil volume of the guide oil tank. If the oil quantity is not enough, you should add the oil in time. At the same time, pay attention to check whether the oil pump can start and stop regularly, and pay attention to check whether the lubricating oil can be supplied at the time of starting.

(2), the protection of the guide rail

In operation and use, care should be taken to prevent chips, abrasive particles or cutting fluid from scattering on the rail surface, otherwise the rail wear will be aggravated, scratched and rusted. To this end, pay attention to the daily inspection of the rail guard to ensure the protection of the rail.

4. Maintenance and maintenance of the rotary table

The circumferential feed motion of CNC machine tools is generally realized by the rotary table. For the machining center, the rotary table has become an indispensable component. Therefore, in operation and use, we must pay attention to the correct operation according to the requirements and operating procedures of the rotary table. Pay special attention to the lubrication of the rotary table drive mechanism and the guide rail.

Second, the maintenance and maintenance of auxiliary equipment CNC machine tool auxiliary equipment maintenance and maintenance mainly include: CNC indexing head, automatic tool changer, hydraulic pressure system maintenance and maintenance.

1. Maintenance and maintenance of CNC indexing head

The numerical control indexing head is a common accessory for CNC milling machines and machining centers. Its function is to make the rotary indexing or continuous rotary feeding motion according to the instructions of the CNC device, so that the CNC machine tool can complete the specified machining accuracy. Therefore, in operation and use. It is necessary to pay attention to the correct operation according to the requirements and operating procedures of the numerical control indexing head.

2. Maintenance and maintenance of automatic tool changer

The automatic tool changer is a feature that distinguishes the machining center from other CNC machine tools. It has the function of automatically changing the required tools according to the processing requirements, to help the CNC machine save the auxiliary time and meet the requirements of multi-process and step processing in one installation. Therefore, in operation and use, it is necessary to check whether the operation of the mechanical structure of each component of the automatic tool changer is normal, whether there is an abnormal phenomenon, whether the lubrication is good, etc., and pay attention to the reliability and safety inspection of the tool change.

3. Maintenance and maintenance of hydraulic system

(1) Regularly inspect, filter, and replace oil in the fuel tank;

(2) Check the performance of the cooler and heater to control the oil temperature;

(3) Regularly check and replace the seals to prevent leakage of the hydraulic system;

(4) Regularly check the cleaning or replacement of hydraulic parts, filter elements, and regularly check the cleaning tank and piping;

(5) Strictly implement the daily inspection system to check whether the leakage, noise, vibration, pressure, temperature, etc. of the system are normal.

4. Maintenance and maintenance of the pneumatic system

(1) Use a suitable filter to remove impurities and moisture from the compressed air;

(2) Check the oil supply of the oil mister in the system to ensure that there is an appropriate amount of lubricating oil in the air to lubricate the pneumatic components to prevent rust, wear and tear, air leakage and component failure;

(3) Maintain the tightness of the pneumatic system and periodically check and replace the seals;

(4) Pay attention to adjusting the working pressure;

(5) Regularly check the cleaning or replacement of pneumatic components and filter elements.


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