Like the position detection element of the linear axis of the CNC machine-tool, it is equivalent to the “eyes” of a person, that is to say once the “surveillance” line tree is executed by the CNC system, if the right axis really works precisely at the location of the instruction of the CNC system. If the CNC machine is not installed with a network rule, when the CNC system emits a movement instruction from the right axis, if the linear axis can reach the location required by the CNC system and rely on The precision and precision of mechanical transmission of the CNC debugging of the system to ensure.
After using the CNC machine for a period of time, due to the modification of electrical debugging parameters and the increase in mechanical errors, the right axis is probably very different from the position required by the instructions of the CNC system. , the CNC system is not known. Consequently, the CNC machine does not have a network rule and the precision of the machine tool must be checked regularly. exceeded or even rebuilt.
If the linear axis of the CNC machine is installed with a network rule, the above problems will not be worried and this mission will be supplemented by the network rule. If the right axis does not reach the position precisely for mechanical or other reasons, the network rule is detected by the position detection component and that the feedback instruction will be issued to the CNC system, so that the Right axis can reach a more precise position. Currently, the network rule acts as the independent supervision function outside the machine. .
In the transformation of new machine tools or old machine tools, the aim of using the network rule is to increase the precision of the line axis. However, the accuracy of the operation does not depend exactly on the network rule, mainly depends on the geometric accuracy of the mechanical part of the right axis. The network rule cannot replace the precision of mechanics, and it can only be “frosting on the cake”. Many people have differences in understanding this problem. Position of operating instruction of the CNC system, due to the low precision of transmission of the right axis, a shock will occur before and after precise positions.
The transmission error generated by the transmission generated by the transmission of the machine tool, the heat deformation error caused by the transmission mechanism during high -speed operation and the error caused by the wear of the system high -speed drive during high -speed operation. During treatment, these errors seriously affected the treatment accuracy and the stability of CNC machines. The right network rule performs a complete control of the linear coordinate coordinate tree loop of CNC machine tools, reducing the above error and improving positioning accuracy, repeated positioning accuracy and reliability of accuracy of the machine tool. As a key component to improve the positioning accuracy of CNC machine tools, it is more and more favored by users.
Precision of CNC machines
There are three main aspects of CNC machine tools: geometric accuracy, positioning precision and treatment accuracy.
The geometric precision of the machine-tool, also known as mechanical precision, is a complete reflection of complete geometric shape errors after assembling the key components of the machine tool. The detection tools and the methods used are fundamentally the same as those of ordinary machine tools, but the requirements are higher. Take the geometric accuracy of an ordinary vertical treatment center as an example:
1) The flatness of the work table
2) Move each other vertical of each coordinate direction
3) The parallel of the movement of the Movement of Coordinates X and Y
4) Rotating precision of the spindle
5) The parallelity of the spindle when the spindle box moves along the steering of the midline of the Z coordinate shaft
6) The pin moves straight in the direction of the coordinate of the Z axis
The precision of positioning of the machine tool refers to the precision of actual position that the main components of the machine can reach at the end of the movement. The error between the actual position and the positioning position is called the positioning error. The positioning accuracy of CNC machine tools can be understood as the movement accuracy of the tool-machine, so that the positioning accuracy determines the CNC system and the mechanical transmission error. The movement of each movement component of the machine tool is completed under the control of the CNC device.
The repeated positioning accuracy refers to the consistency of the position accuracy obtained several times on the CNC machine. The repeated positioning accuracy is affected by factors such as the characteristics of the servomotor system, the gap and the rigidity of the transmission link and the friction characteristics. In normal circumstances, repeated positioning accuracy is an accidental error in normal distribution.
Treatment accuracy
The geometric accuracy and the positioning precision of the machine tools are generally detected without cutting the loads and a low movement or a low movement speed. In the real working state, there are a series of factors that affect the precision of treatment. For example, due to the effect of the cutting force and the tightening force, the components of the machine tool will produce a flexible deformation. Under the influence of the heat source inside the machine (such as the heat rolling of the engine, the thermal rolling of the hydraulic transmission device, the gear friction heat, etc.) and the change of Environmental temperature, machine tools will produce thermal deformation. Due to the effects of cutting and speed strength, the tooltip will cause vibrations. When the movement components of machine tools move to a working speed, due to the effects of the oil membrane and other factors between the relatively sliding surface, the accuracy of the exercise is also different from precision measured at low speed. All this will result in changes in the static precision of the tool-machine and will affect the precision of the treatment of the part. The accuracy of the work states of the machine, the rise in temperature and vibrations is called dynamic precision of the machine tool. In addition to the close relationship with static accuracy, dynamic precision is also largely determined as being rigid, resistance to vibrations and thermal stability of the machine tool.
Currently, in production, the complete dynamic precision of the machine tool is evaluated by cutting the precision of the part, which is called the work precision of the tool-tool. The precision of the work is a complete reflection of various factors on the precision of the treatment.
The precision of the machine-tools is improved
Currently, in the parts processing industry, there are two main methods to improve the accuracy of the treatment of CNC machines: one is the method of prevention of errors; The other is the error compensation method.
SO-SALLED prevention consists in improving the level of quality of the design, processing and assembly of components, effectively controlling environmental factors and achieving the aim of eliminating or reducing the source of errors. For example, the use of high rigid thermal rails and ball screws for ambient temperature control can effectively reduce the thermal deformation of the tool machine and the temperature of the heat source, thus reducing the occurrence of Errors.
The errors prevention methods are mainly divided into three categories: prevention of geometric errors of size error, prevention of thermal deformation errors and other prevention of errors. Error prevention methods can reduce the probability of errors to some extent, but it is almost impossible to completely eliminate thermal deformation and geometric errors. In addition, the processing accuracy of the mother machine has a great impact on it, and the cost of improving the quality of the parts is too high, which is not common in practical applications.
Method of error compensation, install precision component probes, location sensors, network rule and other equipment on CNC machine tools, so that the handwatches processing will be returned to the CNC system. The tool-tool automatically compensates for treatment accuracy, improves the precision of parts treatment and considerably saves the costs of raw materials.
Several types of defects are often found as a position detection components than a linear axis.
1. In the point of reference, the right axis cannot find a zero impulse.
In terms of expression, the axis runs until the reference point of the axis runs to the limit of the axis strike.
The cause of this failure is generally caused by the reading head or the Sovereign of the NO network. Remove the readable head and rinse it with ethanol without water, and use a silk fabric to dip ethanol without water to clean the scaling part.
2. The alarm of the linear axis of the CNC machine appears during operation.
If the alarm “Material Coder Error” seems to use the Siemens 840D system or Lesle CNC; reason:
① Due to vibrations or other reasons, the spacing of the number of heads and network scale in the use of machine tools becomes greater in use, and the CNC system wrongly estimates that the network rule is broken. The failure processing method is to adjust the distance between the readable head and the network rule according to the requirements of the network rule instructions. The distance between the reading head and the body of the gate rule is approximately 1 to 1.5 mm, it is preferable not to exceed 2 mm.
② The installation location of the network rule is not appropriate.
③ The location of the number of reading heads is not appropriate, causing damage to the reading head.
3. The right axis of the CNC machine-tool appears on the run
When the linear axis of the CNC machine generally occurs, the location of the right axis assembly network is contaminated, and the network of the network rule or the reading head must be cleaned to eliminate failure.
4. Other faults
In many years of maintenance of the CNC machine, we found that the network rule as a position detection element of the CNC system. In addition, the network rule can also detect hidden dangers or existing problems in tool machines.
After the CNC transformation of a C61200 tour produced by Wuzhong, it uses the CNC 8055TC system. At one point, because the roller body is oval, when the roller body of the roller is oval, when the tool tool eats the size of the roller size, the X axis moves to the steering of the roller without the movement instruction of the axis x. When the knife is exposed to a place with a relatively small size of the roller, the X axis moves towards the steering near the roller by itself, moving back and forth.
Inspection of the CNC system of the tool-machine, it has been found that the X axis and the “activate” signal were found, and the ACA servomotor added a self-blocking power. When the position of the X axis is protected, change it into a semi-closed loop, then treat it. This phenomenon some people think that there is a problem with the network rule, but thanks to the inspection, it is found that the rear hat of the roller screw of the X axis is therefore loose. When the knife comes into contact with the comparison of the size of the roller body, the comparison in large place, the roll has a “superior” force on the x axis. The network rule used to detect the position of the XA axis revealed that without the number of instructions issued by the CNC system, the “+ x” direction of the X axis (far from the roller direction) has been displaced and the role of the role of the sovereign of network must detect the straight line tree by detecting the tree of the right axis, if the movement is precise under the action of the CNC instruction. CNC system. Therefore, when the knife is contacted with a relatively small size of the roller body, the knife and the roller body have a certain space. and positions it in the X of the CNC system. In this way, each week, when the X axis has no movement of data instructions, the X axis appears “far from the diameter of the roller” and “near the diameter of the roller”. The relaxation of the hat brought him to move back and forth.
A linear axis of the CNC machine adopts the phenomenon of engine jig and the vibration of the axis in a complete loop loop, and the position detection element is protected. Like the Sovereign of Network and the Sovereign and the Sovereign and and if the reading head is clean, if the installation position of the number of readings is reasonable, and the factors which detect the abnormal position of the detection element are excluded.
If you can make sure that the location detection component is good, this is generally a problem with the mechanical transmission chain of the right axis.
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