In this industry, the treatment of treatment is the mantra suspended in the mouth. So what is the precision of treatment of the machine tool to protect? This video is very clear on the precision control of the tooltip, take a look.
The precision of treatment of the CNC machine must be guaranteed by the accuracy of the machine tool itself.The accuracy of the CNC machine includes geometric accuracy, positioning precision, repeated positioning precision and cutting precision。
Geometric accuracy:
Also known as static precision, it is a complete reflection of complete geometric shape errors which are assembled after having assembled the key components of CNC machines.
Positioning precision:
This is the accuracy that the measured parts can be carried out under the control of the NC device. Depending on the measured positioning precision value, you can determine the best part processing accuracy that can be carried out during the automatic machine processing process. It refers aside between the real location and the standard location (theoretical location, ideal location) of parts or tools. This is a prerequisite for the precision of part processing.
Repeat the accuracy of the positioning:
It refers to the consistency of the position accuracy obtained by performing the same program code several times on the CNC machine. This is the consistency of the continuous results obtained by treating a batch of parts under the same conditions (the same operating method, the operating method is different and the same part program).
Cutting precision:
It is a complete inspection of geometric accuracy and the positioning precision of the tool-tool in cutting conditions.
It can be seen from the above aspects of the precision of CNC machines divided into two aspects: mechanical and electrical aspects. Precision of the luminaire during treatment, rigidity of the machine tool, etc. In terms of electricity, there are mainly control methods such as the semi-closed loop, the complete loop, etc., as well as the feedback and compensation methods, the interpolation accuracy during treatment. Consequently, the precision of the machine tool does not depend on the question of whether the machine-tool is a complete closed loop.
1. Principle Introduction
The sports channels of the CNC machine include the CNC device → Coder Servo → Servo Drive → Engine → Screw → Mobile components. .
1. Control entirely closed in the Servo system
Install the location detection detection device (such as the network rule, the right induction synchronizer, etc.) on the movement component of the tool machine (such as the workbench) and automatically give comments on the mobile position . Performs compensation for exercise errors thanks to system instructions. However, because it puts major inertia links such as the screw, the thread and the singage of the tool-tool in the closed loop. In addition, the price of measurement devices such as the network rule and the linear sensor is high and complicated, and the installation can cause an oscillation.
2. Semi-closed control in the servo system
Install the location detection device at the end of the drive engine or the end of the screw to detect the rotation angle of the screw or servomotor, indirectly measure the real location of the movement component of the Machine-tool and return the control system after feedback. Due to improving the level of mechanical manufacturing and the improvement of speed detection elements and the accuracy of the distance snail distance, the semi-ferm cycle control machine can obtain precision of High considerable food. Most machine tool manufacturers have widely used the semi-closed rings control system.
2. Real application
1. Complete closed loop control system
The location detection device (such as the network rule, the linear sensor synchronizer, etc.) has different precision levels (± 0.01 mm, ± 0.005 mm, ± 0.003 mm, ± 0.02 mm) , there will therefore be total control errors, and positioning accuracy is a high and low precision precision.
Location detection device (thermal deformation). High machine tools use various methods, such as large-stroke cooling in the screw, lubrication of rails and constant temperature cooling of the cutting fluid to reduce thermal deformation during the treatment of machine tools.
The installation of the location detection detection system is also very important. Due to the limitation of the structural space, there are only two types of installation in the network rule, one is installed on the underlap side of the nearly shouted, and the other is installed in The outside of the guide rail. It is recommended to choose the first installation method as much as possible, but it is not practical for maintenance and maintenance. Conversely, a high provision network rule is selected and the accuracy of the CNC machine is not really reached. Even in the first case, the installation position of the network rule is relatively close to the driving axis, but after all, the installation location is from a certain distance from the axis of driving . The driver is motivated. When the driving animal swings towards the raster rule, the network rule is wrongly that the movement speed is insufficient during detection, and the system gives the acceleration signal and the reader’s object immediately swings towards the other side. A deceleration signal. The loop is not as good as the semi-closed loop.
Production and environmental impact: generally, the environment of the mechanical processing plant is relatively severe, dust and vibrations are common phenomena, but the network rule and direct induction synchronizers are meta -metal components . The reflection of light. In addition, when the tooltip is treated, the cutting of cutting oil and the water mist are serious, and it has a large impact on the network rule and the induction synchronizer in a straight line. Therefore, we must use a complete control system. Otherwise, this phenomenon will occur.
2.
Since the measurement device is installed at the top of the engine or at the top of the screw, it is easier to seal, so there is no requirement for the environment. The precision error of the semi-fermed control system depends mainly on the front and reverse shortcomings of the screw. With the improvement of mechanical processing technology, the current manufacturing technology of imported screws is high and the lateral coordination of high precision screws has essentially eliminated the front and reverse gaps. In addition, in the assembly session, the screws are used to use the double -column opposite roller screws, which can completely eliminate the front and reverse gaps. In addition, many machine-tool factories, when assembling the machine tool, use a pre-extent method to eliminate the effects of the thermal deformation of the machine tool on the precision of the transmission of screws . Consequently, the semi-fermized control system has been able to ensure that machine tools reach high precision.
3. Conclusion
In summary, we can see that in theory, if the external factors are not taken into account, complete control can improve the basic positioning accuracy that semi-fermized control. However, if factors such as fever, environmental pollution, temperature rise, vibrations and the installation of machine tools cannot be well resolved, the phenomenon of the complete loop is not Not as good as the semi-closed loop. It can be effective in a short period of time, but the effect of changes in dust and temperature on the network rule will be seriously affected, which will seriously affect measurement feedback data, which will lose its effect. At the same time, after a problem with the raster rule, the alarm will occur, which will cause the tool-tool to work.
Due to the cost of production and competitiveness, low-end machine tools have been simplified in fully closed control facilities, such as waterproofing control and temperature control. In this condition, the significant cost of expenses, the simple configuration network rule does not improve the precision of the machine tool.
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