What Kind of Factors Will Affect CNC Machined Accuracy
In the process of CNC machining parts, many factors will affect the final CNC machined accuracy, including the position error of the part, the geometrical error of the machine tool, and the positioning error of the machine tool, etc. And now, let’s take a look at some of the effects and explore strategies for improving accuracy together.
Below are pointing to affect CNC machined accuracy during the process
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The position error of the parts
The position error of the part is the deviation between the actual surface and the axis location relative to the ideal position, it’s mainly based on the machine tool transmission clearance and elastic deformation of the parts and head position errors caused by the friction of the service.
In the open-loop system, this effect of position error one machining precision is very big, but in the closed-loop servo system, it mainly depends on the accuracy of displacement detection device and system amplification coefficient, so the general effect is not too big.
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The geometrical errors of the machine tool
In the process of CNC machining, the tool and fixture are affected by external force and heat cutting can cause the volumetric accuracy of the machine tool is reduced, thus affecting the deformation of the machining parts.
Of course, the reasons for the geometrical errors of the machine tools are internal and external. The internal reason is the factors of the machine tool itself. Such as the horizontal degree of the workbench surface and the geometric accuracy of the machine tool and the fixture. External causes are the external environment and the heat generated during processing, resulting in the deformation of the machine tool.
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The positioning errors of the machine tool
The positioning accuracy of the machine tool will greatly influence the precision of the parts, therefore, positioning errors is an important reason for CNC machining error, and the feed system of the machine tool is the main link that affects location accuracy. The feeding system of the CNC machine is usually composed of a mechanical transmission system and electric control system, the positioning accuracy is related to the mechanical transmission system of the structure design.
In the open-loop system, due to more influence factors and the situation is more complex, so we will be not able to carry out the positioning monitoring, so the machining accuracy of the CNC machine tool is greatly affected. However, in the closed-loop system, the CNC machine tool can usually avoid the position deviation of the main components in the system by locating the detection device.
How to improve the CNC machined accuracy during production
Control the original error of the CNC machine tool
In the process of CNC machine tool machining, there is an inevitable error between the machining parts and CNC machine tool, this error is called as the original error. So control the original error of the CNC machine tool is one of the effective methods to improve the machining accuracy, want to do this, need according to the reason of the error and error types to formulate the corresponding improvement measures. For example:
- By position control and geometric precision control to reduce the influence of position error and geometric error on parts.
- By air cooling and water cooling to control the thermal deformation in the process of machining.
- By reasonable select the tool and fixture to reduce the position error.
Design the core parts of the machine properly.
The core components that affect the positioning accuracy of machine tools include feeding system, guide rail, and working table, etc. when designing CNC machine tools, the need to choose the core components properly. Such as ball screw is the core components widely used in machine tools. When choosing the ball screw, it should give full consideration to its precision and whether the manufacturer’s technology is mature. Of course, the support of the ball screw is not negligible, it’s closely related to the transmission accuracy of the system. The support of the ball screw is determined by axial load and rotary speed, which has an important influence on the machining accuracy of CNC Lathe. And in the design process, the bearing capacity of the ball screw should be strictly checked.
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