What are the cutting errors in machining of mechanical parts?
The machining accuracy depends on the machining error. For enterprises that process mechanical parts, to ensure product quality, the first job is to control the processing errors. What are the most common machining errors in practice? Next, we will discuss this issue in detail.
Errors about machining of mechanical parts
Mainly including spindle rotation error, guide rail error, transmission chain error, etc. The rotation error refers to the variation between the actual rotation axis and the average rotation axis of the rotation axis at each moment, which directly affects the machining accuracy of the workpiece to be machined. The main reasons for the error of the rotating shaft are: the coaxiality error of the rotating shaft, the error of the bearing itself, the coaxiality error between the bearings, the rotation of the rotating shaft, etc. For the machine tool, the guide rail is the reference for determining the relative positional relationship of the various parts of the machine tool and the movement of the machine tool. Machining errors, uneven wear of guide rails, and installation quality are important factors that affect the accuracy of guide rails. Drive chain error refers to the error of the relative motion of each drive element at both ends of the drive chain. The reason for this is the manufacturing, assembly errors and wear of the various components of the drive chain during use.
About the geometric error of the tool
Any kind of tool will inevitably wear during the cutting process, which will cause the workpiece size , the shape change. The influence of cutting geometric error on machining error varies with the type of tool: when using a fixed-size tool for cutting, the cutting error will directly affect the machining accuracy of the workpiece, while for ordinary tools (such as turning tools, etc.), the cutting error does not It will directly affect the machining accuracy.
Errors about the geometry of the tooling
The function of clamping is to make the workpiece have the correct position equivalent to the tool and the machine tool, so the clamping The geometric error has a great influence on the machining error, especially the position error.
Error about position
It includes reference misalignment error, machining error of positioning pair, etc. When machining a workpiece on a machine tool, some geometric elements on the workpiece must be selected as the machining positioning datum. If the selected positioning datum is the same as the design datum (in the part drawing, the machining of mechanical parts is based on the datum that determines the surface size and position) Inconsistent, there will be a benchmark inconsistency error. In the case of the maximum position change of the workpiece caused by the poor machining accuracy and the matching gap between the positioning pairs, that is, the error caused by the poor machining accuracy of the positioning pair, the positioning error of the positioning pair is formed. The machining accuracy error of the positioning pair processed by the adjustment method only occurs in the trial cutting process.
Error caused by force and deformation of the process system
1. Part rigidity:
In the machine tool, tool and When the rigidity of the fixture is low, because the rigidity of the workpiece is not good enough, the deformation under the action of the cutting force has a great influence on the machining error.
2. Tool hardness:
The rigidity of the cutting surface (y) to the outer circle turning tool is relatively large, and its deformation can be ignored. The diameter of the hole is small, the rigidity of the tool bar is poor, and the force deformation of the tool bar has a great influence on the machining accuracy of the hole.
3. Hardness of parts:
The parts are composed of various parts. There is no simple method to calculate the rigidity in the machining of precision mechanical parts. At present, the test method is mainly used to determine it. stiffness of the machine. The influence of contact deformation, friction, low stiffness parts, clearance, etc. on the stiffness of the joint surface.
