Analysis of the top ten sources and effects of machining errors

Manufacturing errors in machine tools

Machine tool manufacturing errorsContaining spindle rotary error, guideway error, transmission chain error and other aspects, spindle rotary error is the spindle axis and the average axis of the actual rotary deviation, related to workpiece processing accuracy, the reasons for the spindle coaxial error, bearing error, bearing coaxial inconsistency, spindle winding, etc., the guideway is a key part of the machine tool, to determine the relative position of the components of the machine tool is the benchmark for machine tool movement. Therefore, the guideway itself manufacturing errors, uneven wear and tear in the use of the process, as well as poor installation quality, will cause the appearance of the guideway error. In addition, the transmission chain error refers to the transmission chain at both ends of the transmission components in the relative movement of the error, which is mainly caused by the transmission chain of each link of the manufacturing and assembly errors, as well as in the use of the process of wear and tear caused by.

Geometrical errors of the tool

During the cutting process, tool wear is inevitable, resulting in changes in the size and shape of the workpiece. This tool geometry error has a significant impact on theMachining errorsThe impact of the tool type will vary. For example, when machining is carried out using a fixed-size tool, the manufacturing error of the tool will have a direct impact on the machining accuracy of the workpiece. However, for general tools (such as turning tools, etc.), the manufacturing error does not have a direct impact on the machining error.

Geometrical errors in fixtures

In machining, fixtures play a crucial role in ensuring that the workpiece is in a precise position with the tool and the machine. However, the fixture itself may have geometric errors, which can have a significant impact on the accuracy of machining, especially on the control of positional accuracy.

positioning error

There are two main types of positioning errors, namely, datum misalignment errors and inaccurate manufacturing of positioning subs. In the machining process, it is absolutely necessary to select specific geometric elements on the workpiece to be used as positioning datums. If these datums do not correspond to the design datums on the part drawing, then datum misalignment errors will occur. At the same time, if the positioning surfaces and the fixture positioning elements together constitute a positioning pair with insufficient manufacturing accuracy or excessive clearance, this will also lead to maximum positional variation of the workpiece, i.e. inaccurate positioning pair manufacturing errors. It is worth noting that such errors generally only appear when machining by the adjustment method, and are not affected by the test-cutting method, which is the case.

Deformation of the process system under stress

In the machining process, the deformation of the process system belongs to an element that can not be ignored, by the workpiece, machine tools, tools and fixtures and other components of the system, under the action of the cutting force, maybe will produce deformation, which in turn affects the machining accuracy. Specifically, if the stiffness of the workpiece is relatively low, then under the action of the cutting force, its deformation will have a more significant impact on the machining error. In addition, the stiffness of the tool is also a key element, especially for the machining surface normal direction of the stiffness. For boring operations, the stiffness of the toolholder has a direct impact on the accuracy of the hole. At the same time, the stiffness of the machine component is a complex factor, which is influenced by the contact deformation of the bonding surfaces, the effect of friction, and the conditions caused by low-stiffness parts, as well as the situation of the gap.

Thermal deformation of process systems

When machining, the process system is deformed by heat, which significantly affects the machining accuracy, especially in the field of precision machining and large parts machining, thermal deformation triggered by the machining error, sometimes up to half of the total error of the workpiece.

adjustment error

In all aspects of machining, it is necessary to make corresponding adjustments to the process system, because these adjustments are often difficult to achieve absolute accuracy, so it will generate the adjustment error, in the process system, the relative position of the workpiece and the tool in the machine tool accuracy, mainly relying on the adjustment of the machine tool, cutting tools, fixtures, or the workpiece and other components to ensure that the machine tool, cutting tools, jigs, as well as the workpiece blanks and other raw accuracy have been When the original accuracy of machine tools, tools, fixtures and workpiece blanks have met the process requirements, and do not take into account the influence of dynamic factors, the adjustment error often becomes the key factor affecting the machining accuracy.

measurement error

In the machining process, the measurement of parts belongs to an indispensable part, however, due to inappropriate measurement methods, precision limitations of the gauge, the workpiece itself has the complexity of the measurement of subjective errors, which may lead to deviations in the measurement results, that is, the measurement error, this error will be adjusted for subsequent processing and product quality has an impact.

internal stress

Internal stress is a kind of stress that exists inside a part without external force. Once internal stresses are generated inside the workpiece, it will cause the workpiece metal to enter an unstable state at a high energy level. In such a state, the workpiece will naturally tend to shift towards a stable state of low energy level, and will also be accompanied by the occurrence of deformation, which will make the workpiece lose the original machining accuracy.