What is the impact of the accuracy of tooling fixtures on machining quality?
Shenjia Hydraulic
Published time:
2025-06-24
The precision of tooling fixtures is one of the key factors affecting the quality of machining. Its precision level directly relates to multiple aspects of the workpiece, including dimensional accuracy, shape accuracy, positional accuracy, and surface quality.
The accuracy of tooling fixtures is one of the key factors affecting the quality of machining. Its accuracy level directly relates to multiple aspects of the workpiece, including dimensional accuracy, shape accuracy, positional accuracy, and surface quality.
Impact on Dimensional Accuracy
Dimensional accuracy refers to the degree of conformity between the actual dimensions of a workpiece and its design dimensions (such as diameter, length, and thickness).
If the accuracy of the fixture's locating elements is insufficient (e.g., excessive diameter tolerance of locating pins, exceeding planarity error of locating planes), it will cause the workpiece's reference position to deviate from the ideal state during clamping, resulting in dimensional deviations after machining. For example, insufficient accuracy of the hole diameter or position of the bushing in a drilling jig will cause the drilled hole diameter to be too large/small, or the depth of the hole to deviate from the design value.
If the fixture's clamping device has accuracy problems (e.g., uneven clamping force, low guiding accuracy of the clamping mechanism), it may cause slight displacement of the workpiece during processing, leading to final dimensional errors. For example, poor concentricity of a three-jaw chuck on a lathe will cause the cylindrical workpiece to exhibit "taper" or inconsistent diameter after processing.
Impact on Positional Accuracy
Positional accuracy refers to the accuracy of the relative positional relationship between various elements (such as holes, surfaces, and axes) on a workpiece (such as parallelism, perpendicularity, concentricity, and position).
The positional accuracy between the locating elements of the fixture directly determines the positional accuracy of the workpiece elements. For example, the concentricity error between two bushings in a boring jig will cause the concentricity of the processed holes to exceed the tolerance; the perpendicularity error between the locating pin and locating hole in a combination fixture will cause the perpendicularity between two planes on the workpiece to not meet the requirements.
The connection accuracy between the fixture and the machine tool (such as the parallelism between the fixture locating base and the machine table, and the concentricity between the fixture mounting holes and the machine spindle) will also affect the positional accuracy. If the alignment accuracy of the fixture during installation on the machine tool is insufficient, it will cause the overall machining datum of the workpiece to shift, resulting in errors in the positional relationship of all related elements.
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