Influence Of Machining Allowance On Machining Accuracy

DALIAN, China - July 25, 2022 - PRLog -- Concept Of Machining Allowance

Machining allowance refers to the thickness of the metal layer cut from the machined surface during machining. Machining allowance can be divided into process machining allowance and total machining allowance. Process machining allowance refers to the thickness of the metal layer removed from a surface in one process, which depends on the difference between the dimensions of the adjacent processes before and after the process. Total machining allowance refers to the total thickness of the metal layer removed from a certain surface during the whole machining process of the part from blank to finished product, that is, the difference between the blank size on the same surface and the part size. The total machining allowance is equal to the sum of machining allowance of each process.

Because there are inevitable errors in the blank manufacturing and the dimensions of each process, both the total machining allowance and the process machining allowance are variable values, resulting in the minimum machining allowance and the maximum machining allowance. The variation range of the process machining allowance (the difference between the maximum machining quantity and the minimum machining allowance) is equal to the sum of the dimensional tolerances of the previous process and the current process. The tolerance zone of process dimension is generally specified in the entry direction of parts. For shaft parts, the basic dimension is the maximum process dimension, while for holes, it is the minimum process dimension.

Influence Of Machining Allowance On Machining Accuracy

1. Influence of excessive machining allowance on machining accuracy

Parts must generate cutting heat in the machining process. Some of these cutting heat are taken away by iron filings and cutting fluid, some are transferred to the tool, and some are transferred to the workpiece to raise the temperature of the parts. The temperature is closely related to the machining allowance. If the machining allowance is large, the rough machining time will inevitably become longer, and the cutting amount will also be appropriately increased, resulting in the continuous increase of cutting heat and part temperature. The greatest harm brought about by the temperature rise of parts is the deformation of parts, especially for materials sensitive to temperature change (such as stainless steel). Moreover, this kind of thermal deformation runs through the whole processing process, increasing the processing difficulty and affecting the product quality.

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