Common Methods To Obtain Workpiece Accuracy In Machining (2)

Method of obtaining shape accuracy

(1) Trajectory method

This machining method uses the trajectory of the tool tip movement to form the shape of the machined surface. Ordinary turning, milling, planing and grinding all belong to the tool tip trajectory method. The shape accuracy obtained by this method mainly depends on the accuracy of the forming movement.

(2) Forming method

The geometry of the forming tool is used to replace certain forming movements of the machine tool to obtain the shape of the machined surface. Such as forming turning, milling, grinding, etc. The shape accuracy obtained by the forming method mainly depends on the shape of the blade.

(3) Generative method

Use the envelope surface formed by the tool and the workpiece to generate the shape of the machined surface, such as gear hobbing, gear shaping, gear grinding, knurled key, etc., all belong to the generative method. The shape accuracy obtained by this method mainly depends on the shape accuracy and generative motion accuracy of the blade.

Method of obtaining position accuracy

In machining, the accuracy of the position of the machined surface on other surfaces is mainly determined by the clamping of the workpiece.

(1) Directly find the correct clamping

This method is to use a dial indicator, marking plate or visual inspection to directly locate the workpiece on the machine tool.

(2) Mark the line to find the correct installation

This method is to first draw the center line, symmetry line and the processing line of each surface to be processed on the blank according to the part drawing, then install the workpiece on the machine tool, and align the clamping position of the workpiece on the machine tool according to the drawn line.

This clamping method has low productivity, low accuracy, and high technical requirements for workers. It is generally used for processing complex and bulky parts in small batch production, or where the blank size tolerance is large and cannot be directly clamped by fixtures.

(3) Clamping with clamps

The fixture is specially designed in accordance with the requirements of the processed process. The positioning elements on the fixture can quickly occupy the correct position of the workpiece relative to the machine tool and the tool. The positioning accuracy of the workpiece can be ensured without alignment, and the clamping productivity with the fixture is high. The positioning accuracy is high, but it is necessary to design and manufacture special fixtures, which are widely used in batch and mass production.

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