Method Of Machining To Obtain Shape And Position Accuracy

Method of obtaining shape accuracy
(1) Trajectory method
This machining method uses the trajectory of the knife tip to form the shape of the machined surface. Ordinary turning, milling, planing and grinding all belong to the tool point trajectory method. The accuracy of the shape obtained by this method mainly depends on the accuracy of the forming motion.
(2) Forming method
The shape of the machined surface is obtained by using the geometry of the forming tool to replace some forming movements of the machine tool. Such as forming turning, milling, grinding, etc. The shape accuracy obtained by the forming method mainly depends on the shape of the cutting edge.
(3) Generative method
Using the envelope surface formed by the forming motion of the tool and the workpiece to get the shape of the machining surface, such as hobbing, gear shaper, gear grinding, hobbing spline, etc., are the forming method. The shape accuracy obtained by this method mainly depends on the shape accuracy of the blade and the resulting motion accuracy.

Method of obtaining position accuracy
In machining, the position accuracy of the machined surface to other surfaces is mainly determined by the clamping of the workpiece.
(1) Find a formal clip directly
This method is a clamping method to find the position of the workpiece directly on the machine tool by using a dial indicator, a marking disk or a visual inspection.
(2) Line to find a formal clip
This method is to first draw the center line, the symmetry line and the processing line of the surface to be machined on the blank according to the part drawing, and then install the workpiece on the machine tool, and find 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 requirements for the technical level of workers, and is generally used for processing complex and bulky parts in single small batch production, or the blank size tolerance is large and cannot be directly clamped with the fixture.
(3) Clamp with fixture
The fixture is specially designed in accordance with the requirements of the processing process, the positioning element on the fixture can make the workpiece relative to the machine tool and the tool quickly occupy the correct position, do not need to find the right to ensure the workpiece clamping positioning accuracy, with the fixture clamping productivity is high, positioning accuracy is high, but the need to design and manufacture special fixture, widely used in batch and mass production.