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Matters needing attention during precision machining

1.Notes on CNC machining
(1) When the workpiece is too high, it should be layered with different lengths of knife to open the thick, after using the large knife to open the thick, the remaining material should be removed with a knife.
(2) Apply a flat-bottom knives to machine the plane, use less ball knives to reduce machining time; if there is a slope, and it is an integer, apply a slanting knife.
(3) Reasonably set the tolerance, so that the machining accuracy and the computer calculation time are balanced with each other, and more processes are performed to reduce the emptying time.
(4) The hardness of the blank material is high, and the back milling is selected; the hardness of the blank material is low, and the down milling is selected. Roughing up-cutting, finishing and down-cutting.
(5) The tool material has good toughness and low hardness, and is suitable for rough machining. The tool material has poor toughness and high hardness and is suitable for finishing.

2. CNC machining process
(1) part clamping method and fixture selection
The clamping method of the machined parts on the machining of CNC machine tools should also choose the positioning reference and clamping scheme reasonably. When making the fine reference selection, the two principles of “baseline uniformity” and “reference coincidence” should generally be followed. Principles, we have to consider:
a. Try to finish all the surfaces in one positioning and clamping. Therefore, choose the positioning method that can be processed on each surface.
b. When the workpiece is clamped once, it should be able to finish processing all the surfaces of the workpiece.
c. When determining the placement position of the workpiece on the workbench, consideration should be given to the ability to take into account the machining of each station, the length of the tool and the stiffness of the tool on the machining quality.
d. Fixtures used in controlled machining should be selected as much as possible, and adjustable clamps can be used to shorten the production preparation cycle.

(2) Arrangement of processing sequence
When arranging the processing sequence, the basic principles must be observed, including “first face back hole”, “first rough and then fine”, etc. In addition to these basic principles, we should also follow the following principles:
a. According to the tool centralized process, avoid the same tool repeated multiple times, reducing the number of times and time.
b. The hole system with high coaxiality requirement should be processed after the positioning of the hole system after one positioning, and then the hole system at other coordinate positions can be processed, which can eliminate the error caused by repeated positioning and improve The coaxiality of the hole system.
c. Choose to determine the good tool point and tool change point. Once it is determined, it should not be replaced.