1. Principles of working procedure formulation
(1) Principle of giving priority to rough work
When cutting, rough work procedure should be arranged first, and a large amount of allowance before precision work should be removed in a short time. When the uniformity of the allowance left after rough work can't meet the requirements of precision work, semi-precision work can be arranged as a transitional procedure, so as to make the allowance of precision work small and uniform, and the final outline of its parts should be continuously completed by precision work procedure.
(2) principle of distance priority
The distance mentioned here is based on the size of the workpiece position relative to the tool alignment point. In rough working hours, the position close to the tool alignment point is usually arranged, so as to shorten the tool moving distance and reduce the idle travel time.
(3) Internal priority principle
For parts with internal and external cutting at the same time, it is usually necessary to arrange to finish the internal mold and cavity before finishing the external surface. This is because it is difficult to control the size and shape of the inner surface, the tool rigidity is relatively poor, the durability of the tool tip is easily affected by cutting heat, and it is difficult to remove chips.
(4) The principle of shortest route
is mainly used to determine the tool path of rough work and idle travel, because the tool path in the precision cutting process is basically along the outline of its parts. On the premise of ensuring quality, having the shortest cutting route can save the execution time of the whole process.
(5) principle of face before hole
For parts such as box, bracket and connecting rod, the plane should be finished first and then the hole should be cut, which can ensure the position accuracy of the plane and the hole, and bring convenience to the hole on the plane.
II. Precautions for working procedure arrangement
(1) Rough machining and fine machining are carried out separately
The cutting amount of rough working hours is large, the cutting force and clamping force on the workpiece are large, the heat generation is high, and the surface is obviously hardened, so there is a large internal stress in the workpiece. If rough and fine machining are carried out at the same time, the precision problem will soon appear because of the redistribution of stress.
(2) Reasonable selection of equipment
Rough machining does not require high precision, so rough machining should be carried out on a machine tool with high power and low precision. Seiko process requires the use of higher precision machine tools. The separation of rough machining and fine machining can not only give full play to the equipment capacity, but also prolong the service life of precision machine tools.
(3) Arrange heat treatment procedures
In order to improve the machinability of metals, annealing, normalizing, quenching and tempering are needed before cutting. In order to eliminate internal stress, it is necessary to carry out aging treatment, quenching and tempering treatment between rough and fine working procedures. In order to improve the mechanical properties of parts, carburizing, quenching and tempering are needed after cutting.
Third, the selection method of high-speed cutting oil
(1) Cooling performance of cutting oil
Because the workpiece is tough and the cutting is not easy to be separated, the cutting oil is required to have high cooling performance to take away a lot of heat.
(2) Lubrication performance of cutting oil
Because of its high viscosity and melting property, it is easy to produce chip lumps during thread cutting, so cutting oil should have high lubrication performance.
(3) Permeability of cutting oil
It is required that the cutting oil has good permeability, which can penetrate into the fine gap lines in the metal area during cutting, so that the chips are easily broken.
(4) Extreme pressure performance of cutting oil
Cutting oil should contain sulfurized extreme pressure and anti-wear additives, which can effectively protect tools and improve process accuracy.
(5) Stability of cutting oil
Compared with rapeseed oil, mechanical oil and recycled oil, special cutting oil has good stability and will not cause harm to equipment, human body and environment.
(6) Other properties of cutting oil
Cutting oil has passed rigorous tests in terms of viscosity, flash point, pour point and thermal conductivity, so as to meet the requirements of various cutting processes.