1. How to program the CNC lathe to determine the amount of cutting and feed
When programming, the programmer must determine the cutting amount for each process. When choosing cutting parameters, we must fully consider various factors that affect cutting, choose the correct cutting conditions, and reasonably determine the cutting parameters, which can effectively improve the machining quality and output. Factors affecting cutting conditions are: machine tool, tool, tool and workpiece rigidity; cutting speed, depth of cut, cutting feed rate; workpiece accuracy and surface roughness; tool life expectancy and maximum productivity; cutting fluid type, cooling method; The hardness and heat treatment condition of the workpiece material; the number of workpieces; the life of the machine tool.
Among the above factors, cutting speed, depth of cut, and cutting feed rate are the main factors.
The cutting speed directly affects the cutting efficiency. If the cutting speed is too low, the cutting time will be longer and the tool cannot perform its functions; if the cutting speed is too fast, although the cutting time can be shortened, the tool is prone to high heat generation, which affects the life of the tool. There are many factors that determine the cutting speed, which can be summarized as follows:
(1) Tool material
Different tool materials have different maximum cutting speeds. The high temperature resistant cutting speed of high-speed steel tools is less than 50m/min, the high temperature resistant cutting speed of carbide tools can reach more than 100m/min, and the high temperature resistant cutting speed of ceramic tools can be as high as 1000m/min.
(2) Workpiece material
The hardness of the workpiece material will affect the cutting speed of the tool. The cutting speed should be reduced when the same tool is processing hard materials, and the cutting speed can be increased when processing softer materials.
(3) Tool life
If the tool service time (life) is long, a lower cutting speed should be used. Conversely, a higher cutting speed can be used.
(4) Cutting depth and cutting amount
The cutting depth and the amount of cutting are large, the cutting resistance is also large, and the cutting heat will increase, so the cutting speed should be reduced.
(5) The shape of the tool
The shape of the tool, the size of the angle, and the sharpness of the cutting edge will all affect the selection of the cutting speed.
(6) Coolant use
The machine tool has good rigidity and high precision, which can increase the cutting speed; on the contrary, it is necessary to reduce the cutting speed.
Among the above-mentioned factors that affect the cutting speed, the material of the tool has the most important influence.
The cutting depth is mainly restricted by the rigidity of the machine tool. When the rigidity of the machine tool allows, the cutting depth should be as large as possible. If it is not limited by the machining accuracy, the cutting depth can be made equal to the machining allowance of the part. This can reduce the number of passes.
The spindle speed should be determined according to the allowable cutting speed of the machine tool and tool. It can be selected by calculation method or look-up table method.
The feed amount f (mm/r) or feed speed F (mm/min) should be selected according to the machining accuracy of the part, surface roughness, tool and workpiece material. The maximum feed rate is limited by the rigidity of the machine tool, the feed drive and the numerical control system.
When selecting the cutting amount, the programmer must choose the cutting amount that suits the characteristics of the machine tool and the best durability of the tool according to the requirements of the machine tool manual and the durability of the tool. Of course, you can also use the analogy method to determine the cutting amount based on experience. No matter what method is used to select the cutting amount, it is necessary to ensure that the durability of the tool can complete the processing of a part, or ensure that the durability of the tool is not less than one work shift, and the minimum time cannot be less than half a shift.
Second, the processing of stainless steel
The strength and hardness of stainless steel are similar to that of medium carbon steel, but it has large plasticity and severe work hardening, which increases the cutting resistance and consumes more power. In addition, the poor thermal conductivity of stainless steel makes the temperature of the cutting zone and the tool high, and the tool is easy to wear. In addition, stainless steel has high plasticity and strong adhesion. It is easy to stick to the knife and form a built-up edge, which increases the roughness of the processed surface, and the chips are not easy to curl and break, resulting in difficulty in chip removal. Therefore, the tool material for cutting stainless steel should be a tool material with good thermal hardness, wear resistance, thermal conductivity, and anti-adhesive performance.