CNC lathe is a high-precision, high-efficiency automatic machine tool. The use of CNC lathe can improve processing efficiency and create more value. The emergence of CNC lathe enables enterprises to get rid of the backward processing technology. The processing technology of CNC lathe is similar, but since the CNC lathe is a one-time clamping and continuous automatic processing completes all the turning processes, the following aspects should be paid attention to.
Reasonable choice of cutting amount
For high-efficiency metal cutting, the material to be processed, cutting tools, and cutting conditions are three major elements. These determine machining time, tool life and machining quality. An economical and effective processing method must be a reasonable choice of cutting conditions.
The three elements of cutting conditions: cutting speed, feed rate and depth of cut directly cause damage to the tool. With the increase of cutting speed, the temperature of the tool tip will rise, which will cause mechanical, chemical and thermal wear. Cutting speed increased by 20%, tool life will be reduced by 1/2.
The relationship between feed conditions and tool back wear occurs within a very small range. However, the feed rate is large, the cutting temperature rises, and the wear behind is large. It has less effect on the tool than cutting speed. Although the effect of depth of cut on the tool is not as large as the cutting speed and feed rate, when cutting with a small depth of cut, the material to be cut will produce a hardened layer, which will also affect the life of the tool.
The user should choose the cutting speed to use according to the material to be processed, hardness, cutting state, material type, feed rate, cutting depth, etc.
The selection of the most suitable processing conditions is selected on the basis of these factors. Regular, steady wear to the end of life is the ideal condition.
However, in actual operation, the choice of tool life is related to tool wear, size change, surface quality, cutting noise, processing heat, etc. When determining the processing conditions, it is necessary to conduct research according to the actual situation. For difficult-to-machine materials such as stainless steel and heat-resistant alloys, coolant can be used or a rigid cutting edge can be used.
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How to determine the three elements of cutting processing
How to correctly select these three elements is a main content of the metal cutting principle course. Metal processing WeChat has extracted some key points, and the basic principles of selecting these three elements:
(1) Cutting speed (linear speed, peripheral speed) V (m/min)
To choose the spindle revolutions per minute, you must first know how much the cutting line speed V should be. The choice of V: depends on the tool material, workpiece material, processing conditions, etc.
Tool material:
Carbide, V can be obtained higher, generally more than 100 m/min, generally provide technical parameters when purchasing blades:
How much line speed can be selected when processing any material. High-speed steel: V can only be lower, generally no more than 70 m/min, and in most cases it is less than 20-30 m/min.
Workpiece material:
High hardness, low V; cast iron, low V, 70~80 m/min when the tool material is cemented carbide; low carbon steel, V above 100 m/min, non-ferrous metal, V higher (100 ~200 m/min). For hardened steel and stainless steel, V should be lower.
Processing conditions:
For rough machining, V should be lower; for fine machining, V should be higher. The rigidity system of the machine tool, workpiece, and tool is poor, and V should be low. If the S used in the NC program is the number of spindle revolutions per minute, then S should be calculated according to the diameter of the workpiece and the cutting line speed V: S (spindle revolutions per minute) = V (cutting line speed) * 1000 / (3.1416 * workpiece Diameter) If the NC program uses a constant linear velocity, then S can directly use the cutting linear velocity V (m/min)
(2) Feed amount (cutting amount)
F mainly depends on the workpiece surface roughness requirements. In finishing machining, the surface requirement is high, and the cutting amount should be small: 0.06~0.12mm/spindle per revolution. When roughing, it is advisable to be larger. It mainly depends on the strength of the tool. Generally, it is more than 0.3. When the main relief angle of the tool is large, the tool strength is poor, and the cutting amount should not be too large. In addition, the power of the machine tool and the rigidity of the workpiece and the tool should also be considered. The NC program uses two units of feed rate: mm/min, mm/spindle per revolution, the unit used above is mm/spindle per revolution, if mm/min is used, the formula can be converted: feed per minute = per Revolving feed amount*spindle revolutions per minute
(3) Cutting depth (cutting depth)
In finishing machining, it is generally less than 0.5 (radius value). During rough machining, it depends on the conditions of the workpiece, cutting tool and machine tool. Generally, small lathes (maximum machining diameter below 400mm) turn the No. 45 steel in the normalized state, and the depth of the cutting knife in the radial direction generally does not exceed 5mm. In addition, it should also be noted that if the spindle speed of the lathe adopts ordinary frequency conversion speed regulation, then when the spindle speed per minute is very low (less than 100~200 rpm), the output power of the motor will be significantly reduced. The depth and the amount of feed can only be obtained very small.
Reasonable choice of knives
1. When rough turning, it is necessary to choose a tool with high strength and good durability, so as to meet the requirements of large cutting capacity and large feed during rough turning.
2. When finishing the car, it is necessary to choose a tool with high precision and good durability to ensure the requirements of machining accuracy.
3. In order to reduce the tool change time and facilitate tool setting, machine clamping tools and machine clamping blades should be used as much as possible.
Reasonable selection of fixtures
1. Try to use general-purpose fixtures to clamp workpieces, and avoid using special fixtures;
2. Part positioning datum coincides to reduce positioning error.
Determine the processing route
The processing route refers to the movement trajectory and direction of the tool relative to the part during the machining process of the CNC machine tool.
1. It should be able to ensure the machining accuracy and surface roughness requirements;
2. The processing route should be shortened as much as possible to reduce the idle travel time of the tool.
The relationship between processing route and processing allowance
At present, under the condition that the CNC lathe has not yet been widely used, generally the excessive allowance on the blank, especially the allowance containing forged and cast hard skin layers, should be processed on the ordinary lathe. If it must be processed with a CNC lathe, attention should be paid to the flexible arrangement of the program.
Fixture installation points
At present, the connection between the hydraulic chuck and the hydraulic clamping cylinder is realized by the pull rod. The main points of hydraulic chuck clamping are as follows: first, use a wrench to remove the nut on the hydraulic cylinder, remove the pull tube, and pull it out from the rear end of the main shaft, and then Use a wrench to remove the chuck fixing screws to remove the chuck.
Post time: Aug-09-2023
