I. Reasonable selection of cutting amount
For high-efficiency metal cutting, the material to be processed, the cutting tool, and the cutting conditions are the three major elements. These determine machining time, tool life and machining quality. An economical and effective machining method must be a reasonable choice of cutting conditions.
The three elements of cutting conditions: cutting speed, feed and depth of cut directly cause tool damage. With the increase of cutting speed, the temperature of the tool tip will rise, which will cause mechanical, chemical and thermal wear. A 20% increase in cutting speed reduces tool life by 1/2.
II. How to determine the three elements of cutting
(1) Cutting speed (linear speed, circle 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.
(2) Feed amount (pass amount)
F mainly depends on the workpiece surface roughness requirements. When finishing, the surface requirements are high, and the cutting amount is small: 0.06~0.12mm/spindle per revolution. When roughing, it is better to be larger. It is mainly determined by the strength of the tool, generally more than 0.3. When the main relief angle of the tool is large, the strength of the tool is poor, and the feed amount cannot be too large. In addition, the power of the machine tool and the rigidity of the workpiece and the tool should be considered. The CNC program uses two units of feed amount: mm/min, mm/spindle per revolution, the above units are mm/spindle per revolution, if mm/min is used, it can be converted by the formula: feed per minute = per revolution Turning feed * Spindle revolutions per minute
(3) Cutting depth (cutting depth)
When finishing, generally less than 0.5 (radius value). During rough machining, it is determined according to the conditions of the workpiece, tool and machine tool. Generally, small lathes (with a maximum machining diameter of less than 400mm) turn 45# steel in a normalized state, and the depth of the cutter in the radial direction generally does not exceed 5mm. In addition, it should be noted that if the spindle speed change of the lathe adopts ordinary frequency conversion speed regulation, then when the spindle speed per minute is very low (below 100~200 rpm), the output power of the motor will be significantly reduced. The depth and infeed can only be achieved very small.
III. Reasonable selection of tools
1. When rough turning, a tool with high strength and good durability should be selected, so as to meet the requirements of large amount of knife and large feed during rough turning.
2. When fine turning, a tool with high precision and good durability should be selected to meet the requirements of machining accuracy.
3. In order to reduce the tool change time and facilitate tool setting, machine-clamped knives and machine-clamped blades should be used as much as possible.
Ⅳ. Reasonable selection of fixtures
1. Try to use general fixtures to clamp the workpiece, and avoid using special fixtures;
2. The positioning datum of the parts is coincident to reduce the positioning error.
Ⅴ. Determine the processing route
The machining route is the movement track and direction of the tool relative to the part during the machining process of the index-controlled machine tool.
1. It should be able to ensure the machining accuracy and surface roughness requirements;
2. The machining route should be shortened as much as possible to reduce the idle travel time of the tool.
Ⅵ. The connection between processing route and machining allowance
At present, under the condition that the numerical control lathe has not yet reached the popular use, the excessive allowance on the blank, especially the allowance containing the forging and cast hard skin layers, should be arranged on the ordinary lathe for processing. If it must be processed with a CNC lathe, it is necessary to pay attention to the flexible arrangement of the program.
Seven, fixture installation points
At present, the connection between the hydraulic chuck and the hydraulic clamping cylinder is realized by a pull rod. The main points of the hydraulic chuck clamping are as follows: first, remove the nut on the hydraulic cylinder with a wrench, remove the pull tube, and pull it out from the rear end of the main shaft, and then The chuck can be removed by removing the chuck fixing screw with a wrench.