The turning thread must be realized by the synchronous running function of the spindle, ie the turning thread requires a spindle pulse generator (encoder). When the spindle speed is selected too high, the positioning pulse sent by the encoder (ie the spindle is issued every revolution) A reference pulse signal) will likely cause a disorder in the workpiece thread due to "overshoot" (especially when the quality of the encoder is unstable).
Therefore, when the thread is threaded, the spindle speed should be determined according to the following principles:
In the case of ensuring production efficiency and normal cutting, it is advisable to select a lower spindle speed;
When the lead length d 1 and the cut length d 2 (as shown) in the threading program block are considered to be sufficient, that is, when the thread feed distance exceeds the length of the specified thread on the pattern, a suitably higher spindle can be selected. Rotating speed;
When the allowable working speed specified by the encoder exceeds the maximum speed of the spindle specified by the machine tool, the spindle speed can be selected as high as possible;
Normally, the spindle speed (n screw ) at the time of threading should be determined according to the calculation formula specified in the manual of the machine or CNC system. The calculation formula is:
n screw ≤ n allowed / L (r / min)
Where: n allows - the maximum operating speed (r / min) allowed by the encoder;
L--pitch of the workpiece thread (or lead, mm).
4 Determine the amount of cutting and feed
When programming, the programmer must determine the amount of cutting for each process. When selecting the cutting amount, we must fully consider the various factors affecting the cutting, correctly select the cutting conditions, and reasonably determine the cutting amount, which can effectively improve the machining quality and output. The factors affecting the cutting conditions are: rigidity of machine tools, tools, tools and workpieces; cutting speed, depth of cut, cutting feed rate; workpiece accuracy and surface roughness; tool life expectancy and maximum productivity; type of cutting fluid, cooling method; The hardness and heat treatment of the workpiece material; the number of workpieces; the life of the machine tool.
Among the above factors, the cutting speed, the cutting depth, and the cutting feed rate are the main factors.
The cutting speed directly affects the cutting efficiency. If the cutting speed is too small, the cutting time will be lengthened, and the tool will not be able to perform its function. If the cutting speed is too fast, the cutting time can be shortened, but the tool is prone to high heat and affects the life of the tool. There are many factors that determine the cutting speed, which are summarized as follows:
Tool material. The maximum cutting speed allowed is different for different tool materials. High-speed steel cutting tools have a high-temperature cutting speed of less than 50m/min, carbide cutting tools with high-temperature cutting speeds of up to 100m/min, and high-temperature cutting speeds of ceramic tools up to 1000m/min.
Workpiece material. The hardness of the workpiece material will affect the cutting speed of the tool. When the same tool is used to process hard materials, the cutting speed should be reduced. When the soft material is processed, the cutting speed can be improved.
Tool life. If the tool life (life) is long, a lower cutting speed should be used. Conversely, a higher cutting speed can be used.
Cutting depth and feed rate. The cutting depth and the amount of cutting are large, the cutting resistance is also large, and the cutting heat is increased, so the cutting speed should be reduced.
The shape of the tool. The shape of the tool, the size of the angle, and the sharpness of the cutting edge all affect the selection of the cutting speed.
Use the coolant. The machine tool has good rigidity and high precision to increase the cutting speed; otherwise, it needs to reduce the cutting speed.
Among the above factors affecting the cutting speed, the influence of the tool material is the most important.
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