Generally, the worm has a large pitch. Due to its profile characteristics, the contact surface between the cutting edge and the workpiece is large, and the cutting tool is easily damaged due to the extrusion of iron chips between the workpiece and the tool. Although the operator can use the tool of the elastic shank and feed it with a small depth of cut, the above problem cannot be fundamentally solved. The same problem is faced when machining a worm on a CNC lathe. The machine tool will never stop automatically due to tool chipping. Therefore, this problem is even more difficult to solve. Manually-operated horizontal lathes, on the other hand, can be flexibly controlled by the operator depending on the cutting conditions, and even half-way through the tool to avoid a worse situation.
First knife
Second knife
The third knife Figure 1
Figure 2 The following method is to use a CNC lathe rigid machining method, and its precise positioning function, the use of "linked into a line" method to synthesize the trapezoidal sideline, which effectively solve this problem. Tools can be used tungsten carbide forming tools. This cutting method is to change one knife to three, which reduces the cutting resistance. The diagram is shown in Figure 1. This method is actually the use of left and right cutting methods. The author changed it to “center, left, and right” cutting, because if you do not first cut a knife from the middle, iron chips will still squeeze the knife, which is obtained from the actual in conclusion. Different from the right-and-left cutting method of non-CNC lathes, the “middle, left, and right” cuttings on CNC lathes require accurate calculations. This calculation takes a little time, but it results in improved processing efficiency and peace of mind at work. Cutting speed can be selected as 70 ~ 90m/min, cutting depth ap = 0.1 ~ 0.15mm (according to the machine performance, determine whether the appropriate depends on the thickness and color of iron). The following describes the coordinate calculation method, see Figure 2. Cot=20°=1:0.364, when the feed rate is 0.1mm in the X direction, the Z direction changes by 0.0364mm from the previous one. This 0.0364mm is in the right and left direction, that is, one knife is eaten from the middle, and then the left and right parts are higher than the previous one. The decrease of the z-direction and increase of 0.0364mm can be listed first as the values shown in the following table to facilitate programming. x 50 49.8 49.6 49.4 49.2 49 W 1.46 1.42 1.39 1.35 1.31 1.28 In the numerical control, the knife is actually the Z coordinate of the starting point when changing the thread. This must be kept in mind. The following will take Figure 2 as an example to give a program and corresponding instructions. The thread instruction is G92, and the end face of the workpiece is Z-Zero and the pitch is 8mm. ... N110 GOO X55 Z10 Quick positioning to starting point of thread N120 G92 X49.8 Z-60 F8 First knife at X49.8 N130 GO1 W-1.42 F1 Changing starting point of thread N140 G92 X49.8 Z-60 F8 Left side N150 G01 Z10 F1 Back to starting point N160 W1.42 Changing starting point of threading N170 G92 X49.8 Z-60 F8 Righting of car N180 G01 Z10 F1 Back to starting point of Z direction N190 G92 X49.6 Z-60 F8 Car X49.6 The first knife... If the "Middle, Left, and Right" is turned many times as shown in the above example, the cutting is easy and the chips are removed smoothly. Achieved the purpose of "linking into a line" and turned the limitation of CNC into a specialty. If coolant is added to the cutting process, the effect will be better. In addition, in the processing of teeth and other parts of the workpiece, you can use a tool that is narrower than the width of the groove to program the above method, but the procedure is much simpler, there is no need for a lot of calculations, the actual effect is also very satisfactory.
