Netherlands launches new dry ink
In the process of low-speed turning triangular threads, the cutting tool is typically made of high-speed steel. When roughing and finishing are performed separately, it is possible to achieve better surface finish and dimensional accuracy. The rake angle for roughing tools is usually set between 5°8.5 to 5°9, while the finishing tool has a smaller rake angle, typically 1 to 1.5° less. During rough turning, the tool cuts to the full depth (i.e., the outer diameter of the thread), and then the finishing tool performs light cuts on the side of the thread. This approach helps protect the cutting edge and saves time. When grinding roughing tools, sharp corners should not be deliberately sharpened; instead, increasing the rake angle appropriately ensures smooth chip removal and reduces the profile angle. However, increasing the rake angle also reduces the wedge angle, which can weaken the tool. Therefore, the relief angle should be adjusted accordingly to compensate for the reduced strength.
Triangular threads can be machined using two main feeding methods: straight-in and oblique. The straight-in method involves cutting with both edges of the tool simultaneously, resulting in greater force, poor heat dissipation, faster wear, and difficulty in chip removal. Each feed depth must be limited. However, this method produces more accurate thread profiles. Due to the engagement of the cutting edge, there is a risk of "chipping" or damaging the tooth surface, potentially breaking the cutting edge due to excessive force, which may lead to tool damage or vibration. Thus, this method is suitable only for finishing threads with a pitch P < 2mm and high-precision requirements.
Modern CNC lathes are equipped with thread-cutting functions. Most have single-thread cutting capabilities, while high-end models support composite cycle cutting. When cutting threads, multiple passes are required based on factors like thread pitch, profile depth, tool material, workpiece material, and lathe feed rate. The cutting depth for each pass follows a diminishing pattern. For example, when machining an M50×4 standard cylindrical thread, the calculated programming diameter is 49.72mm, and the programmed thread diameter is 46.52mm. The feed depth is 3mm, and the retraction depth is 2mm. The single-pass threading command G32 is used. A sample program would look like:
O1111;
N10 G00 X49.72;
N11 G32 Z-32.0 F4;
N12 G00 X50.0;
N13 Z3.0;
N14 X48.72 Z-32.0;
N15 G32 Z-32.0 F4;
...
N50 M30;
Since G32 only serves as a threading instruction, the tool must be manually moved in and out, making the program lengthy. Using advanced commands like G92 or G76 can shorten the code significantly. For instance, for an external thread M30×2-6g, the outer diameter is 30-0.038-0.318mm, and the programmed diameter is 29.7mm. The root radius R is set to 0.2mm, and the root diameter is calculated as 27.2446mm, with a programmed value of 27.3mm. Six passes are planned, with each step reducing the depth by 0.8mm, 0.5mm, 0.4mm, 0.4mm, 0.2mm, and 0.1mm. The Z-axis origin is set on the right side of the workpiece, and the G92 command is used for single-cycle threading.
For high-speed cutting of triangular threads on CNC lathes, the cutting speed is typically set between 40 to 100 m/min. If only straight-forward feeding is possible, chips should be directed into the ball or evenly discharged from the front, avoiding long, curled chips that could be unsafe. Oblique feeding is not recommended, as it may compromise the workpiece surface quality and damage the tool. Hard alloy tools, such as YT15 carbide, are ideal for high-speed operations due to their hardness and impact resistance. For large pitches (P > 2mm) or hard materials, the cutting edges should be ground with a width of 0.2–0.4mm and a -5° negative chamfer. High-speed cutting causes increased material compression, which can enlarge the thread profile angle. Therefore, the tool tip angle should be 0.5° smaller than the thread profile angle to maintain accuracy.
Nylon Hose Assembly,Corrugated Fuel Hose,Corrugated Fuel Pump Hose,Drain And Oil Feed Pipe
Wenzhou Hengyi Auto Parts Co.,Ltd , https://www.autoparts-hy.com