With the development of CNC thread milling technology, especially the advent of three-axis machining centers, CNC thread milling technology has gradually been widely recognized by the machining industry.
Furthermore, it is known that threads can be obtained by familiar traditional threading methods, among which tapping is most similar to thread milling. Because they all form threads through relative rotational movement between the tool and the workpiece. So, faced with different working conditions, how to choose the appropriate method? This article tells you exactly what it is.
Conditions for CNC thread milling:
1. Three-axis linkage machining center (or higher)
2. The length of the thread should not exceed 3 times the cutting edge of the tool
Advantages of CNC thread milling
1. Thread milling cutters can process threads of different diameters and the same shape.
For example, using a thread milling cutter to change the interpolation radius to process M15x1.0, M18x1.0, M20x1.0 threads, the number of tools can be reduced, tool changing time can be saved, efficiency can be improved and tool management can be simplified.
2. Improved thread precision and smoothness.
Thread milling is accomplished through high-speed tool rotation and spindle interpolation. The cutting method is milling, the cutting speed is fast, and the threads produced are beautiful; the cutting speed of the tap is low, the chips are long, and the inner hole surface is easily damaged.
3. Internal thread is easy to unload.
Thread milling breaks the chips, the chips are short, and the diameter of the processing tool is smaller than the diameter of the threaded hole, so the chips are cleared smoothly when the tap continuously cuts, the chips are longer and diameter; The tap is as large as the processing hole, so the chips are difficult to remove.
4. If you use a tap, of course you can use an electric spark to break the broken part, but the process will be very complicated and there will be losses if the parts are damaged.
If you use thread milling cutter, first of all, it is not easy to break because the force is small even if it breaks, since the machined hole diameter is larger than the tool diameter, the part broken can be easily removed. In terms of product throughput, thread milling is far superior to tapping.
5. It is not easy to form sticky chips.
For softer materials, it is easy to produce sticky chips during machining, but thread milling will rotate at high speed and break the chips. The cutting speed of the tap is low, the complete thread and the machined surface are affected, and it is easy to cause chip sticking.
6. The power of the machine should be low.
7. Due to chip breakage during thread milling, the cutting tool is partially contacted and the cutting force is small. The tap is in full contact with the thread and the force is large, so the machine requires high power.
8. Broken tools are easy to deal with.
First of all, thread cutters are less stressed and rarely break. If this happens, because the diameter of the machining hole is larger than that of the tool, the broken part is easy to remove; the tap is under stress, the chip removal is not smooth, it is easy to break, and the hole is large. after breakup. It’s a little easier to manage, but it’s very annoying if it’s a small hole, like:
When machining ordinary threads, thread milling is not cost effective when considering cost per part. Ordinary wires are classified as wires with a general hardness less than 50HRC and a diameter less than 38mm, although this is not an obvious dividing line. Ordinary taps are generally made of high-speed steel, and the market price is tens of dollars, but the price of a thread milling cutter is more than 10 times its price, and the life of a single piece cannot exceed 10 times.
Second, the aspect ratio cannot be too large, usually L/D <3. Since thread milling cutters have one-sided force, when the thread is too long, the aspect ratio will produce a taper and the milling cutter will break easily.
Application of CNC thread milling
1. Processing high hardness materials (hardness >50HRC), suitable for thread milling, because the milling chip breakage, local contact with the tool is small, the blade is made of carbide, with low wear and long general life at high speed; steel taps cannot be processed at all. For example, solid carbide taps are not cheap and are similar in price to thread mills. According to our current processing experience, thread milling is significantly more efficient and economical than tapping.
2. Composite hole machining (with chamfer) is also suitable for thread milling. Thread milling cutters have many functions that can be integrated into threads and chamfers.
3. Thin-walled processing is suitable for thread milling. The thread milling cutter has low processing force, so the deformation is small. In addition, the bottom hole may be flat and the thread may be close to the bottom hole, so the required space is very small.
4. For processing high thread precision, thread milling has higher thread speed, good chip removal performance, higher thread precision and higher smoothness, which is more suitable for thread milling.
5. The material is soft and processed from a titanium alloy, suitable for thread milling because thread milling cutters are not prone to producing sticky debris.
For unstable cuts, thread milling cutters are quite capable of adapting to this situation because the cutting principle itself is intermittent milling.
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