Before the emergence of CNC machine tools, thread processing mainly relied on ordinary machine tools, but the use of ordinary machine tools to process threads has low efficiency and low precision, and the processing quality cannot meet the requirements of customers. Using CNC milling to process threads not only improves the processing efficiency, processing accuracy and processing quality, but also can precisely control the thread size and increase the service life of the thread.
1.1 Thread milling method
There are many ways to process threads. CNC machining centers can process threads by direct milling. This method of machining threads is relatively simple, and can process more complex threads. Therefore, this threading method is widely used, and its processing advantages are also very obvious. Milling thread processing has the characteristics of high precision and high efficiency. The thread milling method can machine left-hand and right-hand threads with the same tool, which is convenient and efficient.
1.2 Tapping process
In addition to the milling method, the tap processing method is also a commonly used method. This machining method is generally used for threading with smaller diameters because of the smaller amount of machining work. This kind of tap is widely used in thread processing, but in order to ensure the accuracy of this processing method, it is necessary to match the drill diameter according to the drilling hole. In order to reduce the workload of thread processing in the later stage, the size of the bottom hole of the thread should be ensured, which can not only ensure the size of the thread processing, but also reduce the wear of the tap to a certain extent.
In the threading process, CNC milling is the most important and most commonly used threading method. In order to improve the machining accuracy and quality of the thread, it is necessary to master the workflow of the tool during thread milling, ensure the reliability and practicability of the programming scheme, and pay attention to the order of use of the tool to avoid unnecessary precision errors and deviations in thread machining. The most important part of thread processing is the processing of the first thread. In the process of processing the first thread, it is necessary to control the helix to ensure that the processed thread and pitch meet the requirements of processing accuracy. After the first thread is processed, it should be measured in time. If there is a machining error, it should be adjusted immediately. In this process, the method of reverse tool retraction and steel ruler inspection is usually used to detect the thread and pitch. The amount of back cutting is also a key content in threading. Machining personnel can obtain real-time data by accurately measuring the pitch and make adjustments to meet the requirements of machining accuracy.
Compared with other machining methods, the thread milling method is less stressed, so there is less wire breakage. Even if the tool is damaged due to mishandling, it is easy to solve and deal with. In the process of tap processing, due to continuous processing and large force, the chips are difficult to discharge, resulting in serious tap wear.
3. Application of thread milling
(1) For threads with low hardness, large production batches, and small thread diameters, tap processing is usually used for processing. The main reason is that this processing method can save processing costs and reduce enterprise expenses. For threads with larger lengths, the tap method is usually used, because longer threads are difficult to machine when milling, while the milling method is suitable for threads with larger diameters and shorter lengths.
(2) When using the tap method to process threads, due to the force everywhere, the entire thread will be in contact with the tap. Therefore, high-power equipment is usually required when using a tap to process threads, while the force during thread milling is small. Therefore, the use of ordinary machine tools is Processing can be completed.
(3) For thin-walled parts, larger-sized parts or threaded parts with complex holes, thread milling is generally used, because the force and deformation are small, and it can be as close to the bottom of the thread as possible. The bottom of the tapered thread is generally not milled because this processing method is not convenient for milling the bottom of the thread.
(4) Threaded parts of general materials can be processed by taps or milling, but threaded parts of special materials are usually processed by milling. There is less contact between the tool and the thread, and it is not easy to damage the thread. The thread milling cutter will not contact the chips of the workpiece and cause sticking phenomenon, which can ensure the thread accuracy during processing.