Thread Special-shaped Axle CNC Turning Technology Design and Programming Example
In the current development of highly automated production technology, CNC machine tools have become the mainstay of modern machining technology. Among them, CNC lathes are one of the most widely used CNC equipment, and can process cylindrical, conical and circular objects. In the machining of complex-shaped parts such as special-shaped screw shafts, the demand for CNC lathes is even greater.
In general, CNC machining of special-shaped screw shafts requires the design of the optimum machining route. This includes considering the cutting depth of each tool, machining parameter selection, the centerline of the special-shaped screw shaft and how to machining the round parts, etc. The cutting process of the special-shaped screw shaft is complex and the cutting amount is large, so the cutting time is long, which needs to be considered.
In this paper, a special-shaped screw shaft CNC turning process design and programming example is given. The special-shaped screw shaft is shown in Figure 1, which is made of 45# steel and its size is Φ 11mm+2-5mm, Φ 10mm+2-5mm, length 27.3mm.
Fig 1 The drawing of the special-shaped screw shaft
To begin with, according to the machining process and requirements of the special-shaped screw shaft, the cutting tools and cutting parameters should be selected. The special-shaped screw shaft machining process includes turning, drilling, chamfering, and threading. Therefore, the selection of cutting tool should meet the requirements of processing accuracy, surface roughness and cutting speed, etc. We select CCGT 060204 as the machining tool. The cutting parameters are shown in Table 1.
Table 1 Cutting parameters
Process Cutting parameters
Spindle speed 420r/min
Turning Feed rate 1.0mm/r
Depth of cut 2.5mm
Drilling FeedRate 0.7mm/r
Depth of Cut 8.5mm
Chamfering FeedRate 0.5mm/r
Threading FeedRate 0.5mm/r
After the tool selection and cutting parameters are determined, we could start to programming the process. The programming should include not only the above mentioned processes, but also the design of process route and the centerline. Firstly, we need to rough the blank to its designed size, for this a turning process is used, as shown in Fig 2 (a). Then, drilling the blank to produce a pocket and the process is shown in Fig 2 (b). After that, the chamfering and threading processes are used to finish the part, as shown in Fig 2 (c).
Fig 2 The special-shaped screw shaft CNC turning program
To optimize CNC turning process, we need to consider the cutting route. Generally, the cutting route is determined by the machining accuracy, surface roughness, cutting speed, tool life and the number of tool changes. For this special-shaped screw shaft, we need to machine complex curved surface, so we need to program the process with a centerline machining method, as shown in Fig 3.
Fig 3 The special-shaped screw shaft CNC turning process route with centerline
Finally, work holding and clamping should be considered in the program. To machining this special-shaped screw shaft, we will use a universal chuck jaw for clamping and a four-jaw independent scroll chuck for work holding. The drawing and photos of this clamping is shown in Fig 4.
Fig 4 The universal chuck jaw and four-jaw independent scroll chuck
In summary, this paper provides a special-shaped screw shaft CNC turning technology design and programming example. We firstly select the cutting tools and cutting parameters for CNC machining. Then the program is designed according to the machining process, considering the cutting route and the centerline. Finally, the clamping method is selected. Through this example, it can be seen that the kind of machining process scheme and programming method of the special-shaped screw shaft is different from that of the general cylindrical or conical shafts. It is generally required to choose special cutting tools and parameters to make full use of the machining performance of CNC lathes, and optimize the programming order and route to realize efficient machining.
