CNC Machining Parts: Structural Characteristics and Difficulties of 4 Axis Machining Parts for Special-Shaped Parts

Due to its advantages and characteristics, CNC vertical machining centers can be used in high-precision, mass-produced machinery manufacturing industries such as aerospace, automotive, instrumentation, textile, electronics, mold manufacturing, military products, and handicrafts. VMT is mainly suitable for machining workpieces with complex shapes, high precision and complex processes.

1) Box Parts

Box-type CNC machining parts refer to machine tools, automobiles, airplanes, engine blocks, gearboxes, headstocks, diesel engine blocks, gear pump housings and other parts, when a vertical machining center is used, 60% to 95% of the machining process of general machine tools Can be done in one go. In addition, CNC VMC has high precision and high efficiency, rigidity and automatic tool changer. As long as the process flow is reasonable and suitable fixtures and tools are used, many problems in the processing of box parts can be solved.

2) Complex surface parts

In the air transportation industry, parts with complex surfaces such as cams, integral impellers of engines, propellers, mold cavities, etc., as well as box or shell parts with complex curves, curved contours or closed cavities, are difficult to achieve the predetermined machining accuracy and are difficult to be processed. Conventional machine tool or precision casting inspection. The multi-axis machining center using automatic programming technology and special tools can greatly improve its production efficiency, ensure the shape accuracy of the curved surface, and make the automatic machining of complex parts easy.

(3) Special or irregular shaped parts

Irregular parts have special shapes, and most parts need multi-point mixed processing of points, lines, and surfaces, such as brackets, bases, etc. When machining special-shaped parts, the more complex the shape, the higher the required precision, and VMC shows its advantages at this moment.

4) Plates, sleeves and plates

Such workpieces typically include keyways and radial holes. Vertical machining centers are often used for end-face hole systems or curved plate shafts, such as bushings, perforated plates, motor covers, etc.; horizontal machining centers are often used for parts with radial holes.

5) New parts in trial production

The machining center has high adaptability and flexibility. When the processing object changes, it is only necessary to generate and input a new program, or even modify some program segments or sometimes use some special instructions. For example, the use of zoom function can realize the processing of special-shaped parts of different sizes, which provides great convenience for single-piece, small batch, multi-variety production and new product testing, and greatly shortens the production preparation and trial production cycle.

Fourth-axis machining is an important branch of the CNC milling world. Haas had actually started building the fourth axis before it built the full CNC machine (pictured right). This is a series of articles to help beginners understand how and why the fourth axis is used with CNC milling machines. In the first part, we'll look at what the fourth axis is used for. In the second part, we'll see how they work.

If you are new to CNC, your first impression may be that the fourth axis is made with the same rotary table that is used for manual machining. In fact, there are many projects where someone converts a manual Rotab to a 4th axis. While there is some truth to this idea, it is largely incorrect.

Most of the work for hand machining the fourth axis is about cutting features along arcs, which is difficult to do with manual machines. With CNC, cutting along arcs is easy - that's what G02 and G03 g-codes are for. In some cases, we use the fourth axis for continuous machining -- in other words, we want the tool to be machined while the fourth axis turns. But there are many other applications too.

If the special-shaped parts produced in large batches, casting, forging or powder metallurgy can be used to reduce the manufacturing cost of the parts, but a large amount of mold costs are required in the early stage, and the mold trial production cycle is long;

If the production batch is small, or the product is in the development process, it is impossible to invest in expensive molds for molding and machining, and there is no time to wait. If the three-dimensional additive printing method is used, the mechanical property requirements of the parts are often not met. Therefore, it is practical to remove material by machining methods. In the past, general equipment was used for processing, which required a lot of procedures and a lot. Fixtures and require highly skilled operators. Therefore, the product development cycle is long and the development cost is high.

With the development and popularization of CNC equipment, it is possible to give full play to the advantages of CNC equipment, and it is possible to quickly process complex special-shaped parts.

The clamping method of the 4 axis CNC parts machining adopts the mandrel positioning, the mandrel is clamped on the rotary table, and the A-axis rotation drives the parts to be linked with the main shaft during the processing. The positioning reference of the mandrel refers to the central axis of rotation of the part, and according to the cavity structure and dimensional tolerance requirements of the special-shaped part, it is determined that the working surface of the mandrel and the inner wall of the special-shaped part are well fitted to keep the circular runout ≤ 0.01, and the coaxiality ≤ 0.02. In terms of function, the mandrel provides torque through static friction to ensure the stability of cutting; the mandrel provides radial support to avoid deformation of thin walls of special-shaped parts caused by cutting force. At the same time, the roughness of the working surface of the mandrel should be above Ra0.8, the surface should be smooth and smooth, and the inner wall of the special-shaped parts will not be scratched.