Dec 11, 2019
Use a CNC lathe to process simple sets of parts as shown in the figure. The length of the workpiece is 44cm. The dimensions of the two outer steps are Φ45㎜ and Φ65㎜. The coaxiality of the two ends must be 0.04㎜ and have a C1 chamfer. . The dimensions of the two steps of the inner hole are Φ30 ㎜, 52㎜. The verticality of the end face of the two steps in the inner hole is required to be 0.02㎜. There is a C5 chamfer and an inner groove of 4㎜ × 2㎜.
1. Analysis of sleeve parts:
The figure shows a simple set of parts. The surface of the part is composed of two stages. Among them, multiple diameter dimensions and axial dimensions have high dimensional accuracy and surface roughness requirements. The dimensions of the parts are complete and are in accordance with the numerical control machining dimensions. Marking requirements; clear and complete outline description; part material is 45 steel, good machining performance, no heat treatment and hardness requirements. Sleeve parts are a common processing form in machining. In addition to the size and shape accuracy, sleeve parts are generally used as the basis for fitting and assembly. The tolerance level of the hole diameter is generally IT7, and precision shaft sleeves are preferably IT6. The shape accuracy of the hole should be controlled within the hole tolerance. For long sleeve parts, in addition to roundness requirements, attention should also be paid to the cylindricalness of the inner hole surface, the round runout and perpendicularity of the inner hole axis of the end face, and the parallelism of the two end faces.
2.Clamping scheme of sleeve parts
The inner and outer circles, end faces and reference axes of sleeve parts have certain form and position accuracy requirements. The fine reference of sleeve parts can choose the outer circle, but the center line and one end face are often used as the finishing reference. For sets of parts with different structures, it is impossible to use a process scheme to ensure their shape and position accuracy requirements.
According to the structural characteristics of sets of parts, three-jaw chucks, four-jaw chucks, or faceplates can be used for CNC turning. Due to the four-year centering accuracy of the three-jaw chucks, it is not suitable for workpieces with high coaxiality requirements. Secondary clamping. For sleeve parts that can complete the inner and outer circular end faces, chamfers and cuts in one operation, three-jaw chucks can be used for clamping; larger parts often use four-jaw chucks or disks for clamping; generally, soft cards can be used for finished parts. Claw clamping can also be performed on a mandrel; for more complicated sets of parts, special fixtures are sometimes used for clamping.
3.Choice of cutter
The tool selection for machining the outer cylindrical surface of sleeve parts is the same as that of shaft parts. Machining inner holes is one of the characteristics of sleeve parts.
According to the requirements of the inner hole technology, there are many processing methods. Commonly used are drilling, reaming, boring, grinding, pulling, and grinding.
Sleeve parts generally include internal and external circles, tapered surfaces, arcs, grooves, holes, threads and other structures. According to processing needs, commonly used
The tools include rough turning boring turning tools, fine turning boring turning tools, inner slot turning tools, internal thread turning tools, and special-shaped forming turning tools.
4. Choice of cutting amount
According to the quality requirements of the machined surface, tool material and workpiece material, refer to the cutting volume manual or related data to select the cutting speed and feed per revolution, and then calculate the spindle speed and feed speed (the calculation process is omitted), and then fill in the results to Process card.
The choice of the number of back-cutting knives varies with roughing and finishing. During roughing, as long as the rigidity of the process system and the capabilities of the machine tool allow it, the feed should be fed back as much as possible to reduce the number of feeds. During finishing, it is required to ensure the surface roughness of the part. Generally, it is more appropriate to take 0.1 to 0.4.
5.Choice of cutting fluid
The machining of sleeve parts is more difficult than the machining of shaft parts. Due to the characteristics of sleeve parts, the cutting fluid cannot easily reach the cutting area, the temperature in the cutting area is higher, and the wear of the cutting tool is more serious. In order to reduce the workpiece deformation and improve the machining accuracy, a suitable cutting fluid pouring position should be selected according to different workpiece materials.
6. Writing processing program
According to the parts shown in the figure, the machining routes of the inner and outer circles and inner grooves of the workpiece are analyzed, and the clamping scheme during processing, as well as the cutting tools and cutting amounts used are divided. According to the process, the three parts are divided according to the process content, and the shadow Program three programs to complete the process.6. Writing processing program.
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