Using a die to machine the face

The crankshaft is a key component in the diesel engine. The dimensional accuracy and shape tolerance accuracy of each part of the crankshaft are quite high. The accuracy of the mounting surface and the holes on the flanges at both ends is also high. It needs to be mutually compatible with other parts. In conjunction with the assembly, precision must be strictly controlled during the processing of each hole to meet the requirements of the drawings.

With the continuous development and expansion of the company, the types of crankshafts produced by our company are also increasing. The size of the crankshaft mounting faces is different, and the selected tools are different. At present, there are two methods for processing and installing faces: 1 drilling, boring and milling threads on the machining center to ensure the machining accuracy of the installed faces, but the machining cost of the machining center is high, if the machining of various types of crankshafts is installed. Faces are arranged in the machining center, and it is necessary to configure various types of downhole drills, thread milling cutters and boring tools of different sizes, sizes and models, which will incur high tool costs. 2 The mounting surface mold clamping is positioned on the crankshaft. The six-point positioning principle is used to machine the surface with the ordinary Z35 drilling machine. This not only ensures the machining accuracy of the hole, but also saves a lot of tool costs. The use of the mounting face mold not only brings convenience to production and processing, but also creates more profits for the company.

1. Mounting surface processing technology

(1) Pattern analysis. The drawing requires machining the threaded hole of M36×3—6H, drilling depth 65mm and depth of attack 50mm on the crankshaft mounting surface, and the angle of the hole is 90° at the angle of the hole, and the vertical line between the center line of the threaded hole and the mounting surface is required. Within 0.002mm, the pin hole of φ25+0.021 +0mm is processed. The hole diameter of the pin hole is 22mm and the depth of the hole is 20mm. The perpendicularity of the center line of the pin hole and the mounting surface is required to be within 0.000 1mm. The holes in the hole and the balance block are assembled by the positioning pin and the bolt connection, and the structural dimensions of a crank mounting face are as shown in FIG.

(2) Choice of process plan. By analyzing the parts of the pattern that are required to be processed, two processing methods can be selected:

1 All the holes on the mounting surface are machined on the turning and milling center. Φ24mm and φ33mm DTH drills, φ25mm boring tools and M36×3mm thread milling cutters are required. 2 The middle positioning pin hole is machined on the turning and milling center, and then the mounting surface is used to drill the mold. The six-point positioning principle is adopted on the crankshaft, and the threaded hole on the mounting surface is processed by the ordinary Z35 drilling machine. The required knife has the ordinary φ32. .5mm twist drill, φ32.9mm reamer, M36×3—6H tap and φ60mm×90° boring drill, through the “drilling-reaming-tapping-boring” process scheme, not only can meet the threaded hole Processing requirements and cost savings in expensive tools.

figure 1

2. Use of the mounting face mold

(1) Structural analysis of the mounting surface. The crankshaft mounting surface drilling die is composed of a drill template, a positioning bolt, a drill sleeve, a hinge sleeve, a tapping sleeve, a ring screw, a diamond pin and a positioning pin, and the assembly of the mounting surface die is shown in FIG. 2 .

The mounting face drilling die is a cover type drilling die, and the cover type drilling die has no clip specific, the positioning component and the clamping device are directly mounted on the drill template, and the drilling die is positioned on the workpiece, which is suitable for large and bulky. Processing of the hole in the workpiece. During the machining process, it is fixed on the positioning reference surface of the crankshaft mounting surface, and the mounting surface drilling mold is fixed by the positioning pin and the diamond pin, and is used to machine the hole system on the same plane on the mounting surface. The mounting surface mold has simple structure, convenient manufacture, high positioning accuracy and light weight, easy to remove chips, and can ensure the processing precision of the hole during processing.

(2) The use of drilling aids. In the production of the face-drilling mold, according to the size of the hole to be machined, the corresponding supporting drill sleeve, hinge sleeve, tapping sleeve and diamond-shaped pin are prepared to solve the problem of the installation of the face. For the machining of the screw hole of the crankshaft mounting surface M33×3—6H, a drill sleeve of the corresponding size is arranged (see Fig. 3).

image 3

The mounting surface is used during the face machining process. The six-point positioning principle is used to insert the positioning pin into the two pin holes that have been machined on the turning and milling center. The direction of the diamond pin must be correctly installed to prevent the mold from being shaken. . During the drilling process, the drill bit is easy to swing and deflect, resulting in the hole being machined. For this purpose, the drill and the drill sleeve are designed to cooperate with each other. Through the clearance fit between the drill sleeve and the drill bit, the drill bit is guided straight into the hole for drilling. After the test cutting, the center line of the hole and the mounting surface are perpendicular to the mounting surface within 0.002 mm, which meets the dimensional requirements of the pattern.

After continuous improvement of the drilling mold and drill sleeve of the installation surface, the mutual cooperation with the drill bit is more stable, the stability of the processed hole is good, and the phenomenon of chip splashing during the processing is avoided, so that the processing process is safe and reliable.

In the process of reaming, in order to ensure the processing precision of the reaming, a hinge is also produced (see Fig. 4). In the reaming process, the aperture is out of tolerance, the inner hole is not round, the center line of the hole after the reaming is not straight, and the surface roughness value cannot meet the requirements. By changing the size of the reamer, the reaming allowance, and the hinge Various methods such as the speed of the knife and the feed rate can not avoid this problem. For this purpose, the mounting surface mold is designed and the φ33+0.025 +0mm joint sleeve and the φ32.9mm reamer clearance fit are designed. Through the trial cutting of a plurality of holes, the accuracy of the holes is quite high, and the reaming allowance is also reduced, thereby improving the processing efficiency.

Figure 4

Tapping has always been the most difficult type of process in processing. When tapping the thread, the tap is almost buried in the workpiece for cutting. The tap has a large contact area with the workpiece along the thread. After the machining, the threaded hole is prone to rotten teeth, pass-through and stop-and-stop. In addition, the spindle of the drilling machine is flexible. During the tapping process, the spindle oscillates at random. Especially when the tap is cut, the swing phenomenon is the most serious. The tapped thread can not meet the requirements, and various measures can not avoid the recurrence of the problem. . After designing the drill and tapping sleeves, the problems in the tapping process are basically solved. The specific structural dimensions of the tapping sleeve are shown in Figure 5.

Figure 5

The designed tapping sleeve and the tap cooperate with the tapping thread to reduce the sway of the tap during tapping, improve the coaxiality between the tap and the spindle of the drill press, and solve the problem of any swing of the tap when tapping the thread, thus ensuring the processed The verticality of the thread center line and the mounting surface avoids the recurrence of problems such as rotten teeth, pass-through and stop-and-stop, and solves the damage of the processed surface mounting surface by subsequent processing during the installation of the face.

3. Conclusion

The problems encountered in the drilling, reaming and tapping of the mounting surface are solved by using the mounting surface drill and the corresponding auxiliary tool to machine the mounting surface. This is a relatively simple way to solve the hole machining problem and it is worth promoting.

references:

[1] Deng Yingjian, Yang Dongsheng. Tolerance Coordination and Measurement Technology [M]. Beijing: National Defence Industry Press, 2007.

[2] Meng Shaonong. Handbook of Mechanical Processing [M]. Beijing: Mechanical Industry Press, 1991.