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Research on Nozzle Parts machining Technology Route

Mar 03, 2020

This part is mainly used to provide lubricating oil to lubricate the internal cavity of the engine. The dimensional tolerance requirements are stricter and the accuracy level is higher. Through a series of studies on the process route, wool structure, and processing methods, a reasonable process route is formulated and completed. Trial machining of parts.

 

1 Part technology analysis

The parts are bracket-type parts with mounting edges, high dimensional accuracy, strict technical requirements, and the parallelism of the center of the outer circle in the direction parallel to the mounting side to the plane B of the mounting side is 0.03mm, and the size of the outer circle is φA-0.013 -0.028mm, the diameter of the two grooves at the outer circle is φB-0.036mm, and the surface brightness is required to be Ra1.6um. In addition, the head of the long rod perpendicular to the mounting side needs to be machined with two stepped square grooves, and the surface luminosity requirements are Ra1.6um, which is particularly difficult to guarantee during processing. The structure of the part is shown in Figure 1.

 

Figure 1 Schematic diagram of part structure

2 Determination of part process route

Selection of part processing standards

Reasonable selection and setting of processing benchmarks is the key to ensuring processing quality. The selection of process benchmarks should mainly consider the following aspects:

(1) Whenever possible, use the design basis as the process basis. When it is difficult to adopt the design basis as the process basis, you can choose another process basis, but you must ensure the design size and technical requirements of the part.

 

(2) The selected process standard should be used as much as possible for the positioning of the workpiece and the inspection of the process size.

(3) Repair the benchmark several times to avoid the accumulation of errors caused by the benchmark during processing.

After analyzing the design drawings, we know that the design basis of the part is the mounting side plane B, and the parallelism of the center of the outer circle in the direction parallel to the mounting side to the mounting side plane B is 0.03 mm. Following the principle of process benchmark selection, it is determined when we process Use reference B as the positioning reference for machining.

 

Determination of parts processing route

The arrangement of process routes must also follow certain principles.The general principles of processing process division are:

(1) Precision Machining and roughing machining . For individual parts, roughing, semi- Precision Machining, and Precision Machining are required. Or a batch of parts, all roughing, semi- Precision Machining, and Precision Machining are required. Between roughing and Precision Machining, it is better to wait for a period of time so that the deformation of the parts after roughing is fully restored, and then finishing is performed to improve the machining accuracy of the parts.

(2) Sorting method by processing area. Generally, first process the plane, positioning surface, and then process the hole; first process the simple geometry, then process the complex geometry; first process the parts with lower accuracy requirements, and then process the parts with higher accuracy requirements.

In short, the division of processing steps depends on the specific situation of the processed parts. The sorting method based on the actual process arrangement is a synthesis of the above sorting methods.

 

Through the determination of the part process benchmark, we divide the main process routes as follows:

Wool (investment casting) → grinding → scribing → first end of the turning → drilling reaming → second end of the turning → milling surface, drilling → electromachining of two grooves → grinding of remelted layer → inspection

 

3 Processing of parts

Machining of reference planes of parts

Turn and install the side plane to ensure the processing standard B, and lay the foundation for the subsequent processing of the process size

Parts drilling reaming

There are two small holes on the mounting side. Since these two holes will be used as positioning reference in the future, the hole tolerance will be reduced to 0.048, and the finished mounting side plane will be used as the reference. As the angular positioning reference, the outer end of the rod can be linked to the machining reference, ensuring the position requirements of the outer portion of the rod.

Machining of high precision outer circle and groove

After the above two steps of processing, the positioning reference and angular reference of the part have been determined, and the subsequent processing is based on the positioning and clamping reference.

When machining the outer circle and groove, roughen the outer circle and two grooves of the part first, and then finish machining it. An auxiliary clamping is added to the lathe fixture to ensure that the wall thickness requirements of the inner and outer diameters are met when drilling the reaming hole.

 

Step square groove processing

The schematic diagram of the processing of the stepped square groove is shown in Figure 2.In the process, electrical processing is used to process the shape of the groove using the formed electrode. The difficulty of square groove processing is mainly the removal of the remelted layer. The previous remelted layer was manually polished. This method is suitable for parts with large tolerances and low surface quality requirements, and is more suitable for external surface processing. The cavity of the two stepped square grooves is too small, and is manually polished, the processing quality is not high, the efficiency is low, and it cannot meet the design drawing requirements.

The removal of the remelted layer is performed by milling. The end mill of ф2 is used to remove it on the vertical machining center, and then polished to ensure surface roughness Ra1.6.

 

Figure 2.

At this point, all the parts have been processed. After inspection, the parts fully meet the requirements of the design drawings.

 

4 Conclusion

Through a series of researches on the process route, wool structure, and processing methods and the production of on-site parts, it is verified that the developed process processing method is reasonable and effective, so that the parts meet the design drawing size and accuracy requirements, which greatly helps the production of similar parts.

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