aluminum machining cnc mechanical spare parts

Aluminum alloy parts have the advantages of strong corrosion resistance, low density and high strength, and are widely used in parts processing and manufacturing and other fields, and are one of the important materials for modern industrial production. Through the introduction of the process characteristics and performance of aluminum alloy materials, the basic situation of CNC machining fixture is analyzed, and then the CNC machining fixture of aluminum alloy thin-wall parts and related problems are comprehensively explored, aiming at improving the design and application level of CNC machining fixture and ensuring the overall processing quality of processed products.

Compared with traditional machining technology, CNC machining has more prominent advantages, which not only has the processing advantages of high automation, high processing precision and low labor intensity, but also can realize the high-quality processing of complex curved parts, and the application advantages are more prominent. The application of CNC machining technology in the machining of thin-walled aluminum alloy parts can achieve an idealized machining mode. In order to optimize the numerical control machining effect of thin-walled aluminum alloy parts, it is very necessary to study the relevant contents of numerical control machining fixture of thin-walled aluminum alloy parts. Before the formal research, the properties and process characteristics of aluminum alloy materials should be analyzed first.

1 Aluminum alloy material process characteristics and properties

Aluminum alloy material is widely used in industrial production and belongs to the category of non-ferrous metal structural materials. Material properties and process characteristics are mainly reflected in the following points: ① flexibility. Aluminum alloy material has the advantages of strong adhesion, good plasticity and ideal toughness, etc., which is not easy to separate when cutting, but it is easy to adhere to the blade, and then generate the steel of the knife. Usually, thin-walled parts have the problem of poor rigidity, and it is easy to deform during processing. Because the coefficient of linear expansion of aluminum is much larger than that of steel, it is easy to produce excessive thermal deformation when cutting; ④ Hardness. Aluminum alloy materials generally have the problem of low hardness, it is easy to scratch and surface roughness is not up to standard when processing, but because the specific strength of aluminum alloy is relatively high, it is widely used in aviation products.

2 CNC machining fixture

2.1 Overview

The fixture is a device used for guiding the tool and clamping the workpiece of the CNC machine tool. It is a fixture designed for a certain process of the workpiece. It is mainly composed of positioning elements, clamping devices, guiding elements, tool elements, connecting elements and clamping elements and other components and devices. According to the structural characteristics and the degree of specialization, the fixture can be divided into adjustable fixture, general fixture, special fixture and combination fixture, etc., with the advantages of convenient operation, rapid, labor-saving, etc., can provide reliable guarantee for high-precision and high-efficiency production, but it also has the characteristics of high manufacturing costs and long processing cycle. At the same time, because the use of the fixture will be directly limited when the product is changed, it is mostly used in the production of mass products.

2.2 Application Function

When CNC machining is carried out, the fixture has the following functions: ① to ensure the workpiece processing accuracy. Under the action of the fixture, the workpiece will not be affected by the technical level of the processing personnel, and the difference in the processing accuracy of a batch of workpieces can be controlled at the minimum 2 compression auxiliary working hours to ensure production efficiency. The use of fixture does not need to implement the marking of the workpiece to find the correct processing, can effectively reduce the auxiliary working hours, and after clamping, the workpiece rigidity will be significantly improved, the cutting amount will be effectively improved ③ the use of the machine tool will be effectively expanded, will be in accordance with the forming movement of the processing machine tool attached to the machine tool with different types of fixture, the machine tool will break through the original process range, Be more widely used ④ reduce processing costs. Because after the use of the fixture, the product production quality will tend to be stable, and the waste productivity will show a significant decline, lower grade workers can be arranged to operate the machine tool, which can achieve the goal of effectively reducing production costs. The operation of the fixture is more convenient, and the effect of effectively reducing the labor intensity of workers can be achieved through the use of hydraulic and pneumatic clamping devices.

3 Aluminum alloy thin-wall parts CNC machining fixture and related problems

3.1 Engineering Examples

In order to meet the production needs, the production department has increased the research on the thin-wall parts of the batch junction box, and this article will also take the thin-wall parts of the junction box as an example, according to the positioning requirements of the processing fashion clip, the special fixture design will be developed, and the fixture design will be optimized and improved according to the actual situation. The use of this fixture to clamp the workpiece in the process of product processing, can achieve the goal of effectively improving the workpiece positioning time and the workpiece clamping efficiency, can achieve good processing accuracy and processing efficiency, and the mass production value of the workpiece will be significantly improved.

3.2 Processing Scheme

This production of junction box products is an important computer accessories, belonging to aluminum alloy materials. The product is expected to produce more than 200,000 pieces per month, which is a mass production product, and the wall thickness of a single product is 0.5mm, which is a typical precision hardware product. According to the production target, the following technical requirements need to be met in the implementation of product processing: ① the bottom surface of the part can not be modified by tools, especially emery cloth, file modification; ② the surface can not appear obvious pores, scratches and other damage; ③ the tolerance of the shape should meet the requirements of IT8; ④ The bottom of the product should be bonded with other objects.

Processing thinking: Because the processed products are thin-walled aluminum alloy parts, if the material is treated by cutting processing means, it will cause a large waste of material, so it is not recommended to use this treatment. Through the analysis of the parts drawing, it can be found that the bottom surface of the product contour roughness can be guaranteed by cutting means, while other surfaces need to be obtained by means of non-removal of materials, except for the bottom surface, other surfaces are relatively smooth. Therefore, when processing parts, it is necessary to use two means to process parts. In the specific processing, it is necessary to use the die casting method to process the product, cast it into a semi-finished product with a wall thickness of 0.5mm, and use the numerical control milling method to start milling on the bottom surface, and the construction can be stopped after the size is qualified.

3.3 Processing Difficulties

After the processing plan is determined, the processing department carries out a detailed analysis of the processing characteristics, and analyzes the specific processing matters and processing standards together with the customer. The abrasive tools used in the shape casting of this product are provided by the customer, the author is mainly responsible for the bottom milling processing, and the other parts of the construction are carried out by the casting workshop. Although the processing is relatively single, but because of the product thin-wall characteristics, the overall construction is still more difficult, such as in the die casting prone to flash problems, or parts around the surface conditions are relatively limited, will directly increase the difficulty of post-processing positioning and other problems, will make the machine tool processing positioning clamping become extremely difficult.

According to the characteristics and shape of the parts, in the processing of such parts, on the one hand, to ensure the accuracy and efficiency of positioning clamping, through the full use of tool resources, effectively control the consumption of tool resources, to ensure that the impact of workpiece vibration on the tool, the workpiece can be controlled to the minimum; On the other hand, it is necessary to ensure the simplicity and convenience of the fixture, and at the same time to carry out a special design in accordance with the production requirements, to ensure that the universal fixture and the use of a long time, in order to prevent repeated replacement. The fixture positioning device is set up 10 stations in total, and the processing position of the workpiece blank will be determined by mutual cooperation means during processing.

3.4 Fixture optimization design

(1) Fixture application problem. After a period of production practice, it was found that there are still some problems in the application of this fixture: first, the clamping time is relatively long, the personnel need to consume a lot of practice to press and install, and it is difficult to meet the specific processing needs of 4 sets of fixtures per person; Second, there are problems in positioning, and the bottom wall thickness of the workpiece is easy to appear in the processing process, or even the problem of penetration, which will affect the machining accuracy of the workpiece; Third, the processing efficiency is not ideal, the base volume is relatively bulky, and the personnel need to spend a lot of energy to implement the fixture taking and placing, which will affect the production efficiency; Fourth, because the fixture and the workpiece belong to the transition mode, it requires a certain amount of strength to complete the taking and placing, and in the process of processing may be affected by cutting force or other forces, so that the individual workpiece is too closely connected with the fixture, which will hinder the taking of the workpiece.

(2) Fixture optimization design. In view of the problems existing in the use of fixture, the following optimization suggestions are put forward :① In order to avoid inaccurate clamping positioning and time-consuming problems, it is decided to carry out the design of pneumatic auxiliary tightening device to form a laying aid for clamping operation and ensure the accuracy of all workpiece positioning. ② In order to change the too thick base, it is decided to make the base into a structure, and will be designed in accordance with the form of an independent prism for the machine tool fixture, the sandwich connecting part of the workpiece, and the whole fixture is composed of the base, the upper positioning plate and the lower positioning plate. (3) Because taking into account the machine tool clamping need to manually complete the corresponding operation tasks, so the manual operation factors need to be taken into account, can not be too pursuit of a clamping workpiece production, need to do a good job of personnel workload bearing capacity analysis, to ensure that the task volume arrangement is reasonable, to prevent the problem of personnel work negative phase is too heavy, should do a good job of the base structure and fixture size adjustment, each layer of production Quantity control is 8, to achieve two layers of simultaneous processing mode, to ensure that the output of each workpiece processing can reach 16. ④ Because there may be individual workpiece and positioning end connection in the process of processing, it will directly increase the difficulty of picking parts by hand, so it is necessary to do a good job of workpiece clamping strength, volume size adjustment, should be in the process of processing positioning plate need height, width size control, to ensure that its dimensions can be less than the size of the working cavity. At the same time, it is necessary to set a small hole in the inner side of the workpiece positioning end to apply external thrust to the workpiece when it is set in the station, so as to effectively deal with the difficult problem of taking parts. It is recommended to set the small hole to the median diameter of 8mm.

3.5 CNC machining program end system

In fact, the CNC milling machine processing complexity is relatively low, not only through the use of the corresponding software to complete the preparation task, but also through manual programming means, in the workshop site commissioning. Since the workpiece is generally fixed in the position of flat pliers, it is necessary to implement comprehensive processing on both sides, and the cutting amount is relatively small, so it is necessary to ensure the one-time processing and processing quality, according to the processing requirements, the processing selection of flat base alloy milling cutter with a diameter of 12mm in the middle circle, and the feed speed is controlled at about 2500mm/min. When milling, the tool only needs to handle the front and back side of the workpiece. In the design of the cutting path of the tool, it is necessary to analyze the cutting tool shape according to the outline, so as to achieve the goal of fully implementing the milling treatment of the workpiece.