Based on the comprehensive analysis of the processing characteristics and burr characteristics of shell parts, the technology of active deburring by mechanical processing is proposed, and the deburring methods and tools suitable for typical parts such as shell holes, surfaces and grooves are explored in combination with actual production , from the source of the processing process to carry out step-by-step control, changing passive deburring to active deburring, thus realizing the mechanized processing of deburring, reducing the amount of labor and improving the quality of product processing.
01
preamble
Shell parts have the characteristics of complex structure and high processing precision. With the application and promotion of advanced manufacturing technology, the competition in the manufacturing industry is becoming increasingly fierce [1], and customers' requirements for product quality and processing efficiency are also increasing. However, our The burr method still stays in the use of tools with abrasives such as files, bonded grinding wheels, spatulas, wire brushes, needle brushes, abrasive belts, and whetstones, and manually removes burrs from the processing parts of the product. At present, this method is far from meeting the needs of customers. The branch factory has gradually realized that deburring is an important link to improve the cleanliness of the shell. How to improve the effect and quality of deburring has become an important issue. The quality of final processing and appearance quality is very important. According to the survey, the current important link of cleanliness control can use active deburring technology [2] to remove burrs generated during processing, improve the processing quality of parts, and avoid cleanliness problems caused by burrs [3].
02
traditional deburring method
During the manufacturing process of shell parts, there will always be burrs or flashes at the junction of the processed surfaces [2]. The content of deburring is mainly to remove the thorns or flashes formed around the processing parts of the shell parts. For shell parts, the main machining features are holes, faces and grooves, and burrs mainly exist on the edges of these features. The traditional deburring method is relatively backward, and the processing efficiency is low, which directly affects the delivery cycle and processing quality of the product. The traditional methods of deburring shell threads are shown in Table 1.
Table 1 Traditional methods for deburring shell threads
03
Classification of shell burrs
According to the requirements of the appearance shape and size of the burrs in the cutting process (see Figure 1), the burrs in the machining process are divided into micro burrs, small burrs and large burrs according to their size (see Table 2).
H is the burr height, which is the maximum distance between the workpiece terminal surface and the burr cross-sectional profile measured on the cross section; B is the thickness of the burr root, which is the burr convex point measured on the workpiece terminal surface to the ideal processing surface of the workpiece The distance between; r is the radius of the burr root circle, which is one of the burr section dimensions measured on the cross section.
04
Machining deburring method
Machining is the source of burr generation, and it is also the key point of burr control. In order to further improve the processing quality of burr removal and ensure the processing efficiency of parts, the method of numerical control processing is adopted, which is more conducive to ensuring the processing quality of shell parts. According to the division method of burr size, follow the principle of burr from big to small, small to none [3] to carry out step-by-step control and removal.
The basic principles of shell burr control: First, it is necessary to eliminate the large burrs generated during the processing and reduce the generation of small and micro burrs, so as to reduce the workload of later burr removal; secondly, the tool must be sharp during the processing, so that the cutting There will be no large burrs in the process. When a large burr occurs, the tool should be replaced in time to ensure that the size of the burr is within a controllable range; finally, in the process of processing, certain processing principles should be followed to ensure that the direction of the burr is in a certain direction. Facilitate the removal of parts. The specific method is as follows.
(1) Behind the first hole The shell is mainly processed with holes, and burrs often appear inside the holes or on the edge of the processed surface. For this kind of processing, the method of processing the hole first and then processing the surface can achieve less and no burrs on the processed surface [4].
(2) Adjust the processing sequence. For intersecting or intersecting hole systems, burrs usually appear at the junction of two holes. The control principle for this type of burr is to adjust the processing sequence so that the burr is generated in a position that is conducive to burr observation and easy removal.
(3) Change the tool path. The teeth of the up-cut milling process wear quickly, and the quality of the machined surface is poor. Climb milling does not have the sliding phenomenon of cutter teeth during up milling, the degree of work hardening is greatly reduced, and the quality of the processed surface is higher.
(4) Optimizing cutting parameters According to the cutting tools and cutting parameters selected during the processing of shell parts, a CNC tool cutting parameter library is established to facilitate on-site better control of the size and formation of burrs during processing.
05
Deburring method for typical features of shell parts
Shell parts are mainly formed by the superposition of three types of features: holes, surfaces and slots [5]. Hole features are mainly to provide hydraulic power and through the oil circuit through movement; surface features are mainly the characteristics of connecting holes and hole systems, which form the entities of shell parts; groove features are mainly the connection between connecting holes and hole systems, which is convenient The oil circuit is connected.
5.1 Deburring method for hole features
(1) Classification of hole features Holes are one of the most common features of shell parts. According to the complexity of their processing, holes can be divided into simple hole systems and complex hole systems. The simple pore system is mainly composed of a single element that constitutes the pore, and the structure is single; the complex pore system is composed of multiple elements and has a complex structure.
(2) Features of hole burrs Hole features are mainly processed by drilling, and the burrs mainly exist on the edge of hole features [6]. The processing elements of the simple hole system are single, and the burrs are mainly concentrated in the parts of the drilled hole and the drilled hole (see Figure 2). The edge of each processing step.
Image a) Drilling into the burr b) Drilling out of the burr
Figure 2 Drilling in and out of burrs
(3) Removal method of hole burr feature ① Simple hole burr feature removal method. Simple hole system burrs are mainly concentrated in the drilled holes and drilled holes. The size of the drilled burrs is relatively small, and the burrs mainly exist on the processing surface of the parts. To remove such burrs, a special rounding and chamfering tool can be used to compile the corresponding processing program to remove the burrs generated after the hole is processed; to drill out the burrs The size of the drill bit is relatively large, and it is difficult to remove the burr. According to the actual processing conditions of the shell, the dwell time can be increased during the drilling process to ensure that the drill bit removes the burr during the drilling process. ②Removal method of complex pore system burrs. During the processing of complex holes, small features are often combined together. Traditional processing methods will use different diameter tools to process them according to the processing characteristics of the parts. This will easily cause the burrs generated during the processing to concentrate on each The edges of parts processed with different diameters will cause larger burrs. In order to reduce the generation of such burrs, sort out the processing characteristics of shell parts, and design a special combined tool (see Figure 3) to ensure that the hole system is processed and formed at one time. This will not only improve the processing efficiency of the hole system, but also reduce the occurrence of burrs. Generated, reducing the workload of subsequent burr removal.
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a) Feature hole system b) Tool
Figure 3 Complex hole system and its special combination tool
5.2 Control and removal methods of surface feature burrs
(1) Classification of surface features Surfaces are the basic elements that make up shell parts and mainly exist on the outer surfaces of shell parts. According to their regularity, they can be divided into regular planes and irregular planes. The regular plane mainly refers to the regular shape of the plane with boundaries; the irregular plane mainly refers to the curved surface in the process of processing, and this kind of plane is uneven [7].
(2) Surface burr features Surface features are mainly processed by milling, and burrs are mainly generated at the edge. After the regular plane is processed, the burrs mainly exist on the edge of the plane; after the irregular plane is processed, the burrs mainly exist on the edge of the irregular plane. Such burrs are highly concealed and difficult to remove during processing.
(3) Removal method of surface burr features ①Removal method of regular surface burrs. The regular surface is generally machined along the contour of the part with a face milling cutter, and the burrs generated are mainly concentrated at the edge of the surface. For the removal of such burrs, up-cut milling is first used to reduce the generation of large burrs, and then the corresponding processing program is compiled, and the burrs are removed along the edge of the regular plane with a tool with a circular arc to ensure that the contact parts are smooth and burr-free. ②Removal method of irregular surface burrs. After the irregular surface is processed, the surface has different heights. When using a tool with an R angle to remove burrs along the shape of the part, it is easy to overcut or not be removed. For this purpose, design and manufacture a special floating deburring tool [8] (see Figure 4), select different deburring grinding heads according to the characteristics of the burr generation part (see Figure 5), and remove the burr along the processing edge of the part until there is no obvious burr and highs.
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Figure 4 Floating deburring tool
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Figure 5 Deburring grinding head
5.3 Control and removal method of groove feature burrs
(1) Classification of groove features Groove features are mainly concentrated on the surface of the part and the junction of the hole system. Due to its strong concealment, it can be divided into annular grooves, special-shaped grooves and T-shaped grooves according to the realized functions (see Fig. 6), where the annular groove [9] and the special-shaped groove are mainly used to install the rubber ring. Since there must be no oil leakage and oil leakage during the assembly process, the requirements for removing the edge burr are relatively strict, and the edge must be uniform and smooth. The T-shaped slot mainly exists in the hole system, and is mainly sealed by the hole system itself. However, since the rubber ring must pass through the edge of the T-shaped slot during the assembly process, it is required that the intersection of the T-shaped slot and the hole must be regular and smooth, so as to avoid There are burrs scratching the apron.
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a) Annular groove
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b) Shaped groove
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c) T-slot
Figure 6 Slot feature classification
(2) Removal method of groove characteristic burr ① Removal method of special-shaped groove burr. Since the processing of special-shaped grooves mainly depends on the point position to control the groove structure of the parts, so according to the processing characteristics of the parts, a special multi-step R knife is designed (see Figure 7). After the special-shaped grooves are processed, use the R knife along the The shape of the groove is processed to remove the large burrs during the processing of the ring groove, and then the wool wheel is used to polish along the shape of the groove to ensure that the edge of the special-shaped groove is smooth and even. ②How to remove the burr from the ring groove. When the ring groove is designed, it is concentric with the hole system or the hole, and the parts are sealed by the ring groove during the assembly process. Generally, the hole system and the ring groove are processed together. When using a machining center to process, design and manufacture the R knife, mill along the shape of the part in a concentric circle to remove the burrs generated during the processing of the part, and then use a wool wheel to polish along the shape of the ring groove to achieve the purpose of removing burrs Purpose. ③T-slot burr removal method. T-shaped grooves generally exist in the hole system. When processing, the hole system is processed first, and the T-shaped groove is processed last. The burrs are mainly concentrated at the junction of the hole system and the T-shaped groove. In order to facilitate the removal of the burrs, a special groove cutter (see Figure 8) is designed and manufactured. Cut into 0.02 ~ 0.03mm at the edge of the cutting edge to remove the burrs generated during the processing.
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Figure 7 Multi-step R knife for special-shaped groove deburring
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Figure 8 T-shaped groove deburring special groove knife
06
Implementation Effect
Through deburring research on several aspects such as the hole, surface and groove of the shell, the quantitative control of the burr size during the processing of the shell is realized, the large burrs generated during the processing are eliminated, and the small and micro burrs are reduced or eliminated. Burrs fundamentally reduce the generation of burrs and achieve the purpose of reducing the workload of manual deburring. After verification on typical parts, it is ensured that the removal of large burrs reaches more than 90%, the small and micro burrs are reduced by more than 20%, and the workload of manual deburring is reduced by more than 30%.
07
conclusion
In this paper, the specific characteristics of different parts of the shell are analyzed in detail, and the large burrs are removed first, and then the small and micro burrs are removed, so as to achieve less and no burrs in the processing process. Through the implementation of the active deburring scheme of the machining center, the burrs generated in the processing parts are effectively removed, and the production bottleneck problems of irregular burrs in the shell, low processing efficiency and poor cleanliness are solved. Finally, the deburring methods of typical parts of the shell are summarized, and the deburring methods and tools suitable for shell holes, surfaces and grooves are explored in combination with the actual production, which solves the time-consuming and labor-intensive problem of manual deburring. The production efficiency has been greatly improved and good results have been achieved.
Expert Reviews
For the shell part in this example, burrs exist on the edges of inner holes, flats, and grooved features, and the traditional manual deburring method is inefficient. According to the processing characteristics of the shell parts, the author proposes the method of actively removing burrs by mechanical processing, and controls and eliminates the burrs step by step at the source and process of mechanical processing, which improves the product quality.
The highlight of the article is the active deburring technology of mechanical processing. Based on the numerical control machining method, the burring characteristics of typical parts of the shell parts are summarized, and the deburring methods suitable for the shell holes, surfaces and grooves are explored in combination with the actual production. and tools to achieve less and no burrs in the process of processing.
