The Fastest China Rapid Prototype,Small To Large Batch Manufacturer to Bring Your Ideal Project to Life - Be-Cu Discover Our Top Manufacturing Wiki And Guide in 2024 Eamil us : [email protected]

Research On NC machining Technology Of Ring Thin——Walled Aluminum Alloy Parts


In the process of machining thin—waHed parts,the clamping deformation,process deformation and other issues have been affecting the machining precision and efficiency,this paper studies the one ring thin—wall aluminum alloy parts of NC machining process,to solve the problem of poor rigidity,easy to deform—ation of the parts,to reserve a supporting body and design way to suppress the deformation of the special fixture parts,finite element analysis proves the rationality;A reasonable NC machining process is devel—oped,and the part is simulated in Vericut by UG programming.Finally,the actual processing is carried out on the machine t001.The results show that high machining accuracy can be obtained.

Thin-walled parts have the characteristics of light weight, material saving, compact structure, etc., but the parts have poor rigidity, weak strength, and easy deformation during machining [1], while thin-walled aluminum alloy parts are lighter and softer, and the machining process It is more complicated, the machining time is long, and it is difficult to ensure the machining accuracy. In this regard, scholars have carried out a series of studies. Liu Jianlong et al. [2] optimized the overall machining technology of frame thin-walled parts, providing ideas for the machining of frame thin-walled parts; research on thin-walled aluminum alloy boxes , to achieve high-speed and high-quality machining of the part on the machining center; Du Haiqing et al. [4] used sludge to fill the cavity of thin-walled parts instead of fixtures. It is possible to reduce costs while maintaining machining accuracy in small-scale production. It can be seen from this. Formulating a reasonable machining technology and designing a suitable clamping method can effectively solve the problems of deformation and low precision in the machining of thin-walled parts. The most important factors affecting the machining accuracy of the workpiece are clamping deformation and machining deformation. In order to reduce the deformation, In the rough machining stage, the method of reserving the support body is adopted to avoid direct contact between the workpiece and the fixture, and special fixtures are used in the semi-finishing and finishing stages. The feasibility is verified by finite element analysis, and reasonable machining technology is designed, programming and simulation machining are carried out, and then higher machining quality can be obtained.

1 Structural analysis of parts

This ring-shaped thin-walled aluminum alloy part is used in the internal connector structure of a certain type of aviation motor, and has high surface roughness and precision requirements. The main machining difficulty is that the poor rigidity of the aluminum alloy material will cause clamping deformation and machining deformation. Figure 1 is a three-dimensional diagram of a ring-shaped part. The part is hollow in the middle and is annular. It needs to be processed on the front and back, with stepped surfaces and through holes. Two screw holes and a rectangular connector hole need to be processed on the straight side of the side. Note that the front and back of the part are slightly different. The side of area 1 higher than area 2 is the front side, and the side of area 2 higher than area 1 is the reverse side.

2 CNC machining process formulation

The annular thin-walled parts are affected by many aspects such as the characteristics of the blank material, the size of the machining allowance, the thickness of the annular wall, and the clamping method. Deformation is easy to occur in the process of machining. The process design in CNC machining determines the use efficiency of CNC machine tools, the machining quality of parts, the number of tools and the economy [5]. Machining technology analysis, taking into account various influencing factors, so as to formulate a reasonable machining plan.

2.1 Analysis of machining technology

The blank material of the part is 7075 aluminum alloy plate, and the blank size is 180 mm×l30 mm×20 mm. The engineering drawing of the part is shown in Figure 2. The main machining surface is the front and back of the part, and the machining accuracy and tolerance requirements are high. The fillet R3 is not noted, and the tolerance is GB/T 1804-f.

The rough machining should remove the allowance as much as possible. The allowance is the normal inter-process allowance plus the appropriate amount of deformation [6]. From the blank to the machining, a large amount of material must be removed, the machining allowance is large, the machining time is long, and it is easy to produce A lot of cutting heat. Causes deformation of the workpiece, so the work of removing peripheral material is spread over multiple roughing and finishing processes. Because the shape of the part is not conducive to clamping. When roughing the front side, the outer contour of the part cannot be directly processed, and the support body needs to be reserved, and the support body is clamped by the flat-nose pliers during roughing, semi-finishing and finishing on the reverse side to reduce the contact stress between the fixture and the workpiece. The support body is shown in Figure 3. The difficulty in machining is that the poor rigidity of the aluminum alloy material will cause clamping deformation and machining deformation. Figure 1 is a three-dimensional diagram of a ring-shaped part. The part is hollow in the middle and is annular. It needs to be processed on the front and back, with stepped surfaces and through holes. Two screw holes and a rectangular connector hole need to be processed on the straight side of the side. Note that the front and back of the part are slightly different. The side of area 1 higher than area 2 is the front side, and the side of area 2 higher than area 1 is the reverse side.

2 CNC machining process formulation

The annular thin-walled parts are affected by many aspects such as the characteristics of the blank material, the size of the machining allowance, the thickness of the annular wall, and the clamping method. Deformation is easy to occur in the process of machining. The process design in CNC machining determines the use efficiency of CNC machine tools, the machining quality of parts, the number of tools and the economy [5]. Machining technology analysis, taking into account various influencing factors, so as to formulate a reasonable machining plan.

2.1 Analysis of machining technology

The blank material of the part is 7075 aluminum alloy plate, and the blank size is 180 mm×l30 mm×20 mm. The engineering drawing of the part is shown in Figure 2. The main machining surface is the front and back of the part, and the machining accuracy and tolerance requirements are high. The fillet R3 is not noted, and the tolerance is GB/T 1804-f.

2.2 Tool selection

Parts machining requires milling, drilling, chamfering and other processes. It is necessary to take into account the machining quality and machining efficiency, minimize the number of tool changes, and select high-speed steel tools based on the structure and material characteristics of the parts. When roughing, use a tool with a larger diameter. When cleaning the corner, the tool should be smaller than the radius of the fillet. Before drilling, a center drill should be used for positioning. The detailed tool card is shown in Table 1.

2.3 Machining technology arrangement

In accordance with the principle of “face first, then hole, first rough and then fine, first master and second, base first”. The process of arranging the machining of parts is: rough milling the front side of the leaf, rough milling the back side_+ semi-finish milling back side_finish milling back side_÷semi-finish milling front side_finish milling front side. In the first face-up clamping stage, the front face is roughed and the support body is milled out. When roughing the front hollow part, multi-layer milling is required: in the back-up loading and clamping stage, the support body is lightly clamped with flat-nose pliers, rough machining and semi-finishing. , Finishing the reverse side, drilling through holes and threaded holes; using a special fixture in the second front-up clamping stage, semi-finishing, finishing the front side, milling out the support body; for better secondary clamping and correction. The edges are deburred after each clamping operation. The machining procedure card is shown in Table 2.

Specialized Fixture Design and Analysis

The thinnest part of the final product of the part is 2 mm, and the problems of thin wall and soft material and easy deformation bring difficulties to the workpiece clamping. In the semi-finishing and finishing stages of the front side of the workpiece (the second front-up clamping), if the workpiece is fixed with a pressure plate and bolts, it needs to be clamped in two times. First, press the support body with the pressure plate on the tooling plate, as shown in Figure 4b As shown in the figure, after machining the inside of the workpiece, remove the pressure plate, and then use bolts to fix it at the through hole inside the workpiece, as shown in Figure 4c. Machining the outside of the workpiece.

(b) Press plate fixing support (c) Bolt fixing at the through hole

Figure 4 Fixing the platen and the black bolt

Multiple clamping will reduce machining efficiency and positioning accuracy. The clamping method needs to be redesigned when clamping. To ensure the following

Require:

  • (1) Ensure that the parts are not deformed or deformed as little as possible after clamping.
  • (2) To ensure the position accuracy.
  • (3) Easy to load and unload.

Analyze the structure of this thin-walled annular part. The side is a straight edge and an arc edge, which is difficult to locate. The reverse side after finishing has through holes and small planes, and it is necessary to ensure that the workpiece is not deformed as much as possible after clamping. It is necessary to clamp in the direction that the workpiece is not easily deformed. The front and back sides of the second front-up clamping have been finished. The plane of the back area 1 is flush with the back side of the support body, which can be used as a positioning surface, and there are through holes that can be used as positioning holes. Therefore, one side and two pins are used for positioning, that is, in the second When the secondary face is clamped up, the combination of the finished hole and the plane of the back area 1 and the back side of the support body that is flush with it is used for positioning.

In the front semi-finishing and finishing stages (the second front-up clamping), a special fixture was designed as an improvement method, as shown in Figure 5. A diamond-shaped pin and a cylindrical pin are respectively pierced at the upper and lower right side of the workpiece corresponding to the workpiece on the upper and lower right side of the clamping body. A diamond-shaped pin and a cylindrical pin are respectively. The long side of the diamond-shaped pin is perpendicular to the center line of the two pins, and the top of the two pins is low. At the height of the through hole after finishing finishing, the convex part on the reverse side of the semi-finished workpiece (reverse area 2) is stuck in the groove of the clamp body, and there is a raised spacer under area 3. The bottom of the groove and the top of the spacer are the same as the semi-finished product. There is a gap between the workpieces, and black glue is applied to the gap to fix the semi-finished workpiece. During machining, the clamp body can be directly clamped with a flat-nose pliers to avoid direct contact with the workpiece. Obviously, it is more convenient to use a special fixture to process.

(a) Clamp body (b) Assembly drawing of semi-finished workpiece and fixture

Figure 5 Fixing with special fixture

During the milling process, the workpiece will be deformed. Therefore, the finite element analysis and comparison of the two forms of the pressure plate and bolt fixation and the special fixture fixation in the front finishing and semi-finishing stages are carried out to verify the effectiveness of the improved method. The cutting force when cutting metal is affected by many factors, and the general form of the empirical formula of milling force is [7]:

F=C·dirty. · Convex: · Wide · Mouth: · d (1)

In the formula: c is the machining material, cutting condition coefficient, shift is the cutting speed, 口. is the depth of cut, factory is the feed, n. is the milling width and d is the tool diameter. Take the logarithm of both sides of the equation (1) and convert it into a linear equation. have to:

lgF=lgC+lgd+xlgv+ylgap+

ml mine + nlga. (2)

Transforming according to the quaternary linear model, the linear regression equation can be obtained as:

Xi=bo+blxI+62 mushroom 2+b3x3+b4x4 (3)

According to the data regression analysis of the literature [7], the exponential formula of the component force of the milling force in the Ge, y, and z directions can be obtained:

only = 9.105 mouth: 8974 shift one o’47” wide 0271 n: 78″ d k

F, = 15.8 · mouth: 9190 · mouth one n4 舳 5 · wide 0255 · mouth: 7 porridge 3 · d · k

t=5.487·n: 8431·hoe ton 5413·Guangbi·n: 7277·d

(4) According to the actual trial machining on site. The machining deformation that affects the dimensional accuracy of the part occurs when the straight edge of the outer wall is semi-finished, that is, when the fixture is fixed with bolts at the through hole to semi-finish the outer straight edge of the workpiece, and after using a special fixture, the straight edge of the outer wall is semi-finished. Set the depth of cut at this time. =5 llllll, the feed amount. Factory = 800 mm/min, milling speed v = 78 m/min, milling width n. = 1.5 nlin, tool diameter d = 10 nlln, no cutting fluid is used, so take k = 1, in formula (4), only = 81.0 N, F, = 134.7 N, t = 27.5N. Theoretically, the cutting force and the theoretical binding force reach a static balance, but in actual machining, the milling force calculation formula [8] should be multiplied by the safety factor K,

Be-cu.com
Logo