CN109623265B - Precise machining method for complex thin-wall variable-thickness large opening cover - Google Patents

Abstract

The invention discloses a precise processing method of a complex thin-wall variable-thickness large opening cover, which comprises the following steps: according to the geometric parameters of the large opening cover, simulating flattening and calculating a minimum blank; designing and manufacturing a tool concave-convex die required by hot-press molding according to the specific structure and size of the large opening cover; hot-press molding the large opening cover by adopting a die assembly hot-press molding method; a chemical milling method is adopted to etch and process the weight-reducing cavity on the inner profile of the large opening cover; designing and manufacturing a conformal tool required by the machining of the large opening cover according to the specific structure and size of the large opening cover; clamping and fixing the large opening cover by adopting a conformal tool, and filling the gap between the large opening cover and the tool with solid paraffin so as to bond the large opening cover and the tool into a whole; and (5) performing finish machining on the large opening cover by adopting a five-axis numerical control machining center. The invention effectively controls and reduces the vibration and deformation of the large-size thin-wall part in the machining process, and obviously improves the profile and the size precision of the large opening cover.

Description

A precise machining method for complex thin-walled and variable-thickness large-mouth cover

technical field

The invention belongs to the technical field of machinery and sheet metal processing, and in particular relates to a precise processing method for a complex thin-walled and variable-thickness large opening cover.

Background technique

At present, in the field of aerospace, as various types of aircraft and projectiles have higher and higher requirements for maneuverability and load capacity, their structures also put forward higher requirements for light weight and high strength. More and more parts are used in the aerospace field, such as aircraft wings, fuselage panels, variable thickness skins, etc. However, due to the large size, thin wall, variable thickness and many other difficulties of this type of parts, the parts have obvious vibration and large deformation during processing, and the size and profile accuracy are not easy to guarantee, which has always plagued their large-scale applications in the aerospace field. Promote the application.

At present, in the manufacturing process of this type of parts, some features such as weight reduction cavity are first processed in a flat state, and then processed by traditional cold forming methods such as bending or circle. The wall thickness is thin, the parts are deformed greatly due to stress release during the machining process, the uniformity of the wall thickness cannot be guaranteed, and the forming surface precision is low, and the pass rate is low; some parts are first bent and formed, and then the five-axis CNC machining center is used. Machining the weight-reducing cavity and other related features, CNC machining is difficult, and the thin-walled parts cannot be closely fitted with the tooling due to deformation. During the processing, the vibration is obvious, the deformation is large, and the dimensional accuracy is not guaranteed, which seriously affects the progress of the model product.

SUMMARY OF THE INVENTION

The present invention is aimed at the problems of the existing complex thin-walled and variable-thickness large opening cover, due to its large size and thin wall thickness, obvious vibration and large deformation during the processing of the parts, and provides a complex thin-walled cover of this type. The precise processing method of the large-cap with variable thickness can effectively solve the problems of obvious vibration and large deformation of the large-cap with thin wall during the processing, and further improve the size and surface accuracy of the large-cap.

The precise processing method of the complex thin-walled and variable-thickness large mouth cover of the present invention includes: step 1, collecting original geometric parameters according to the specific structure of the large mouth cover, and then constructing a three-dimensional model of the large mouth cover by using three-dimensional modeling software, and analyzing the large mouth cover. It simulates flattening, and calculates the minimum blank size that can envelop the large-mouth cover according to the flattened parameters; step 2, design and manufacture the tooling concave-convex mold required for hot pressing according to the specific structure and size of the large-mouth cover; Step 3, adopt the method of mold clamping and hot pressing to make the rough embryo of the large mouth cover; Step 4, use the chemical milling method to corrode and process the weight-reducing cavity on the inner profile of the rough cover of the large mouth cover; Step 5, according to the specific structure of the large mouth cover and size, design and manufacture the conformal tooling required for the machining of the large-mouth cover; Step 6, use the conformal tooling to fix the large-mouth cover, and fill the gap between the large-mouth cover and the tooling with solid paraffin to make it bond as a whole. ; Step 7. Use a five-axis CNC machining center to finish the large mouth cover.

Preferably, in the third step, according to the material and thickness of the parts, the temperature is controlled between 300 and 350°C during mold clamping and hot pressing, and the upper and lower mold clamping time is controlled within 30 minutes during hot pressing.

Preferably, in the fourth step, the parts of the large mouth cover are first cleaned and degreasing, and the inner and outer surfaces of the large mouth cover are coated with a peelable protective coating that can resist the action of the corrosive solution. After curing at room temperature, engraving is carried out. To determine the position and size of the weight-reduction cavity, peel off the protective paint applied to the part of the weight-reduction cavity, and then immerse the large-mouth cover parts in the corrosive solution to corrode the exposed surface of the weight-reduction cavity.

Preferably, in the sixth step, after the large-mouth cover and the conformal tooling are clamped, the solid paraffin is first softened by means of assisted heating by an electric baking gun, and then the softened paraffin is filled into the gap reserved between the large-mouth cover and the tooling, Fill the perimeter once, and after the paraffin solidifies at room temperature, glue the large opening cover and the conformal tooling together.

Preferably, in the seventh step, the UG8.0 three-dimensional numerical control machining module is used to perform finishing programming on the shape features of the large mouth cover, and a five-axis numerical control machining center is used to finish the large mouth cover to ensure the corresponding dimensional accuracy.

Preferably, the material of the large opening cover is a 5A06 aluminum alloy plate.

Preferably, the length, width, and thickness of the large mouth cover in the flattened state are 1600×750×3 mm, respectively.

Preferably, the large surface wall thickness of the large mouth cover is 3 mm, and the wall thickness of the weight-reducing cavity distributed on the inner profile surface is 1.5 mm.

The beneficial results of the present invention compared with the prior art are:

Faced with the problems of poor molding surface accuracy, obvious vibration and easy deformation during the processing of complex thin-walled and variable-thickness large-mouth caps, the invention can effectively control the vibration and deformation during the large-mouth cap processing, and improve the large-mouth cap's profile and size. precision.

First of all, the large-mouth cover is hot-pressed by the method of clamping and hot-pressing, which greatly improves the surface accuracy of the large-mouth cover compared with the traditional circular cold forming of sheet metal bending rings.

Secondly, the chemical milling method is used to corrode and process the features such as the weight-reducing cavity distributed on the inner profile of the large-mouth cover. Compared with the traditional CNC milling method, it effectively solves the problem of the large-sized sheet due to stress release during the processing. The problems of warping deformation and uneven wall thickness effectively ensure the uniformity of the wall thickness of the weight-reducing cavity and reduce the deformation of the large mouth cover.

Then, a conformal tooling is used to fix and clamp the large-mouth cover, and the heated and softened paraffin is filled into the gap reserved between the large-mouthed cover and the conformal tooling. After the paraffin is cured at room temperature, the large-mouth cover and the conformal tooling are bonded. As a whole, it effectively solves the problem of obvious vibration of the large mouth cover during the five-axis CNC machining process.

Finally, according to the requirements of the design drawings, a five-axis CNC machining center is used to finish the large mouth cover, which greatly improves the dimensional accuracy of the large mouth cover.

Description of drawings

FIG. 1 is a schematic diagram of the structure of a complex thin-walled and variable-thickness large-mouth cover.

FIG. 2 is a schematic diagram of the flattening structure of a complex thin-walled and variable-thickness large-mouth cover.

Figure 3 is a schematic diagram of the structure of a concave-convex die for large-mouth lid clamping and hot-pressing.

Figure 4 is a schematic diagram of using solid paraffin to bond the large mouth cover and the conformal tooling.

FIG. 5 is a schematic diagram of the five-axis machining clamping and fixing structure of the large mouth cover.

Detailed ways

The selected test part in the present invention is a large mouth cover of a certain type of aircraft lap joint. The material of this part is 5A06 aluminum alloy plate, and the product structure is a large thin-walled variable-thickness part with a complex inner cavity. The wall thickness of the large surface of the large mouth cover is 3mm, and the length, width and thickness of the flat state are 1600×750×3mm respectively, as shown in Figure 1 and Figure 2. The specific implementation is as follows:

(1) Collect the geometric parameters of the original large mouth cover, use the UG8.0 3D modeling software to build the 3D model of the large mouth cover, and simulate and flatten it, and then calculate the shape that can wrap the part according to the flattened parameters. Minimum blank size.

Principle: According to the specific structure and size of the large mouth cover, as well as the characteristics of flat sheet metal bending and circle, a series of geometric parameters such as reasonable plate elongation and compensation coefficient are selected, and the perimeter of the central axis of the large mouth cover is reasonably calculated. Then use the UG sheet metal module to expand the 3D model of the big mouth cover to its state under the flat plate, and calculate the minimum blank size.

(2) The large mouth cover is hot-pressed by the process of mold clamping and hot-pressing.

According to the specific structure and size of the large mouth cover, design and manufacture the tooling molds required for hot pressing, including upper and lower molds (ie, concave mold and punch), and then use the method of clamping and hot pressing to hot press the large mouth cover. And in order to prevent the large mouth cover from being displaced during the mold clamping and hot pressing process, it is necessary to process positioning pins and positioning holes on the mold and the large mouth cover in advance, as shown in Figure 3.

Key points: Pay attention to the temperature control during mold clamping and hot pressing. According to the material and thickness of the parts, the temperature of the test furnace is controlled between 300 and 350 °C, and the clamping time of the upper and lower molds during hot pressing is controlled at about 30min.

(3) The chemical milling method is used to corrode and process the features such as the weight-reducing cavity on the inner profile of the large mouth cover.

First, clean and degrease the parts of the large-mouth cap, and coat the inner and outer surfaces with a peelable protective coating that can resist the action of corrosive solutions. After curing at room temperature, engraving is carried out. According to the position and size of the weight-reducing cavity on the inner surface of the large-mouth cap , peel off the protective paint coated on the weight-reducing cavity, and then immerse the large-mouth cover parts in the corrosive solution to etch the exposed surface of the weight-reducing cavity.

Key points: It is necessary to select the appropriate corrosion solution and protective coating according to the material of the parts. The corrosion solution in this test is an alkaline corrosion solution with sodium hydroxide as the main component, and the peelable protective coating is selected from neoprene, butyl rubber, poly It is prepared from vinyl chloride, etc. By adjusting the composition, concentration, working temperature and immersion time of the corrosion solution to control the processing depth, speed and surface quality after processing, the unidirectional corrosion processing rate in this test is controlled at about 30 μm/min.

(4) Use conformal tooling clamps to fix the large mouth cover, and fill the gap between the large mouth cover and the tooling with solid paraffin to bond them together.

According to the specific structure and size of the large-mouth cover, design and manufacture the conformal tooling required for the machining of the large-mouth cover, and after the large-mouth cover and the conformal tooling are clamped, the solid paraffin is softened by auxiliary heating with an electric baking gun, and then Fill the softened paraffin into the space reserved between the large mouth cover and the tooling, and fill the circumference. After the paraffin is cured at room temperature, the large mouth cover and the conformal tooling are bonded together, as shown in Figure 4.

Key point: First, put the large mouth cover on the outer surface of the conformal tooling. Due to the large size and thin wall thickness of the large mouth cover, there is a certain deformation between its actual and theoretical surfaces, so the large mouth cover and the conformal tooling cannot be completely fitted , heat the solid paraffin with the aid of an electric roasting gun, then fill the softened paraffin into a groove reserved on the tooling, and wait for the paraffin to solidify at room temperature, that is, the large mouth cover and the conformal tooling are tightly bonded into one, and finally used The pressure plate matched with the conformal tooling presses and fixes the large mouth cover tightly.

(5) Using a five-axis CNC machining center to finish the large mouth cover.

Using the UG8.0 3D CNC machining module, the shape features of the large mouth cover are finished and programmed, and the five-axis CNC machining center is used to finish the large mouth cover to ensure the corresponding dimensional accuracy, as shown in Figure 5.

The precise processing method of the large-scale complex thin-walled variable-thickness large-mouth cap provided by the invention can effectively ensure the uniformity of the wall thickness of the large-mouth cap and improve the dimensional accuracy and profile accuracy of the large-mouth cap. At present, the method of the present invention has been applied to solve practical problems in actual production, and has a strong application prospect.

Claims (8)

1. The precise machining method of the complex thin-wall variable-thickness large opening cover is characterized by comprising the following steps of:

acquiring original geometric parameters according to a specific structure of a required large opening cover, constructing a three-dimensional model of the large opening cover by using three-dimensional modeling software, performing simulated flattening on the three-dimensional model, and calculating the minimum blank size capable of enveloping the large opening cover according to parameters after flattening;

designing and manufacturing a concave-convex die of a tool required by hot press molding according to the specific structure and size of the large opening cover;

thirdly, manufacturing a large-opening-cover rough blank by adopting a die-closing hot-press molding method, wherein positioning pins and positioning holes are processed on the die and the large-opening cover in advance in order to prevent the large-opening cover from displacing in the die-closing hot-press process;

corroding and processing a weight reduction cavity on the inner molded surface of the large-opening-cover coarse blank by adopting a chemical milling method;

designing and manufacturing a conformal tool required by the machining of the large opening cover according to the specific structure and size of the large opening cover;

step six, reserving a circle of groove on the tool, clamping and fixing the large opening cover by adopting a conformal tool, filling a gap between the large opening cover and the tool with solid paraffin, and filling a circle of gap to bond the large opening cover and the tool into a whole;

and seventhly, performing finish machining on the large opening cover by adopting a five-axis numerical control machining center.

2. The method for precisely processing the complex thin-wall cover with the variable thickness and the large opening cover according to claim 1, wherein the method comprises the following steps: and in the third step, according to the material and the thickness of the part, controlling the temperature to be 300-350 ℃ during die assembly and hot pressing, and controlling the die assembly time of an upper die and a lower die to be 30min during hot pressing.

3. The method for precisely processing the complex thin-wall cover with the variable thickness and the large opening cover according to claim 1, wherein the method comprises the following steps: and in the fourth step, cleaning and removing oil from the large opening cover part, coating strippable protective paint capable of resisting the action of corrosive solution on the inner surface and the outer surface of the large opening cover part, carving the large opening cover part after curing at room temperature, stripping the protective paint at the position of the weight-reducing cavity according to the position and the size of the weight-reducing cavity on the inner molded surface of the large opening cover part, immersing the large opening cover part in the corrosive solution, and corroding the surface of the exposed weight-reducing cavity.

4. The method for precisely processing the complex thin-wall cover with the variable thickness and the large opening cover according to claim 1, wherein the method comprises the following steps: and sixthly, after the large opening cover and the conformal tool are clamped, softening the solid paraffin in an electric baking gun auxiliary heating mode, filling the softened paraffin into a reserved gap between the large opening cover and the tool, filling a circle of the gap, and bonding the large opening cover and the conformal tool into a whole after the paraffin is solidified at room temperature.

5. The method for precisely processing the complex thin-wall cover with the variable thickness and the large opening cover according to claim 1, wherein the method comprises the following steps: and seventhly, performing finish machining programming on the appearance characteristics of the large opening cover by using a UG8.0 three-dimensional numerical control machining module, and performing finish machining on the large opening cover by using a five-axis numerical control machining center.

6. The method for precisely processing the complex thin-wall cover with the variable thickness and the large opening cover according to claim 1, wherein the method comprises the following steps: the material of big flap is 5A06 aluminum alloy plate.

7. The precise processing method of the complex thin-wall variable-thickness large opening cover according to any one of claims 1 to 6, characterized in that: the length, width and thickness of the large opening cover in a flattened state are 1600 multiplied by 750 multiplied by 3 mm.

8. The precise processing method of the complex thin-wall variable-thickness large opening cover according to any one of claims 1 to 6, characterized in that: the wall thickness of the large surface of the large opening cover is 3mm, and the wall thickness of the weight reducing cavity distributed on the inner molded surface is 1.5 mm.

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