Precision machining method for hard foam concave cavity

Abstract

The invention relates to the technical field of hard foam, in particular to a hard foam concave cavity precision machining method which comprises the following steps that S1, foam and an anti-deformation metal plate are bonded; s2, a concave cavity is machined; s3, bonding a radiation sheet; and S4, the anti-deformation metal plate is milled and removed. The method for processing the hard foam concave cavity for placing the metal radiation sheet has the following advantages: 1) the size of the concave cavity is accurate and is not influenced by environmental temperature and humidity; 2) the method does not depend on enterprise turnover and scheduling capabilities; 3) the method does not depend on a drying oven and temperature control equipment;

Description

Technical Field

[0001] The present invention relates to the technical field of rigid foams, and particularly to a precise machining method for cavities in rigid foams. Background Art

[0002] Radiating sheets are mainly used for transmitting or receiving electromagnetic waves. They are usually thin and need to be supported by materials with low dielectric constants, such as PMI (polymethacrylimide) foam. PMI foam has a higher specific strength and specific modulus than traditional foams. It is a kind of so-called "rigid foam" and has good machining properties. The rigid foam mentioned in this article generally refers to foams with high strength and low dielectric constants including PMI foam.

[0003] Foams are divided into open-cell foams and closed-cell foams. However, even for closed-cell foams, there are inevitably certain defects. Some pores are not completely closed, and there may be some tiny channels, having a certain degree of water absorption. When the rigid foam absorbs water, its volume will increase; conversely, when the water volatilizes, its volume will decrease. In addition, the foam has a certain thermal expansion property, that is, it shrinks or expands with temperature changes.

[0004] For metal radiating sheets with larger sizes, the size of the supporting rigid foam is usually between 200 mm and 1000 mm. Due to water absorption or thermal expansion, the dimensional changes in the length and width directions of its cavity are about ±1 - 3 mm, and this change process can usually be completed within 2 hours after the cavity is machined by several milling operations. Once the cavity size changes, it will cause the radiating sheet to be unable to be placed or located, affecting subsequent assembly.

[0005] The accuracy of the position of the radiating sheet directly affects the subsequent welding quality of solder joints and the radiation pattern. Therefore, the cavity size must be strictly guaranteed. The existing methods generally are: 1) Bond the radiating sheet within a short time (usually not exceeding 2 hours) after the cavity is machined. However, since bonding is a harmful operation, it requires an independent site and is separated from other workstations, which requires a relatively high level of enterprise turnover and scheduling capabilities. 2) Put the workpiece into an oven to dry the moisture before machining the cavity and before bonding the radiating sheet, and machine and bond in a relatively stable ambient temperature, which requires the enterprise to configure an oven and temperature control equipment. Summary of the Invention

[0006] The purpose of the present invention is to provide a precise machining method for cavities in rigid foams, so as to solve the technical problem that in the prior art, the change in the cavity size will cause the radiating sheet to be unable to be placed or located, affecting subsequent assembly.

[0007] The present invention discloses a precise machining method for cavities in rigid foams, including the following steps:

[0008] Step S1: Bond the foam and the anti-deformation metal plate;

[0009] Step S2: Machine the cavity;

[0010] Step S3: Bond the radiation sheet.

[0011] Step S4: Milling to remove the anti-deformation metal plate.

[0012] Furthermore, the anti-deformation metal plate is made of aluminum alloy, copper alloy, steel plate or stainless steel plate.

[0013] The anti-deformation metal plate has good mechanical strength. It can resist the deformation of the foam caused by environmental temperature and humidity, and maintain the accuracy of the cavity size.

[0014] Furthermore, the yield strength of the anti-deformation metal plate is greater than 2 times the bonding strength of the epoxy adhesive, preferably greater than 3 times the bonding strength of the epoxy adhesive.

[0015] Furthermore, the thickness of the anti-deformation metal plate is 0.5 mm - 3 mm.

[0016] If it is less than 0.5 mm, the anti-deformation effect is poor. If it is greater than 3 mm, the machining amount of the metal plate is large when machining the cavity, which is likely to introduce machining stress and cause overall deformation of the metal plate and the hard foam.

[0017] Furthermore, the foam and the anti-deformation metal plate are connected by epoxy adhesive.

[0018] The bonding strength of the epoxy adhesive is generally above 30 MPa after complete curing.

[0019] Furthermore, in step S2, the cavity is machined with the cutter entering from the side of the anti-deformation metal plate. The cavity contour is consistent with the shape of the radiation sheet, and the fit tolerance is set as a small clearance fit.

[0020] Furthermore, the cavity depth is the sum of the designed cavity depth, the thickness of the anti-deformation metal plate, and the machining allowance on the foam surface.

[0021] Furthermore, in step S3, the radiation sheet is bonded in the cavity with epoxy adhesive and completely cured.

[0022] Furthermore, the curing is room temperature curing or heating curing.

[0023] Furthermore, for room temperature curing, the curing time is more than 48 hours; for heating curing, the temperature is 60 - 80 °C and the curing time is at least 2 hours.

[0024] Furthermore, during the curing process, it is necessary to make the anti-deformation metal plate and the hard foam fit tightly. It can be made to fit by using a C-clamp (a kind of clamping device), placing heavy objects to press, or using an air bag to evacuate the vacuum, etc.

[0025] Furthermore, when milling in step S4, the machining allowance of the foam around the anti-deformation metal plate is 2 mm.

[0026] A hard foam cavity is obtained by using the above method.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] The present invention provides a processing method for a hard foam cavity for placing a metal radiation sheet, which has the following advantages: 1) The cavity size is precise and not affected by environmental temperature and humidity; 2) It does not depend on the enterprise's turnover and scheduling capabilities; 3) It does not depend on ovens and temperature control equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0030] Figure 1 It is a three-dimensional structure diagram of the metal radiation sheet of the present invention.

[0031] Figure 2 It is a structure diagram of the deformation of the foam cavity of the present invention affected by temperature and humidity.

[0032] Figure 3 It is a structure diagram of the bonding of the foam and the anti-deformation metal plate of the present invention.

[0033] Figure 4 It is a three-dimensional structure diagram of the integral processing of the cavity of the foam and the anti-deformation metal plate of the present invention.

[0034] Figure 5 It is a three-dimensional structure diagram of the integral structure after bonding the metal radiation sheet of the present invention.

[0035] Figure 6 It is a three-dimensional structure diagram of the present invention after milling to remove the processing allowance of the anti-deformation metal plate and the foam.

[0036] In the above drawings, the meanings represented by each label are as follows: 1 - anti-deformation metal plate, 2 - foam, 3 - metal radiation sheet. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] To make the purpose, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention.

[0038] Embodiment 1

[0039] A precision machining method for hard foam cavities using the above device in this embodiment, the specific structure is as Figures 1 - 6 shown, including the following steps:

[0040] Step S1: Bond the foam to the anti-deformation metal plate, Step S2: Machine the cavity, Step S3: Bond the radiation sheet, Step S4: Milling to remove the anti-deformation metal plate.

[0041] Step S1: Bond the foam to the anti-deformation metal plate: The anti-deformation metal plate is made of metal materials such as aluminum alloy, copper alloy, steel plate, stainless steel plate, etc., and is required to have good mechanical strength. Bond the anti-deformation metal plate and the foam together with epoxy glue. The bonding strength of the epoxy glue is generally above 30 MPa after complete curing.

[0042] Step S2: Machine the cavity: After the epoxy glue is completely cured, machine the cavity from the side of the anti-deformation metal plate. The cavity contour is the same as the outer shape of the radiation sheet, and the fit tolerance is set as a small clearance fit. The cavity depth is the sum of the designed depth of the cavity, the thickness of the anti-deformation metal plate, and the machining allowance on the foam surface. After the cavity is machined, the anti-deformation metal plate can resist the deformation of the foam caused by environmental temperature and humidity, and maintain the accuracy of the cavity size.

[0043] Step S3: Bond the radiation sheet: Bond the radiation sheet in the cavity with epoxy glue and completely cure it.

[0044] Step S4: Milling to remove the anti-deformation metal plate: After the epoxy glue is completely cured, the radiation sheet is supported in the cavity. Remove the anti-deformation metal plate by milling. Since the anti-deformation metal plate and the foam are bonded with epoxy glue and the bonding strength is relatively large, about 1 mm or less of the shallow foam will inevitably be torn during the machining process. Therefore, a machining allowance of more than 2 mm is reserved on the foam surface and removed together during milling. Since the radiation sheet is supported in the cavity, the cavity can be kept from deforming after the anti-deformation metal plate is removed.

[0045] Comparative Example 1

[0046] As a comparative example of the present invention, this example discloses a precision machining method for hard foam cavities, including the following steps: Based on Example 1, the only change is that the thickness of the anti-deformation metal plate < 0.5 mm, and the anti-deformation ability of the metal plate is insufficient, and the machining size of the hard foam cavity is still out of tolerance.

[0047] Comparative Example 2

[0048] As a comparative example of the present invention, this example discloses a precision machining method for hard foam cavities. Based on Example 1, the only change is that the thickness of the anti-deformation metal plate > 3 mm, and machining stress is introduced when machining the cavity on the metal plate, resulting in the cavity size being out of tolerance.

[0049] Comparative Example 3

[0050] This example is a comparative example of the present invention, which discloses a precision machining method for hard foam cavities. The only change based on Example 1 is that the anti-deformation metal plate uses lead. Due to insufficient yield strength, it cannot offset the deformation stress of the hard foam and cannot improve the deformation.

[0051] Comparative Example 4

[0052] This example is a comparative example of the present invention, which discloses a precision machining method for hard foam cavities. The only change based on Example 1 is that the anti-deformation metal plate uses tin. Due to insufficient yield strength, it cannot offset the deformation stress of the hard foam and cannot improve the deformation.

[0053] Comparative Example 5

[0054] This example is a comparative example of the present invention, which discloses a precision machining method for hard foam cavities. The only change based on Example 1 is that epoxy glue is not used for bonding, and silicone rubber (with a bonding strength of only 2-5 MPa) is used. It cannot offset the deformation stress of the hard foam and cannot improve the deformation.

[0055] The above are the implementation manners listed in this embodiment. However, this embodiment is not limited to the above optional implementation manners. Those skilled in the art can obtain many other implementation manners by arbitrarily combining the above manners. Anyone can obtain other various forms of implementation manners under the inspiration of this embodiment. The above specific implementation manners should not be construed as limiting the protection scope of this embodiment. The protection scope of this embodiment should be defined by the claims, and the specification can be used to interpret the claims.

Claims

1. A precision machining method for hard foam cavities, characterized in that: It includes the following steps: Step S1: Bond the foam and the anti-deformation metal plate; Step S2: Machine the concave cavity; Step S3: Bond the radiation sheet; Step S4: Milling to remove the anti-deformation metal plate.

2. A precision machining method for a hard foam cavity according to claim 1, characterized in that: The anti-deformation metal plate is an aluminum alloy, a copper alloy, a steel plate or a stainless steel plate.

3. A precision machining method for a hard foam cavity according to claim 2, characterized in that: The foam and the anti-deformation metal plate are connected by epoxy glue.

4. A precision machining method for hard foam cavities according to claim 1, characterized in that: In step S2, the concave cavity is machined by feeding from the side of the anti-deformation metal plate, and the contour of the concave cavity is consistent with the outer shape of the radiation sheet, and the fit tolerance is set as a small clearance fit.

5. A precision machining method for a hard foam cavity according to claim 1, characterized in that: The depth of the concave cavity is the sum of the designed depth of the concave cavity, the thickness of the anti-deformation metal plate and the machining allowance on the surface of the foam.

6. The precision machining method for a hard foam cavity according to claim 1, characterized in that: In step S3, the radiation sheet is bonded in the concave cavity with epoxy glue and completely cured.

7. A precision machining method for a hard foam cavity according to claim 6, characterized in that: The curing is normal temperature curing or temperature-rising curing.

8. A precision machining method for a hard foam cavity according to claim 7, characterized in that: For normal temperature curing, the curing time is more than 48 hours; for temperature-rising curing, the temperature is 60-80 °C and the curing time is at least 2 hours.

9. A precision machining method for hard foam cavities according to claim 1, characterized in that: When milling in step S4, the machining allowance of the foam around the anti-deformation metal plate is 2 mm.

10. A hard foam cavity, characterized in that: It is obtained by using the precision machining method for hard foam concave cavity according to any one of claims 1-9.

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