Weak-rigid double-interface bevel thread machining method

Abstract

The invention discloses a weak-rigidity double-interface bevel thread machining method, and relates to the field of composite material structure product machining, and the weak-rigidity double-interface bevel thread machining method comprises the steps that a bottom hole of a threaded hole is machined, and the bottom hole penetrates through a heat-proof layer from the surface of the heat-proof layer and extends into a force bearing structure; strengthening the bottom hole at the position of the heat-proof layer; and threaded hole machining is conducted, the area, facing the heat-proof layer by 0.5-1.0 mm, of the boundary of the heat-proof layer and the force-bearing structure serves as a process control area, and when the heat-proof layer is machined to the process control area, the machining cutting depth parameter is reduced. The control problem of the double-interface thread machining state of the outer heat-proof layer and the inner force-bearing structure in the heat-proof structure is solved.

Description

Technical Field

[0001] The invention belongs to a processing technology after composite molding of heat-proof material and metal structure or honeycomb sandwich structure, and is applied to the research and development of composite material structure products. Background Art

[0002] With the continuous development of spacecraft Earth return and re-entry or other planetary entry exploration technology, efficient thermal protection technology plays a key role. The thermal protection structure is generally formed by bonding the thermal protection layer and the load-bearing structure, and the thermal protection structure is connected to the outside through a mechanical interface for installation.

[0003] Heat-resistant structural products involve a large number of installation and connection threaded holes for external connections, involving various forms, including threaded holes, straight through holes or blind holes at the end of the outer heat-resistant layer, threaded holes, straight through holes or blind holes on the inner load-bearing structure, and threaded holes, straight through holes or blind holes that penetrate the double interfaces of the heat-resistant layer and the load-bearing structure. The processing of connection holes of the same material belongs to conventional processing. For the processing of double-interface connection holes that penetrate the heat protection layer and the load-bearing structure of different materials, the mechanical strength difference from the outer heat protection layer to the inner load-bearing structure (generally a metal structure, a honeycomb sandwich structure or a laminated structure, etc.) is large. At the same time, there are inclined thread connection holes with materials in the conical and other special-shaped structures of the heat protection structure, resulting in weak-rigid double-interface inclined threads and variable thread wall thickness in the heat protection structure. It is very easy for the stiffness to change and cause the machining tool to chatter, affecting the coaxiality of the double-interface threads and the thread size accuracy deviation. At the same time, the chattering of the interface stiffness change during the machining process, the machining backing off, and the tapping or tapping through the hole are all likely to cause the outer heat protection layer to become thicker, the thread to become thinner, or the tip to be damaged, etc., affecting the external connection accuracy of the final heat protection structure thread interface, the installation accuracy of the screw plug, the adaptation accuracy of the entire cabin structure, and the reassembly matching accuracy of repeated disassembly and assembly. Summary of the invention

[0004] The technical problem solved by the present application is: to overcome the deficiencies of the prior art, to provide a weak-rigid double-interface bevel thread processing method, and to solve the problem of controlling the processing state of the double-interface thread of the outer heat-proof layer and the inner load-bearing structure in the heat-proof structure.

[0005] The technical solutions provided by this application are as follows:

[0006] A weak-rigid dual-interface inclined surface thread processing method is used for processing threaded holes on a load-bearing structure with a heat-proof layer on the surface, comprising:

[0007] Processing the bottom hole of the threaded hole, the bottom hole starts from the surface of the heat-proof layer, penetrates the heat-proof layer and extends into the load-bearing structure;

[0008] Strengthen the bottom hole at the heat protection layer;

[0009] When processing threaded holes, the area 0.5 to 1.0 mm from the interface between the heat-proof layer and the load-bearing structure facing the heat-proof layer is used as the process control area. When the heat-proof layer is processed to the process control area, the processing cutting depth parameter is reduced.

[0010] When processing the bottom hole of the threaded hole, a carbide cutter head is used, the processing speed is 2000-5500 r / min, the processing cutting depth is 0.5-1.5 mm, and the processing step distance is 0.5-1.2 mm.

[0011] The strengthening treatment of the bottom hole at the heat protection layer position includes: using an organic resin or an adhesive as a strengthening medium, brushing or spraying the strengthening medium onto the surface of the bottom hole and hardening it.

[0012] During the threaded hole processing, when processing the threaded holes at the heat protection layer position, the processing tool adopts a diamond grinding head or a carbide milling cutter; when processing the threaded holes at the load-bearing structure position, the processing tool adopts a carbide milling cutter, a high-speed steel milling cutter or a PCD milling cutter.

[0013] When the threaded hole is processed, the processing tool is withdrawn in the process control area, and the processing tool for the load-bearing structure part is switched.

[0014] When the threaded hole is processed, the processing parameters of the heat protection layer position are: processing speed is 2000-6000r / min, processing cutting depth is 0.3-0.5mm, and processing step distance is 0.1-0.5mm.

[0015] When the threaded hole is processed, the processing parameters at the process control area are: the processing cutting depth is 0.1-0.2 mm.

[0016] In summary, this application at least includes the following beneficial technical effects:

[0017] The present invention is based on the technical difficulties and requirements in the double-interface bevel thread forming process between two materials with large stiffness differences of a special-shaped high-efficiency heat-proof structure, which is formed by a composite of a heat-proof layer with relatively weak outer strength (fiber-reinforced heat-proof functional resin-based material) and a load-bearing structure with relatively strong inner strength (metal structure, honeycomb sandwich structure or laminated structure, etc.), and describes a heat-proof structure weak-rigid double-interface bevel thread processing control technology. In view of the material characteristics and processing characteristics of this type of heat-proof structure, the traditional method of using a set of processing parameters for one-piece homogeneous materials or structures is not applicable, and it is easy for the tool to chatter in the areas of different rigidity materials or structural attachments, causing micro-deviations and micro-vibrations in the tool movement, resulting in different problems such as thread accuracy deviations or damage to the thread teeth near the interface of the weak rigid thread, or damage to the thin part or tip of the variable wall thickness thread, or damage to the interface connection adhesive layer, causing problems in the subsequent external connection of the heat-proof structure, and failing to meet the requirements of engineering applications. Therefore, ensuring the thread forming accuracy and thread processing quality during the processing of the double-interface bevel thread of the heat-proof structure is a technical difficulty of the present invention.

[0018] The technical solution of the present invention is represented by a heat-proof structure obtained by combining an outer heat-proof layer and an inner load-bearing structure, and a method for processing weak-rigid double-interface bevel threads of a heat-proof structure is proposed. The principle is to use two processing parameter switching methods during the thread processing process according to the different processing characteristics of the two materials. At the same time, the variable thickness thread wall of the heat-proof layer at the weak rigid end is strengthened to improve the dimensional strength and anti-destruction ability of the bevel thread during the processing and subsequent use, and to improve the processing quality of the double-interface bevel thread connection holes of the heat-proof structure, the connection accuracy during subsequent installation and use, and the dimensional quality of maintenance and repair.

[0019] The present invention is a method for processing weak-rigid dual-interface bevel threads in heat-resistant structures. Different from the single-material thread processing method, the present invention formulates two processing parameters for two materials and switches the parameters at the dual interfaces, ensuring the smooth transition of tool parameters at the interface during thread processing, reducing tool chatter and processing accuracy deviation near the interface, improving the processing quality, installation accuracy and reinstallation accuracy of the heat-resistant structure, and simultaneously completing the bevel thread strengthening during the processing to ensure the dimensional strength and reusability of the threaded connection hole for subsequent connection, installation and repair. The invention is suitable for thread processing of two material media, effectively improving the processing control accuracy and stability of the heat-resistant structure, reducing the technical risk of damage to the dual-interface bevel thread processing, stable process control, strong feasibility, and a wide range of applications. It has strong applicability and great engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1Schematic diagram of the processing principle of the present invention, wherein (1) is a schematic diagram of the double-interface threaded area, (2) is a schematic diagram after bottom hole processing, (3) is a schematic diagram of heat-resistant layer hardening and tool switching, and (4) is a schematic diagram after processing is completed.

[0021] Explanation of the accompanying drawings: 1. Heat protection layer; 2. Load-bearing structure; 3. Bottom hole; 4. Process control area. DETAILED DESCRIPTION

[0022] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments disclosed in the present invention will be further described in detail below with reference to the accompanying drawings.

[0023] The present application embodiment discloses a weak-rigid dual-interface bevel thread processing method, such as Figure 1 As shown, the following steps are included:

[0024] Step 1: The heat-proof structure is formed by a composite of a relatively weak outer heat-proof layer 1 (fiber-reinforced heat-proof functional resin-based material) and a strong inner load-bearing structure 2 (metal structure, honeycomb sandwich structure or laminated structure, etc.). The heat-proof structure is generally a plane, a curved surface, or a rotating body. The threaded holes, straight holes, or blind holes that penetrate the heat-proof layer and the load-bearing structure in the heat-proof structure are processed, and the process area of ​​the heat-proof structure workpiece is clamped. It is strictly forbidden to contact the product area and there is no clamping indentation on the material surface;

[0025] Step 2: The inclined thread processing control adopts a processing method of changing two processing parameters with two material media, wherein the inclined thread processing refers to the state that the surface of the threaded hole to be processed and the surface of the heat protection layer 1 are not non-vertical. According to the traditional method of thread processing: first process the bottom hole 3, and then process the forming thread. First, different processing tools are selected according to the two materials of the heat protection structure. The tool for the weak rigid heat protection material generally adopts a diamond grinding head or a carbide milling cutter, etc. The tool used for the load-bearing structure with strong rigidity is a carbide milling cutter, a high-speed steel milling cutter or a PCD milling cutter, etc.;

[0026] Step 3: In the thread bottom hole processing stage, the product size is not involved. One tool and one processing parameter are used. A carbide cutter head is selected. The processing speed is 2000-5500r / min, the processing depth is 0.5-1.5mm, and the processing step is 0.5-1.2mm. The processing parameters are adjusted and selected according to the different product process allowances;

[0027] Step 4: After the bottom hole processing is completed, the bottom hole of the heat-resistant layer of the heat-resistant structure is strengthened: the strengthening treatment uses organic resin or adhesive as the strengthening medium, and according to the viscosity or processability of the selected resin or adhesive, it is manually brushed or sprayed (brushed or sprayed 2 to 5 times along the circumference of the bottom hole size), and the hardening conditions are based on the curing mechanism of the selected resin or adhesive. The corresponding room temperature hardening conditions (25°C) or high temperature hardening methods (<150°C);

[0028] Step 5: After the heat-resistant layer of the heat-resistant structure is strengthened, the thread processing is carried out. According to the inclined thread structure of the heat-resistant structure product, the thread section of the heat-resistant layer (L F ) and the thread of the load-bearing structure thread section (L c ), in the thread section of the heat protection layer (L F ) and the thread of the load-bearing structure thread section (L c ) between the heat protection layer end and the interface, the area of ​​0.5 to 1.0 mm is set as process control area 4;

[0029] Step 6: During the thread processing, when processing the heat-resistant layer end of the heat-resistant structure, a diamond grinding head is selected, the processing speed is 2000-6000r / min, the processing cutting depth is 0.3-0.5mm, and the processing step is 0.1-0.5mm. When the heat-resistant layer is processed to the process control area, the processing cutting depth parameter is reduced to 0.1-0.2mm, and the tool movement process in the process control area is observed and confirmed. When the tool begins to contact the load-bearing structure, the processing is stopped, and the tool is switched to perform thread processing at the load-bearing structure end;

[0030] Step 7: When processing the load-bearing structure end of the heat-resistant structure, exit the processing tool in the process control area, switch the processing tool for the load-bearing structure end, select a carbide milling cutter, 3500-7000r / min, the processing depth is 0.1-0.5mm, the processing step is 0.1-0.5mm, until the size is processed;

[0031] Step 8: Clean and remove excess debris, dust particles, and other waste materials during the processing at any time to avoid particles or chopped fibers adhering to the tool, causing long-term tool wear, tool overheating, and reduced cutting efficiency.

[0032] The following is to illustrate the application effect of the present invention.

[0033] According to the traditional processing method, this type of weak-rigid double-interface thread including a heat-proof layer-metal structure is traditionally processed using a carbide milling cutter, and no special tool change and process transition treatment with fine parameter control are performed in the interface bonding area. At the same time, the heat-proof material on the side with weaker rigidity is not strengthened during the processing, resulting in poor ability to resist the impact of tool speed on the bottom hole processing of the heat-proof layer of this type of double-interface thread completed by the traditional processing method and the influence of tool vibration caused by the interface transformation process. The thread tips and thin-walled parts with three-dimensional inclined surface gradients are extremely difficult to maintain and are easily damaged during the processing of feed or retract, resulting in a large deviation between the processing coaxial position accuracy and the metal structure. At the same time, the thread's own thread accuracy, thread size accuracy and strength all deviate, the thread quality is poor, the accuracy and damage of repeated disassembly and assembly are serious, and the service life is greatly reduced, which cannot meet the subsequent engineering application requirements of high-precision installation and repeated use of heat-proof screw plugs.

[0034] The specific comparison of threaded holes obtained by using the technical solution of the present invention and the traditional processing method is shown in Table 1.

[0035] Table 1 Effect of treatment by the method of the present invention

[0036]

[0037] The contents not described in detail in this application specification belong to the common knowledge of those skilled in the art.

[0038] The present application is described in detail above in conjunction with specific implementation methods and exemplary examples, but these descriptions cannot be understood as limiting the present application. Those skilled in the art understand that, without departing from the spirit and scope of the present application, a variety of equivalent replacements, modifications or improvements can be made to the technical solution of the present application and its implementation methods, all of which fall within the scope of the present application. The scope of protection of the present application shall be subject to the attached claims.

Claims

1. A weak-rigid dual-interface inclined surface thread processing method, used for processing threaded holes on a load-bearing structure (2) with a heat-proof layer (1) on the surface, characterized in that: include: Processing a bottom hole (3) of the threaded hole, the bottom hole starting from the surface of the heat-proof layer (1), penetrating the heat-proof layer (1) and extending into the load-bearing structure (2); Strengthening the bottom hole at the location of the heat protection layer (1); The threaded hole is processed, and the area of ​​0.5 to 1.0 mm from the interface between the heat-proof layer (1) and the load-bearing structure (2) in the direction of the heat-proof layer (1) is used as the process control area (4). When the heat-proof layer (1) is processed to the process control area (4), the processing cutting depth parameter is reduced.

2. A weak-rigid dual-interface bevel thread processing method according to claim 1, characterized in that: When processing the bottom hole (3) of the threaded hole, a hard alloy cutter head is used, the processing speed is 2000-5500 r / min, the processing cutting depth is 0.5-1.5 mm, and the processing step distance is 0.5-1.2 mm.

3. A weak-rigid dual-interface bevel thread processing method according to claim 2, characterized in that: The strengthening treatment of the bottom hole at the position of the heat protection layer (1) comprises: using an organic resin or an adhesive as a strengthening medium, brushing or spraying the strengthening medium onto the surface of the bottom hole and hardening it.

4. A weak-rigid dual-interface bevel thread processing method according to claim 1, characterized in that: During the threaded hole processing, when processing the threaded hole at the position of the heat protection layer (1), the processing tool adopts a diamond grinding tool head or a carbide milling cutter; when processing the threaded hole at the position of the load-bearing structure (2), the processing tool adopts a carbide milling cutter, a high-speed steel milling cutter or a PCD milling cutter.

5. A weak-rigid dual-interface bevel thread machining method according to claim 4, characterized in that: When the threaded hole is processed, the processing tool is withdrawn in the process control area (4) and the processing tool is switched to the load-bearing structure (2).

6. A weak-rigid dual-interface bevel thread machining method according to claim 1, characterized in that: When the threaded hole is processed, the processing parameters of the heat protection layer (1) are: processing speed of 2000-6000 r / min, processing cutting depth of 0.3-0.5 mm, and processing step distance of 0.1-0.5 mm.

7. A weak-rigid dual-interface bevel thread machining method according to claim 6, characterized in that: When the threaded hole is processed, the processing parameters at the process control area (4) are: the processing cutting depth is 0.1-0.2 mm.

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