1 The problem and its cause analysis Our company has appeared self-acting many times in the assembly process of a certain part of the aircraft.
In response to this problem, the combination of the bolt HB 8252-M6X1 was first selected for research.
The clamping is not clamped when the tightening torque of the bolt and nut has reached the standard value of 6 N.m. After that, the bolts and nuts are tested separately. Firstly, the bolt head and tail of the bolt HB and the technical procedure are tested, and the bolt is considered to meet the standard. Then, the nut HB1 was measured with a thread plug gauge. It was found that the nut's pre-plated dimensional tolerance band was the same as the post-plated dimensional tolerance band, which was 4H5H. If the thickness of the 5ym8ym (single-sided) coating was added, the nut was out of tolerance.
The problem was initially identified because the relationship between the tolerance band of the bolt and the nut thread and the thickness of the coating was not well controlled, causing interference between the bolt and the nut during assembly, and a part of the tightening force of the force wrench was offset by friction.
Liao Liping (Shenyang Aircraft Industry (Group) Co., Ltd., Shenyang, Liaoning, through the use of standard parts such as fasteners, pipe joints, etc. for ordinary threaded parts, M-threaded parts, etc. The problems that arise are analyzed to find out the problem and further study on the relationship between the pre-plated dimensions of the plated screw and the thickness of the coating.
Thread; standard parts: pre-plated size; plating; assembly analysis. In the case of not considering the dimensional tolerance band before plating, according to the limit size specification of GB3.2A-2003M threaded bolts and nuts, the diameter of the internal thread is (5.445max, 5.350min); GB/T15756-1995 China Machinery Industry Standards Compilation A threaded coil specifies the diameter of the external thread to be (5.350max, 5.279min). If the inner and outer threads are manufactured according to the minimum and maximum deviation, interference must occur after plating.
1The combination thread type is different, the nut is M thread, the root part is arc-shaped, which plays the role of strengthening; the bolt is the common screw worm Z00Z type 绺 迪 迪 射 ​​I table 1 internal and external thread tolerance fit and coating thickness test No. Standard part name Standard part number Thread size diameter X pitch inner and outer thread plating front tolerance tolerance plating material plating thickness (um) 1M thread small hexagonal groove nut HB angle groove type thick nut HB angle groove type thin nut HB angle thin Nut HB angle groove type thin nut HB female HB because the thickness of the plating on the threaded joint is not uniform, the thread head and root are thicker than the middle plating, the larger the length to diameter ratio, the greater the difference in coating thickness, so The possibility of interference is also greater.
After analysis, it is concluded that the main reason for the interference during the assembly of bolts and nuts is that the thread tolerance of the nut before plating is unreasonable and the thickness of the coating is contradictory.
2 Problem Solving The standard parts materials for aircraft produced by aviation companies are generally divided into two categories. One type is non-surface plating fasteners (such as aluminum, stainless steel, etc.), and the other type is surface-plated fasteners (such as: 3.3A2003M thread common standard, the limit size does not indicate the plating thread before plating The relationship between dimensional tolerance and coating thickness, however, it is very important for the standard parts manufacturer to clarify this relationship. To this end, we conducted special research to make up for the gap in our company's pre-plated dimensional standards for threaded parts. .
According to the problem, the self-made fasteners were trial-produced according to the relationship between the pre-plated dimensional tolerance band and the coating thickness of foreign fasteners, and compared with foreign fasteners. The conclusion is: the tolerance of the foreign bolts and nuts after finished products. When the belts are h and H respectively, the tolerance bands before bolting and nut plating are e and E, and the matching clearance is relatively large, and there is no stuck phenomenon after screwing, and the fit is good.
In combination with the company's actual situation and better implementation of GB/T197-2003 common thread tolerance regulations, we choose the tolerance band before bolting and nut plating to g, G, also ensure the thread pair fit, so that the threaded fastener connection is more Reliable, at the same time also has good anti-tripping characteristics, to ensure sufficient thread contact height between the internal and external threads, reasonable assembly clearance, therefore, we have chosen a tolerance band that is closer to the national standard. Usually the external thread has three kinds of tolerance zone positions: g, f, e, and the internal thread has two kinds of tolerance zone positions: H, G. The coordination relationship generally takes the priority of H/g, H/h, G/h.
1-217-95 bolt, screw and screw technical conditions, HB6443-90 nut special technical conditions, GB 3.1A-2003M thread general requirements: for pipe joints, the internal thread plating thickness is 6 melon 9 melon, The outer thread plating thickness is 9 melons and 12 melons.
For fasteners, the thickness of the thread coating is related to the pitch and the position of the thread tolerance band: <0.8, the thickness of the coating is about 3um5um; when the pitch is P1.5, the thickness of the coating is about 18 different sizes for testing the above theory. Tests of fasteners of different specifications and materials (see Table 1).
Continued Table 1 (End) No. Standard Parts Name Standard Part No. Thread Size Diameter X Pitch Internal and External Threading Pre-Tag Tolerance Plated Tolerance Material Coated Hexagon Head Bolt HB Table 2 Internal Thread Recommended Tolerance Tolerance Accuracy Tolerance Belt Position G Tolerance Band Position HSNLSNL Precision 1 - 4H5H6H Medium (5G) 6G (7G) 5H 晟 7H Rough one (7G) (8G) - 7H8H Note: S - short twist length; N - medium twist length; L long stitch length .
The priority order of the tolerance band is: bold tolerance band, general font tolerance band, and bracket tolerance band.
The bold tolerances of the belt are used for mass produced fastener threads.
Table 3 Recommended tolerances for external threads with tolerance accuracy tolerances with position e tolerance zone position f tolerance zone position g tolerance zone position h precision one medium one rough one note: S - short rotation length; N - medium rotation length; L one Long twist length.
The priority order of the tolerance band is: bold tolerance band, general font tolerance band, and bracket tolerance band.
The bold tolerances of the belt are used for mass produced fastener threads.
(Continued on page 51) Continued Table 1 (End) ISO/IEC11577: 1995 Information Technology Open System Interconnection Network Layer Security Protocol ISO17799 Information Security Management Practice Code Conformance Test Standard ISO/IEC10373 Identification Card Test Method ISO/IEC10373. 7 Identification card test method Proximity card ISO/IEC18047 Information technology Radio frequency identification equipment conformance test method ISO/IEC18047.3 Part 3 13.56MHz air interface communication test method ISO/IEC18047.4 Part 4 2.45MHz air interface communication test method ISO/IEC18047.7 Part 7 433MHz Air Interface Communication Test Method ISO/IECPRFTR18046 Information Technology Automatic Identification and Data Acquisition Technology Electronic Label Device Performance Test Method Application Standard ISO/AWI10374 Freight Container Automatic Identification ISO/DIS14814 Road Transportation and Traffic Telematics Automatic Vehicle and Equipment Identification Architecture and Terminology ISO/DIS14816 Road Transportation and Traffic Telematics Automatic Vehicle and Equipment Identification Code and Data Structure ISO/TS17261 Automatic Vehicle and Equipment Identification Combined Transportation of Goods Delivery Architecture and Terminology ISO/TS17262 Automatic Vehicles and Equipment Identification of cargo transport codes and data knots for joint transport Radio Frequency Identification (RFID) technology ISO/IEC18000: 2004 information technology automatic identification and number theory and application. Beijing: Electronic Industry Press, 2005. According to acquisition technology. The editing process (edited by Laobian) (continued on page 46) is fully automated and is very easy to exchange data with aircraft operators and suppliers. In addition, its distribution form (such as the electronic manual for CD-ROM) has excellent features such as portability, small storage space, fast access and low cost.
At present, domestic users have already presented a strong demand for digital technology publications. It is imperative to develop a system for the publication of aircraft digital technology based on a single data source technology. The ATA2200 specification has far-reaching international influence and detailed content. Strong applicability will inevitably become an important basis for the digitization of aircraft technology publications in China. k (edit: Yuqing) locust zooz type joint 呤 and 呤 '' brother bookmark1 (continued on page 36) through the assembly of any combination of the above test pieces have not found interference, and the mechanical properties are unchanged, fully meet the standard requirements When the tolerance bands of the self-made bolts and nuts are h and H respectively, the tolerance bands before bolting and nut plating are g, G. We have not found the tightening or interference phenomenon in the assembly test, and the one-time assembly is qualified. . Threaded tolerance band before plating (only for thin coated threads) Scope of application Recommended in Table 2 and Table 3. 3 It is recommended to use the same standard tooth type when bolts and nuts are matched. If the bolts are M thread Then, the nut also uses M thread; if the bolt uses ordinary thread, the nut also uses ordinary thread to reduce the probability of interference. k
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