Research and innovative design on the standardization of elliptical tenon joint? Ye Yujing 1 Xu Wei 1 Huang qiongtao 2 Chen Changhua 3 Tang Xianliang 4
(1. School of home furnishing and industrial design, Nanjing Forestry University, Nanjing 210037, 2. Yihua Life Technology Co., Ltd., Shantou 515834, 3. Jiangsu youzun home furnishing Manufacturing Co., Ltd., Yancheng 224000, 4. Yuhuan Innovation Service Center for mass creative talents, Yuhuan 317605)
Abstract: Based on the existing solid wood furniture components elliptical tenon joint form, the evaluation and innovative design are carried out. According to the standardization principle of furniture products, a kind of "step type" oval tenon is designed, and its manufacturing technology and joint method are explored. The results show that the stepped elliptical tenon has the advantages of high machining efficiency and low machining cost.
Key words: Oval tenon; standardization; tenon structure; solid wood furniture
Tenon joint is one of many joint methods of solid wood furniture components. The corresponding components of tenon joint furniture must have tenon and mortise. As an improved type of tenon, oval tenon overcomes the defects such as rough surface of tenon wall, low production efficiency and high labor intensity of workers. Its strength is similar to that of tenon. It is machined and suitable for large-scale production. It is widely used in modern solid wood furniture [1-6]. There are many kinds of solid wood furniture components, the size and specification of tenon structure are complex, the processing process is complex, and the tenon structure of different sizes is identified, which is easy to be reworked and consumes a lot of production time, reducing the production efficiency of the enterprise [7]. The standardized design of wood furniture tenon interface aims to solve the processing inconvenience caused by various types of tenon structure, effectively reduce the number of parts, poor interchangeability and other problems.
Based on the size and specification of tenon structure, the author optimizes the design of elliptical tenon interface on the premise of meeting the needs of product modeling and reasonable process, improves the repetition rate of parts, strengthens the universality, and then improves the standardization degree of tenon interface [8-9].
1. Standardization of mortise and tenon interface 1.1 furniture standardization is to implement furniture production, inspection, sales and other links according to furniture standards [10]. Furniture standardization plays a significant role in rational utilization of various resources, saving raw materials, improving product quality, reducing production costs and improving labor production efficiency. Domestic furniture standardization is reflected in five aspects: raw material standardization, product design standardization, parts standardization, production link standardization and operation standardization [11]. Furniture standardization enables furniture enterprises to adapt to the production mode of small batch and multiple types, and make rapid response to market changes to adapt to the changes of consumer demand. Product design standardization is related to the whole production and even sales process, and it is the source of furniture design standardization. The quality of product design determines whether the production process and assembly process are efficient and convenient.
Solid wood furniture is in the transition stage from frame structure to "component + interface" standardized structure. To standardize the components of solid wood furniture, it is necessary to standardize and modularize the size and interface form of mortise and tenon, and the core of the standardization of solid wood furniture is to realize the interface standardization [12-14]. As a widely used form of mortise and tenon in the production of modern solid wood furniture, the standardized design is particularly important.
1.2 the necessity of standardization of mortise and tenon interface there are many ways to classify mortise and tenon interface. According to the relationship between mortise and parts, mortise and tenon can be divided into integral mortise, split mortise and compound mortise, and elliptical mortise is one of integral mortise and tenon. Compared with mortise and tenon, elliptical tenon has a higher degree of standardization, but there are many sizes of mortise and tenon and specification of cutter. It is necessary to adjust the machine several times to process different sizes of tenon structure. It is necessary to further optimize the design, and constantly improve the degree of standardization, so as to improve production efficiency and reduce manufacturing cost [15-16].
The standardized design of elliptical tenon aims to improve the problems of excessive or insufficient local strength of elliptical tenon, such as waste of wood resources, low yield and potential safety hazards. The standardized design can make the oval tenon have many adaptability and higher generality, which is suitable for different modeling components. The standardization of oval tenon is not only of great significance to the standardization of solid wood furniture, but also provides some references for the blank of dimension standard of tenon interface in furniture industry.
2. Based on the standardized interface innovative design of elliptical tenon for existing solid wood furniture components 2.1 the stepped elliptical tenon innovative design "stepped" elliptical tenon consists of three different sizes of elliptical tenon "superposition combination", forming a unified standardized stepped elliptical tenon. Different kinds of solid wood furniture need different strength to join different parts, so "step type" oval mortise is used with different mortise of four kinds of joint parts to meet the appropriate size and strength requirements. "Step type" oval tenon, while realizing generalization, improves the adaptability of oval tenon to different joint strength, and improves the standardization degree of furniture component tenon joint. "Step type" oval tenon is suitable for large-size T-shaped components, such as bed furniture or some furniture such as tables and chairs.
Step type oval tenon, which imitates the form of step, consists of three sizes of oval tenon: "large", "medium" and "small", decreasing from left to right, respectively marked as 1-first oval tenon, 2-second oval tenon and 3-third oval tenon; the third oval tenon is set on the end face of the second oval tenon, the second oval tenon is set on the end face of the first Oval tenon, and the first Oval tenon is set on the end face of the first Oval tenon Protruding and resting on timber. The length and width of the first Oval tenon are 18 mm and the thickness of the tenon is 10 mm; the length of the second oval tenon is 8 mm, the width of the tenon is 12 mm and the thickness of the tenon is 8 mm; the length of the third oval tenon is 8 mm, the width of the tenon is 8 mm and the thickness is 6 mm. The above-mentioned oval tenon is made of a whole piece of wood, three oval tenons are connected in turn, and four different tenons are used together with step type oval tenon.
Fig. 1 structural diagram of stepped oval mortise
Fig.1 Stepped elliptical structure diagram
2.2 matching design of step type oval mortise there are four different forms of step type oval mortise to match the "step type" oval mortise. The joint modes of mortise a, B, C and D (as shown in Figure 2, the shadow part is mortise) are a, B, C and D respectively. When the type of adhesive is the same, the joint strength mainly depends on the joint area of mortise and mortise [17], so the joint strength of the four joint modes is a > b > C > d from high to low.
Figure 2 sectional view of four stepped oval mortise
Fig.2 Four stepped mortise sectional view
As shown in Figure 3, the joint of step type oval tenon and mortise A is the first Oval tenon, the second oval tenon and the third oval tenon. The tenon and the first, the second and the third oval tenon completely fit, and the joint area of joint mode a is the largest and the strength is the highest; the joint part of mortise B is the first Oval tenon, the second oval tenon, the third oval tenon does not join with the mortise, and the tenon The joint area of mortise B corresponding to joint mode B is larger than that of C and D, and the strength is higher; the joint part of mortise C is the first and the third ellipse mortise, the second ellipse mortise is not connected with the mortise, the mortise is completely connected with the first and the third ellipse mortise, the joint area of mortise C corresponding to joint mode C is larger than that of D, and the strength is moderate; the joint area of mortise D is larger than that of mortise D The joint part is the first ellipse mortise, the mortise does not contact with the second and third ellipse mortise, the mortise completely matches with the first mortise, the joint mode D has the smallest joint area and the lowest strength.
Fig. 3 four joint modes of a / B / C / D
Fig.3 Bonding method A/B/C/D
3. Manufacturing method and joint method of stepped oval tenon solid wood furniture manufacturing method of stepped oval tenon structure [18-20], including the following steps:
3.1 before processing "step type" oval mortise, it shall be confirmed that the maximum length of the mortise can meet the size requirements of "step type" oval mortise, and the maximum length of the mortise can be processed is more than 40 mm [21-22]. Adjust the position of the workpiece, fix the workpiece on the mountain to ensure the consistency of the processed workpiece, select a datum plane to place the workpiece on the CNC mortise machine, press the square material against the mountain, and fasten the fixture; select the processing program, start the mortise machine, and the processing sequence is the third ellipse mortise, the second ellipse mortise, the first ellipse mortise, and the cutting speed increases in turn; take out the mortise after the processing and Stack in order. The concrete structure of the step type oval tenon is the step type, and the processed step tenon is finished and sanded at last.
Fig. 4 Schematic diagram of the third tenon machining
Fig.4 The third head processing
3.2 the machining process of stepped oval mortise is similar to that of tenon. Select a suitable mortise machine, adjust the distance between the processed oval mortise and the cutter, use the fixed by the mountain to ensure that the processed workpiece is consistent, select a unified datum plane for the square materials to be mortised and place it on the mortise machine, and fasten the fixture. According to the different joint ways of mortise and tenon, the processing of mortise A is divided into three stages. The joint parts are the first elliptical tenon, the second elliptical tenon and the third elliptical tenon. The depth of tenon is 18, 8 and 8 respectively Mm; the processing of mortise B is divided into two stages, the joint part is the first Oval mortise and the second oval mortise, and the mortise depth is respectively 18 and 16 mm; the processing of mortise C is divided into two stages, the joint part is the first Oval mortise and the third oval mortise, and the mortise depth is respectively 26 and 8 Mm; the joint part of mortise D is only the first Oval mortise, and only the mortise of matching size with the first Oval mortise needs to be processed, and the mortise depth is 34 mm.
3.3 step type ellipse mortise joint method step type ellipse mortise structure joint method, including the ellipse mortise and mortise joint. After the components are sanded, the mortise and the step ellipse tenon joint are selected according to the required joint strength. The polyvinyl acetate emulsion adhesive (PVAC) is coated on the control joint, and after coating for 80~100 s, the mortise is knocked into the tenon elliptical tenon, so that it is tightly bonded and the adhesive is solidified after about 12 h.
Table 1 joint position and strength of stepped oval tenon
Tab.1 Stepped elliptical joint and strength
Four In conclusion, based on the investigation of the present situation of the mortise and tenon joint of solid wood furniture, aiming at the technical problems such as the disunity and nonstandard of the size of the oval tenon, the surplus or deficiency of the strength of the tenon joint, the author puts forward an innovative design of the "step type" oval tenon of solid wood furniture, expounds its manufacturing technology and joint method, and solves the problems of low production efficiency, waste of wood resources and production in the production process of the oval tenon of solid wood furniture The quality of the products is not up to the standard, which improves the output rate and provides a new idea for the size standardization of oval tenon and the standardized interface design of furniture industry.
4.1 based on the size of oval tenon commonly used in modern solid wood furniture, the structure is redesigned to get the tenon with appropriate length, width and thickness ratio. According to the optimal proportion of oval tenon size, the "step type" oval tenon is made to standardize the size of oval tenon of solid wood furniture.
4.2 standardized "step type" oval tenon uses three sizes of tenon, which can meet the requirements of higher joint strength of tenon structure, improve the adaptability and combinability of tenon structure, and provide the basis for the furniture standardization process under the diversified design. In the process of production, the types of oval tenon and mortise are reduced, and the difficulty of parts identification is reduced in product classification storage and assembly, which makes the production efficiency of furniture enterprises higher.
4.3 wide applicability through the longitudinal arrangement of three tenons, it is solved that the elliptical tenon can not be used for machining double tenon and large volume