Research on the forming scheme of the integrated TV back panel
The back panel, plastic frame, middle frame, front shell, and rear shell are the main components of the TV, as well as the structural skeleton of the TV. They carry the liquid crystal panel, fix the electronic and optical components, and optimize the appearance. Combining the research of market and user needs, and comparing the research and development direction of TV products in the industry, the ultra-thin frameless TV structure will lead the trend of the future.
The integrated appearance structure is the integrated solution of the backplane and the middle frame. The backplane can be directly used as the middle frame to reduce the amount of materials of the TV module structure, reduce the module material cost, simplify the existing module manufacturing process, and improve the back-end mold The production efficiency of the whole machine line body. And relying on the current application research of DLED and ELED TV product structure solutions, a new form of borderless TV with thinner thickness, lower cost, and simpler manufacturing process can be realized. While improving the appearance of the product, it also increases its market share and industry influence.
For the appearance structure of the one-piece backplane, the complexity and difficulty of the backplane forming process have increased sharply, the dimensions of the dead edge of the backplane, left and right sides, the size of the corner splicing gap, the size of the splicing end section, and the corner welding after stamping The control of the process is the main difficulty in forming the integrated TV backplane.
Design scheme of splicing structure of back plate corner
The back panel structure of the integrated TV is flat on the three sides of the sky, left and right, and the left and right corners of the sky side are spliced. After splicing, laser welding is performed to seal the backlight light and block foreign objects. In order to achieve a good appearance effect, polish after welding Polished.
In order to ensure the appearance effect of the welded and polished product, and at the same time carry out structural design according to the principle of product deployment, consider the corner splicing structure plan as shown in Figure 1, and the corresponding corner splicing structure after welding is shown in Figure 2.
Figure 1 The corner splicing structure scheme
Figure 2 The state of the corner splicing structure after welding
Solution a: After the corners are spliced, the top and middle of the welding are severely collapsed, and the natural R angle after welding cannot be formed, which does not meet the appearance requirements of the product.
Solution b: After the corners are spliced, the welding trajectory is stable, and the transition is smooth after the splicing side welding, but the top collapses after welding, and there is an obvious step difference, which does not meet the appearance requirements of the product.
Scheme c: The corner splicing scheme can form a natural R angle after welding, and it can meet the appearance requirements with the grinding and polishing process.
Forming scheme of integrated TV back panel
In summary, the corner splicing structure design of scheme c can not only realize the integrated structure of the back plate and the middle frame, but also meet the appearance requirements of the product after welding and polishing.
Corner splicing key size control
As mentioned above, the integrated TV back panel adopts a three-sided flattening and corner splicing structure, that is, the middle frame of the back panel is integrated. Scheme c. The details of the corner splicing structure and key control dimensions are shown in Figure 3. The sky, left, and right bending edges are pushed flat to form a dead edge structure, and the sky side bending edge is pressed against the left/right bending edge Afterwards, laser welding is performed at the seams. In order to meet the appearance effect after corner welding, the tolerance of the height h of the bend edge is ±0.2mm; the tolerance of the height H of the bend is ±0.2mm, and the thickness of the blind edge (twice the material thickness) T tolerance is 0 ~ 0.1mm ; Control the three gaps of the corner splicing A, B, C within 0.15mm, and the height difference between the sky side and the left and right splicing within 0.2mm.
Mold forming process
In order to realize this backplane structure, the mold is divided into 8 process forming: M1 process stretching, embossing → M2 process stretching and shaping, punching hooks, corner punching and blanking → M3 process trimming, punching, back bending Folding line → M4 process trimming, sprouting → M5 process pressing burrs, bending → M6 process days, left and right side push and pat dead edges → M7 process days, left and right bending splicing → M8 process riveting.
The corner splicing structure forming process first carries out punching and blanking, and then the dead edge part is folded down, the insert knife is pushed and flattened by the side, and the corner is spliced and formed. The details are shown in Figure 4. In order to ensure the quality of subsequent welding, the gap size of A, B, and C should be controlled within 0.15mm.
Figure 3 Schematic diagram of corner splicing structure and key control dimensions
Figure 4 Mold forming process of splicing structure of dead edges and corners
⑴For the control of the gap A, the design value of the unfolding gap is 0, that is, an L-shaped step with material thickness is reserved on the left and right sides when unfolding to ensure the L-shaped blanking size, and at the same time control the thickness of the dead edge T to be 2 times the material thickness , The bending angle is 90°, and the tolerance range is -0.5°～1°.
⑵For the control of the gap B, adjust the depth and position of the pre-folding line to ensure the height of the dead edge h, and control the height of the bending edge H to ensure the size of the dead edge.
⑶For the control of the gap C, the cutting length of the sky side is 10.54mm when unfolding, the cutting length of the left and right sides is 9.74mm, and a material thickness of 0.8mm is reserved, that is, the sky side can be bent with the left and right sides. The right side bends at the corner splicing gap C to achieve zero clearance fit.
At the same time, to ensure the bending angle, the bending punch is designed to be adjustable, so that the bending angle and edge height can be quickly adjusted online. For the splicing height difference should be within 0.2mm, through the movable knife and bending punch design, to ensure the bending edge height dimension H tolerance, thereby ensuring the splicing difference.
In order to realize the dead edges on the three sides of the sky, left and right, the die structure of the dead edges is shown in Figure 5. The insert knife 4 is fixed on the upper splint 2 and locked to the upper die seat 1, and the push block 5 is connected to the contour sleeve 7 In order to reduce the friction between the push block 5 and the lower backing plate 8 when the push block 5 moves, the bottom of the push block 5 is equipped with an oil groove, and the spring is fixed between the contour sleeve 7 and the lower template 13. In the initial stage of forming, the support plate 11 moves downwards. Work with the lower template 13 to press the material to ensure the forming stability of the blank 12. The inserting knife 4 moves downwards, and pushes the push block 5 to push sideways. When pushing the block on the side to push the straight body, reserve 3 times the thickness of the material than the length of the dead edge, and the gap between the push block 5 and the supporting plate 11 is 2 times the material thickness to reduce the rebound after flattening. At this time, the spring 6 is in a compressed state. After forming, the spring 6 acts on the contour sleeve 7, and the contour sleeve 7 exerts a pulling force on the push block 5 to restore it to the initial position.
Welding and grinding process
Figure 5 The structure diagram of the die on the dead side
Figure 6 Schematic diagram of laser welding track
Figure 7 Product status
In order to achieve the appearance effect of the splicing of the corners of the back plate, both the cost and the welding energy to meet the dead-end welding penetration are considered. At the same time, to ensure high welding production efficiency, use 500W continuous laser for welding, adjust the best matching welding power of 230W and welding speed of 5mm/s, which can not only meet the welding energy of 1.6T thickness, but also ensure the welding cycle. Control within 4s.
Refer to Figure 6 for the laser welding track. In order to ensure that there is no collapse after welding, the welding track must not cross, and the splicing gap must be avoided. The laser welding head is arranged in the (-1, -11) direction and moves along the trajectory shown in Figure 6 to ensure that the splicing part of the bending edge forms a natural R angle. After welding, the corners are polished. The whole process of welding and polishing is automated to ensure production efficiency and product appearance stability. First, use 180# sandpaper for rough polishing on the welding surface, welding adjacent surface and the top surface of the opening. Use 800# scouring pad for polishing treatment to ensure the appearance of the product after powder spraying. The entire automated polishing process can be completed within 20s. The product status at each stage is shown in Figure 7. The reasonable mold forming process is matched with the welding and polishing process. , It can realize the good appearance effect of the integrated TV back panel.
⑴The integrated appearance structure is the integrated solution of the backplane and the middle frame. The backplane can be directly used as the middle frame to reduce the amount of materials of the TV module structure, reduce the module material cost, simplify the existing module manufacturing process, and improve the back-end The production efficiency of the whole module line.
⑵Through reasonable structure and mold design scheme, the left and right sides of the backplane are guaranteed to be the size of the dead edge, the size of the corner splicing gap, and the size of the splicing end segment difference. With a reasonable automatic welding and polishing process, an integrated TV backplane is finally realized. Stable mass production.