Application and development of the hottest roll fo

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Application and development of roll forming cad/cam technology

Abstract: This paper introduces the technical achievements of the cooperative research and development between Northern Polytechnic University and German data M company in recent years, and gives an application example of roll forming cad/cam technology. Using CAD technology, the forming datum and process are determined according to the geometric characteristics of the cross section in the design of asymmetric profile. The design characteristics of the undercut closed profile are introduced, and an example of computer simulation technology in the design of wide profiled plate is given. CAM technology is applied to solve the computer-aided machining of special-shaped rollers. Based on the computer numerical control envelope method, different contour curves can be machined with a piece of grinding wheel. The application of roll forming cad/cam integration technology has achieved good results. The development direction of this technology is also put forward

key words: CAD CAM roll forming

1 Computer aided design of roll forming

in the past ten years, the computer aided design technology of roll forming (also known as cold-formed steel) has been widely used. At present, the problem is how much computer can "assist" designers to complete tasks. Many people only use computer to replace manual geometric calculation when designing rollers, which still relies on the practical experience of designers to a great extent

with the rapid development of computer technology, the CAD software used for roll forming should reach a higher level. First of all, we should develop to a deeper aspect. Computers can help designers in more aspects to get the best design results. For example, CAD software should have the following functions: simulating the forming process, giving expert guidance by using artificial intelligence and fuzzy neural network technology. Secondly, CAD technology develops to a wider field, including computer-aided manufacturing, production management, cost accounting, quality control, CAE and CIMS. Copra, developed by German data m, is an integrated software for roll forming design

the following is an example of some cold-formed steel sections completed by copra

1.1 asymmetric section

professor konahiro of [thermostatic chamber] of Japanese colonization University gave an estimation method of forming passes of asymmetric section. Compared with the symmetrical section, the unbalanced torque will lead to the distortion of the strip. The geometric deformation of the strip during the section forming process is closely related to its static properties. The author found that if an inertia axis of the section is used as the reference line for expansion, some asymmetric sections can get good molding quality

1.1.1 take the inertia axis as the unfolding reference

the part used for the container (Figure 1) is an asymmetric section. A company takes the longest straight-line segment as the horizontal benchmark of forming, sharing 12 passes of forming, and produces obvious torsion. Using copra, the angle of the main inertia axis can be easily calculated. Taking one of the inertia axes as the forming datum plane, it only needs 6 passes. Now it is possible to design and manufacture plastic melt gear pump products, such as 28/28 (center distance/tooth width), 56/56, 70/70, 90/90, and so on, and obtain a section with better quality than the previous method

Figure 1 forming roller of container parts Figure 2 V-shaped section with different forming angles on both sides

Figure 2 is a part of ceiling. Although its shape is simple, its forming is not easy, because the maximum deflection in each direction per meter of forming length must be no more than 0.5mm when the plate thickness is 0.4mm. For forming this high-precision part, the author adopts the method of taking one of the inertia spindles as the forming benchmark, and the deformation angles on both sides are given according to different values, so as to balance the deformation torque on both sides. In addition, to ensure the flatness of its ridge line, it is also very important to set new parameters for adjustment of roll installation and adjustment. With the above measures, the straightness error per meter of the final produced material shape is less than 0.3mm

1. 1.2 take the horizontal axis as the unfolding benchmark

Figure 3 is another component for ceiling produced according to the user's requirements. This is simplified by the symmetrical "t" ceiling keel. Although the deformation of its left side is much larger than that of its right side, the angle between one of its inertia axes and the horizontal plane is close to 0 degrees. In this case, the author uses the longest linear voxel as the horizontal expansion benchmark

Figure 3 forming steps of T-shaped section

Figure 4 shows the sectional static characteristics of electric control cabinet components. The intersection of the two inertial axes is close to the right voxel. The author takes the right voxel as the first datum of forming and unfolding, and the horizontal voxel at the bottom as the second datum of forming

Figure 4 static characteristics of electric control cabinet components

Figure 5 forming roller pattern of asymmetric section electric control cabinet components

1.2 forming of undercut material type

some steel door and window materials are made of color coated steel plate by roll forming process. In order to ensure the strength of doors and windows, closed sections are used. The welding method will damage the surface of the steel plate, so the bite structure is widely used. In order to avoid interference in the biting process, avoid damage to the surface of the color coating, and ensure the air tightness and water tightness of doors and windows and the matching requirements, the roll design and manufacturing are required to achieve high accuracy. Surface roughness of roll RA ≤ 0.63 μ m. The circumferential speed of the roll shall be as close to the driving speed as possible. If the linear speed difference of the roll is large, the idling structure shall be adopted in the design

for general roll forming, the forming roll axis is configured horizontally or vertically. The auxiliary roll with spatial structure is widely used in the forming of undercut profile. This auxiliary roll structure is installed between two main rolls, and the roll axis can be inclined at any angle. Its structural form is different from the main roll and vertical roll. Figure 6 shows the assembly relationship of an auxiliary roller. In order to obtain accurate size and shape, the core is used in the final molding pass. Figure 7 shows the forming process of a color coated steel window material

Figure 6 assembly diagram of auxiliary roll for undercut material type

1.3 wide profiled plate

profiled plate is mostly formed by roll bending of wide and large thin plates, which is prone to various defects. Professor xiaonaihong gave a very useful conclusion based on his experiments: defects such as edge waves and bag waves are caused by excessive deformation stress or different distribution of tensile and compressive stress. If the stress and strain values of the forming area can be calculated in the design process, defects can be avoided. Using the finite element technology and experimental results, it is known that in the forming process of each pass, the strain state of a certain point in the deformation area of the plate changes alternately in tensile stress and compressive stress, even if the thin plate has different strain states on different layers. An important conclusion is that longitudinal deformation is the main cause of defects such as residual internal stress and side wave [3]

the deformation technology module (DTM) developed by data m and its collaborators is based on the finite element method and a large number of experiments. According to the geometric deformation conditions and material properties, the deformation simulation of roll forming can be realized on the computer. DTM can give the maximum longitudinal strain of each pass, and can also calculate the tensile strain and compressive strain of the upper, middle and lower layers of the plate respectively. If the maximum tensile strain exceeds the yield point of the material (the maximum value for low carbon steel is 0.35%), or the minimum compressive strain is lower than a certain value (for example, the value given by Professor xiaonaihong is less than 0.3*), defects will occur. According to the results obtained on the computer screen, the deformation sequence and forming angle can be modified. Using computer simulation, we can predict which deformation pass will produce defects, and then modify the design. Using DTM simulation technology, we have done computer optimization of roll forming for many enterprises. Some enterprises have problems in trial production. We input their design data into the computer and find that the peak value of strain is too large in some passes, which is completely consistent with the situation that deformation defects are produced in this pass and accompanied by a lot of noise during trial rolling. After modifying the design, these profiled plates were formed smoothly. Figure 8 shows an example of computer simulation of wide width profiled plate

figure 8 computer simulation results of a profiled plate

2 Computer aided manufacturing of roll forming

to realize roll forming of a complex section requires hundreds of rolls with different shapes. The roll profile of the roll is closely related to the forming of the sheet metal. It is very important to ensure the accuracy of the geometric coordinates of the forming part. The axial accuracy of the roll is more important than the radial accuracy. In the actual machining process, using general measuring tools, the radial measurement of the roll is much easier than the axial measurement; Using traditional lathe processing, the control of axial accuracy is much more difficult than radial. Computer numerical control technology can solve the problem of machining special-shaped rollers

2.1 CNC processing roller

use the CNC lathe with 8-Position cutter table to process the roller with HRC hardness (see Figure 9). Using special ceramic cutting tools, we can get quite good surface quality. The author adopts a two coordinate CNC system with a control resolution of 0.001mm

Figure 9 roller processed by CNC lathe

because the shape and size of each roller are different, it is not feasible to use the "first piece test cutting method" to check the NC program. Generally, the low efficiency of manual programming will affect the function of NC. It is difficult to avoid errors in data calculation and programming, and any error may cause workpiece scrap or serious machine tool and personal accidents. Computer aided manufacturing technology can automatically generate NC programs and verify simulated NC instructions. Copra can automatically generate NC code according to different NC formats of machine tools according to CAD data, and can simulate the running path of tools in an animated way on the computer screen according to the information we have

2.2 computer communication

the author realizes the seamless integration of computer in the whole process of roll forming CAD and CAM technology, from design to manufacturing. In the past, the input of numerical control program was code by code manually. A long program took about 10 minutes, which was not much different from the time of completing a part. It is difficult to avoid errors in manual input, and any error will cause workpiece scrap or machine tool accident. Using the communication interface technology between computer and CNC machine tool, the compiled program can be sent to CNC machine tool quickly and accurately, which improves the utilization rate of machine tool. Because of the communication between computer and CNC machine tool, thousands of sentences can be transmitted in a few seconds. A 3-inch small disk can store the processing data of the sheet roll. For the finishing of rolls with complex profile, the utilization rate of machine tool can be increased by%. It is very convenient to save the roll sheet data, repeat production and repair the roll sheet

2.3 CNC envelope grinder

special shaped rolls are widely used in the production of welded steel pipes. In the past, its grinding was difficult. Some enterprises adopt the forming method for grinding, and each arc adopts a grinding wheel of one specification, which not only has a large number of grinding wheels, but also cannot process the roll shape with complex contour. In order to realize the precision grinding of high hardness special-shaped roller surface, computer numerical control based on envelope principle can solve this problem well

according to the envelope principle in the conjugate surface, an enveloped plane contour curve can be obtained by controlling the trajectory of the grinding wheel under the condition that the curvature radius of the grinding wheel is unchanged (see Figure 10)

Figure 10 envelope curve and control track of grinding wheel

set the roll profile as a plane curve and the outer contour of the grinding wheel as a circle Γ Part of its equation is:

according to the coordinate transformation and envelope conditions, one side of the envelope surface is:

the curve in the equation Γ 0 is the trajectory equation controlled during NC machining:

for any plane

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