[Production Process Technology] Sheet Metal Working Techniques.ppt

Sheet metal workingThe scope of work in this field involves the application of sheet metal technology in the manufacture of mechanical products. This entails the fabrication and machining of components or assemblies—primarily made from steel (sheet metal, tubular sections and structural steel)—using advanced and systematic manufacturing processes, alongside high-quality, practical and state-of-the-art tooling and equipment. As for the manufacturing procedures, these also involve the application of sheet metal technology in the manufacture of mechanical products; through advanced and well-organised manufacturing processes, and with the aid of high-quality, practical and advanced tooling and equipment, components or assemblies—primarily made of steel (sheet metal, tubular steel and structural steel)—are manufactured and processed. Every stage of the process involves these elements! Sheet metal technology is associated with mechanical products across various industries, particularly in the chemical and shipbuilding sectors. It is also relevant to fields such as bridge construction, rolling stock and the building industry, involving a series of process procedures, specifically comprising the preparation stage, marking-out, cutting, forming, assembly, welding and inspection. The tools and gauges commonly used in sheet metal work include hammers, are categorised by material into iron, wood and copper; by weight into small, medium and large; and by purpose into notches, flat hammers, curved hammers, chopping hammers and profile hammers; categorised by function, they come in various shapes such as straight-headed, round-headed and square-headed. Workbenches and vices; vices are used to clamp workpieces, clamps are used to secure workpieces, and levers are used to apply force; the marking tools, sawing tools, chiselling tools, filing tools, drilling tools, tapping and threading tools, electric tools and pneumatic tools, measuring instruments such as steel rulers, set squares, plumb lines, vernier calipers fitted with spirit levels and levelling instruments, universal angle rulers, arc gauges, weld inspection gauges, levelling instruments, theodolites, as well as geometric drafting and layout; calculations and marking methods for notches when bending angle steel; determination of the minimum bending radius; the material must be in an annealed or normalised condition, or in a work-hardened state; the direction of the bending line must be taken into account; situations where the bending line is first perpendicular to and then parallel to the grain direction, perpendicular to the grain direction, and parallel to the grain direction; this covers grades 08, 10, A1, A2, 15, 20, A3, 25, 30, A4, 35, 40, 60; aluminium, red copper, soft brass, semi-hard brass and phosphor bronze. This content concerns the method of sheet metal development drawings and layout. Development and layout is the process of using the development drawing method to unfold curved components in sheet metal workpieces into flat surfaces. The development method is a process of unfolding complex components into two-dimensional planes; it is a relatively complex task, requiring the operator to possess a thorough understanding of solid geometry, as well as comprehensive knowledge and skills in geometric drafting. It necessitates the integration of theory and practice, applied with flexibility, to ensure the development and layout work is carried out effectively. Development and layout prepare the workpiece for marking out and cutting; it prepares the workpiece for marking out and cutting. The components typically subject to development include the cylinders and heads of chemical process vessels, pipe elbows, as well as conventional sheet metal workpieces such as hoppers and conveyor pipes. The calculation of the actual length of the generatrix of a solid intersecting a cross-section can be performed using the parallel line development method. First, draw a front view indicating the height and a cross-sectional view indicating the circumference. Next, divide the cross-sectional view into equal parts; the number of divisions may be determined at one’s discretion based on actual circumstances; for circular shapes, 12 equal parts are generally used. Finally, draw a straight line of a length equal to the circumference of the cross-sectional view. 4. Divide the line segment into equal parts and draw vertical lines upwards from each point on the segment; the lengths of these vertical lines correspond sequentially to the heights of the generatrices in the front view. 5. Connect the individual points using straight lines or smooth curves to produce the developed view of the solid. The method and steps for the developed view of a 90° elbow with two sections of circular pipe of equal diameter comprise the following: first, determine the true length of the base; second, determine the true height of the prism; then, connect the points in sequence. The surface development A of the prism has two projected views: d(h) a(e) a′(d′) b′(c′) e′(h′) f′(g′) In this case, there is also the situation with two projection diagrams: b(f), b′(c′), d(h), a(e), a′(d′), e′(h′) and f′(g′). In this case, (1) take the true length of the base; the developed diagram will resemble E F G H E. Using horizontal projection, extend the true lengths of each base into a horizontal line, and mark the points EE, FF, GG, HH and EE. For each point, c(g), (22) take the true length of the edge height; take the true length of the edge height A to produce the developed diagram, AB, CDE, FG, H Eb (f) for the two-plane projection diagram; a (e), a′ (d′), b′ (c′), e′ (h′), f′ (g′); draw perpendiculars from the marked points and measure the true lengths of the edges along them, to obtain the respective endpoints: AA, BB, CC, DD, AA. Connect points c, g, d, h and A on the developed diagram, the projection diagrams onto the AB and CDE, F, G, H, E planes: a′ (d′), b′ (c′), e′ (h′), f′ (g′). Connect the points in sequence, connect the points in sequence, connect in sequence, connect the points A, A, B, B, C, C, D, D and A in sequence; this yields the net of the prism. b(f) a(e) c(g) d(h) A net, Projections onto the AB and CDE, F G, H E planes: a′(d′), b′(c′), e′(h′), f′(g′). Connect the points in sequence, first connecting points A, B, C, D, AA in turn; this yields the net of the prism. This is the case. b (f) a (e) c (g) d (h) 22. When the net of the pyramid is unfolded, it takes the form of a quadrangular frustum dust hood; if its four edges are extended, they will intersect at a point S, thereby forming a quadrangular pyramid, This quadrangular pyramid is composed of four congruent isosceles triangles. To determine its net, one need only calculate the actual area of one of these triangles and then proceed accordingly. (1) Determine the true lengths of the edges; (2) Construct an isosceles triangle; (3) Cut the edges to their true lengths; (4) Connect the points in sequence; (1) Determine the true lengths of the edges. sefb′(a′)′g′(h′)f′(e′)c′(d′) o′e1′a1′a1. For the two-sided projection, use the rotation method: draw a circle with centre s and radius sasa, which intersects the axis of horizontal symmetry at aa11; draw a perpendicular through aa11 intersecting the horizontal line drawn through a′a′ at aa11′′; join s′as′a11′′ to obtain the true length of the leg of triangle SASA. Next, draw a horizontal line through e′e′ intersecting and intersects s′as′a11′′, intersecting at e′e′11′′, from which the actual length of the ridge line AEAE can be determined. (22) Construct an isosceles triangle with b′ (a′) aa1′′ g′ (h′) f′ (e′) c′ (d′) o′e1′a1, and the two-sided projection unfolded diagram A.B.C.D.A.S. Construct the base, SS. AA = S = S; BB = s′a = s′a11′′. The bases AA and BB are equal to AB; these are isosceles triangles of that type, with sides SS, AA and BB. By the same token, construct the other three in the same manner. (33) Cut off the actual lengths of the edges: b′ (a′), aa1′′, as well as g′ (h′), f′ (e′), c′ (d′), o′, e1′ and a1; their corresponding two-view projections are A, B. C. D. A. E. H. G. F. E. The net is S. On each side, cut off the actual lengths of the edges of the four-sided prism, such that AA.EE equals a equals a11′e′e11′′, resulting in EE. FF, and so on. b′ (a′)′ g′ (h′) f′ (e′) c′ (d′) o′ e1′ a1′ a1 has two projections: A. (44) Connect the points in sequence: B. C. The developed diagram D. A. E. H. G. F. E. S. Connect them again in sequence: EE, FF, GG, HH, EE, to obtain the developed diagram. Thus, the development of a developable surface—to reiterate, the development of a developable surface— where the development of a cylindrical surface is such that the resulting diagram is a rectangle, with one pair of opposite sides representing the circumferences of the upper and lower bases of the cylinder, and the other pair representing the actual length of the generatrix. In the method for constructing the development diagram of a two-view projection where HHL equals πDΦD, the two-view projection development diagram is constructed as shown in the accompanying diagram, by unfolding the horizontal circumference in the top view into a straight line, and drawing perpendicular lines at the two endpoints of this line, such that the height of the perpendicular lines equals the height of the cylinder; the resulting closed figure is the net. 2.2. The development of a conical surface is as follows: when the surface of a cone is developed, it forms a sector. The figure shows the two-view projections of the cone and its development. In the net, the centre of the sector is the centre of the cone; the radius of the sector is equal to the length L of the generatrix of the cone; and the arc length of the sector is equal to the circumference of the base circle of the cone. Let the angle of the sector be θ; since θ° 180°, then θ° 180° D, 360° 2πL. Therefore, the net of a frustum of a cone is the difference in area between two sectors with the same centre, as shown in the figure, which depicts the two projections of the frustum and its net. The parts shown in the figure are the projections of the two faces of the frustum and their net diagrams; where the developed diagrams of the two projections include θ3 3, as well as the development of a bevelled cylindrical tube. The method and steps for developing a bevelled cylindrical tube are as follows: first, divide the circumference into equal parts (11), then proceed with the circumferential development (22), then (33) measure the actual lengths, and finally (44) join the curves to form the net Ga′b′c′d′e′f′g′1′ 2′ 3′ 4′ 5′ 6′ 7′ 1. 2. 3. 4. 5. 6. 7. Perform the operation of dividing the circumference into equal parts (as in (11)) on points a (1), b (2), c (3), d (4), e (5), f (6) and g (7) in the two orthogonal projections; a′b′c′d′e′f′g′, 1′, 2′, 3′, 4′, 5′, 6′, 7′ form another set of two-view projections. Divide the circumference of the top view into twelve equal parts, then divide the circumference of the top view into twelve equal parts again, and draw the lengths of the generatrices of each division point on the front view; g (7) is also included. Finally, the developed views of the two-view projection are presented, including 1., 2., 3., 4., 5., 6. and 7. First come a′b′c′d′, followed by 4′, 5′, 6′ and 7′, then a (1), b (2), c (3), d (4), e (5), f (6) and g (7), and finally ( (22) circumferential development), the circumferential development; in the development diagram, the circle is then developed along its circumference to form a straight line, and the circumference is divided into twelve equal parts; followed by e′f′g′, 1′ , 2′, 3′, followed by the two-view projection, then ((33) measuring the actual length), measuring the actual length, followed by Gc′d′e′f′g′, 4′, 5′, 6′, 7′, followed by a (1), b (2), c (3), d(4), e(5), f(6), g(7), and finally 1, 2, 3, 4, 5, 6, 7. The net must pass through each division point; there are eleven, ,, twenty-two,,, thirty-three,,, and so on. Draw perpendicular lines; on each of these perpendicular lines, draw further perpendicular lines. Measure the actual lengths of the generatrices on each perpendicular line, then determine the respective endpoints; the endpoints are A,,, B,,, C,,, and so on. Three slashes, one slash, two slashes, b slash, a slash, ((four four)) connected by a curve; the developed diagram is G, one, two, three, four, five, six, seven. In pipework design, there are equal-diameter right-angle bends, which are used to connect two circular pipes that intersect at right angles and have equal diameters. When performing a two-view projection, the following appear: d′ e′ f′ g′ 3′ 4′ 5′ 6′ 7′ a (1) b (2) c (3) d (4) e (5) f (6) g (7). Next, smooth curves are used to connect the points AA, BB, CC, … … and so on, in sequence. This yields the developed diagram of the tapered cylindrical tube, which also includes b′c′a′1′ 2′ . As the annulus is a non-developable surface, it is generally not used in the design of bent tubes; when designing bent tubes, the annulus as depicted in Figure (aa) is not typically employed, but rather a configuration composed of multiple cylindrical segments, as illustrated in Figure (bb). As shown in Figure (bb). Figure (bb) illustrates a right-angle bend commonly used in engineering, assembled from five sections of beveled circular tubing. The three central sections are referred to as ‘full sections’, whilst the two end sections are called ‘half sections’; These half-sections can be obtained by splitting a full section along its plane of symmetry. Equal-diameter right-angle bends, the existence of equal-diameter right-angle bends, the development of equal-diameter right-angle bends, the development of equal-diameter right-angle bends, performing operations related to the development of equal-diameter right-angle bends, ABCD E (b) Cylindrical pipe, , (a) Annular pipe, components of a constant-diameter right-angle bend, components of a constant-diameter right-angle bend, decomposition of an annular pipe, composition of a cylindrical pipe, DR(a), given that the pipe diameter of the five-section right-angle bend is DD, and the bending radius is RR, then for the elbow, the process of drawing its front projection can be derived; the process of drawing its front projection is shown in Figures (aa), (), (bb), (), and (cc): ) shown: (b) Perform the corresponding operations at the symmetrical positions of each section; draw tangent arcs at the symmetrical positions of each section, and connect the corresponding intersection points. Connect the corresponding intersection points, draw the arcs, and then draw the arcs further; also draw the lines at the symmetrical positions of each section. Erase the auxiliary lines, and then trace the lines. For the B unit section of the constant-diameter right-angle elbow—that is, Section B—its developed drawing is first selected from among the five sections of the constant-diameter right-angle elbow; specifically, one unit section, namely Section BB, is chosen from the five sections of the constant-diameter right-angle elbow. Next, it is developed in accordance with the method used for beveled cylindrical tubes, in accordance with the method used for beveled cylindrical tubes, The resulting developed drawing is as shown in the figure, as shown in the figure. To cut the material for the ABCD constant-diameter right-angle bend cylindrical pipe (a), (b) and (c), rotate sections BB and DD of the illustrated constant-diameter right-angle bend around their respective axes, as shown in Figure (a). The sections can then be assembled into a cylindrical pipe, as illustrated in (b). Therefore, the cylindrical tube can be cut into the required number of sections as shown in (c), and subsequently welded to form the desired bent tube. To produce the required bent tube, flat plates ABCD are cut to size (a), (b), (c). Figure (aa) is developed into five sections using the development method for beveled cylindrical tubes, which falls under the category of beveled cylindrical tube development methods; the result is shown in Figure (bb). Based on this, the method illustrated in the figure may be adopted. This method can be used for sheet metal cutting. When cutting the sheet metal, first create a half-section development diagram to serve as a template. On a single sheet of metal, mark out the lines according to Figure (using the half-section development diagram as a template, mark out the lines on a single sheet of metal according to Figure (bb), then cut the parts, and subsequently weld them into the individual sections shown in Figure (cc); in this way, bent tubes can be fabricated as required. Approximate development of non-developable surfaces: The core principle of approximate development for non-developable surfaces is to divide the non-developable surface into several smaller sections, then treat the surface of each of these sections as a developable surface, and proceed with approximate development. For example, there are several illustrated methods for partitioning a spherical surface, such as (aa), (bb) and (cc). Below, the development of a spherical surface is used as an example to illustrate these various methods of approximate development. Below, the development of a spherical surface is used as an example to explain the principle of approximate development. The principle of development. (a) (b) (c) (a) (b) (c) 1. 1. The approximate cone method involves drawing several horizontal meridians on the spherical surface to divide it into several equal parts; each of these smaller sections can then be approximated as a cone, as illustrated in Figures (aa) and (bb). (Figure (cc) shows) the projections of the two hemispheres of the sphere; based on these projections, the net diagrams of the individual cones can be drawn respectively. I II III, I II III, The net of a cone takes the form of a sector; the shapes of the individual cones when unfolded are as shown in Figure (dd). (d) Therefore, by following the net diagrams to mark out and cut the sheet metal, and then welding each piece into a cone, Next, these are assembled into conical shapes. The individual cones are then combined, and welding operations are carried out on the assembled cones to form a sphere. (a), (b), (c), 2. 2. Approximate trapezoidal method: The surface of the sphere is divided into equal cones, which are then divided into equal trapezoids, as shown in Figure (aa). When cutting out the parts, as shown in Figure (bb), cut into small trapezoidal units; these trapezoidal units are then welded into cones, as shown in Figure (cc), and finally welded together to form a sphere. (a) 3. 3. The approximate deformation method, as illustrated in Figure (aa), is applied to a tank-shaped vessel. This vessel comprises a cylinder and two hemispheres, one at the top and one at the bottom. When manufacturing the spherical section of a container from steel plate, the cut-to-size steel plate is usually heated and bent to induce plastic deformation, followed by welding. To facilitate blanking and the manufacturing process, the hemispherical surface may be decomposed into a top plate, plus eight identical side panels, after which an approximate development of the spherical surface is carried out as described below, as illustrated in Figures (bb) and (cc); this method is known as the approximate deformation method. Tank animation, 3D diagram of the tank, exploded view. (b) o′o (c), approximate development of the top panel, approximate development of the top panel, (Figure (bb) shows the two-view projection of the hemisphere, taking into account the plastic deformation that occurs during bending), the developed diagram of the top panel can be drawn as a circle, the radius of which is equal to the length of the arc o′1′o′1′, as shown in the upper part of Figure (cc). (b) o′o′o (b), (c) Approximate development of the side panels, Approximate development of the side panels, (11) Divide the side panels equally; in the front projection shown in Figure (b), divide the right-hand side panel into three equal parts, yielding points 1′, 2′, ………… In the horizontal projection, draw concentric arcs aa, ………… through each division point. a′b′c′1′2′3′d′ 4′ 4abd1 3o. For the case of ((22) arc development), the arc is developed; specifically, the arc o′4′ is developed into a straight line oo.44. In this process, oo. 11. The relevant steps and operations here are (c), (b), 1, 3, 4, 2. (1) Divide the side panels in (11) into equal parts; (2) When performing (b)(33), construct a concentric arc; (3) When dividing into equal parts, with oo. as the centre, pass through 11. and 22. (3) Note that this concerns the approximate development of the side panels; (3) As mentioned, points 11 and 22 must be passed through at the approximate development points of the side panels: 1′d′ 2o′d′oaabb c1 2; points 3 4d4′a′b′2′c′ 3′ must also be passed through; and points 2 3 4o.a. a. b. b. c. c. d. d. 1. 2. 3. 4. For the side panels, concentric arcs must be drawn separately; further concentric arcs must also be drawn, and operations must be carried out on the corresponding arcs, with measurements taken symmetrically on the corresponding arcs; the measurements are 11. aa must equal 1a, equal to 1a, …, o′a′b′c′1′2′3′d′ 4′. Furthermore, (22) the arc development must be carried out, and the side panel development is approximated as follows: (11) the side panel must be divided into equal parts.