metal deep drawing
What is metal deep drawing forming？
Metal deep drawing forming is a method of pressing a flat blank into a variety of open hollow workpieces using a deep drawing die, or a stamping process in which the open hollow parts have been made into other shaped hollow parts.
Its deformation process is: with the convex die downward, the outer diameter of the blank left on the end surface of the concave die shrinks continuously, the round blank is gradually pulled into the gap between the convex and concave die to form a straight wall, and the material below the convex die becomes the bottom of the deep-drawing parts, when the plate material all into the gap between the convex and concave die is the end of the deep-drawing process, the flat blank becomes a cup-shaped part with a certain diameter and height. Compared with the punching die, the working part of the deep-drawing convex and concave die should not have sharp edges, but have certain rounded corners, and the one-sided gap between the convex and concave die is slightly larger than the material thickness.
Advantages of metal deep drawing
metal deep drawing process
drawing of a flanged cylinder. The flange and the bottom are straight, the cylinder is axisymmetric, the deformation is uniform on the same circumference, the flange on the blank produces deep drawing deformation.
The flange on the blank stretching deformation, but the amount of deformation and deformation ratio changes accordingly. The greater the curvature of the part of the blank deformation is greater; curvature of the smaller part of the blank deformation is smaller.
A low rectangular part formed in one stretch. The tensile resistance at the rounded corners of the flange deformation area is greater than the tensile resistance at the straight edge when stretching, and the degree of deformation at the rounded corners is greater than the degree of deformation at the straight edge.
The side walls are suspended during the process and are not applied to the mould until the end of the forming process. The deformation characteristics of the different parts of the sidewall during forming are not identical.
The deformation of a mounded cover during the forming process is not a simple stretching deformation, but a compound forming in which both stretching and swelling deformation exist.
When a spherical part is stretched, the blank is in partial contact with the top of the sphere of the convex die and most of the rest is in a suspended state.
The flanged part is stretched shallowly. The stress-strain situation is similar to that of a compression flange.
Angular re-stretching of the flange section, requiring good deformation of the material.
Requires two or more multiple stretches to complete. For wide flange stretched parts, the flange diameter is stretched to the required flange diameter on the first stretch and remains the same on subsequent stretches.
Deep tapered parts are prone to excessive local thinning and even rupture due to the large degree of depth deformation, and need to be gradually shaped after several transitions.
High rectangular parts formed by multiple stretching, whose deformation is not only different from the stretching of deep cylindrical parts, but also differs greatly from the deformation of low box-shaped parts.
Curved surface stretching and forming, so that the outer flange part of the flat metal blank is reduced, the inner flange part is elongated, becoming a non-straight wall non-flat bottom curved shape of the press forming method.
The initial stretching is re-stretched to form a step-shaped bottom. The deeper part is deformed at the beginning of the stretching process, and the shallower part is deformed at the end of the stretching process
The workpiece that has been stretched in the previous process is stretched in reverse as a form of redrawing. The reverse stretching method increases the radial tensile stress and is more effective in preventing wrinkling. It is also possible to increase the tensile coefficient of redrawing.
Unlike normal stretching, thinning stretching mainly involves changing the thickness of the barrel wall of the stretched part during the stretching process.
The surface shape of the panel is complex. In the stretching process, the deformation of the blank is complex, and the nature of its forming is no longer simple stretching, but a compound forming where deep drawing and expansion exist at the same time.
Determination of the programme of metal drawing process
(1) Design review: according to the workpiece drawing, analyse the shape characteristics, size, accuracy requirements, raw material size and mechanical properties of the workpiece, and combine them with the available equipment and the batch size and other factors. A good stretching process should ensure low material consumption, a low number of processes and a low number of occupied equipment.
(2) Determine the programme: the main process parameters are calculated on the basis of the analysis of the stamping process, to find out the characteristics and difficulties of the process, and to propose various possible drawing process solutions according to the actual situation, including the nature of the process, the number of processes, the sequence of processes and the way of combination. Sometimes there may be more than one feasible process solution for the same workpiece, and usually each solution has its own advantages and disadvantages, so comprehensive analysis and comparison should be carried out to determine the best suitable solution.
(3) Process parameters to determine: process parameters refer to the development of process solutions based on data, such as a variety of forming coefficients (drawing coefficient, expansion coefficient, etc.), part size and various stresses, etc.. Calculation of two kinds of cases, the first is the process parameters can be calculated more accurately, such as parts of the material utilization rate, workpiece area, etc.; the second is the process parameters can only be calculated approximately, such as general bending or deep-drawing forming force, complex parts blank unfolding size, etc., to determine such process parameters are generally based on empirical formulas or charts for rough calculations, some need to be adjusted by test.
(4) Metal deep drawing process: select the drawing equipment according to the nature of the process to be completed and a variety of equipment force characteristics, consider the required deformation force and size of the main factors, combined with the existing equipment to reasonably select the type of equipment and tonnage