There are many kinds of stamping process, stretching is one of them. This process has a wide range of applications, in automobiles, decorative shell of some cover parts, cover parts and electric meter housing and many daily necessities have a certain role. There are three geometric shapes of drawing parts: rotary parts, box parts and complex curved parts.
Stamping and stretching processing requirements:
1, the shape of the drawing parts should be as simple and symmetrical as possible
In the circumferential direction, axismetrical tensile parts will be evenly deformed, and the mold is easier to process at this time, and the process is the best. For other shapes, sharp contour changes should be avoided as far as possible. For example, car muffler back cover, under the premise of ensuring the use of requirements, shape simplification, will make the production process from multiple processes into one to two processes, material consumption will also be reduced by half.
2. The size proportion of each part of the stretching parts should be appropriate
Design flanges and deep drawing parts should be avoided as much as possible because they require more drawing times. For example, the size of the upper part of the workpiece is too different from the size of the lower part, which does not meet the requirements of the tensile process. If you want to make it compound, it can be divided into two parts, respectively for processing and manufacturing, and then connected. If the workpiece cavity is not deep, but the flange diameter is very large, manufacturing is also very difficult, the middle also needs annealing treatment. Intermediate annealing may not be required if flange diameter is reduced. If the width of the flange is not consistent, it is not only difficult to stretch, but also need to relax the trimming allowance and increase metal consumption.
3. The fillet radius of the drawing parts should be appropriate
In order to facilitate forming and reduce the number of drawing, the fillet radius of drawing parts should be increased as much as possible. The fillet radius between the bottom and the wall, the flange and the wall, and the four walls of the rectangular parts should meet the requirements.
4. The uneven thickness of tensile parts should be considered
On the inner and outer walls of the workpiece repeatedly drawn or on the flange surface of the drawing parts with flanges, the imprint produced in the drawing process shall be allowed. Unless the workpiece has special requirements can be used to shape or shape the method to eliminate these marks
5. The holes on the drawing parts should be reasonably arranged
In the main structural plane to stretch the hole location set, so that it is kept in a plane, or make the hole wall perpendicular to the plane, so that punching and trimming at the same time in a process to complete.
6, the dimensional accuracy of tensile parts should not be too high
The manufacturing precision of tensile parts includes the precision of diameter direction and height direction. In general, the accuracy of tensile parts should not exceed the specified value. The size on the product drawing should be indicated to ensure the external size or the internal cavity size, not simultaneously marked the internal external size.
7, the choice of stretching oil
In the selection of stretch oil, in addition to the lubrication and cooling properties of stretch oil, we should also consider the rust resistance, cost and easy maintenance of stretch oil. Tensile oil is easy to choose the base oil with relatively low viscosity to add anti-wear additives, so as to achieve lubrication and friction reduction, but also can have good cooling and easy to worry. However, the problems of stretch oil are low flash point, high temperature in stamping forming, easy deformation, high risk factor, and fast volatilization, and the user cost becomes high accordingly. Therefore, if conditions permit, try to choose stretch oil with high compression resistance and wear resistance.
Advantages of stretching oil:
(1) the appearance of the tensile oil is clear and transparent, and will not change the surface color of the workpiece; Mild smell, reduce pollution to workshop environment.
(2) Corrosion performance of stretch oil on metal is the key index of oil development. Acid value and sulfur content are controlled to ensure that stretch oil does not corrode metal, especially the water-soluble acid and base of stretch oil.
(3) Quick-dry no-wash stretching oil, good volatilization effect after operation, no residual stains on the working surface after volatilization, so there is no need for further cleaning of the workpiece.
(4) In order to meet the needs of high-speed stamping processing, precision tensile oil has good extreme pressure lubrication performance, rust resistance and metal forming ability. Can reduce the stamping die friction heat, prevent the mold temperature is too high, resulting in convex and concave die clearance reduction, sintering, strain, etc.; Can reduce the stamping die wear and chip adhesion, prolong the service life of stamping die.
(5) The use of environmental protection additives, the use of the process of low odor, no harmful gas.
(6) Tensile oil viscosity is low, cooling performance is good, improve production efficiency and workpiece processing quality
