Die technology of ultra limit drawing

Cold stamping and drawing die is a kind of product which uses the forming characteristics of metal materials to draw. Each material has a limit drawing coefficient. If the limit drawing coefficient of material is exceeded in the process design of die, cracking will occur, leading to failure of forming, so the process must be increased. This article will share with you a kind of ultra limit drawing coefficient of die technology and structure.
Before the process design of cold stamping and drawing die, the drawing process of the product should be designed, that is, the distribution of drawing process. Taking stainless steel material as an example, the first limit drawing coefficient is 0.5 ~ 0.52. If the drawing coefficient is less than 0.5, it can not be drawn in theory, and the material will fracture due to exceeding the plastic deformation limit in the deformation process.
Introduction of die structure for ultra limit drawing
The die introduced in this paper is a kind of drawing die with heating and cooling functions. Its characteristic is that the first drawing coefficient can be taken below 0.5. The die plane and structure are shown in Fig. 1 and Fig. 2.
The working principle is that the cooling water circulation is formed in the punch through the water inlet pipe and outlet pipe installed on the punch plate (20) (the cooling water comes from the external water cooler), so that the die temperature is not increased and the cooling water temperature is maintained below 5 ℃; at the same time, the electric heating pipe is installed on the concave template (05) and the pressing plate (04) to heat the mold and keep the mold in the temperature range of 5 ℃ At a certain temperature, it is usually 80-100 ℃. (the electric heating tube automatically heats the mold by controlling the electric box, and the thermocouple installed in the concave mold and the supporting plate measures the mold temperature. When the mold temperature is lower than the set temperature, the electric heating tube is automatically powered on and heated. After heating to the set temperature, the electric heating tube automatically cuts off power and works repeatedly. )In this way, the material is cold inside and hot outside in the process of drawing deformation, and the plastic deformation ability is greatly improved. The first drawing coefficient breaks through the original material limit drawing coefficient, which can reach 0.46. So as to reduce the drawing process and improve the production efficiency. At the same time, after using this drawing process, the punch and die drawing damage are reduced, the mold polishing maintenance frequency is reduced, and the die life can be increased by more than 2 times.
Fig. 1 die plane diagram
Fig. 2 Schematic diagram of die structure
00 – lower die base 01 – lower base plate 02 – limit block 03 – pressing plate 04 – blanking plate 05 – concave template 06 – die plate 07 – hollow plate 08 – drawing products 09 – upper die base 10 – upper foot 11 – punching rod 12 – blanking plate 13 – sealing ring 14 – drawing punch 15 – sealing cover plate 16 – sealing ring 17 – electric heating tube 18 – sealing ring 19 – electric heating tube 20 – punch plate
Technical key points of ultra limit drawing die
Several technical details should be paid attention to in the process of design and manufacture
(1) firstly, the sheet size is determined according to the product development size, and then the outer diameter and height of the drawing product are determined according to the drawing coefficient.
(2) flange edge can be reserved for drawing products or complete drawing is straight body according to product requirements.
(3) if the product has further drawing or shaping process, the head of the product should be designed as a slope transition during the first drawing, and the slope angle should be 20 ° to 30 °.
(4) the head of the drawing punch is designed as a cavity to store cooling water, and special attention should be paid to the design of water channel seal. Ordinary sealing gasket can be used, but the fitting tolerance of sealing parts should be paid attention to in the die processing. The flow difference between the inlet and outlet water can be realized by the diameter difference of the inlet and outlet holes, and can also be adjusted by the ball valve in the pipeline.
(5) the drawing die and pressing plate should have enough thickness to ensure the strength of the die, because the groove for placing the heating pipe should be processed on the two templates. The gap between the heating pipe groove and the heating pipe should not be too large. The contact area between the heating pipe and the mold should be as large as possible to improve the energy efficiency.
(6) the gap limiting device is set between the blank holder plate and the die to ensure that the blank gap is uniform and the blank holder force is evenly distributed on the material surface. By adjusting the blank holder force of the machine table, the material is stressed evenly in the process of drawing and forming smoothly.
(7) a stop block should be set in the lower die to prevent the pressure plate from crushing the inlet pipe and outlet pipe.