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How to calculate the tolerance of drawing die of punch press?
The tolerance of deep parts is closely related to the blank thickness, drawing die structure and drawing method. Its value is based on

/t 139 14- 1922。 For parts with high dimensional accuracy, you can add a shaping process after drawing!

What is the material thickness and drawing height of your product? The thickness of the material and the height of the drawing part have a great relationship with the design of the drawing die. Deep drawing is one of the common processes of precision punch. In actual drawing, in order to avoid wrinkling of finished products, it is necessary to apply a certain blank holder force to the material. When a single-shaft small-tonnage precision punch is used in deep drawing production, a spring or rubber plate is usually added to the die as a pressing device; However, when drawing on a twin-shaft large-tonnage precision punch, the drawing material is usually large and the drawing depth is deep, so it is necessary to equip a special drawing pad. Stretching pad is a supporting device of Jin Zhide's double-shaft precision punch. Its function is not only to compress the material during the drawing process of the precision punch, but also to eject the material or partially form the bottom of the punched product, which can improve the processing application range of the double-shaft precision punch.

There are two kinds of stretching pads used in precision punching machines, one is air cushion type and the other is oil pressure type. These two drawing pads are installed on the base of Jin Zhide double-shaft precision punch.

1, precision perforated air cushion elastic pad

The cylinder of the air cushion stretching pad of the precision punch is fixed at the bottom of the punch table. When compressed air enters the cylinder of the stretching pad, its piston and support plate move upward to the lowest position, and the stretching pad is in working condition at this time. When the slide block of the precision punch moves downwards to make the material shape on the punch, the supporting plate of the stretching pad and the piston move downwards synchronously due to the action of the slide block and the ejector rod, and appropriate pressure is applied to the edge of the material until the slide block of the punch continues to move and the punching work is completed. At the same time, when the slider of the punch returns, the compressed air pushes the piston of the stretching pad to rise to the uppermost position with the slider to complete the ejection work.

2. Oil pressure stretching pad for precision punching machine

Due to the pressure of compressed air source, the blank holder force of air cushion stretching pad is limited. In some large-tonnage twin-shaft presses, the pressure of air cushion stretching force pad is far from meeting the demand, so oil pressure stretching pad is needed at this time.

The working cylinder of the hydraulic stretching pad of the precision punch is communicated with the overflow valve through the one-way valve and the oil cylinder through the pipeline. In addition to hydraulic oil, the cylinder is also filled with compressed air, and the pressure can be adjusted by the pressure regulating valve. Under the action of compressed air at its upper part, the oil in the oil cylinder is pressed into the working oil cylinder through the pipe jacking check valve, and the working oil cylinder and the support plate are jacked up until reaching the limit position. When it is actually used with a double-axis precision punch, the main motor drives the punch slider to press down until the upper die contacts the material rack, and the oil pressure in the working cylinder of the oil pressure stretching pad starts to increase with the upper die pressing down. When this pressure rises to the rated pressure, the oil in the hydraulic stretching pad working cylinder will open the overflow valve, and at this time, the oil will flow back to the stretching pad cylinder through the pipeline, so that the stretching pad support plate will always maintain the rated pressure and continue to descend to the bottom dead center with the slider to complete the stretching operation.