Design of Multi-station Deep Drawing Automatic Die
The multi-station automatic drawing die design is an advanced technology for fully automatic drawing of small cylindrical and box-shaped parts. It is widely used in mass production in the fields of home appliances, electronics, and automobiles, such as thermos liner, micro motor housing, etc. Its core advantage is that it integrates automatic feeding, multi-pass drawing, waste handling and other functions to achieve unmanned production from coils to finished products. The production efficiency can reach 100-300 pieces per minute, and the part size accuracy is stable at IT8-IT10 level. In the early stage of design, the station layout needs to be determined according to the number of drawing times (usually 3-6 times), material thickness (0.3-2mm) and mechanical properties (such as the elongation of aluminum alloy must be ≥15%) of the parts. The drawing stations are arranged in increasing order of deformation, and the distance between adjacent stations is 1.2-1.5 times the maximum diameter of the part to ensure smooth material flow. For example, an aluminum alloy cup-shaped part with a diameter of 40mm and a height of 50mm requires 5 drawing stations. The first station draws the part to a diameter of 30mm, and the diameter decreases by 5mm at each subsequent station until it is gradually formed to the target size.
The mold structure consists of an automatic feeding system, multiple sets of deep drawing convex and concave dies, positioning devices, detection systems and discharge mechanisms. The deep drawing convex die is made of Cr12MoV alloy tool steel, and the hardness reaches HRC60-62 after deep cold treatment. The surface is hard chrome plated (thickness 0.005-0.01mm) to reduce the friction coefficient to below 0.1; the concave die is made of cemented carbide (WC-Co content 90%), with a hardness of HRA90-92, and a service life of more than 1 million times. The radius of the concave die of each station is designed to be 6-10 times the thickness of the material, and is reduced by 0.5-1mm at each station. For example, for a material with a thickness of 1mm, the first station has a radius of 8mm, and the last station has a radius of 5mm, which guides the material to deform evenly. The automatic feeding system uses a roller feeder driven by a servo motor, and cooperates with a high-precision ball screw to control the feeding step distance, with an accuracy of ±0.01mm. The feeding speed is synchronized with the stamping frequency to ensure continuous and stable feeding of the strip.
The automatic control system is the “brain” of the multi-station automatic deep drawing die. It utilizes a PLC (Programmable Logic Controller) and a touch screen to form a human-machine interface, enabling real-time monitoring of the drawing force, die temperature, and feed position at each station. The system features a built-in fault diagnosis module. Upon detecting abnormal drawing force (exceeding 10% of the set value), material deviation (deviation > 0.05mm), or excessive die temperature (> 60°C), it immediately issues an alarm and shuts down the machine, preventing die damage and batch scrap. For materials prone to springback (such as stainless steel), the system uses a servo motor to adjust the punch stroke in real time to compensate for the springback (typically 0.5°-2°). Furthermore, the control system supports parameter storage, storing process parameters for over 100 parts. This eliminates the need for re-commissioning when changing products, with a changeover time of less than 10 minutes.
The lubrication and cooling systems need to adapt to the needs of high-speed automatic production. A spray lubrication device is set at the entrance of the coil, and the extreme pressure emulsion (concentration 5%-8%) is evenly sprayed on both sides of the strip in a mist form. The amount per square meter is controlled at 5-8ml, which not only ensures the lubrication effect but also avoids oil residue. A water cooling circulation system is set up in the deep drawing station. A spiral water channel (diameter 6-8mm) is opened inside the die. The water flow rate is 1.5-2m/s. The mold temperature is stabilized at 40-50℃ through a temperature control valve to prevent the material from overheating and causing the plasticity to decrease. The lubrication system is equipped with a liquid level sensor, which automatically replenishes the liquid when it is lower than the set value; the cooling system is equipped with a filter (accuracy 5μm), which automatically backwashes every 8 working hours to ensure that the water channel is unobstructed.
The mold maintenance and debugging adopts a modular design. Each drawing station is installed independently and connected to the mold base through a positioning pin. It only takes 15-20 minutes to replace the male and female dies of a single station. The “progressive debugging method” is used when testing the mold: first manually run the single-step operation to check the coordination of each mechanism, then trial produce 50 pieces at 50% of the rated speed, and use a three-coordinate measuring machine to detect key dimensions (such as the thickness difference of the barrel wall needs to be less than 8%), and finally gradually increase to the rated speed. In daily maintenance, the wear of the punch coating needs to be checked every 50,000 pieces produced, and the chrome plating is re-plated when the wear is greater than 0.003mm; the die cutting edge is replaced every 100,000 pieces to ensure the accuracy of the fillet. The feed roller is cleaned once a week to remove surface oil and metal debris to maintain feeding accuracy.
