Research On The Deep Drawing Forming Quality Control Of Thin-walled Stainless Steel Cup-shaped Parts

With the development of science and technology, the quantity demand of precision parts is increasing gradually, as well as the requirement of processing accuracy. High-precision thin-wall stainless steel cup-shaped parts are widely used in instruments, aerospace and other industries. Deep drawing is the most commonly used plastic shaping method in manufacturing thin-wall cup-shaped parts because of its high material utilization and high production efficiency. As the major research in this paper, the forming quality of drawing thin-walled stainless steel cup-shaped parts was explored through finite element simulation analysis and experiments, the traditional forming parameters(material performance, die radius, clearance between punch and die, blank holder force and friction coefficient) as well as the non-traditional forming parameters(draw bead and gradient-arc die radius) in deep drawing of cup-shaped parts were analyzed, and influence rule of non-traditional forming parameters on the forming quality of thin-walled stainless steel cup-shaped parts was obtained. The specific research contents and conclusions are as follows:1. Combined with the analysis of a instrument shell part, the quality problems of out-of-tolerance dimension, such as the mouth of cup-shaped parts is not round, the wall is not straight, the wall thickness is thinning seriously and so on, were found in the deep drawing process of thin-walled stainless steel cup-shaped parts. The factors were analyzed and the optimization goal was determined.2. The influence rule of traditional forming in deep drawing of cup-shaped parts on ovality of mouth, straightness of sidewall, bulges of sidewall and maximum thinning ratio was analyzed using the finite element simulation software Dynaform. The results showed that increasing sheet thickness, blank holder force and friction coefficient between the punch and sheet, and decreasing die radius and clearance between the punch and die, can improve the ovality of mouth and straightness of sidewall of thin-walled stainless steel cup-shaped parts. Decreasing sheet thickness, blank holder force and friction coefficient between the punch and sheet, and increasing die fillet radius and clearance between the punch and die, can improve the bulges of sidewall and maximum thinning ratio of thin-walled stainless steel cup-shaped parts. The forming quality in traditional forming parameters was predicted through analyzing the traditional forming parameters. The preliminary analysis results show that the minimum ovality of cup-shaped parts mouth can decrease to 0.28 mm, but it has not yet satisfied with the dimensional accuracy of 0.1mm.3. Influence rule of friction coefficient between the punch and the sheet and blank holder force on drawing forming quality of thin-walled stainless steel cup-shaped parts was verified through experiments. The experimental results are similar to the simulation results. It is proved that the prediction of ovality of mouth and straightness of sidewall in the finite element simulation is credibility.4. Influence regularity of the non-traditional forming parameters in deep drawing of cup-shaped parts(draw bead and gradient-arc die radius) on ovality of mouth was explored. The result shows that the optimum ovality of mouth is by using the semicircular draw bead and two-tangent-arc die radius. Adapting orthogonal experimental method, the influence sequence of the ovality of mouth was obtained: the height of draw bead > the small radius > the large radius >the location of arc tangent point.5. Taking the ovality of mouth as optimal target, the four parameters(included the height of draw bead, the large radius, the small radius and the location of arc tangent point) were optimized by means of SVM and GA. The ovality of thin-walled stainless steel cup-shaped parts mouth reduced from 0.28 mm to 0.09 mm, which was less than 0.1mm and was consistent with the ovality tolerance requirement. The optimize parameters are as follow: the height of draw bead is 4mm, the large radius is 6.0 mm, the small radius is 3.1 mm, the location of arc tangent point is 0.687. Other forming qualities of thin-walled stainless steel cup-shaped parts conformed to the requirements.