Deep drawing stainless steel is not for the faint of heart, but it’s work we’ve been doing long enough to have the process dialed in. This past quarter we ran a production order for 304 stainless cups used as housings for a medical device component. The cups were 2.5″ diameter by 2.8″ deep — a draw ratio of about 1.12, which means a single-stage draw with good tooling design and the right lubrication.
Blank size was calculated at 6.5″ to give us the right wall height with trim allowance. We ran the draw on a 150-ton hydraulic press with a nitrogen-spring blankholder — critical for keeping wrinkles out of the flange on stainless. Draw speed was slow and controlled, around 15 feet per minute. Lubricant was a heavy sulphurized drawing compound applied to both faces of the blank before each hit.
We drew the cups in one shot with a redraw to bring the wall thickness variation into a tighter range. After trimming and a light annealing cycle to relieve work hardening, all parts were checked for wall thickness, depth, and diameter. Rejects ran under 1.5% across the 2,000-piece run. Medical customers have high standards, and this is one of those jobs where the process control has to be locked in from the start.