Give deep drawn parts a bottom (punch) radius of at least 4× material thickness, a die radius of 5–10× thickness, and rectangular corner radii of at least 3× thickness. Limit the first draw to a 40–45% diameter reduction and each redraw to 20–30%. Expect 10–20% wall thinning near the bottom radius, diameters of ±0.002–0.005 in (±0.05–0.13 mm), and looser trimmed heights.
SSG MFG · design guideDG-03 · 11 rules
11 rules, in the order you meet them on a model. Every value is typical; the principal quoting your part confirms its own limits.
| # | Rule | |
|---|---|---|
| 01 | Specify drawing-quality materialASTM A1008 DS or DDS steel, annealed 300-series stainless, 5052-O aluminum | ASTM A1008 DS or DDS steel, annealed 300-series stainless, 5052-O aluminum |
| 02 | Size the blank from surface areaFor a round cup, blank diameter D ≈ √(d² + 4dh), plus trim allowance | For a round cup, blank diameter D ≈ √(d² + 4dh), plus trim allowance |
| 03 | Leave a trim allowance on heightTypically 3–8% of drawn height, at least about 0.060 in (1.5 mm) | Typically 3–8% of drawn height, at least about 0.060 in (1.5 mm) |
| 04 | Limit reduction per drawFirst draw no more than 40–45% diameter reduction; redraws 20–30% | First draw no more than 40–45% diameter reduction; redraws 20–30% |
| 05 | Open up the bottom (punch) radiusAt least 4× material thickness; sharper corners need a restrike station | At least 4× material thickness; sharper corners need a restrike station |
| 06 | Size the flange (die) radius5–10× material thickness | 5–10× material thickness |
| 07 | Give rectangular shells generous cornersVertical corner radius at least 3× thickness; larger is cheaper | Vertical corner radius at least 3× thickness; larger is cheaper |
| 08 | Prefer straight walls over tapersStraight cylindrical walls with no draft; each step or taper adds a station | Straight cylindrical walls with no draft; each step or taper adds a station |
| 09 | Design around the thinnest wallExpect 10–20% thinning near the bottom radius; the rim may thicken | Expect 10–20% thinning near the bottom radius; the rim may thicken |
| 10 | Keep holes off the draw radiiBottom holes at least the punch radius plus 1× thickness from the wall | Bottom holes at least the punch radius plus 1× thickness from the wall |
| 11 | Separate diameter and height tolerancesHold diameter to ±0.002–0.005 in (±0.05–0.13 mm); allow ±0.005–0.010 in (±0.13–0.25 mm) on trimmed height | Hold diameter to ±0.002–0.005 in (±0.05–0.13 mm); allow ±0.005–0.010 in (±0.13–0.25 mm) on trimmed height |
These build on the short list on the deep draw process page, with the failure each rule prevents and a drawing for each.
Set the cup diameter and height to see the blank size it needs, the resulting draw ratio, and how many draw stations it takes to get there without splitting the cup.
CUP ⌀1.50 × 1.00 IN · BLANK ⌀2.87 IN · 2 DRAWS
Costs more: 2 draws
Each redraw is another die station or transfer step. Typical for 0.7:1 cups, and priced into the tooling.
Typical first-draw reduction of 40% and 25% per redraw; the range is 40–45% and 20–30% by material and lubrication. The blank formula ignores corner radii and trim allowance, which add a few percent.
Each rule with its typical value, the reason behind it and what happens on the floor when it's ignored. Switch any drawing between Do and Avoid; point at a callout to pick it out.
Rule 01
ASTM A1008 DS or DDS steel, annealed 300-series stainless, 5052-O aluminum
Standard: ASTM A1008 DS / DDS
Rule 02
For a round cup, blank diameter D ≈ √(d² + 4dh), plus trim allowance
Fig. 1Reduction per draw
Do. Take the height in stages: up to 40–45% diameter reduction on the first draw, 20–30% on each redraw, annealing between if the material needs it.
Avoid. Asking for a tall, narrow cup in one hit tears the bottom out before the flange can feed in.
Rule 03
Typically 3–8% of drawn height, at least about 0.060 in (1.5 mm)
Rule 04
First draw no more than 40–45% diameter reduction; redraws 20–30%
Rule 05
At least 4× material thickness; sharper corners need a restrike station
Fig. 2Punch and die radii
Do. Punch radius at least 4 T and die radius 5–10 T let metal flow over the die and down the wall; expect 10–20% thinning at the punch radius.
Avoid. Tight radii stop the flange from feeding: the wall stretches instead of drawing and splits just above the punch radius.
Rule 06
5–10× material thickness
Rule 07
Vertical corner radius at least 3× thickness; larger is cheaper
Fig. 3Inside and outside radii
Do. Inside radius at least half the wall and outside radius equal to inside plus T: the corner stays at thickness T and flow turns smoothly.
Avoid. A sharp inside corner concentrates stress about 3× and the corner runs thick: cracks start there, and it cools last.
Rule 08
Straight cylindrical walls with no draft; each step or taper adds a station
Rule 09
Expect 10–20% thinning near the bottom radius; the rim may thicken
Rule 10
Bottom holes at least the punch radius plus 1× thickness from the wall
Fig. 4Hole size and spacing
Do. Holes at least T in diameter, at least 1.5 T from an edge and 2 T from each other: the punch shears clean and the web holds.
Avoid. Too close to an edge the metal bulges out; too close together the web between holes stretches or tears, and small punches break.
Rule 11
Hold diameter to ±0.002–0.005 in (±0.05–0.13 mm); allow ±0.005–0.010 in (±0.13–0.25 mm) on trimmed height
Fig. 5A complete drawing package
Do. Every requirement is on the drawing: general tolerance, material by specification, finish by specification, critical dimensions and revision.
Avoid. Whatever the drawing leaves blank, the supplier decides, usually with the cheapest local equivalent.
Diameters are sized by the punch and die and hold closely. Height depends on trim, earing and thinning, and wall thickness depends on whether the wall is ironed.
| Feature | Typical | Tight | Cost of tight |
|---|---|---|---|
| Drawn diameterTight usually needs ironing or a sizing station | ±0.002–0.005 in (±0.05–0.13 mm) | ±0.001 in (±0.025 mm) | Moderate |
| Trimmed heightTight usually needs turn trimming | ±0.005–0.010 in (±0.13–0.25 mm) | ±0.003 in (±0.08 mm) | High |
| Wall thickness | Starting gauge less 10–20% | ±0.001 in (±0.025 mm) ironed | Moderate |
| Roundness | 0.003–0.005 in (0.08–0.13 mm) | 0.001–0.002 in (0.025–0.05 mm) | Moderate |
| Bottom flatnessTight needs a restrike | 0.005 in (0.13 mm) | 0.002 in (0.05 mm) | Moderate |
| Pierced hole position in bottom | ±0.005 in (±0.13 mm) | ±0.002 in (±0.05 mm) | Moderate |
| Flange flatness | 0.005 in (0.13 mm) | 0.002 in (0.05 mm) | Moderate |
Basis: Industry-typical deep draw practice. Put a general tolerance note on the drawing and tighten only the features that need it; every tight callout is priced. See the tolerance guide.
The same deep draw rules shift with the alloy or compound.
Order as ASTM A1008 DS or DDS for deep draws, or EDDS for the most severe. It draws to a ratio of about 2.0 and rarely needs anneals between draws.
Draws well but work hardens quickly, so parts with several redraws often need an intermediate anneal. Expect higher tonnage and die wear than steel.
Higher nickel makes it more stable and less prone to work hardening than 304 in drawing. It costs more and is chosen for corrosion, not drawability.
Ferritic and lower cost, with good draw ratios on moderate depths. Surface ridging can show on drawn walls, so check it on cosmetic parts.
Use 5052-O for deep draws and keep H32 for shallow parts. Aluminum galls on the die without the right lubricant and thins faster than steel.
Very ductile and draws deep in soft tempers, but work hardens with each draw and may need anneals on tall parts.
Run these against the model before it goes out for quote. The builder's DFM check catches most of them on an uploaded part.
0 of 12 checked
For a round flat-bottom cup with small radii, the blank diameter is about √(d² + 4dh), where d is cup diameter and h is height. A 2 in (51 mm) diameter cup 2 in tall needs a blank of about 4.47 in (114 mm) before trim allowance. Toolmakers correct for corner radii and wall thinning during blank development.
The limiting draw ratio is the largest blank diameter divided by punch diameter that can be drawn in one station without splitting. It is about 2.0 for drawing-quality steel and similar for 300-series stainless. Production tools stay below it, using a 40–45% reduction on the first draw and 20–30% on each redraw.
Divide the blank diameter by the cup diameter. At a ratio under about 1.8, one draw usually works. Above that, add redraws: the first draw reduces diameter by up to 40–45%, then each redraw by 20–30%. A cup twice as tall as its diameter typically needs three or four stations.
Wrinkles form when the flange compresses as it feeds toward the die and has nothing holding it flat. Too little blank holder pressure, a die radius larger than about 10× thickness, or a tapered wall with unsupported metal all cause it. Straight walls and a controlled blank holder prevent most wrinkling.
Rolled sheet has different properties along and across the rolling direction, so the rim draws higher in some directions than others. The high points are ears, usually four. Designs include a trim allowance, typically 3–8% of drawn height, and the rim is trimmed to final height after drawing.
No. Drawn walls leave the die straight, and parts strip off the punch without draft. Tapered walls are harder to draw than straight ones because metal between the punch and die is unsupported and tends to wrinkle. Specify straight walls unless a taper is needed for nesting or assembly.
Check your part against these rules.
Drop a STEP file in the builder for an instant DFM check and a budgetary estimate, then send it to principals who run deep draw every day.
