KEVOS® MAKEOS · Fabrication
Drawn Shell Blank Diameter and Draws
What blank diameter is needed for this drawn cup, and how many draws will it take?
Blank diameter for a cylindrical drawn shell with or without a flange, the first drawing ratio against a limit, the estimated number of draws and the first-draw force.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Shell diameter (mean) | mm | Mean diameter of the finished shell. |
| Shell height | mm | Height of the shell (to the flange face if flanged). |
| Bottom corner radius | mm | Inside corner radius between wall and bottom. |
| Flange outside diameter (0 = no flange) | mm | Outside diameter of the flange; 0 for a plain cup. |
| Material thickness | mm | Sheet thickness. |
| Tensile strength | MPa | Ultimate tensile strength of the sheet. |
| Limiting first drawing ratio d ÷ D | Smallest first-draw ratio d ÷ D for your material and relative thickness, from drawing ratio tables (about 0.48–0.63). | |
| Limiting redrawing ratio | Smallest redraw ratio for later draws (about 0.73–0.82). |
Method and formulas
- D = √(d_f² + 4 d h − 0.5 r d), with d_f = flange diameter (or d for a plain shell).
- First drawing ratio m = d ÷ D; one draw if m ≥ the limiting ratio.
- Further draws reduce the diameter by the redraw ratio each time.
- First-draw force ≈ π d₁ t UTS (D ÷ d₁ − 0.7), with d₁ the first-draw diameter.
- Example: a 60 × 50 mm cup needs a 124.42 mm blank and 2 draw(s).
Limitations
- Thin-wall, constant-thickness approximation; trim allowance (often 3–5 mm on the diameter) must be added.
- Corner radius correction is approximate.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Size blanks for drawn cups and cans
- Plan the number of drawing operations
- Estimate first-draw press force
Who it is for
- Fabrication supervisors
- Manufacturing engineers
- Estimators
What you get
- Blank diameter
- First drawing ratio
- Estimated number of draws
- First-draw force
Interpreting the result
- Add trim allowance and confirm with a trial draw.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1353–1360. Topic reference; no source tables or recommended settings are reproduced.
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