Calculate a preliminary starting blank size for a cylindrical deep-drawn part from finished diameter, height and forming geometry.
| Parameter | Value | Calculation Role | Effect |
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For a simple cylindrical cup with a flat bottom and straight cylindrical wall, a common first-pass development uses conservation of surface area.
Where D₀ is the starting blank diameter, d is the finished cup diameter and h is the finished cup height.
This relationship comes from approximating the blank area as equal to the bottom area plus the cylindrical wall area:
Real deep-drawn cups contain radiused transitions rather than perfectly sharp corners. Bottom and corner radii change the actual developed surface area and can therefore affect the blank size.
Sheet thickness also changes the effective geometry. The simple area equation does not fully model thickness distribution, material flow or the neutral surface through the sheet.
For that reason, the calculator treats the radius and thickness inputs as engineering context while using allowance factors to create a practical starting blank estimate.
The blank-to-cup diameter ratio provides a useful preliminary indication of how much diameter reduction is being attempted in the drawing operation.
A larger ratio represents a larger amount of material being drawn into the cup. Whether a part can be produced in one draw depends on material properties, thickness, tooling, lubrication, blank-holder force and the specific drawing process.
The calculator provides two optional allowances:
These are adjustable engineering inputs rather than universal standards.
What does this calculator calculate?
It calculates a preliminary circular blank diameter for a cylindrical deep-drawn cup using the finished cup diameter and height, with optional allowances.
Why is the blank larger than the cup?
The blank contains the material that forms both the cup bottom and cylindrical wall, so its original diameter must be larger than the finished cup diameter.
What is the basic formula?
A common first-pass formula is D₀ ≈ √(d² + 4dh), based on approximate conservation of surface area.
Does the calculator account for bottom radius?
The bottom radius is included as a geometry input and is used to apply a small geometry-development adjustment. Exact radius compensation is tooling and geometry dependent.
Does thickness affect the blank diameter?
Thickness affects actual material flow and developed geometry, but the basic area calculation is primarily controlled by the finished diameter and height.
Can this be used for rectangular deep drawing?
No. The main calculation is intended for approximately cylindrical cups. Rectangular, oval and irregular shapes require different blank-development methods.
Can one draw produce any calculated cup?
No. Blank diameter is only one part of deep-drawing design. The required draw ratio, material ductility, tooling and process conditions determine whether one or multiple drawing stages are appropriate.