Direct answer: The eight failures that come up in every deep drawing job, with the cause and the tooling-side remedy.
Where it goes wrong, and why the fix is usually tooling
A drawn cup fails in five predictable zones: earing on the top edge, wrinkling in the flange and wall, tearing at the bottom radius, thinning in the wall, and draw marks on the wall.
Almost every remedy in this document is a tooling change, not a material change.
That is why deep drawing tooling is a design problem first and a production problem second, and why a DFM review before the die is cut is cheaper than fixing after.
Source: Balford deep drawing technical guide, balford.net/deep-drawing/.
Wrinkling
| Aspect | Detail |
|---|---|
| Appearance | Folds in the wall or flange |
| Usual cause | Blank holder force too low; flange unsupported |
| Usual remedy | Increase blank holder pressure; adjust the draw radius; add draw beads |
| Why it happens | The flange circumference has to shrink as it is pulled inward. Whatever does not go into the wall buckles out of plane. |
Blank holder force is a balance: too low wrinkles the flange, too high stops the material flowing and tears the wall at the die radius.
Tearing and fracture
| Aspect | Detail |
|---|---|
| Appearance | Split at the die radius or in the wall |
| Usual cause | Draw ratio above the material limit; die radius too tight; clearance too small; friction too high |
| Usual remedy | Add a redraw, open the die radius, correct the clearance, improve lubrication |
| First thing to check | The draw ratio against the material single-draw limit. Stainless is about 1.6-1.8; low-carbon steel 1.8-2.0. |
Lubricant is not optional: it controls friction at the die radius, which is where tearing starts.
Earing and excessive thinning
| Defect | Appearance | Usual cause | Usual remedy |
|---|---|---|---|
| Earing | Wavy, scalloped top edge | Planar anisotropy in the sheet | Accept and trim; change material or rolling direction; adjust blank shape |
| Excessive thinning | Wall too thin at the radius | Die radius too tight; excessive tension | Increase die radius; add a redraw; anneal |
Earing is why a trim allowance on the top edge is normal engineering, not sloppy work: the drawn edge is never perfectly even.
Springback and orange peel
| Defect | Appearance | Usual cause | Usual remedy |
|---|---|---|---|
| Springback | Diameter or shape relaxes after forming | Elastic recovery, worse in high-strength material | Adjust tool dimensions to compensate; restrike; change material |
| Orange peel | Grainy stretched surface | Coarse grain structure; excessive stretch | Finer grain material; reduce local strain |
Springback is a tool-compensation problem. Chasing it in the material specification usually costs more than compensating in the die.
Draw marks and bottom fracture
| Defect | Appearance | Usual cause | Usual remedy |
|---|---|---|---|
| Draw marks / scoring | Longitudinal scratches on the wall | Tooling wear, galling, inadequate lubricant | Polish the die radius; re-coat or re-polish tooling; review lubricant |
| Bottom fracture | Split across the base | Punch radius too small; too little material available | Increase punch radius; enlarge the blank |
Draw marks are inherent to forming. If the outside wall is visible, say so before tooling so that a finishing route can be planned.
Wall thickness is a gradient, not a number
- Bottom centre: about 1.00 - effectively undeformed
- Lower wall: thinning to roughly 0.85, worst where it passes over the die radius
- Top edge: recovering to about 1.05, because the flange thickened as its circumference shrank
Relative wall thickness through a drawn part, measured against nominal:
The gradient is not a defect. It becomes a problem only when a drawing specifies a wall thickness without saying where it is measured: the supplier and the customer then measure at different heights and both are correct.
Diameters repeat well because they are set by tooling. Wall height is the least precise dimension because the top edge is trimmed.
State the measurement position on the drawing. It is the cheapest tolerance decision you will make.
Ten design rules that prevent most of the above
- Keep the depth-to-diameter ratio realistic. Below about 0.5 you probably do not need deep drawing; above about 2, plan for multiple draws and possibly anneals.
- Do not specify a sharp corner at the bottom: punch radius has a minimum, and it grows with material thickness.
- Give the wall a generous die radius. Too tight a radius is the most common cause of tearing.
- Specify wall thickness with a measurement location.
- Allow a trim allowance on the top edge.
- Prefer a simpler profile over a stepped or tapered one; each change of diameter can add a draw.
- Define which diameter is functional.
- Do not put a fine thread on a drawn wall unless it has been ironed.
- Think about the blank layout; nesting affects material cost, the largest part of the unit price.
- State the cosmetic requirement early.
Every rule above maps to a defect in this document.
Related pages
- All Balford engineering resources
- RFQ, IMDS and supplier audit checklists
- Deep drawing: the complete technical guide
- Send a drawing for a DFM review
Printable version
This document is also available as a PDF: Deep Drawing Defects and Remedies (PDF).