Common Deep-Drawn Part Defects and How to Fix Them
Deep drawing turns flat sheet metal into seamless cup, shell, tube, and box-shaped components in a single press stroke — or a short sequence of draws. It is one of the most material-efficient ways to make stainless steel and aluminum enclosures, sensor housings, and structural shells. But the process lives on a knife-edge between controlled plastic flow and failure: when blank-holder force, die radius, draw ratio, or lubrication drift even slightly out of window, the part tells you immediately — through a crack, a wrinkle, or a wall that is suddenly too thin to seal.
This guide consolidates the ten defects our engineering team sees most often on production lines, the mechanism behind each, and the concrete adjustment that usually fixes it. It is written for process, tooling, and quality engineers who need a fast, reliable reference on the shop floor. For context, AUNOV’s own process envelope is 5–500 T presses, draw depth ≤150 mm, wall thickness 0.15–3.0 mm, tolerance ±0.05 mm (±0.02 mm after ironing), with measured limiting draw ratios (LDR) of 2.1–2.2 for DC04, 1.85–2.05 for 304 stainless steel, and 1.80–1.95 for 5052 aluminum.
Quick-Reference Table
| # | Defect | What you see | First check | Quick fix |
|---|---|---|---|---|
| 1 | Cracking / Splitting | Tear on wall or base | Draw ratio, corner radius | Increase die radius R, reduce single-draw depth, improve lubrication |
| 2 | Wrinkling | Wavy flange or side wall | Blank-holder force | Raise BHF, optimize blank-holder ring, revise die structure |
| 3 | Earing | Uneven ears at rim | Material anisotropy (Δr) | Adjust blank shape, specify low-Δr sheet, tune draw |
| 4 | Wall thinning | Uniformly thin side wall | Draw ratio too high | Lower draw depth, increase R, use multi-stage drawing |
| 5 | Base thinning / rupture | Thin or burst base | Draw force, material flow | Optimize BHF, improve lubrication, control draw speed |
| 6 | Surface scoring | Scratches / streaks | Die finish, cleanliness | Polish die, upgrade lubrication, clean tooling |
| 7 | Dimensional error | Over / under / out-of-round | Springback, die wear | Compensate springback, rework die, stabilize process |
| 8 | Base bulging | Domed or wavy base | Material flow, BHF | Adjust BHF, optimize die corner radius |
| 9 | Flange cracking | Cracks at flanged edge | Flange radius, ductility | Increase flange radius R, reserve flange stock, anneal |
| 10 | Orange peel / dull | Rough, grainy finish | Material grade, lubrication | Use higher-quality sheet, improve lubrication, tune speed |
01 Cracking (Splitting)
Direct answer: Cracking at the punch radius is a tensile tear. Open the punch and die corner radii, split the depth over two draws, and anneal work-hardened stock.
Appearance
A clean or fibrous tear, most often running vertically up the side wall near the punch radius, or across the base.
Why it happens
The material at the punch corner is placed in tension as it is pulled over the radius. When the draw ratio is too aggressive, the die corner radius too tight, or the sheet’s ductility too low, the tensile stress exceeds the local necking limit and the wall splits.
How to fix it
Prevention
Validate the LDR on sample blanks before committing to a die; anneal work-hardened stock.
02 Wrinkling
Direct answer: Wrinkling is compressive buckling of the flange. Raise blank-holder force until the flange stays flat; if that risks splitting, re-profile the blank edge.
Appearance
A fluted or wavy flange, and in severe cases waves climbing the side wall.
Why it happens
The flat annulus of material outside the punch is in compression as it feeds inward. If the blank-holder force (BHF) is too low, that annulus has nothing to keep it flat and it buckles.
How to fix it
Prevention
Set BHF from the forming-limit window, not by feel; verify holder flatness across the stroke.
03 Earing
Direct answer: Earing comes from planar anisotropy. Specify low-delta-r sheet or rotate the blank so the ears average out, then trim.
Appearance
Symmetric “ears” standing up around the cut rim after trimming — usually 4 or 6, tied to the sheet’s rolling direction.
Why it happens
Rolled sheet is anisotropic: it flows more easily along some in-plane directions than others (planar anisotropy, Δr). Under draw, the rim rises where flow is easiest.
How to fix it
Prevention
Request earing test data from the mill; choose grades with tight Δr for critical parts.
04 Wall Thinning
Direct answer: Wall thinning means too much reduction per stroke. Reduce depth per draw, open the die radius, and spread the total reduction across multiple draws.
Appearance
The side wall measures thinner than the blank gauge, sometimes uniformly, sometimes worst near the punch corner.
Why it happens
Stretching the wall over a tight radius or pushing too much reduction per stroke converts sheet thickness into length. A draw ratio above the material’s limit thins the wall as it elongates.
How to fix it
Prevention
Model wall strain at the quote stage. For 5052 aluminum (deep-drawable 5xxx) stay within the 1.80–1.95 LDR; remember 6xxx alloys only suit shallow draws or post-form T6.
05 Base Thinning / Rupture
Direct answer: Base rupture means uneven flow concentrates stress at the base. Balance blank-holder force, improve base lubrication, and control draw speed.
Appearance
The base is thinner than spec, or — at the extreme — punched through.
Why it happens
Excessive drawing force and uneven material flow concentrate stress at the base, especially where the wall meets the bottom radius.
How to fix it
Prevention
Watch base-radius wear — a worn radius spikes local stress.
06 Surface Scoring / Scratching
Direct answer: Scoring is abrasive die contact. Polish the die to spec, upgrade lubrication, and keep the blank path clean.
Appearance
Straight or angled scratch lines, often shiny from burnishing, running up the wall.
Why it happens
A rough or contaminated die surface, poor lubrication, or embedded particles gouge the sheet as it slides.
How to fix it
Prevention
A routine die-finish check and a clean blank path prevent most scoring.
07 Dimensional Out-of-Tolerance
Direct answer: Dimensional drift comes from springback, die wear, or an unstable window. Compensate springback in the die, rework worn tooling, and lock a process control plan.
Appearance
The part is oversized, undersized, or out-of-round versus the drawing.
Why it happens
Springback after the punch releases, gradual die wear, or an unstable process window all shift the final geometry.
How to fix it
Prevention
Lock parameters with a control plan; schedule die rework before wear drifts the dimension.
08 Base Bulging
Direct answer: Base bulging means the center pushes out. Balance blank-holder force and optimize the die corner radius so the base forms flat.
Appearance
The base is not flat — it domes or shows a wavy contour instead of seating cleanly.
Why it happens
Uneven material flow and an improperly set BHF let the center of the base push out instead of staying supported.
How to fix it
Prevention
Verify base support in the die; check BHF symmetry.
09 Flange Cracking
Direct answer: Flange cracking is over-bending a tight radius. Increase the flange radius, reserve enough flange stock, and anneal before severe flanging.
Appearance
Cracks at the flanged or redrawn edge, typically during a flanging or wall-ironing operation.
Why it happens
The flange is bent or stretched over too small a radius for the material’s ductility, or there is not enough material reserved to form the flange cleanly.
How to fix it
Prevention
Size the flange allowance from the bend allowance; anneal before severe flanging.
10 Orange Peel / Dull Surface
Direct answer: Orange peel exposes coarse grain. Specify finer-surface sheet, improve lubrication, and tune draw speed.
Appearance
A rough, grainy, or dull finish — like orange skin — instead of a clean drawn surface.
Why it happens
Coarse-grained or low-surface-quality sheet, poor lubrication, or an unsuitable draw speed exposes the grain structure as the surface deforms.
How to fix it
Prevention
Set a surface-grade spec at sourcing; confirm it on the first article.
How AUNOV prevents these in production
Most of the ten defects above are solved before the first part is run, not after. In-house tooling lets us tune die corner radii, blank-holder geometry, and draw beads to the specific alloy and gauge; measured LDR data for DC04, 304 stainless steel, and 5052 aluminum keeps every quote inside a proven forming window; and a 24-hour quoting turnaround means the process plan — not a guess — reaches the press. Typical programs start at MOQ 1,000 pieces with wall tolerances held to ±0.05 mm (±0.02 mm after ironing).
If you are fighting a persistent draw defect on a current part, send the drawing and a sample and we will diagnose the root cause from the mechanism, not the symptom.
Frequently Asked Questions
How do I stop a deep drawn cup from cracking at the punch radius?
Cracking at the punch radius is a tensile failure, so the fix is to lower tensile strain at that point. Open the punch radius to at least 4 to 6 times the sheet thickness, increase the clearance between punch and die to about 1.1 times the blank thickness, and add an intermediate redraw so no single stroke exceeds the material’s limiting draw ratio. For 304 stainless the LDR sits at 1.85 to 2.05 and for 5052 aluminum at 1.80 to 1.95, so keep each draw below those values. AUNOV holds wall tolerances to plus or minus 0.05 mm (plus or minus 0.02 mm after ironing) and flags corner-radius and draw-ratio risks at the quoting stage.
Why does my deep drawn part score or scratch, and how do I stop it?
Scoring and scratching come from abrasive contact between the sheet and the tool surface: a burr on the die edge, embedded grit, weak lubrication, or a worn draw ring. The fix is to deburr and polish the draw radius, switch to a higher film-strength lubricant, keep the blank and tool face clean, and add a chrome or DLC coating on high-wear surfaces. For 300-series stainless this matters most because the material work-hardens and grabs the tool. AUNOV inspects tooling between runs and specifies lubrication per material so the drawn surface stays free of score marks.
What is the safe wall-thinning limit for a deep drawn part, and how do I stay above it?
As a rule of thumb keep wall thinning below 10 percent of the nominal blank thickness for structural parts and below 15 percent for non-load-bearing covers. Thinning concentrates at the punch radius and the redraw transition, so control it with adequate corner radii, correct redraw reductions, and ironing passes where a tight tolerance is required; AUNOV holds plus or minus 0.05 mm walls (plus or minus 0.02 mm after ironing). Measure the thinnest section on a cross-sectioned sample rather than the as-drawn surface, because the minimum is always hidden inside the radius.
What causes orange peel on deep drawn stainless steel, and can it be removed?
Orange peel is the surface revealing the underlying coarse grain after heavy cold deformation, most visible on 300-series stainless and on large-radius draws. It cannot be polished away once formed because it is a grain-size effect, so the fix is upstream: use a finer, more uniform grain-size coil, reduce the total reduction per draw, or specify a grade less prone to coarse grains. In some cases a light skin-pass or temper roll before drawing suppresses it. AUNOV selects coil batches by grain uniformity when surface finish matters.
How do I prevent bottom bulging on a deep drawn cup?
Bottom bulging means the punch bottom is stretching the base faster than the wall can feed, leaving a dome instead of a flat floor. Prevent it by keeping the punch-bottom radius generous, limiting the reduction in the final draw, and making sure the blank holder does not over-clamp the wall. For shallow pans a single draw is enough; for deeper parts add a reverse-redraw or a sizing station. AUNOV verifies flatness on a surface plate and holds the floor within the part’s dimensional tolerance at first-article inspection.
When should a deep drawn part be scrapped rather than reworked?
Scrap the part when the defect reaches a structural limit: a crack of any length at the punch radius, wall thinning beyond the 10 to 15 percent allowance, or a dimension outside the drawing tolerance that cannot be recovered by a sizing pass. Rework only surface-level issues such as light flange wrinkle (trim away), minor scoring (polish), or cosmetic orange peel on non-contact faces. If you are unsure, send the drawing and a sample to AUNOV and we will diagnose from the mechanism; most defects are set at the design stage, so the cheaper fix is usually in the next tool rather than the current batch.
Standards That Define the Failure Modes
The defect names and root causes below map directly to the material properties measured by these standards. Catching them starts with checking these properties on the incoming material.
- ASTM E646 — Standard Test Method for Tensile Strain-Hardening Exponents (n) of Metallic Sheet Materials. The n-value sets how much a wall can thin before necking.
- ASTM E517 — Standard Test Method for Plastic Strain Ratio (r) of Sheet Metal. The r-value predicts earing in drawn cups.
- DIN 8584 — Manufacturing processes, forming: classification of deep drawing operations and their subgroups.
- Wikipedia: Work hardening — why redraws and intermediate annealing matter.
- Wikipedia: Anisotropy — explains the r-value and why earing directions form.
- Wikipedia: Strain rate — why draw speed affects cracking and wrinkling.