A drawn aluminum pan or cup can have a sound wall yet emerge with a rim that rises and falls around its circumference. Before changing the alloy or rejecting the circles, establish whether this is earing, wrinkling or uneven drawing. The distinction affects material selection, trial design, trimming and the information needed for a useful quotation.
Why Does an Aluminum Circle Form Ears?
Rolling and subsequent processing develop crystallographic texture. The sheet can therefore deform differently along different directions in its plane. As a circular blank feeds into a drawing die, this directional response can produce an uneven rim. A circle cut from rolled sheet retains that directional behavior even though its outline is round.
The repeatability and angular position of the peaks are useful clues. Ear patterns can vary with the material and processing history; a particular number of ears should not be assumed for every alloy or production lot. Keep the rolling direction identifiable on trial blanks where possible, and record the rim profile relative to that direction.
Does O Temper Eliminate Earing?
No. Annealing can improve forming latitude, but an O designation does not certify an isotropic structure or a zero-earing result. Two lots of the same alloy and temper may perform differently in the same draw. A tensile elongation result alone also does not describe the full directional rim response.
For a sourcing starting point, review the SASA ALUMINUM circle product page. Identify the required alloy, temper and disc dimensions in the inquiry, and specify the forming acceptance requirements separately.
Earing, Wrinkling or an Off-Center Draw?
Uneven height is an observation, not a complete diagnosis. Inspect the cup before trimming and compare several samples from an identified lot.
| Observed condition | What to investigate | Useful evidence |
|---|---|---|
| Repeated peaks and valleys at consistent angles to the blank direction | Material directional behavior, with forming conditions held constant | Full rim profiles, rolling-direction marks and results from multiple blanks |
| Folds or buckles in the flange or wall | Wrinkling and the balance of material restraint and flow | Untrimmed parts, flange photographs and blank-holder settings |
| One side consistently taller or an irregular asymmetric profile | Blank centering, tool alignment, uneven clamping or lubrication | Setup checks and controlled repeat trials |
| Local tearing, severe thinning or scoring | Drawing severity, radii, friction, surface or blank-edge condition | Defect location, wall measurements and forming-stage records |
How to Run a Useful Comparison Trial
A controlled trial should separate a material change from a setup change. Randomly adjusting lubrication, blank-holder force and blank size while changing the lot makes the result difficult to interpret.
- Identify the blanks. Record alloy, temper, thickness, diameter, lot identity, edge condition and rolling direction when available.
- Hold the tooling and process constant. Record punch and die geometry, blank-holder conditions, lubrication, centering, draw sequence and relevant machine settings.
- Inspect before trimming. Retain the rim profile and note wrinkles, splits, scoring and local thinning separately.
- Compare repeat samples. Look at profile shape and variation between cups, rather than choosing only the best-looking specimen.
- Change one factor at a time. Where a change is needed, document it and repeat the comparison before approving the production route.
Tooling or restraint changes may influence the final rim, but they should not be treated as a universal way to remove the material’s directional response. A trial using the intended production route remains necessary for a critical component.
Specify the Measurement Before the Percentage
An earing percentage is only useful when both parties understand how the specimen was formed and how the result was calculated. State the test method and agreed revision, specimen geometry, forming conditions, measurement datum, rim sampling method, calculation and acceptance limit.
For troubleshooting, record the full circumferential height profile where practical, including peaks, valleys and their angular positions. A few isolated readings can miss local features. Thin rims require suitable support and measuring force so the measurement does not deform the edge.
Separate Material Testing from Finished-Part Approval
A standardized cup test is intended to compare material behavior under defined conditions. A production part may use a different draw ratio, restraint, redraw sequence or wall-ironing operation. Record which test controls material acceptance and which trial controls approval of the actual component. Do not compare percentages from unlike methods as though they were interchangeable.
Plan Trim Allowance Around the Finished Height
Trimming removes the high portions of the rim, but it cannot replace missing material at a low valley. The production trial must show that the lowest usable rim region leaves enough material for the specified finished height, trimming operation and any later edge forming.
For a pan, cover or cylindrical shell, tell the supplier whether the drawing height applies before or after trimming. Include flange, rolled-edge or sealing features that consume material after drawing. Confirm wall-thickness requirements at defined locations as a separate acceptance item.
Additional allowance can increase material consumption, scrap and processing cost. It should follow a validated blank and draw plan rather than an arbitrary increase in disc diameter. A larger blank also changes the draw conditions and may require a fresh trial.
Choose the Material and Acceptance Package Together
For formable circles, buyers commonly consider commercially pure grades such as 1050 or 1100 and alloys such as 3003. The correct choice also depends on finished strength, corrosion exposure, appearance and subsequent processing. None of these grade names guarantees a particular earing result.
A useful purchasing specification connects material identity to the part trial. It should distinguish ordinary dimensional inspection from any agreed drawing test, and distinguish a requested test report from a guarantee of finished-part performance.
| RFQ item | Information to provide | Decision it supports |
|---|---|---|
| Material and blank | Alloy, complete temper, governing specification, thickness and diameter tolerances | Defines the material and trial starting condition |
| Part and drawing route | Controlled drawing, finished height, draw stages and planned edge operations | Clarifies deformation and required trim stock |
| Earing acceptance | Agreed test method, calculation, sampling and acceptance criterion | Makes supplier and buyer results comparable |
| Other quality requirements | Surface limits, burr direction, local wall thickness and relevant inspection records | Prevents one rim metric from substituting for complete inspection |
| Lot and shipment | Lot identification, quantity, interleaving, moisture protection and destination | Supports traceability and protects blanks before forming |
Review Aluminum Circle Product Information
Discuss Your Aluminum Circle Requirement
Send the alloy, temper, thickness, diameter, part drawing, forming route, earing acceptance method, quantity and destination. Include untrimmed trial photographs or rim records when investigating an existing forming problem.
Post time: Nov-06-2026