Clad material for cookware stamping
A press shop judges material by how it runs, not by how it is described. The specification that matters is the one that survives the draw.
At a glance
Specification at a glance
| Process step | Material property that matters | What goes wrong when it is wrong |
|---|---|---|
| Blanking | Flatness, edge quality | Dished blanks, burr that starts a separation |
| Drawing | Elongation and anneal condition | Wrinkling at the flange, cracking at the wall |
| Wall thinning | Uniformity of the stainless face | Thin wall that fails a pressure or drop test |
| Flanging and trimming | Edge ductility | Edge cracks, exposed core at the rim |
| Polishing | Face hardness and finish | Orange peel, pattern fade |
| Assembly | Flatness of the base | Rocking pan, poor hob contact |
The draw decides the specification
A shallow pan and a deep stock pot need different material even at the same diameter. Draw ratio sets the elongation the material has to deliver, and that in turn sets the anneal and the layer split. Sending a drawing without the draw ratio is sending half the specification.
Where the failures come from
Wrinkling at the flange is normally a blank-holder or lubrication issue, but it can be a material that is too soft or too thin. Cracking at the wall is usually elongation, which points at the anneal. Edge opening points at the sheared edge and the bond.
Knowing which failure belongs to which cause is what makes a trial useful: the failure mode is the diagnosis.
Lubrication and coating
Clad material is drawn with lubricant, and the choice affects both the draw and the cleaning step afterwards. A lubricant that suits stainless may not suit the exposed aluminium at the edge, and residue left in a pattern is hard to remove. Agree the lubricant with the press shop rather than inheriting it from another product.
Handling and storage on the shop floor
Blanks stacked wet, or dragged across a steel bench, arrive at the press with marks that are rejected later at polishing. Felt pads, dry storage and a lift rather than a slide are cheaper than the rejection.
What to send with an enquiry
Part drawing, draw ratio, press tonnage, blank size, lubricant, target cycle time, and the failure history if the part already exists in another material. That set lets a supplier propose a structure that suits the press rather than the catalogue.
Questions
Common questions
What draw ratio can clad material take?
It depends on the structure and the anneal, so it is confirmed against the part. Send the draw ratio and the supplier will state whether the structure can hold it.
Why does the material wrinkle in our press?
Flange wrinkling is usually blank-holder pressure or lubrication, but a soft or thin material makes it worse. The first check is the same blank in a different anneal.
Can you supply blanks instead of circles?
Yes: square, rectangular and single-ear blanks, cut to the drawing.
Does the pattern survive drawing?
On the base, yes; on the wall it flattens as the material stretches. Pattern depth and draw ratio have to be agreed together.
How do we test a new structure without a full run?
A trial quantity drawn in production tooling. Three to five good parts settle more than a datasheet.