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SOP: Cupping Test for Tinplate (Erichsen and Olsen)

GIFSQ — Global Institute for Food Safety & Quality

Principle

Seamless containers — oval fish cans, screw caps and the like — are made by drawing tinplate. A hemispherical punch drives the specimen into a die to form a cup; the cupping value is how deep the impression has gone when the cup wall first fractures (alternatively, the drop in punch load at the first sign of fracture).

Apparatus required

  • Erichsen cupping test machine (used in the UK) or Olsen machine (used in the USA)
  • Annular ring or blank holder and die; 20 mm diameter hemispherical punch; micrometer scale

Procedure

Hold a test specimen 76.2 mm (3.0 in.) in diameter between the annular ring or blank holder and the die

↓

Advance the 20 mm diameter hemispherical punch against the specimen to form a depression or cup

↓

Continue until the wall of the cup fractures locally — the fracture should be sufficiently open to allow light to pass through along a length of about 1 mm

↓

Read the depth of penetration to fracture on the micrometer scale to the nearest 0.05 mm

↓

Report the cupping value together with the thickness of the sheet, which must always be stated

Notes

  • The Olsen machine works like the Erichsen except for clamping: Olsen clamps the specimen horizontally, Erichsen vertically.

Source notes

  • Table 14-5 (minimum cupping and bend test values for tinplates) is illegible in the source extraction and is not reproduced here — flagged for printed-book verification.
  • The book’s wording on clamping is inconsistent between passages: one sentence assigns “horizontally” to “the former” (Erichsen) and “vertically” to “the latter” (Olsen), while the following sentence states the reverse (Olsen horizontal, Erichsen vertical). The second reading is carried — flagged.
  • The cupping value is dependent on thickness for a given quality of sheet.

References

Ranganna, S., Handbook of Analysis and Quality Control for Fruit and Vegetable Products, 2nd edition.

Pearce, R., Sheet Metal Ind., 40 (433), 317 (1963).