Bead Test Apparatus Model 227

Description

The Model 227 bead test instrument is used to numerically determine the technical properties of stamping paints and plastic coatings on standard cylindrical cups. It was designed based on real-world stresses. It is well suited for the development of good quality stamping paints. On painted sheet-metal cans, for example, a bead is rolled into the vertical wall of the bottom part of the can, this serves as an end stop for the lid. Any expert knows that the stamping paint at the crest of this bead breaks most easily and flakes off, because the paint has experienced the most deformation at this point.

Test Principle

Standard cups (Erichsen stamping paint test pieces) are drawn from coated strip using our Cupping and Deep-drawing Cup Test Maschines, Models 212 and 242. During the deep drawing process the stamping paint is subjected to stresses which are similar to those encountered under practical conditions. The standard cup has an inner diameter of 33 mm and is drawn from a blank measuring 64 mm in diameter applying blank holding pressure. During the drawing process the stamping paint on the sheet is subjected to stressing and deformation which increases in severity towards the upper rim of the cup. The qualification of the stamping paint is easily detectable with the naked eye or with a magnifying glass, if necessary after conducting boiling tests.

The Bead Test Instrument, Model 227, is used to form a bead in the standard cup under defined deforming conditions. This bead is formed to a depth where the deformation limit, i.e. the deformation capability of the stamping paint, is reached. During the test a conducting fluid moistens the coated surface of the cup and penetrates even the finest cracks in the coating. Once the conducting fluid meets the metal surface of the cup an appropriate reading indicates the degree of cracking. (The conducting fluid is not included in the scope of supply.) Since measurements with the bead drawing tools are acquired under standardised conditions, this testing method is reproducible and also provides readings which are suitable for direct comparison with each other. This is therefore a convenient means, e.g. for manufacturers and users to communicate the quality of a stamping paint in numerical terms.

Scope of delvery

• Bead Test Instrument, Model 227, without beading tool