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Sheet metal testing machines

These machines (type BUP) are used to determine and evaluate properties of sheet metals.

Typical test methods include Erichsen cupping tests (EN ISO 20482), in which a hemispherical punch is pressed into a clamped test piece until a crack appears. There is no in-flow of the sheet metal. The drawing formability of the sheet metal is determined from the punch penetration depth.

Another test method frequently used is the earing test to EN 1669. In this test circular blanks are punched or inserted and drawn into cups (metal in-flow). The deep-drawing characteristics of the metal are determined via the percentage ear height ratio.

Other metal-forming test methods include square cup tests, hole expansion tests, FLC tests and bulge tests.

  • BUP testing machines are available in 5 versions with a maximum ram force of 100, 200, 400, 600 or 1000 kN.
  • Bayonet mountings allow test fixtures to be changed quickly and easily.
  • Low actuator-piston friction ensures accurate measurement recordings and excellent test reproducibility.
  • Very quiet in operation - motor and hydraulic pump only run during test.
  • Compact build - easily transportable.
  • A punch function is incorporated into the BUP testing machine, allowing a blank to be pressed and a cup drawn in one operation (from BUP 200 onwards).
  • A hydraulic cup extractor integrated into the drawing-punch simplifies removal of cups (from BUP 200).
  • All functions are hydraulically and electrically interlocked. The test is not performed until all safety contacts have been monitored.
  • Individual adjustments to the test sequence are possible, e.g. deep drawing speed and clamping force.
  • With optional testXpert II testing software the test results can also be evaluated as graphs and saved .

Sheet metal test methods

Sheet metal testing for innovative materials

Sheet-metal forming is a basic metalworking and metal-processing technique and is among the oldest production technologies. Innovation is largely driven by transport technology, particularly the automotive industry. Increasing demands on sheet-metal materials under the general heading of lightweight construction have led to the development of high-tensile and ultra-high-tensile steel materials, although their reduced ductility and higher elastic recovery are setting new challenges for forming technology and process control.

Sheet metal testing machines assist the process of development in characterizing new alloys and new metalworking technologies, as well as in eventual series production. Zwick sheet metal testing machines score with their flexibility, fast, easy fixture changes for different tests and individually controllable integrated functions such as holding down, punching, drawing and ejection.

Typical sheet-metal forming applications include the classical Erichsen cupping test (EN ISO 20482), the earing test (EN 1669) and hole-expansion tests, which are seeing increasing use with high-tensile steel materials.

Particular importance is attached to determination of the forming limit curve (FLC), which is used in a two-stage experiment to generate critical deformations in tests. These are then compared with existing deformations on actual components and evaluated. Once the FLC has been determined, it is used at the component design stage to help optimize forming, thereby speeding up the development process. In addition to a sheet metal testing machine, these tests (ISO 12004) also require a suitable optical evaluation system.

Spring-back properties are generally determined on customer-specific specimens. Similarly, customized fixtures incorporated into the sheet metal testing machine allow tests to be performed quickly and easily.