Quality assurance for DruckWege resins: Three-point bending test

Quality assurance for DruckWege resins: Three-point bending test

We would like to give you a small overview of how our DruckWege resins are tested for 3D printers. In a small series of articles, we want to provide information on the determination of the properties of our products and provide transparency for analysis.

For the determination of the mechanical properties the 3-point bending test according to EN ISO 178 and the hardness test according to ISO 7619-1 were used.

Below we would like to give an overview of the EN ISO 178 to which we expose our products. The tests were carried out in cooperation with the Technical University of Cologne and University for Applied Sciences Bonn-Rhein-Sieg.

The aim of the three-point bending test is to describe the deformation behaviour of the material under mechanical load. In order to determine the mechanical bending properties of the resin by means of a bending test, standardized rectangular test specimens (80 x 10 x 4 mm) are placed on two supports and broken through in the middle of the two supports with constant speed and increasing force. The applied forces and deflection are measured. During the measurement of the bending test, further material parameters such as bending strength, bending modulus, bending stress and bending strain are determined.

Strength is a property that describes how a solid resists external forces or moments without plastic deformations or cracks occurring and ultimately leading to fracture.

The bending strength is defined by the bending stress at which the body breaks and is determined in MPa. The bending fracture stress represents the comparison of two mechanical moments, the bending moment occurring from the outside and the resistance moment occurring in the body against the deflection.

The bending strain describes the change in length of the contact surface of the test specimen when the force is applied, which is calculated as a percentage. The flexural modulus is the ratio of the stress difference and the strain difference. The flexural modulus is determined in MPa and is an approximate value of the modulus of elasticity (modulus of elasticity).

An important factor in 3D printing is certainly the orientation in which the model is constructed (printed), which of course also influences the mechanical properties. Important influencing factors are, among others, the direction of the layer-wise material application and the exposure. These and other factors are varied and tested by us for the different test series.

In order to allow a targeted analysis of the mechanical properties, several test series with always five identical specimens are used.

Specimens with a horizontal layer structure show a higher stability and thus a higher strength compared to vertically produced specimens. The mean value of the determined strength values was calculated from the different test series.

Under the influence of our pre-defined exposure times, significant increases in strength and modulus of elasticity are achieved by longer exposure of the material.

All technical properties for our resins can be found here at our technical datasheets.

 

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