General

If dimensional changes occurring over time after manufacturing are relevant to the function of the (plastic) parts, these must be taken into account when defining the dimensional position, dimensional shift and dimensional scatter.

The determination of dimensional changes under application conditions (AC) requires the consideration of condition parameters and material properties. If users do not have their own data and experience, they can establish an orientation basis using the determination scheme described below. The fundamental principle is that the functionally required dimensional stability must be ensured at all times during the service life.

Due to the temperature dependence of material properties, reference temperatures may have to be taken into account. Material data can be obtained from manufacturers’ data sheets or other sources. The software itself also includes a large number of commercial plastic material grades.

The condition parameters result from the specific application environment of the parts. These include indoor climate conditions, outdoor climate regions of the world, as well as special application conditions caused by heat sources (e.g., engine heat, greenhouse effect, heating systems) and heat sinks (e.g., cooling devices or refrigerated rooms).

Relative Dimensional Changes with Respect to the Acceptance Conditions of Production (ACP)

An arbitrary number and various types of dimensional change progressions during the service life are bounded by the extreme values εmax and εmin.

Assuming normally distributed progressions, the mean relative dimensional shift and the relative dimensional scatter are calculated.

If dimensional changes caused by mechanical loads must be considered, they must be differentiated according to elongation and compression. Likewise, possible wear specifications must be taken into account by means of wear rates V (in %), distinguished between internal parts (shafts) and external parts (holes).

Calculation modules to support the definition of application conditions are integrated into the software.