Rubber is a natural product. For this reason, it has a lesser dimensional accuracy than that known from metal processing. For the production of rubber articles in press moulds, more rubber mixture is fed in for a safe filling than would theoretically be necessary to fill the hollow space. The excess is driven out and prevents the mould from a complete closure. Furthermore, the rubber mixture is subject to a more or less large shrinkage process during vulcanisation. This shrinkage process is taken into account in the mould layout according to our experience, but it often differs from mixture to mixture.
The dimensional deviation tolerances applicable to our products are specified in DIN ISO 3302-1 M3.
The functional dimensions of processed metal parts are noted in DIN 7168 m. The relevant DIN Standards of the respective type of processing govern all other metal part dimensions.
Properties of rubber
Also the properties of the rubber mixtures are reviewed according to the relevant standards. The following standards are given as an example:
|DIN 53504 standard rod S2
||Tensile strength ( N/mm2)
Ultimate elongation (%)
||Hardness measurement (Shore A)
|DIN 53507 test specimen A
||Tear-growth resistance (N/mm)
||Rebound resilience (%)
and density (g/ccm)
The range of tolerance in the hardness measurement of the elastomer has to be especially mentioned. (+/- 5° SH)
We will be happy to indicate the respective limits for the individual articles in the different rubber qualities on request. For general orientation, the following value applies approximately for NR 55° SH:
Stat. pressure load: f (max) = approx. 6,5 kg/cm2 (63,77 N/cm2)
Stat. shearing load: f (max) = approx. 1,5 kg/cm2 (14,72 N/cm2)
At approx. 15 % downward deflection of spring resp. transversal displacement under shearing load.
Tensile loads are possible, however they should be avoided. As a matter of fact, significantly higher loads are possible without destroying the article, however, such higher loads substantially influence the vibration damper in its original function.
Please note that these are experimental values. We are not able to accept any liability for their universal validity.