Rub­ber & Met­al in Con­struc­tion — Dif­fer­ences and Similarities

Rub­ber is an elas­tic mate­r­i­al that expands and con­tracts and reacts to exter­nal influ­ences. This is an advan­tage when it comes to seal­ing and damp­ing, because rub­ber can flex­i­bly adapt to dynam­ic forces. In con­struc­tion, on the oth­er hand, this prop­er­ty can pose a problem.

The elas­tic char­ac­ter­is­tics of rub­ber lim­it the pos­si­ble tol­er­ances in pro­duc­tion. Elas­tomers can­not be man­u­fac­tured as pre­cise­ly as met­als. The prop­er­ties of the mate­r­i­al do not allow this. In met­al con­struc­tion, for exam­ple, fil­i­gree geome­tries are pos­si­ble that are a frac­tion of a mil­lime­ter wide. Just think of knife blades. In elas­tomers, on the oth­er hand, a width of 0.5 mm is pos­si­ble with a great deal of effort.
Below that, the pro­duc­tion of rub­ber can no longer be car­ried out with process reliability.

Many design­ers are used to tol­er­ances in the hun­dredth or thou­sandth range and expect the same from rub­ber mold­ed parts. For this rea­son, pro­duc­ers often receive inquiries about geome­tries that can­not be real­ized. This leads to addi­tion­al tech­ni­cal arrange­ments and adjust­ments that can drag out the devel­op­ment project and often have a neg­a­tive impact on costs.

Anoth­er fac­tor con­cerns the vul­can­iza­tion process. Very fine geome­tries require opti­mum flow behav­ior in order to guide the raw rub­ber into all cor­ners of the mold. Even slight pre­ma­ture vul­can­iza­tion can mean that the raw rub­ber can no longer fill the fil­i­gree recess­es of the mold.

Under cer­tain cir­cum­stances, the tem­per­a­ture of the pre­heat­ed mold may already be suf­fi­cient to influ­ence the flow behav­ior of the raw rub­ber in such a way that the geom­e­try can no longer be real­ized. It would be pos­si­ble to allow the mold to cool down com­plete­ly, but this would have a neg­a­tive effect on cycle times and dri­ve up the price of the mold­ed arti­cles significantly.