Surface treatment to reduce squeak noise in vinyl parts 2018-36-0061

It is a common practice of automotive industry to avoid dynamic contact between two surfaces with similar roughness for plastics and interior trim parts. That means reduce the friction and, consequently the squeak noise to the minimum level to meet zero noise level. Unfortunately, for design or economics reasons, that is not possible for some applications and a very disturbing noise may bother the costumer. A material incompatibility leads to an acute noise when two similar surfaces have relative movement due to multiple adherences between the surfaces, that is called stick-slip phenomenon. To characterize this noise, a Squeak and Rattle Evaluation testing should be performed in the worst case condition over the life of the vehicle. As a result, a scale of Risk Priority Number (RPN) provides a pass/fail judgement to implement any improvement required to address the issue. There are several ways to avoid this phenomenon during the product development: applying lubricants, tapes, coatings, material change or surface treatments. To solve this kind of undesirable user experience, an anti-squeak treatment was developed in water base using polymeric material, applied in a process similar to coating and cured thereafter by heat. The concept of this anti-squeak treatment is to reduce surface tension and the resistance of relative movement when fractioning similar material that leads to a reduction of noise, consequently. The aim of this paper is to show how this surface treatment can reduce the noise level related to material similarity, applying this into a vinyl surface, with no changes in mechanical properties and no need to run a new design verification plan. In the present study, it could be observed a reduction from 10 RPN to 2 RPN, related to an improvement from material match critical to material match in order. This corresponds to a customer satisfaction perception improvement from material audible annoying noise caused by stick- slip expected to not perceived noise.