Seal-ready Surfaces: Testing & Quality Assurance

The proliferation of aluminum in the automotive sector continues to surge. Not long ago, aluminum components were rare; now, they can make up 30% of a vehicle’s weight. From engine blocks and gearbox housings to oil pans and battery racks, many of these aluminum components require exact roughness and crosshatch patterns to provide proper surfaces for gasket and sealant adhesion. Seemingly miniscule differentials in surface topography —also known as framed roughness — can affect the ability of sealants to adhere, impacting the quality of the seal and, ultimately, the viability of the entire part.

Meeting strict surface roughness guidelines in aluminum requires precise measurement, a careful machining approach and cutting tools optimized for the task. The right combination of these key elements can boost machine shop productivity while producing reliable, gasket- grade components.

To guide you down that path, here are six steps that will help you achieve a gasket-grade surface finish in aluminum.

1. Measure roughness correctly

Most manufacturers have in-house measuring devices that can provide accurate Ra (arithmetical mean roughness) and Rz (mean roughness depth) values. Use them. Even experienced machinists should not rely on their eyes or fingertips where surface topography is concerned. Throughout the machining process, verify the framed roughness with precision instruments to promote long-term component dependability.

2. Program to reduce smear

When an indexable milling tool first enters the material, it can create an irregular, unintentional “smear” if not executed carefully. The same risk holds for the cutting tool’s exit path. These smears present hazards to the roughness profile and the overall integrity of the component by forming pockets where oil or fluid can pool. Programming a slight taper into the cutting path or beginning each pass with the back side of the cutter can mitigate these risks. Work with your tooling provider to determine the proper programming techniques for your tool and the component in question.