Spray-Formed Tooling with Micro-Scale Features
Molds, dies, and related tooling are used to shape many of the plastic and metal components we use every day at home and work. Traditional mold-making practices are labor and capital equipment intensive, involving multiple machining, benching and heat treatment operations. Spray forming is an alternative method to manufacture molds and dies. The general concept is to atomize and deposit droplets of a tooling alloy onto a pattern to form a thick deposit while imaging the pattern’s shape, surface texture and details. Unlike conventional machining, this approach can be used to fabricate tooling with micro-scale surface features. This paper describes a research effort to spray form molds and dies that are used to image micro-scale surface textures into polymers. The goal of the study is to replicate textures that give rise to superhydrophobic behavior by mimicking the surface structure of highly water repellent biological materials such as the lotus leaf. Spray conditions leading to high transfer fidelity of features into the surface of molded polymers will be described. Improvements in water repellency of these materials was quantified by measuring the static contact angle of water droplets on flat and textured surfaces.