Hoowaki LLC has developed innovative technologies for micro manufacturing that allow for micro structures to be moulded onto large surface areas. Hoowaki micro structures are designed to improve performance without changing the materials or the moulding process. The negative features are manufactured on the existing mould to mould the positive features on the product during the moulding process. In this way, Hoowaki’s micro manufacturing process is different from coatings or surface finishes in the market. The micro features on the mould reduce the need for coatings or lubricants on the finished product or allow use of lower cost materials.
These microstructures are designed to solve a wide range of friction problems on many different applications. Different micro pattern designs can be moulded onto a surface to either reduce or increase friction, depending on the desired use of the product. For example, Hoowaki micro structure pattern #021AP provides greater friction with fabrics. This allows manufacturing equipment to have better grip and control on the fabric being processed. Conversely, other patterns such as #009AH can be used on products such as seals to reduce friction. Modified seals such as these are particularly applicable to the automotive industry, with the current focus on energy efficiency.
The friction reduction achieved by surface micro structures can be attributed to several physical effects, which depend upon the properties of the underlying material and how it is used. One of the friction reduction mechanisms is reduced contact area between the micro structured surface and the surface over which it slides. This reduced contact area results in lower adhesion between the two surfaces. When the micro structured surface is lubricated, the micrometer-scale cavities in the surface act as reservoirs for the lubricant. The presence of this added lubricant can reduce sliding friction. Finally, when the sliding surfaces are not touching – in hydrodynamic lubrication – the lubricant flow near the micrometer-scale cavities generates hydrodynamic lift. The size and shape of the micro structures can be tailored for maximum friction reduction. The engineering calculations for the optimal friction reducing micro structures depend upon the lubricant properties, the sliding speed, and other application details. Hoowaki’s customers have been using Hoowaki tools to make micro structured surfaces that achieve greater than 20% friction reduction in dry sliding and up to 80% reduction in lubricated sliding.
Hoowaki’s unique micro manufacturing process offers customers seeking increased or reduced friction a distinct advantage. Having features moulded directly onto a product reduces the cost of additional lubricants and eliminates the need for extra manufacturing steps.