Corner radii are usually described as acute corners or “as acute as possible”. When trying to achieve this in an extrusion design, certain issues must be taken into account:
An exterior corner is created by an interior corner in the tool, and vice versa.
It is not possible to produce an exterior corner with a radius of less than 0.20 mm
This is primarily due to the fact that wire spark technology is constrained as a result of the limitations imposed on wire diameters (>0.25 mm). In addition, the extrusion process is limited in terms of filling material in small components. These problems become magnified as material quantities and material hardness increase. In principle, it should be possible to make interior corners wholly acute. However, tool wear accrued over time leads to what were originally acute corners becoming rounded.
Minimum interior and exterior corner radii
Solutions are available for instances where an acute interior corner is required. It is possible to design an extrusion corner using a reduction as shown in the figure below: