What is the significance of marking “exposed surfaces” on the extrusion design drawing?
Marking exposed surfaces provides thoughtful design techniques for producing a superior extrusion. The extruder knows to give these surfaces special attention and protection during the extrusion process for either functional or cosmetic reasons. The narrower an exposed surface, the more uniform the finish will be. Webs, flanges and abrupt changes in metal thickness may show up as marks on the extrusion’s opposite surface, particularly on thin sections. Additional precautions can be taken in the extrusion tool design and extrusion run-out to minimize surface blemishes. If the exposed surface is highly critical, your extruder may be able to suggest a secondary finishing operation such as buffing, brushing or polishing.
