Sheffield-based Tecomet, formerly Symmetry Medical, has recently installed three Hermle trunnion-type 5-axis machining centres for manufacturing stainless steel medical components. Two of the Hermle C 400 machining centres have 87-tool magazines, allowing all component variants to be produced without changing cutters, so minimising downtime. The other machine has a standard, 38-tool magazine and is reserved for larger batch quantities.
Components are produced from two grades of 316 stainless steel forgings produced on the Sheffield site. Generally they undergo two operations, although some require only one. Programs are long, as the components have complex shapes to match the human anatomy, and some cycles run to 300,000 lines of code.
Machining operations are mainly 3-axis with the other two positioned and clamped, while some components require 4+1-axis cycles. They involve taper milling, slotting, drilling and tapping and take between 25 and 90 minutes.
Tecomet production engineer Steve Jackson said that any restriction in the specification of the latest three Hermle machines does not affect production. Through-spindle coolant delivery, essential for machining stainless steel, is provided as well as tool measuring and breakage monitoring. Minimal idle times result from 6 m/s2 acceleration to 35 m/min rapids in all linear axes. Trunnion swivel is 25 rpm through +91 / -139 degrees, while C-axis positioning is at 35 rpm. Control is provided by a Heidenhain iTNC 530.
