Development of a cyclic liquid nitrogen injection system and its application to minimum quantity lubrication milling of the Ti-6Al-4V alloy

The Ti-6Al-4V alloy represents a large portion of the material used in medical and aerospace applications due to its excellent properties. Its machining requires unique conditions, and new machining proposals are presented every day. This work describes a condition of sustainable manufacturing, minimizing the waste of cutting fluid by a cycle lubrication approach. The system developed has an electronic circuit for controlling the flow of liquid nitrogen under pressure applied to a commercial valve. A 2(3) factorial planning design following the recommendations of the cutting insert manufacturer was carried out; the machining tests were performed under the conditions stipulated. Roughness studies were carried out for different cooling strategies as well as the insert flank wear. The cycle system showed that liquid nitrogen is saved and there are lower S-a and S-z roughness values compared with machining without lubrication and classical nitrogen injection. Simulations using the computational fluid dynamics approach were implemented. The behavior of a drop of liquid nitrogen under the action of gravity and its behavior in the bulkhead were simulated. The specified tool height when machining allows the adequate lubrication of the tool.