The OEM took advantage of a sustainable manufacturing initiative sponsored by the US Air Force and applied one of its flexible machining cells to the project. Its aim was to discover how much energy could be saved in machining a titanium 6AI-4V sample aircraft part designed with deep pockets. The trial used a 10-year old horizontal machining centre.

Using a power meter, researchers measured the effects of various attempts to save energy during machining. They discovered that strategic choices relating to tools, coolant, programming and parameters could combine to reduce energy use by 73% of that usually consumed by the plant’s processes.

Among the main areas of focus was the effectiveness of through-tool coolant delivery. Standard solid carbide end mills using only flood coolant were run against otherwise identical end mills that had been modified to deliver coolant through ports near the flute tips.

Both methods used TRIM MicroSol 585 from Master Chemical which was selected against four competitor coolants following trials.

While tool life would be the determining factor, the chosen coolant had to address secondary issues. For instance, it had to minimise mist and eliminate any sticky residue that might cause the titanium chips to adhere to the machine tool.  

Each candidate fluid was run at 6% concentration, diluted in de-ionised water.  After machining tests were completed, lab tests were run to compare the fluids for these non-cutting functions along with health and safety concerns, bio-stability and sump life.

Once TRIM MicroSol 585 was chosen, Master Chemical says that nominal tool life improved, and wear from flute-to-flute on the same tool was more consistent. Testing of through-tool coolant demonstrated tool life improvements of up to 30%.

“Coolant is vital to tool life and selecting the correct chemistries will immensely improve tooling performance,” says Monte Dhatt, global aerospace manager at Master Chemical. “Of course, a proper plant audit should be conducted before selecting the correct coolant for each individual application.”

According to Master Chemical, coolant selection considerations should include the type of machine, materials being cut, operations, cycle time, tooling type, quantity of machine tramp oil, water type (RO, DI, hardness), operator contact, foam and filtration.

“Through-tool operations typically encompass high pressure in the range of 1000 – 1500 psi,” says Dhatt. “With high pressure you want to use coolants that are low foaming and can break the foam quickly, otherwise spill-overs can occur.

“Modern machines have sensors that will stop the machine in mid-cycle when it senses a spill-over. This can be costly as it can scrap a part in mid-cut. Typically, synthetic and semi-synthetic chemistries will provide the best foam control.”

Energy savings

The machining process that combined these improvements with others relating to cutting tools and programming techniques consumed 0.32kWh/in³, a 73% reduction in energy from the way the plant machined parts before the research began. Now, various parts have been re-programmed for cycle time savings. Such savings provide for sustainability in a number of ways.

While the term usually implies lowering energy use, keeping a job commercially sustainable involves holding costs low enough that the part remains in production. The findings of the sustainability testing are particularly promising for the aerospace manufacturer, not only for energy reduction, but for cost reduction and increased capacity resulting from cycle time improvements.

Dhatt continues: “Under this philosophy, costs savings – including energy – are something we can measure for customers. This particular customer is now using TRIM MicroSol 585XT which is an upgrade to the original formula.  Foam and sump life were improved to address minor shortfalls identified in the study. In fact, the success story allowed us to establish a corporate contract with the company and expand the use of TRIM MicroSol 585XT in many of its other facilities.

While it is well suited to machining and grinding mixed metals, TRIM MicroSol 585XT is an effective coolant for cutting titanium alloys. Indeed, for another customer it eliminated a host of problems experienced with some alternative fluids – bad smells, excessive carry-off, smoking and seal damage.

TRIM MicroSol 585XT is a high lubrication, semi-synthetic micro-emulsion coolant. Fast wetting gets the fluid to the point-of-cut quickly and ensures workpiece and chips are coated thoroughly.

Although the coolant contains elemental boron, any boric acid has been fully reacted in the formula so there is no free boric acid which is an item of concern for some manufacturers.