The Titan of Aerospace

Hello again! This is the second in a series of discussions and investigations of manufacturing technologies focused on the Aerospace Industry and the challenges that we face.

This month, I would like to take a look at Titanium. The name originates from the Greek word titanos meaning "titans" from Greek mythology, and is defined as: "A strong, low-density, highly corrosionresistant, lustrous white metallic element that occurs widely in igneous rocks and is used to alloy aircraft metals for low weight, strength and high-temperature stability."

Titanium, and its alloys, are extremely corrosion-resistant, makes up only 60% of steels weight, and has twice the elasticity. These same characteristics that make titanium so appealing also make it one of the most difficult materials to machine; however, shops that understand Titanium's unique properties are successful at transforming it into one of the world most sought-after metals.

The biggest challenge for today's metalsmiths is how to achieve high metal removal rates (MRR) with cost-effective tool life. With recent advances in tooling and machine technology, manufactures are finding it easier to produce high quality parts with increased tool life and reduced cycle times.

Machine tool selection, tooling selection and cutting strategies are critical to maximize the manufacturing process. The first of these to be considered is the cutting strategy.

There are two predominant strategies in the industry: the "high speed" cutting strategy and the more traditional "heavy" cutting strategy.

The heavy cutting strategy is generally used during the roughing process to remove large amounts of material in the shortest time possible with acceptable tool life. This method relies heavily on the machine tools stiffness and horsepower capabilities as well as the tooling's ability to withstand very high cutting forces.

The high speed strategy is used for final part finishing, achieving good surface quality and accuracy, and is very dependent on part geometry and tooling capabilities.

While using the right cutting strategy can reduce the manufacturing challenges, machining at high speeds will be negated if proper chip evacuation is ignored.

If the chips are not removed from the cutting zone, the work hardened chips will cause damage to the workpiece and the tool, reducing tool life and affecting the accuracy and machineability of the part.

The chips must be evacuated out of the cutting area and cooled to facilitate their breakage into smaller pieces.

The traditional "flood" delivery systems cover the entire area and do not evacuate the chips properly, while high pressure through the spindle systems are far superior and can be critical to success.

The properties that make titanium so popular for use in the aerospace industry also make it the bane of many shops around the world, and have earned it the reputation of being hard to machine and expensive to tame.

However, with the proper machine tool selection and tooling strategy, titanium can be, and is being, tamed for practical and cost-effective production.