June 2007 Edition

Cutting Tools and Tooling

Aerospace Manufacturing Places Tough Demands on Cutting Tools

Making space shuttle parts from titanium to tight specs required a trade-off between tool life and production speed

Family-owned Reil Industrial Enterprises, Missasauga, Ont., Canada, has been involved with the aerospace industry since the dawn of commercial jet aviation. William H. Reil, the company owner who founded the firm in 1965, worked in the aerospace industry. He was following in the footsteps of his father who had also worked in aviation some 50 years ago.

Today, Reil Industrial is run by both William Reil Sr. and William Reil Jr. and is known for precision machining of castings, forgings, and intricate parts for space vehicles and military systems.

Low-Volume, High-Value
Recent low-volume, high-value parts it has manufactured include components of the space shuttle’s 50' Orbital Boom Sensor System – OBSS – inspect ion boom for Shuttle Discovery. This system attaches to the shuttle’s existing arm and is equipped with cameras and laser systems to inspect the craft’s thermal protection system while in space.

The boom consists of more than 100 detailed parts. Every component involved in this project has critical tolerances – often in the 0.0003" range. To add to the manufacturing challenges, many of the components – such as tethers, cleats, brackets, bolts, and some housings – are produced from titanium. The surface finishes of these parts are crucial as they cannot have burrs or rough spots that can snag astronaut pressure suits.

The titanium arrives at Reil as a solid block of raw material worth about $8,000. It takes 200 hours of machining time to produce a single housing.

The project was so critical that NASA personnel visited Reil.

Cutting When the Chips Are Down
The first operation for a housing component is roughing deep pockets out of the titanium block. The initial operation was Reil machinist Adam Peek Blair’s first experience with titanium. The trick to working with it, he learned, was to never let the heat build.

“If you do,” Blair said, “the workpiece will harden and then it’s like dealing with glass. So, I use a lot of coolant, get rid of the chips, and cool down the material as fast as possible.”

For the OBSS components, he hogged out material for the inside pockets using a 2" high-feed insert with a trigon radius and a Combimaster head from Seco Canada, Milton, Ont. At a 0.0003" depth of cut, he got about one hour of life per insert.

“I was pleased with this tool,” Blair said, “The only limitation is that it has to be fully engaged in the material or it will not last – the angle of the insert has to be more than 70° at entry. With some of these parts, you just cannot achieve that angle. But, even though I sacrifi ced a little tool life, I still found these tools faster than anything else.”

For contouring, Blair said that with Jabro endmills and Seco’s 12 mm ballnose cutters, he reached feedrates from 80 ipm to 90 ipm at 4,500 rpm, unusual in titanium.“.

After finishing one housing, I estimate that I can use one Jabro tool to produce three pieces – that’s semi- and completefi nish from 0.03" stock per surface,” Blair said. Seco purchased the Jabro brand in 2001.

Finishing operations were only needed on spots too deep to be programmed to reach.

“Any place where I could reach with the Jabros didn’t require polishing. You just want to buff some of the cutting marks on the flat surfaces.”

For other OBSS titanium components – such as the hand rails, which are part of the tethers – Reil started using solid high-speed steel endmills, but found they burned out too quickly. Blair switched to the Nano Turbo using an insert with a 0.032" radius.

“In aerospace components there can’t be a sharp corner anywhere,” Blair said. “The corners must be a radius. That has to do with strength and fracture points. It’s common industry knowledge that a 0.03" radius for small component corners is the optional choice.” The switch permitted Reil to reach the speed, feed, and 0.01" to 0.015" cutting depth of cut it needed.

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