The precision machine shops we run are set up with extensive capabilities for complex, tight tolerance work. This includes 4 and 5-axis machining centers and a range of turning, milling, and grinding equipment. This blog showcases our aerospace part machining competencies, describing what’s involved and how we tackle the challenges.

Application First

After safety, mass is the biggest consideration in anything aerospace-related, because a lighter aircraft and helicopter can carry a bigger payload. This focus on weight dictates the materials used and part geometries.

The most widely used metals are 7000 series aluminum and titanium. These are chosen for their high strength-to-weight ratios and their corrosion resistance. Heat-resistant alloys like Inconel are used in specialized applications, and especially for some engine components.

A consequence of focusing on mass is that aerospace components tend to be very complex. Rather than use assemblies, there’s an emphasis on component consolidation. This eliminates fasteners but results in tight tolerances and complicated geometries. In addition, removing unnecessary material often means machining deep pockets and leaving thin walls.

Machining Overview

Many aerospace components are milled rather than turned, because they’re made from solid billet, forgings or castings and just need pockets, flats, and holes. Hydraulic system components are the exception because generally these are turned.

The alloys used for aerospace components are often difficult to machine. The 7000 series aluminum alloys need high cutting speeds to avoid ‘built up edge’ on the inserts, and the new aluminum-lithium alloys are even more challenging.

Machining titanium is difficult, as poor thermal conductivity means much of the heat from cutting goes into the tool and not the chip. In addition, the chips are tough and abrasive, and tend to stick to the cutting edge and form strings.

To deal with this, when machining aerospace alloys it’s essential to pay close attention to the cutting conditions, cutting fluids, and the inserts used.

Milling Aerospace Components

CNC machining is almost mandatory for these parts, because of the high levels of accuracy and repeatability it delivers. What’s more, the complexity of many aerospace parts means 5-axis machining is often the only way to produce them.

With true 5-axis, the workpiece is moved while in-cut to produce complex contours and mill deep pockets. Plus, as more work can be done in a single setup, features are held in tighter geometric relationships with less part-to-part variation.

High spindle speeds and horsepower are needed to minimize cycle times. When milling 7000 series alloys, it’s best to use machines with spindle speeds of 20 – 30,000 rpm, and horsepower of 80hp or more to maximize material removal rates.

Pocket milling, which is needed for many aerospace parts, presents two additional challenges. First is the problem of chip removal. Selecting suitable cutting tools helps, but another approach is to let gravity assist by putting the tool axis horizontal, (which is something a 5-axis machine can do or come close to.)

In addition, when pockets have thin walls it’s important not to apply too much lateral force while cutting. This is another benefit of using high rpms and surface speeds.

Turning Aerospace Components

CNC turning ensures high accuracy and repeatability, even with difficult-to-machine materials. These machines can also performing the boring and threading needed on many cylindrical aerospace parts.

Additional Requirements for Aerospace Machining

World-class CNC machining capabilities are only part of what’s needed. A machine shop that wants to deliver aerospace parts must operate a rigorous quality system certified to AS 9100. It should also have industry-leading inspection resources and the ability to finish parts to the standards needed. With in-house value-added services such as Nadcap-certified heat treatment and surface treatment, a machine shop can provide one-stop manufacturing solutions to reduce overall product costs and lead times.

Impro meets all these requirements in full. If you need a source for precision machined aerospace parts, we’d like to talk. Contact us.