When manufacturing everyday items like furniture, guard rails, or even some household tools, a difference of 0.01” likely won’t make much of a difference in the final product’s performance. However, when manufacturing for the aerospace industry, a difference of even 0.0001” or smaller can be a matter of life and death. Each aircraft is meticulously engineered from nose to tip down to the last rivet, and deviating from that intended design can bring catastrophic results, making precision a crucial element of aerospace manufacturing. In today’s article, we’ll be going over the importance of precision material in the aerospace industry and explore how it helps manufacturers achieve the tight tolerances that they need.

Advanced Materials and Advanced Challenges

Before diving into tolerances, we first have to define the materials that are used to meet those tolerance limits. Aerospace applications demand extremely high quality alloys, often outlined in standards like AS9100. While some of these materials include more common alloys like varieties of steel, aluminum, and titanium, there are also many cases which call for more unique metals. These metals, widely categorized as special alloys, have been engineered to display characteristics which distinguish them from other groups of metals. Some of these characteristics include enhanced performance at high or low operating temperatures, shape memory, exceptional corrosion resistance, magnetic properties, and more.

Sourcing Materials

While these special alloys boast impressive performance in their intended applications, they can often be hard to come by. Since they are designed with specific circumstances in mind, their demand is inherently lower than say, a more common aluminum alloy. Naturally, supply follows suit.

It’s also not uncommon for aerospace and defense manufacturers to use their own proprietary alloy blends. These alloys are sometimes prepared in-house, while others are sourced by a supplier, depending on the company.
With these challenges in mind, the importance of a reliable supplier cannot be overstated. At Boston Centerless, sourcing these hard to find materials is just one of our areas of expertise.

Machining Materials

If simply obtaining the material is one challenge, achieving your desired results with it is a whole other beast. While special alloys and custom alloys may boast unmatched performance or properties, there is sometimes a tradeoff between that performance and machining difficulty. When a part is difficult to machine, it becomes that much harder to stay within tight aerospace tolerances. This problem is especially prevalent when creating small components, such as those made using Swiss machining. Yet, these parts must be crafted with extreme attention to detail, as every little bit counts towards a successful takeoff.

Defects Lead to Rejects

So, what happens if a part does not meet the defined tolerance? That’s a lesson which no supplier or manufacturer wants to learn firsthand. As one example, let’s take a look at what goes into crafting an aircraft fuselage.

A fuselage is held together by many rivets, sometimes hundreds. These rivets must be precisely sized in order to both fit the pre-drilled holes on the fuselage panels, and meet the tolerances required for the finished part to function properly. Out of all these rivets, if just a single one is found to be out of spec before the assembly process begins, the entire lot gets rejected.

From the manufacturer’s perspective, out of spec parts and fasteners can put a huge dent in their schedule and their budget. As for suppliers, replacing the rejected lot does more than just consume additional time, labor, and resources. Sending out even one faulty product can do irreparable damage to their reputation, too.

At Boston Centerless, we are precise in everything we do.
Find out more about how centerless ground bars help
manufacturers meet tight aerospace tolerances.

Detecting Defects Early

Thankfully, there are ways for manufacturers to prevent any defective parts from making their way to a customer by choosing a quality material supplier. One with in-house material testing and validation capabilities can not only provide peace of mind, but also keep costs and lead times low. When scouting suppliers, look for those who carry valid, relevant quality certifications and can pinpoint the following defects.

Surface Defects

Some surface defects can be spotted instantly, while others may be quite easy to miss. To prevent any materials with surface defects from making their way through to production, it is crucial to perform the right tests. At Boston Centerless, we do this with Eddy Current Testing. This nondestructive testing  (NDT) method allows us to detect surface defects in electrically conductive materials, including both special and custom alloys. But what about imperfections that lie beneath the surface?

Internal Defects

Internal defects can present issues during both manufacturing and operation. For instance, say that a stainless steel blank is being made into a screw. If that particular specimen is hiding a void or a contaminant just beneath the surface, complications can arise shortly after machining has begun. A void may prevent the blank from being able to reach its intended shape, resulting in a reject—or if the blank contains a contaminant, machinists run the risk of damaging their tool inserts and winding up with a reject part in the end, too.

What if the defect is deep within the center of the blank? That’s where operation issues can arise. A void or contaminant can prevent the screw from performing as intended and potentially compromise an entire assembly. Internal defects are trickier to unearth, as they’re not visible to the naked eye. Spotting these faults before it’s too late requires a different approach.

At Boston Centerless, this is done using a method called Ultrasonic Testing. Another NDT method, this test is used on bars from 0.180” in diameter to 1.000±0 ” in diameter to detect imperfections within approximately 1mm of the bar’s surface. If a defect is found, the bar is automatically rejected from the lot. This in turn eliminates any chance of a part or product falling outside of tolerance due to material defects.

Aerospace tolerances can be challenging to navigate, but they don’t have to be. By working with a trusted partner like Boston Centerless, aerospace manufacturers can more easily stay within spec and avoid defects by using high-quality, precision ground materials. To find out if we can supply your alloy of choice, contact us today.