Quality Department Discovers Reason for Aerospace Engine Threading Failure


More goes on than measuring in PTI’s quality department. Assuring quality results is a dynamic process that isn’t limited to meeting the customer’s definition of quality. It’s going above and beyond the scope of quality department work to satisfy every customer requirement.

Sometimes this involves satisfying a requirement for a problem that a customer doesn’t know exists. For Dawn Stokes, Quality Assurance Manager, making sure everyone is following the rules is her primary focus. But when every rule is adhered to and something comes back flagged as a problem, it’s time to dig deeper.

PTI experienced a problem solving challenge with a major aerospace company’s parts that came in for dry film lubrication. “That’s how we discovered it. They thought it was a dry film issue because after our process, it wasn’t working,” Stokes said.

Dry Film Lubrication (DFL), also known as solid film lubrication, is the ideal solution for lubricating your parts when liquid-based lubricants fail to function properly. The dry film protective coating is more reliable for reducing surface friction between part surfaces.

The DFL department treated the engine parts with a protective coating and sent them on to quality. They passed inspection and were returned to the customer who promptly discovered a threading issue. During assembly, the parts, involving several engine orders, weren’t torqueing together correctly. The problem was believed to be in the dry film application and presented again to quality for inspection.

The quality department got help troubleshooting the problem parts from their “threading expert” who has background knowledge with threaded parts. Why weren’t the parts working properly under the specific threading dimensions they needed to adhere to? The problem wasn’t the dry film process, the expert determined, but the threading dimensions as defined in the blueprint.

“Looking closer at the prints, it just jumped out at him with all his thread knowledge,” Stokes said. “So he did the math to adjust the pitch in the threading,” and many conference calls with the customer later, the problem was resolved.

After careful review of the problem internally, the customer found that there was more than one engine group that had this same threading issue, and they ended up changing the requirements on their prints. They were able to apply this same engineering solution to another engine within the same part family.

Fixing problems in the quality department involves understanding the customer’s real needs and applying problem-solving skills that deliver true resolution and not just temporary fixes. Whatever special processes need you have, we have the expert to give you quality that goes beyond your requirements.

How Can Four Equal One? – A Case Study in Streamlining Multiple Special Processes

blog-pic-41pti-300x245In a previous post we spoke about streamlining your special processes to improve your bottom line. Now we’ll take a look at how one part would move through our multi-process shop. Four processes can equal one when a part has four sequential special processes done in one shop on one purchase order. To illustrate this, let’s look at a section of the value stream map for a Locking Nut that mates up to an LPT Shaft, which ultimately ends up in a jet engine.

This life limited part starts out as a 410 stainless steel bar. After machining and heat-treating, we receive the part in to perform Magnetic Particle Inspection (MPI) which is a form of Non-Destructive Testing. This special process is done to ensure there are no cracks or voids in the parent material that could result in an in-flight failure.

Having passed MPI, the part travels immediately into our Dry Film Lubricant (DFL) Department, where it has a thin layer of Molybdeum Disulfide (a type of DFL) applied to its threads. This ensures it will rotate smoothly when mated up to an LPT shaft at assembly.

Next, the part moves right into our Bonded Products Division where a special low-friction fabric washer that we laser cut to exacting tolerances is adhered to its bearing surface using our Adhesive Bonding technology.

This special fiber washer acts as a maintenance-free thrust bearing when it mates up to the adjoining surface on the LPT shaft.

The final stop for this part is in our Precision Cleaning Division. Here it will undergo a thorough cleaning and inspection to a microscopic level to ensure there are no particles on it that could damage the part itself or other sensitive components within the engine during use.

It is PTI’s unique Multi-Process capabilities that make it possible for Four to equal One. Streamlining your processes in our shop will result in reduced shipping, handling, paperwork, downtime and all related peripheral activities that will save you money in the long run.

Dry Film Lubrication Gives Critical Long-Term Protection

dryfilm-homeDry Film Lubrication (DFL), also known as solid film lubrication, is the ideal solution for lubricating your parts when liquid-based lubricants fail to function properly. The dry film protective coating is more reliable for reducing surface friction between part surfaces.

For operations where cleanliness of your parts is critical, dry film coating offers a protective layer that won’t become easily contaminated by attracting dirt, metal, or other foreign particles. It provides long-term protection in conditions where damage occurs from lack of use, and interacting surfaces that are immobile seize up. Rust, corrosion, and oxidation are prevented in parts that could undergo damage before even being put into service.

Dry Film Lubrication advantages include:

  • Unaffected by extreme hot or cold temperatures
  • Excellent load-bearing capacity
  • Long-term protection, including storage
  • Effective moisture barrier
  • Clean, dry, and odorless
  • Appropriate for all metals, as well as plastic, wood, and synthetics
  • Resists contamination or removal by most solvents
  • Ideal for components that have to be removed repeatedly from inaccessible areas

PTI uses graphite and molybdenum disulfide (MoS2), or moly, as effective dry film lubricants to protect your parts’ surfaces when liquid lubricants won’t survive. The effect of these dry film coatings is similar to a person trying to walk across a floor covered with layers of playing cards. Each card slides easily against its contacting card, creating a reduction in total surface friction and resistance.

The DFL can be applied by dipping, brushing, or spraying. PTI typically uses spray, because both graphite and moly are suspended in a solvent that acts as a sprayable carrier similar to paint. The solvent evaporates off your part, leaving the dry film coating as a protective coating.

Dry film lubricants are used in many applications, including engines and airframes for both commercial and military aerospace, ground engines for power generation, and laser components and heat exchangers.

Many specifications for solid film lubricants require an additional process before it’s applied. Precision cleaning, vapor degreasing, passivation, and other special processes are performed to ensure maximum results in adhesion and effectiveness of the dry film coating.

At PTI, your special processes are available at one stop, saving you time and money with qualified solutions to your manufacturing needs.

This is the first in a series providing detailed information on the special processes provided by PTI.

Part Two: Get Quality Control for Your Parts with Nondestructive Testing
Part Three: Liquid Penetrant Inspection Is Economical and Versatile
Part Four: Magnetic Particle Inspection