Stefan Hokuf

AMT Magazine Cover

Aeroscan Featured in AMT Magazine

Are you an AMT AviationPros.com subscriber? Our article on 3D scanning for aviation applications just made the latest cover! We were scanning on a P-51C “Lopes Hope III” at AirCorps Aviation.

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TBM Avenger Tail Weight Box

TBM Avenger Aircraft Counterbalance Fabrication

Problem: Removing original equipment, like machine guns and ammo, from the aft belly machine gun on a TBM Avenger made a noticeable difference in flying characteristics.

Proposed solution: Add a counterbalance to an open area in the same vicinity, as identified by a maintenance director.

Question: How to measure a complex space in order to fabricate an exact-fitting steel container in a short time frame?

Answer: Use 3D scanning

PROJECT BENEFITS USING 3D SCANNING

  • Quantity of design and fitment errors are greatly reduced compared to traditional means of measuring.
  • Volume of available space was maximized from accuracy of scan.
  • Time to fabrication greatly reduced by producing CAD model faster.
  • No re-work of fabricated part – perfect fitment on first attempt.
  • Estimated time savings compared to traditional means of measuring and designing: 8-12 hours.


example of a triangulated mesh model data

What should you know before you 3D scan your aircraft part...

In my first blog post of “Delivering a True Time Savings: 3D Laser Scanning for Aviation.” I touched on what a portable 3D laser scanner is, the process for 3D scanning, but only briefly how it compares to its other scanning counterparts.  As I prepared for my next post I realized that just as important in understanding the scanning process is grasping the differences between the various types of 3D scanners on the market.  Yes, technically they all output 3D data representing the form of a real-world object, however, it’s what that data will be used for that sets the stage for what type of scanner to use.  By not using the correct scanner the returning data may prove useless because it does not contain the level of accuracy, or it is physically unable to scan what’s necessary for the project’s goals. In this post we’ll look at the various scanner types, their pros and cons, and finally our preference for a majority of aviation applications.

To contact or not to contact?

The main classification of 3D scanners fall into two categories, contact and non-contact.  These category titles are self-descriptive so I will spend more time delving into the types of scanners that are within these two categories.

Contact:

Typically defined as CMM (Coordinate Measuring Machines), these machines record positions in the X, Y, and Z coordinates utilizing a mechanical probe. Early machines have become antiquated due to their operators requirements to move the machines manually and results proving suspect due to the different amounts of pressure applied during probing or touching the object.  The process of recording positions is also very time-consuming because of the quantity of points necessary to accurately build three dimensional data.  In addition to the scan time consumption, physical constraints are realized because of the table or bed that the part must be contained within.  Some of those issues have been alleviated with the introduction of jointed arms that allow the probe to articulate in multiple directions.  However, the probe is still at the limitations of the full extension of the arm that is typically fastened to a table or other base structure.  It should be mentioned that newer models of probing-type scanners have eliminated the need for touching the part.  This has increased the accuracy and speed of data acquisition.

While it may seem that these scanners are altogether outdated, that is not true.  Like many tools, there are many that produce similar results, however, it’s the requirements of the project that typically select the best tool for the job.  In the case of CMM, objects that are required to be verified in a consistent manner and in a controlled environment are well-suited to this type of scanning.  The best example is in manufacturing quality assurance settings where products are constantly checked for tolerance against CAD design models and specifications.  In addition, the latest technology in CMM has provided for handheld portable devices that lend themselves well to production floor conditions.

An example of an early CMM. Note the permanent setup and its scanning limitations due to dimensions of the table area.

Non-contact:

Even the title lends itself to describe what sounds like better technology doesn’t it?  These types of scanners own the most advanced and preferred scanning features. What these types of scanners utilize are some kind of light, laser, or even radiation that detects an object’s features’ reflection back to the scanner, digitally recreating a 3D object within the scanner’s line of sight.  In this category, I will compare four major scanner types: 1. Time of flight 2. Structured light 3. Handheld laser (triangulation) and, 4. Volumetric or passive.

1. Time of flight scanners use a laser light that is emitted from its position. An internal range-finder records the distance of a surface by timing the lasers round-trip time of flight. Due to this time measurement, these scanners accuracy depend on how precisely they can measure time. Output is typically in the form of a “point cloud”, typically millions of points that assemble in relation to their measurement through the scan. The data’s appearance resembles a cloud in the sense that the points are floating and are not faces or surfaces. These types of scanners typically benefit the architecture, construction, and building / facility management industries because of the vast amount of space that they can capture.

Their major disadvantage is a lack of high accuracy due to timing the high speed of light over this large distance. While these tolerances are acceptable for large scale measurement, they fall short for the precision necessary on parts fabricated for an aircraft. In addition, due to the process of data capturing, any motion in the subject or scanner will distort and degrade accuracy. This means using large tripod mounted platforms that limit line of sight and stopping any work in and or around the scan area can be cost prohibitive if other work is being performed in the vicinity.

2. Using a reliable light source, structured light scanners emit a unique pattern of light on a subject. Internal cameras slightly offset from the light source capture the shape of the pattern and measure the distance of every view point on the object. Advantages of structured light 3D scanners include data acquisition speed and precision because they can scan multiple points at once and build data as a triangulated mesh model. These polygon mesh models are advantageous for export to CAD software that uses the mesh as reference to build parametric, editable surface models. These CAD models are what are used for final fabrication efforts.

The disadvantage with these types of scanners is the necessity to mount on a tripod because of the light projector and camera’s relatively large and heavy physical size. In addition, line of site is then limited due to the static mounting. Often, rotary tables are required as an accessory to help automate the scanning process. These efforts require more setup time and don’t lend themselves well to environments outside of an office per se.

3. Handheld laser triangulation type scanners are certainly the most revolutionary in the field of 3D scanning. In particular because of their portability, speed, and accuracy. Portable laser scanners create 3D data by emitting a laser(s) that duplicates the object by traveling across its surface. Because the internal coordinate system is defined by characteristics or by positioning targets on or around the object, the object is not subject to static placement or vibrations during scanning. In fact, often the part can be held in one hand to provide line of sight while the other hand moves the scanner! Similar to structured light sources, laser scanners generate polygon mesh 3D data that is excellent reference for downstream CAD workflow. Laser scanning can be considered for NDT (non-destructive testing) efforts because the lasers are not physically touching the part.

If there is a disadvantage to handheld laser scanners that use positioning targets, it is the time involved in applying them. If the application is a wing or fuselage and the entire area is to be scanned, a large portion of setup time can be involved in randomly applying the targets and then removing them if necessary. There are laser scanners that self-coordinate off of the the part’s characteristics (not requiring positioning targets), however, you are then held to the constrictions of keeping the subject stationary and eliminating movement that could affect the accuracy.

4. Finally, the last category of scanners to mention is volumetric types.  These scanners are referred to as volumetric types because they actually scan the volume of a subject and are able to “see inside” or through the part.  Computed tomography, more often referred to as a CT scan, is common in the medical industry for visualization of the body’s internals.  However, for inspection of internal makeup, fatigue, or stress of a part, this can be a very useful type of scan.  NDT services typically provide this type of scanning since it also not physically touching the part to achieve data that is rich in the details that are not visible to the naked eye.  An additional subtype is phased array which is ultrasonic scanning used for a component’s internal failure detection.

Because this data can be difficult to interpret and uses equipment that takes longer specialized training, it is usually reserved for unique parts that could result in critical failure situations.  The equipment that performs these types of scans are the most complex and are operated by more experienced individuals so the costs for results are delivered at a premium.  If your application does not require an internal inspection you would most likely overpay for the data delivered by these volumetric types as opposed to the previously mentioned scanner types.

Click images to view larger.

To contact or not to contact?

I assembled this quick table to visually display the features previously described by each scanner type.  Note how Portable Laser type scanners score the highest in a variety of features and scanning benefits.

  Scanner Type
Scanner Benefits CMM Time of Flight Structured Light Portable Laser - Triangulation Computed tomology (CT)
High tolerance accuracy
Data acquisition speed
Long distant measurements
Setup time & portability
Freedom of movement around subject
Versatility of scan subject types
Self positioning (no targeting) *
Passive scan - internal (x-ray)

* Some laser scanners do not require positioning targets, while some do.

Handheld laser scanning benefits are recognizable when scanning in areas like a wheel well, under a wing or in confined areas. Scanning contoured parts in their native position is ideal to preserve their shape in reverse engineering efforts.

What does it all mean?

Certainly there are a lot of features and technical verbiage used to define the various 3D scanners that are available on the market.  However, my goal in this post was to define the major scanner types and then explain the basic differences that make them advantageous or disadvantageous to their users.  As with so many advancements in technology, scanning features are ever-evolving so it’s best to verify with whomever is selling their services that the results will prove beneficial.

What does the future of scanning behold?  Most likely handheld scanners that have the onboard processing to negate the wired connection to a laptop or other processor necessary for computing the vast amount of data that scanning generates.  With the ever increase of processing speed put in the palm of our hands with mobile devices, will we see the addition of aftermarket “snap on” lasers or additional cameras to scan objects at a moment’s notice?  Not really that far fetched if you think about it.  Whatever the case, 3D scanning technology is here now and the you should leverage it to make your projects more successful.  I hope that this information will provide you with the ammunition you need to ask the right questions when you decide to begin.

Summary of what to remember about 3D scanning:

  • Using the right type of scanner for the application is important. Using the wrong type can result in unusable or unreliable data that cost you valuable time & money.
  • Handheld 3D laser scanning is the currently the most versatile type of scanning for the majority of inspection & reverse engineering applications.
  • What is the project’s end goal? The results you need from your project should select the type of scanner to be used.
  • Scanners are like many specialized tools. Selecting the right one for the job will insure your project success and ROI.

Are you ready to talk about an application?  Still not sure which type of scanning is best for your project?  Feel free to contact us and we would love to discuss your questions in person.


Beech 99 Engine Cowl Modification

A regional cargo carrier operates with Beechcraft model 99s. They needed a solution for repairing cracks in the engine cowl. This case study explains how Aeroscan got involved and used 3D scanning to reverse engineer and fabricate a perfectly fit doubler for a repair.

When it comes to repairs, the real challenge is constructing the steps to arrive at a solution. This was the situation that presented itself to the maintenance team at Bemidji Aviation Services Inc. (BASI). The team decided they needed a repair solution for cracking engine cowls on Beech 99s. The solution—fabricating a doubler that could be installed to strengthen the cracking area. Yet because of the difficult shape and challenging nature of trying to measure a cylindrical shape like a cowl, how would they possibly fabricate anything that would fit accurately? If 3D scanning technology was a viable option, would it provide the level of accuracy necessary for fabricating a perfectly fitting part and not exceed the budget assigned to the project?

Immediately upon inspecting the existing conditions, Aeroscan determined that this was an excellent application for 3D scanning.  Aeroscan explained that as an object’s measurable surface becomes more complex, the benefits from 3D scanning directly coincide.  The project began with scanning the cowl on the ramp.  Within 1 hour a full scan of the entire affected cowl was captured.  The typical reverse engineering workflow of importing the 3D scan reference used in modeling the new piece in CAD could begin.  After another 4 hours Aeroscan had a working CAD model.  This CAD model is what is used for whatever is the best determined fabrication process. In this case, because of its cone shape, an operation termed spin forming was used on 2024-O, 0.032” aluminum.  Finally, following a T42 heat treatment, conductivity, and hardness tests were performed to bring the new doubler to specifications.

The new spun doubler fit perfectly and on the first attempt!  The time saving benefits are not only made on the front-end when measuring the part but at the back-end when the part fits flawlessly for the mechanic, post fabrication.

In this case, the time to complete this project utilizing 3D scanning is difficult to compare against traditional measuring efforts because those steps were too risky and challenging to even attempt.  ROI is often measured in dollars and cents.  However, when taking advantage of technology that conquers efforts that were previously deemed too difficult, it’s the value in solving a problem that provided this maintenance team with another level of ROI–simply executing the steps to arrive at a solution.

PORTABLE 3D LASER SCANNING BENEFITS

  • Versatile: Virtually limitless 3d scanning – any part size, complexity, material or color.
  • Metrology-Grade Measurements: Accuracy of up to 0.0012 in., resolution of up to 0.002 in., high repeatability and traceable certificate.
  • Standalone Device: no external positioning system, no arms, no tripod or fixture.
  • No Rigid Setup Required: the part and scanner can be moved freely during scanning. Take it from place to place or use it in-house or on-site.
  • Automatic Mesh Output: real-time visualization.


P-51 Windshield assembly scan

Delivering a True Time Savings: 3D Laser Scanning For Aviation

Have you ever stepped back at the end of a project and wondered if there would have been an easier way?  Considering how much technology has advanced, in even in the last decade, it’s an easy question.  It seems recently the challenge is figuring out which technology works the best or is the most applicable to one’s project.

AirCorps Aviation knew that applying 3D scanning to reverse engineering rare aircraft parts would save time in their restoration efforts, but with a variety of scanners on the market, which would work the best?  Through research and testing, it was apparent that leaps in accuracy, speed and quality have made portable 3D laser scanning the most viable and best return on investment of time.  Over a series of these blogs, we invite you to follow along and learn how 3D scanning has become an integral tool in the aviation industry for a variety of applications, especially for reverse engineering aircraft parts.

In this first post, we’ll break down the basics of portable 3D laser scanning, learn what it outputs and why that saves you time.

What is a portable 3D laser scanner?

At it’s basic definition, a 3D scanner is a device that analyzes a real-world object to collect data based on its shape and possibly its appearance (e.g. color).  This data instantly builds itself as a replication of the object in 3D in the form of millions of points or connected together appearing as triangle mesh.  The collected data can then be used to construct a digital 3D model or take specific measurements at any given point, often referred to as metrology.

When 3D scanning comes to mind, images of cameras and units fastened to a tripod or arm traditionally appear.  While these units still provide highly accurate data, it’s their portability and physical limitations that separate them from a portable 3D laser scanner.  Within the last decade, huge leaps in accuracy, speed and quality have catapulted hand held scanners utilizing self-positioning technology to the top. It’s this portability that allows for flexibility in a myriad of scanning tasks inside or even outside of hangars. This portable 3D laser scanning is what AirCorps Aviation has invested in and has successfully been applying to a variety of aircraft projects.

Stefan using our portable 3D scanner for reverse engineering a P-51 cowl former.
The basic ingredients for portable 3D laser scanning: Laptop with software for capturing the scan data, a portable 3D scanner and finally the targeted subject for scanning.

What is the 3D scanning process?

The first step of the process in any potential 3D scanning project is having a conversation with an application engineer and determining if 3D scanning will provide benefit.  Even with 3D scanning the old truism applies- just because you can, doesn’t always mean you should.  If one determines that 3D scanning is applicable, the next step is to define what the deliverables are.  Can you work with scan data reference alone?  Can you build your own CAD model?  Do you have the equipment to fabricate parts yourself once you have created a CAD model?  Where will the scanning happen?  Objects are usually scanned in 3D for two primary purposes: Reverse engineering and Inspections. They each have different workflow paths and along them you may be able to perform some of the work yourself.  Whatever the case, these are just some of the questions that are necessary before starting actual scanning and are all ones that our application engineers can help you answer.

Once the project has been approved to proceed and it’s deliverables defined, self-positioning targets are applied to or around the object.  These positioning targets are the breakthrough innovation that allows the object being scanned as the reference for positioning.  If you have the opportunity to see the scanning in person you will probably be amazed just how fast the object is captured!  This data is what provides the base or platform for what we refer to as reference.

P-51 Windshield assembly scan. Note the presence of the randomly placed positioning targets. This scanning project’s efforts were for reverse engineering and fabricating replacement side glass.
Triangle mesh scan data.

What are the results?

Most people who experience the instant results of 3D scanning are justifiably impressed. However, this process typically only represents only the first step in a reverse engineering project. Without a software to clean, repair, and produce usable reference that can be exported from the scan, it has little value. This next step of cleaning, repairing and generating reference is referred to as post-processing. This step is critical and not all scanners provide the software in order to perform this task. This post-processing software is the bridge to CAD (computer aided design). The post-processed model can be typically be exported as an STL (STereoLithography or Standard Tessellation Language) file or converted to Non-Uniform Rational B-Spline (NURBS). These files are what provide the platform and base for useful reference when starting in CAD and reverse engineering.

I often get the following question: “Why is it necessary to model the part in CAD since in theory I have just obtained a model by scanning it?” The answer is because the scanned model is not in a format that allows for editing or modifications to its properties.  On the contrary, CAD models can produce a parametric solid body part that can be modified, edited and referenced for building additional tooling necessary to fabricate the duplicate part.

If you think about it, often the parts that are scanned are damaged and or only a portion of them is available to be scanned. If you replicated them in this state you would only be producing another damaged or incomplete part. Another common questions is – can I just 3D print the part?  Answering this question usually requires more information.  While it is true that a 3D scanned part can be post-processed and then 3D printed, it’s not likely that the part can be printed in a material that is serviceable. At least not cost-effectively. In addition, it goes back to the question – why would I want to print a damaged part? Remember, most of the time the goal of the reverse engineering workflow is to obtain a perfectly made duplicate part from the original specified material. It’s the CAD software that provides the platform to perform that critical task. The post-processed 3D scan reference is imported simply to aid in efficiency and accuracy of replicating that part.

An example of a cowl former scanned, post-processed (scan reference), and finally the cowl former modeled from that scan reference in CAD with tooling for forming. In future posts we’ll look at more of these scan to fabricate projects.

Wrapping up

In conclusion, I hope that the process of 3D scanning does not sound too complex or daunting.  Rather, that within this first post you gain insight on the basics of what a 3D scanner is, what steps are taken to produce data, and finally what you can expect it to generate.  One important point to keep in mind with this technology is that it excels in capturing complex aircraft shapes, very accurately, and puts you into the fabrication stages at a much faster rate.  In conjunction, those resulting fabricated parts have a much higher percentage to fit perfectly the first time.  How many times have you seen reverse engineered parts not quite fit, only to start the measurement process over again.  Not only is that money wasted on materials but have you added up the man hours spent measuring that part?

Still not quite sure how scanning can be applied to your aircraft?  Hang in there, in future posts we will start to look at specific aircraft applications in detail and how 3D scanning benefited them.  Hey, we’ll even look at a project that benefited from 3D scanning and printing!

If you can’t wait to see these applications, visit our reverse engineering page to learn more.  Or, of course, contact us and we can discuss your applications in person.