Qualifying Stainless Bellows using Industrial CT Scanning

CT Scanning Bellows

Bellows are a type of expansion joint used in piping applications for a variety of industries like oil & gas, aerospace and defense. Bellows allow complex systems to move according to the forces applied to them (system vibrations, pressure changes, & rapid temperature shifts).

Because bellows are used to sustain a system through the above factors their structural integrity is paramount. This case study demonstrates the method of CT scanning to image and qualify bellows welds and ply separation.

UNROLL METHOD

The “Unroll” technique offers a planar viewing method for cylindrical features or parts. Below is an unrolled, higher zoom view of the weld, porosity, and sleeve seam.

FOCUS SCAN (20um RESOLUTION)

During process development engineers often request the highest possible resolution of an area of interest. This characterization helps inform the engineer for process changes and product viability.

DIMENSIONAL INSPECTION

Industrial CT data, and surface data acquired using laser scanning (click here to learn more), is exported to .stl for dimensional inspection. We are able to inspect complex, inaccessible geometries that more conventional systems cannot reach. For example, we measured ID axis perpendicularity and inside ply diameter centerpoints of each bellow and found this bellow consistently deviates in +Y.

Industrial CT Scanning Battery Cells & Battery Modules

THE DEFINITIVE GUIDE TO CT SCANNING BATTERIES

Modern electrification is taking over many industries and battery technology is rapidly evolving to ensure new energy sources have a reliable storage mechanism. Industrial CT imaging, a technology that offers the ability to see inside objects non-destructively, is critical for evaluating manufacturing processes and comparing technology changes.

This case study demonstrates the viability of scanning various battery types from small battery cells to large EV battery modules.

COIN & BUTTON CELL BATTERIES

Micro-CT imaging is a critical tool for characterizing the geometry of small batteries. With variable resolution between 3um and 125um, no battery is too small to be imaged.

CT characterization is used for evaluating new technologies, comparing process changes, and determining points of failure.

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CYLINDRICAL BATTERY CELL (AA)

There are several imaging methods and variables to consider for a given application. When we scan cylindrical cells a useful tool called “Unroll” is often deployed.

Unroll allows the inspector to planarize cylinders. For example, imagine cutting a toilet paper roll and laying it flat on your desk. The digital equivalent allows the inspector to scroll through a planar view at any distance from the specified axis.

The video to the right demonstrates “Unroll.”

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POUCH & PRISMATIC CELLS

Foreign object debris is one of the primary causes of battery thermal runaway resulting in increased temperatures, destruction of the battery, and fires.

Reliable detection of foreign objects is critical for the safe manufacture, storage, and long term use of battery cells. If there is a manufacturing failure it is best to inspect cells before assembling them into full battery modules. Because cells are smaller and easier to handle resolution and x-ray penetration can be improved.

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BATTERY MODULES

Industrial Inspection staff has CT scanned thousands of battery modules. Customized criteria are used for each project with regard to what the issue may be. Some typical rejectable indications include:

> Foreign Object Debris

> WELD DEFECTS

> ANODE AND CATHODE ALIGNMENTS

> CELL TEARS & LEAKS

CT Scanning Materials for Porosity & Fiber Orientation

INTERNAL INSPECTION OF ADVANCED MATERIALS

Industrial CT scanning is used to inspect advanced materials for defects like porosity, inclusions, cracks, delaminations, and fiber orientation.

These are aircraft phenolics and their structural integrity is paramount. Pores have been located in proximity to the edge and other indications are characterized throughout the samples.

BATCH SCANNING SAVES TIME AND COST

Batch scanning is a technique that can be used to scan several parts at once. This can significantly decrease required scan times and their associated cost. The two samples below were scanned next to each other and separated in Volume Graphics. One drawback to batch scanning is the reduced resolution to fit both samples into the field of view.

Seen below is a significant linear indication found along the length of one of the samples.

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CORE SAMPLE ANALYSIS

Due to penetration and volume limitations of CT scanning, core sampling is used to test a batch of much larger parts to characterize their quality. Clients may section material out of an area of interest (a functionally critical zone or area that is more prone to manufacturing flaws). These core samples are then used to qualify batches of product or compare different vendor processes or lots.

This carbon fiber sample demonstrates porosity, inclusions, and fiber orientation.

Minimum density filter showing all pores across a range
Minimum density filter showing all pores across a range
3D rendered fiber orientation
3D rendered fiber orientation

CT Scanning & Reverse Engineering Complex Assemblies

Reverse Engineering Complex Assemblies

Combining high resolution scan data from devices like our Nikon CT scanners and Hexagon Laser arms with best in class inspection softwares (PolyWorks & Geomagic Design X) allows us to reverse engineer complex component and assemblies.

This multi-material camera lens zoom housing has the makings of a very difficult and time consuming project. Within the capability of CT to produce water tight scan geometry non-destructively, several of these components would need to be sectioned to acquire all necessary geometry.

There are three steps to reverse engineering:

1. ACQUIRE DATA

Data for modeling can be acquired using several methods – at Industrial Inspection we use hand tools, laser scanners, and X-Ray & CT scanners.

2. MODEL THE DATA

Part data is aligned and then designers use Geomagic Design X to sketch and blend features and correct geometries for flatness, symmetry, and patterns.

3. VERIFY ACCURACY

PolyWorks is used to compare produced models back to original scan data for accuracy and tuning.

3D SCAN

2D SKETCHES

SOLID MODEL

Reverse engineering lenses is particularly easy using CT technology. No spray is required like with surface scanners, and there is no noise caused by the part transparency.

One technique for modeling complex assemblies is to scan everything in the assembled state, disassemble everything, rescan the individual components, and then refit those components back to the assembly scan. This ensures everything is aligned properly and mitigates material interference so that all geometries can be modeled.

We also can use profiles from one component as a guide for additional components to minimize factors like rattling. For example, we used the ID profile of this housing as the same profile of the OD of the lens guide, ensuring a perfect fit.

Internal Component
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Scan to CAD profile comparisons are the critical last step of any reverse engineering job. The color coded heat map shows which surfaces are high, low, or out of position compared to the scan data. With this information the model can be tuned to an acceptable level of deviation. A report of this deviation is provided alongside the model at the end of the project.

Reverse Engineering Components for Fit & Function

Reverse Engineering Components for Perfect Fit & Function

We combine exceptional technologies like CT scanning and modeling and inspection softwares to re-create perfect fit and function components. For example, these gaskets were worn and cracked and the client was unable to find replacement parts. Scanning just the casting or gaskets alone would not be adequate. 

Instead, we CT scanned all three components and virtually aligned them to ensure no critical design intent was missed.

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Using Geomagic Design X’s silhouette cross sectioning feature allows us to model these gaskets using the full profile of a line even though the gaskets aren’t perfectly flat. We then use the center points of the casting to ensure bolts pass through with no interference. Then, we extrude the design cross section to the exact width of the gaskets.

Geometric Magnification Explained – 40um vs 8um CT Scan of Sensor

WHY RESOLUTION MATTERS

For x-ray & CT imaging there is a dynamic called Geometric Magnification. GeoMag (Mg) is the calculation of the distance between the x-ray source to test object and detector (Source to Object Distance, SOd) & (Source to Detector Distance, SDd).

If the detector remains stationary, the closer the object moves to the x-ray source the higher the resolution becomes. However, the further the object moves from the detector, the smaller the field of view. Put simply, the higher the resolution, the smaller the area of interest to be imaged.

A proper understanding of the project requirements determines the appropriate resolution and field of view. If a client needs to check for hairline fractures or micro-porosity, maximum resolution is necessary. If these defects are smaller than the resolution of the data they may not be resolved.

The below sensor is being scanned to evaluate potential leak paths in the soldered tip. The advantage of the 40um scan is that the entire part is characterized. However, the fine details of the area of interest are best resolved in an area of interest scan at 5x that resolution. At this resolution we can see micro-porosity not seen in the larger GeoMag scan.

40um Full Part Scan

8um Area of Interest Scan

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X-Ray Repeatability of PCB Components

HIGH RESOLUTION X-RAY REPEATABILITY

High resolution x-ray is used to characterize PCB components for failure avoidance and analysis. With electrostatic discharge mechanisms in place, we image and sort safety and mission critical PCBs against customer specified metrics like porosity percentage, FOD size and location, bond wire straightness, general failure points, and many other indication types.

With programmable part manipulators and low density custom fixturing solutions, we guarantee the highest quality digital x-ray solutions.

The below image set is an example of our resolution, contrast, and positioning capabilities.

CAN YOU CAN SPOT THE FAILED SAMPLE?

Failure in the Field – Medical Instrument Carrier

Failure in the Field

This vessel is designed to hold and suspend implant screws in sterile liquid. The slots allow for various sizes to be carried using the same vessel. The vessel came to us because a screw was out of place inside the vessel prior to opening. Because of the occurrence the entire unit was quarantined for investigation.

The blue arrows point to a crack found in the seat of the carrier. The most probable explanation is that because some force is applied to hold the screw upright the seat cracked during loading. Then, during transit or handling the screw dislodged.

Versatility of CT Data

While this investigation was completed quickly, there is much more that can be learned from this dataset. For example, a common application for Industrial CT Scanning is seal and thread engagement analysis. This data can be exported to .STL for dimensional inspection, CAD comparison, and wall thickness calculations.

CAD comparison is useful to understand why the seat may have cracked. Perhaps the seat is accurate to CAD but the slots are out of position, causing stress fractures.