A glossary of key terms frequently used within 3D scanning and reverse engineering processes
2D Drawing- In CAD we can create a two-dimensional view of a product or object, this object is perceived with reference to 2 axes, where a 3D model would be with reference to the 3rd Z axes.
3D Laser Scanning- Laser stands for Light amplified by stimulated emission of radiation. 3D scanning device that uses a laser to allow the scanner to determine and create coordinates. The laser scanner omits an intense single beam onto the surface of the object, unlike the Optical scanner that projects a ‘volume of light’ projecting a ‘fringe pattern’ onto the surface of the object. Due to the intensity of the laser it is less susceptible to changes in ambient light conditions. There is a debate on which system, optical or laser have the greatest resolution / accuracy. Both systems have their own advantages, depending on multiple factors.
3D Modelling-Is the use of software to create the representation of a three-dimensional model of an object so it can be designed in a 3-dimensional space. Through the use of powerful CAD software large 3D models can be generated to enhance and speed up the design process.
3D Optical scanning-This is where digitised scan data is obtained shot by shot, as a ‘fringe pattern’ of light which is projected and laid over the component being scanned. As a scan is completed the digitised point cloud data is modified, and the software determines the 3D coordinates by calculating the returned patterns of high accuracy divergence and convergence of the fringe pattern. This type of scanning can be used within a white light scanner and a blue light scanner. PES Scanning uses the internationally-respected German measurement company GOM’s structured blue light 3D scanning system as the most accurate. This system is the system of choice for the major OEMS Rolls Royce, Jaguar Land Rover and Boeing etc.
3D Scanning- This is a process that involves measuring an item and capturing its data, using one of a number of systems including: 3D optical Scanning, CT Scanning and Laser scanning. This data forms a point cloud which is then imported into CAD. Note that the data imported into CAD is a ‘dumb data’ and cannot be used until it has been reformatted in CAD using specialist ‘bolt on’ software
As Scanned or As Built- This is the process of using the scan data without modification, therefore the PES Performance engineers would reverse engineer the part from the data and reproduce all the ware, distortions and defects as per the original scanned part. (This excludes and breakages or stress fractures etc).
Blue Light Scanning- In 3D optical scanning this refers to the colour of the light projected onto the surface of the object. Blue light scanners are less sensitive to heat and reflectivity than white light scanners, so produce more accurate results. PES Scanning uses a blue light GOM system capturing 5 million data points per scan.
CAD-Stands for Computer Aided Design and is a type of software used to create precise models or technical illustrations. CAD has become the main tool of design engineers. There are varying CAD software packages on the market to basic entry to advanced packages. Both PES Performance and PES Scanning use the advanced CAD packages, Siemens NX Version 10 to 12, Catia.
Colour Map Deviation Report- Is one of the reporting processes we use for our clients to highlight deviation to the original CAD model or controlled part. The deviation or surfaces outside the specified tolerance band are highlighted using colour mapping to identify deviations. This allows the client to quickly identify areas, out of tolerance, from the inspection scan data. This approach is very easy to monitor for inspection purposes.
Competitor Bench-marking- This process is used by clients to review and carry out analysis of a competitor’s product. Competitors will not give their CAD models and data away for the product they have on the market. The only way it can be analysed or ‘Bench-marked’ and compared against the client’s own products will be through, scanning all the components parts, importing the digitised data into CAD and then turning that data into a 3D model. This process is known as reverse engineering. Once the 3 models have been produced the parts can be tested and run through simulation software, i.e. FEA & CFD, as a single component or as a complete, digitised assembly. It must be noted that to prevent infringement of intellectual property it is crucial that the data is only used for analysis.
Cross Section Analysis Report-Compares cross sections of CAD model data against the original designs and can be used for the verification of part thickness cross section as selected and or to inspect the geometry.
CT Scanning- Stands for computed tomography and is a non-destructive process which uses x-ray equipment to inspect the internal and external features of a component and produce 3D representations of the component. This is a very powerful tool for inspecting internal components without destroying the part being inspected. It has limitations based on material thickness and type.
Design Intent-As opposed to ‘As scanned’ the PES Engineers would use the scan data as a guide, reverse engineer and produce the part as he or she believed it was originally designed, design intent. This process could include repairing any worn or broken sections, truing up bores and creating flat planes to name a few.
Design Optimisation- This is to achieve the “best” design relative to a set of prioritised criteria or constraints set by the client or design engineer. Engineers are often required to identify a few appropriate design solutions and then decide which one best meets the need of the client. This decision-making process is known as optimisation. For the scanning and reverse engineering of legacy parts, our engineers, using the data could reproduce the part ‘as design intent’. However, they could then look to make improvements to the design and function not available to the original designers as the technology either did not exit or was not cost effect. Optimisation could include manufacturing the part in lighter, stronger materials, change bearings to reduce friction, wear and heat and improve lubrication through design. The options are varied.
Digital Archiving- This is the use of data capture technology to create a digitised copy of a part or object. The data is stored in a digital archive and used as and when required. PES Scanning use it for multiple applications. One main area in engineering is during a clients Planned Preventative Maintenance period. PPM is used to have a defined period of maintenance for critical machinery, so the client can limit production down time. With large legacy equipment where spares are limited, expensive or no longer available, the components can be scanned, and the digital data archived used when required. E.g. The last critical part has been used to repair the machinery and if it fails there will be a long and costly lead time to make a replacement. However, as there is already a digital data base the part can now be reverse engineered and manufactured to reduce the risk and cost of a failure. Archiving is also used to create a digital file of priceless items either for insurance purposes, identification, repair or making a reproduction for display therefore protecting the original piece. It is also used in the high-end classic car market when a car is damaged the car can be brought back to its original condition using the archived data. Simply data archive allows our clients to have back up data to ensure if anything happened to the item, there is digital data available to fall back on if you needed to identify, repair or reproduce the item.
Dumb Data- There is an assumption that scan data, or the mesh can be manipulated from the raw data. This is not the case as it needs to be imported into a suitable CAD software to transform it into a working geometry. This process can take hours or for more complex geometry, days. Therefore, the data in known as ‘Dumb data’.
Geometric Dimensioning & Tolerance (GD&T)-It is a system or process of symbols, rules and definitions used to define the geometry of mechanical parts. It is one of the most powerful tools available that can improve quality, reduce cost and shorten delivery time. It is an international language used on drawings and models to accurately describe a part. The language consists of a well-defined set of symbols, rules, definitions, and conventions to describe the size, form, orientation, and location tolerances of part features.
Legacy Part-There are still machines and parts operating today that, whilst still very effective are becoming difficult to maintain due to shortage or no spares. 3D scanning, through reverse engineering can help to reduce the costs and eliminate the risks through PPM. A Legacy part is any part or equipment that was not designed in the digital age and has no or limited drawing available. This can be from a 100-year-old 1000-ton press and large 100-ton gear box to a classic car or aircraft. Through 3D optical scanning we can scan the parts or even a worn broken part, import the data into CAD and through reverse engineering produce and new part, either with the wear built in, or a brand-new worn part. This is so it can interface and fit this existing component in the system or produce a completely new part. The parts can be produced ‘as scanned or commonly known ‘as built’ to ‘design intent or the part could be completely optimised.
Line of Sight-Excluding CT scanning 3D scanning systems can only capture ‘line of sight’ data. It is a literal term as the scanners can only capture surface data you can see. This is also dependent on line of sight if the scanning head can be positioned to capture the data. i.e. If you have a bracket and the inside face is close to another feature you may not be able to capture the data.
Photogrammetry- Is a technique of taking measurements from photographs. A camera is positioned close to the subject and is typically hand-held or on a tripod. The output of photogrammetry is a 3D model of a real-world object.
Planned Preventative Maintenance (PPM)- This is all about minimising the risk of lost production time if crucial equipment fails. If you as a company have a scheduled maintenance period then this is the best time to undertake 3D scanning of your key components, parts, equipment and produce a digital archive. Once you have the digital archives you have the point cloud data to produce spare parts or replacement parts and at the same time reducing the down-time to minimise impact on production.
Point Cloud data- Is a set of data points in space which are generally produced by 3D scanners. PES GOM 3D Optical Scanning system will produce up to 5 million data points of the object being scanned.
Polygon mesh- This is where a collection of edges and faces are made up to represent a polyhedral object in 3D computer graphics, either in our GOM inspect software or in our Siemens NX CAD software. The faces usually consist of triangles that make up this model.
Post Data Clean Up-If after scanning, the scan data or mesh is not water tight the data would have to be imported into our GOM inspection software and then the mesh would be filled manually be one of the design engineers. For a large complex part this could take a number of days.
Quality Inspection Part- Through data capture processes such as 3D Optical Scanning, CT scanning and 3D Laser scanning we can undertake quality inspection by using the digitised data or large data set point cloud. This highly accurate data is used to compare a physical part against the original CAD models to ensure the manufactured part is ‘as designed’. The data can also be used to compare against original scan data of a part, inspecting changes or variances in tolerance ‘tolerance creep’ during the manufacturing process. PES scanning can generate a bespoke inspection report tailored to the requirement of the client and can be used to refine the manufacturing process or archived for auditing purposes, such as in Aerospace and medical sectors.
Quality Inspection Tooling- As with quality inspection a brand-new tool can be scanned and inspected against the CAD model to ensure the tool is within the correct tolerance band before manufacture. This can ensure the tooling can be tuned or crapped before production starts. See also Tooling trend analysis and inspection.
Reference Points or Un-coded markers- These round un-coded markers are geometrically accurate and are placed on the part to be scanned, or around the part onto a jig or fixture. They are used within 3D scanning to ensure high accuracy in the measurement. The markers come in a variety of sizes, which size you use will depend upon the volume and lenses selected on the scanners, which is dictated by the size of the part and the resolution required. By using un-coded markers, the part and the scanner can be moved, once the first scan has taken place, which is a key feature of our GOM Optical scanning systems.
Reverse Engineering-This is the process of collecting data from an item, component, piece of equipment, through analysing its function and structure. For example, if there is no original documentation of the item available we can use reverse engineering to produce CAD models for several purposes. i.e. analysis, reproduction or replacement part, optimisation.
Siemens NX- This is an advanced CAD software package used by the PES Performance team. We are currently working on version 10 to 12, but also use CATIA. The software also has additional features allowing the team to import .stl file format from the scanner.
Small and Large Batch Bureau Service-This is where we can 3D scan large or small numbers of parts, for inspection or reverse engineering in our scanning workshop facility. In the case of large quantities, to save time and money for the customer and to be more efficient, instead of placing coded markers on the part, we can design and manufacture or 3D print, in house, multiple jigs that will help to secure the part to speed up the process
.Stl file format- This is an acronym for a variety of things e.g. ‘stereolithography’, ‘standard tessellation language’ and ‘standard triangle language’. It is a type of file format which has a triangular representation of a 3D object and the surface of the object is made up of a series of connected triangles. It is widely used for rapid prototyping, 3D printing and computer-aided manufacturing. Not all CAD software packages have the capability of reading. stl formats and in most cases require the user to purchase a ‘bolt on’ package. More CNC machining software are now able to manufacture a part directly from. stl format scan data, removing the requirement for a manufacturing drawing. (This approach can only be used in certain circumstances).
Tooling Trend Analysis and inspection-This is the process of measuring the piece of tooling or fixture to understand the point at which it moved outside of an acceptable tolerance band for the part being produced. The process is to first scan the part and inspect against the original CAD model then at regular intervals carry out further inspection and measure to monitor changes in shape and form during the life of the tools. The information can be used to build up analysis of how the tool performs over time. The data can also be used to compare against other tooling performance in the same family. Using this data our PES Performance team can help clients to improve and optimise the process, maintain quality, reduce wastage and improve margins.
Water tight Scan- A water tight scan or mesh is when you can scan and capture all the surface data. If there are line of site challenges some data may be omitted, leaving gaps in the mesh, and therefore the scan would not be completely ‘water tight’ and would therefore require post data clean up.
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