3-D Machine Vision in Reverse Engineering . . . . by Nello Zuech, Contributing Editor

3-D machine vision systems are becoming more pervasive in manufacturing industries especially to collect design data in conjunction with reverse engineering applications. The underlying technology has converged to yield cost effective solutions regardless of the actual technical approach. By far the most popular approach uses a laser or white light to scan across the object and a camera viewing the positional changes of the known structured light pattern to calculate range data based on triangulation math. However, there are other approaches as well: stereo photogrammetry, various interferometric approaches.

In some cases these scanners are stand-alone designs with the capacity to make measurements over some fixed volume envelope – generally under one cubic foot. In some cases the scanner is integrated to an articulating arm or into an X-Y positioning system or into a coordinate measuring machine. In these cases a much larger measurement envelope is possible.

Significantly, each technical approach has some specific performance parameters that can be met. Not all approaches are equal when it comes to speed, accuracy and/or repeatability. Similarly, not all approaches are equal when it comes to ability to handle specular surfaces or vibrations. In some cases, the object to be measured must be fitted with cooperative targets and in some cases, to handle specular issues the surface has to be specially prepared for making the measurements. Hence, it is important to map the capabilities of the system to the application requirements.

To gain further insights into the use of 3-D-based machine vision systems for reverse engineering applications, suppliers of 3-D systems being promoted for reverse engineering applications were canvassed for input to this article. The following provided answers to the questions posed.

Susan Dineen – Marketing Manager – Arius 3D

C. Martin Schuster – President – Laser Design

Chris Dryden - Business Development Director, Aerospace – Metris

Giles Gaskell - Director of Business Development – Nvision, Inc.

1. How would you describe your product line?

[Susan Dineen – Arius3D] Arius3D offers:   

• Services: 3D Image Service Centers
• Services: Arius3D Image Library of 3D Image Models
• Solutions: Foundation 3D color laser scanner + Pointstream 3DImageSuite Software
• Software: Pointstream 3DimageSuite

C. Martin Schuster – Laser Design] Laser Design has laser line scanning triangulation systems that are noted for primarily three important attributes: Accuracy, automation and speed. Our product line is the SURVEYOR family of 3D laser scanning systems that includes both portable Faro Arm based scanning systems, tripod based scanning systems as well as CMM machine base scanning systems known for their accuracy and highly automated results. LDI has scanning systems that can scan objects – all sides fast and with a minimum of part set up by the operator.

[Chris Dryden – Metris] We refer to this technology generically as 3D scanners rather than machine vision systems because that more closely describes what our products do.

Metris develops and supplies laser stripe scanners for integration with articulated arm, traditional (Cartesian) and also our own revolutionary Krypton optical hand-held CMMs for the scanning of 3D surfaces.

[Giles Gaskell – NVision] 3D Non-contact laser scanners.

2. What specifically differentiates the models you offer?

[Marty] The model of SURVEYOR scanning systems is differentiated primarily by the size of part that can be scanned and by whether or not the system can automatically scan a part or is a manually operated scanner. Since most of our laser scanning probes can be used on any of the SURVEYOR scanning systems, the scanner size is a variable and so is its manual or computer controlled motions capabilities. Accuracy of scan relates to the series model we offer. Automation is dependent upon whether the model of scanner has an integrated motion control system or is a manually operated system.

[Chris] Metris recognizes that customers need solutions and not just technology, we also recognize the high levels of investment that customers make when choosing our products. Our value proposition is to provide the most accurate, productive, reliable and simple to use solutions on the market in order to provide the customers with the return on their investments that they demand.

[Giles] Flexibility to scan a wide range of applications, sizes and colors.

[Susan] Our 3D color laser scanning technology is a precise scientific instrument able to capture 100 microns x, y-axis and 25 microns on the z-axis. Our approach is capable of simultaneous capture of both color and geometry.

3. Would you characterize 3D-based machine vision-based systems used in reverse engineering as ‘‘hardware-centric’‘ or ‘‘software-centric’‘ and why?

[Chris] Both. The system contains components of hardware and software so it is difficult to separate the two; one without the other provides no value. 

[Giles] Software–centric. The sensors tend to be off the shelf items, the clever bit and the differentiator is the software.

[Susan] I believe that a good result requires both hardware and software.

[Marty] Reverse engineering systems are much more variable than inspection systems. Not many of the many scanners available industry-wide can be used in inspection primarily because of the systems’ inherent accuracy and repeatability. Thus, almost any system can be used for reverse engineering. Accuracy requirements for reverse engineering are much more open as most customers don’t know exactly how accurate they have to be to get the job done and many only want to be in the ‘‘looks good – is good’‘ type range. Thus reverse engineering is much more software centric due to the relative forgiveness that the reverse engineering market has for scanning accuracy. You can make a bad scanner look good with software massaging downstream from the scanner if the software is powerful and the operator able to use critical reference points to make the part look and feel accurate to the original.

4. What are the critical parameters of a 3D-based machine vision system that a prospective reverse engineering customer should understand?

[Giles] How big are the things you want to scan, what accuracy do you need and can it be sprayed white?

[Susan] Accuracy of the data capture relative to the project requirements.

[Marty] Since reverse engineering applications rarely are highly repetitive for the typical customer, the parameters of importance are: wide range of part size scanning, decent overall accuracy (+/- 0.003’‘) or better, ease of use, fast scanning speeds, and whether or not the system is portable. Sometimes it is difficult to get the parts to the scanning system due to size or weight.

[Chris] Accuracy is the often first parameter that a customer will focus on, but because of a lack of standardization within this segment of metrology, defining accuracy is not as simple as providing a single number. For example, which reverse engineering solution most accurately defines the object surface: one which provides 1000 points at 1 micron accuracy or one which provides 10,000,000 points at 50 micron accuracy? The answer is that it depends on what the customer wants to achieve. It is therefore essential that the customer and solution provider understand implicitly how the accuracy, resolution, speed, productivity, flexibility or ease of use of a system apply to their needs. Fitness for purpose is key.

5. What are the skills required to program and operate a 3D-based machine vision system in a reverse engineering application?

[Susan] Attention to detail; knowledge of 3D visualization; knowledge of industrial applications; and software.

[Marty] The skills needed to operate a scanning system which includes the scan data processing software are becoming fewer and fewer due to easier-to-use scanners and easier-to-use scan data processing software. Typically this is a technician level technology. An understanding of PC/ Windows technology is the most desirable, with some idea of what CAD is about is very helpful as well. The CAD technology, however, is not an engineering degree level CAD understanding. The CAD modeling is becoming more of a video game level technology with highly automated features and operator prompts for input. This makes it relatively easy for a beginner CAD level person to quickly master the reverse engineering software like Geomagic to quickly become a CAD model producing employee.

[Chris] Relatively few. At Metris we are constantly seeking to simplify the operation of our products, an easy to use system requires lower training and operation cost, and is also a more enjoyable experience for the operator.

[Giles] Basic computer skills, an understanding of coordinate systems (x,y,z) and if possible CAD experience.

6. How do you support your products – training, documentation, warranty, post- installation service, software revisions? Are these free or is there a fee?

[Marty] Training is provided free for the scanning technology as is installation and first year warranty support and first year updates. Phone support is first level. Parts can be sent for operator installation in some cases. Technician on site is the next level of support and is included with every system sold that is not portable. Portable scanning systems are returned to the factory for warranty repair. Extended Warranty is provided based upon fees for both hardware and software items.

[Chris] Initial support is included in the solution price, typically for 12 months. Additional costs are incurred for extended periods of support.

[Giles] All of the above. Training is charged as is an annual fee after the first year.

[Susan] We provide complete training, documentation and one year complete maintenance and support; software revisions and hardware upgrades within the product line purchased are included at no additional cost. The customer can purchase ongoing support and maintenance services after the first year.

7. Where do you see breakthroughs coming in the specific infrastructure technologies (hardware and software) that are the basis of 3D-based machine vision systems used in reverse engineering in the near future – next three years?

[Chris] Dominant designs have already emerged for most technology innovations within reverse engineering (and inspection). Once this happens, product innovation slows to an incremental level and process innovation and standardisation increase, with process automation becoming an integral part.

The majority of software used within these applications is already ‘‘automatable’‘ with macros enabling repetitive processing of multiple files. It is interesting to note, however, that the majority of dominant hardware designs that have emerged for reverse engineering require a degree of manual operation (e.g. white-light area scanners and laser-stripe scanning on articulated arms). Attempts are made to interface these scanners to standard production robots to solve the automation challenge, however standard robots are heavy, inaccurate and non-portable and are, therefore, not really suited to the job.

Metris are developing what is currently referred to as a ‘‘Robot CMM’‘, a device that combines all the advantages of a CMM with those of articulated measuring arms in a robotized fashion.

[Giles] Wireless localizers, closer CAD integration of REsoftware.

[Susan] As noted above, for us it will be speed of data capture; expanding the size and material characteristics of objects suitable for scanning and portability (anytime/anywhere).

[Marty] Breakthroughs come slowly and are usually hardware technology based. These advancements usually are related to scanning speed. Advancements related to making the scanner cheaper are almost always at a cost of accuracy or ease of use. Thus, not many of the cheaper scanning technologies have been widely accepted because less accurate means harder to use when doing reverse engineering. More accurate means easier to use because the data processing is easier with more accurate data.

8. What specific performance improvements are anticipated driven by these forthcoming technological changes? How will they impact the use of these systems?

[Giles] Improved ease of use and usability.

[Susan] I can only answer relative to our technology and we are working on increasing the range of view and speed of capture. Both of these advancements will open the range of objects that can be scanned as well as the time it takes to complete a project. Obviously this affects profitability.

[Marty] It is safer to say that more specific, expected enhancements will be forthcoming from the data processing software side where easier to use and more push button CAD models from scan data will be available. This type of advancement is usually preceded by a number of product introductions heralding automated data processing with little operator intervention long before it actually happens. We are seeing this now with a number of products claiming to be automated and easy to use, and are actually not or are problem plagued.

[Chris] As explained, the absolute improvement of the scanners will be incremental; the key innovation is how these scanners can be applied to solve problems in a way that returns increasing levels of value to the customer. The impact will be the opportunity for major cost reduction through immense increases in process efficiency.

9. What are the main industries using for these 3D-based machine vision systems for reverse engineering and are there market changes within those industries that are driving the adoption of 3D-based machine vision systems?

[Susan] Industrial clients are predominant. Requests include scanning of objects and creating a CAD file that can be modified. Cultural organizations are increasing as they want to create replica items that are faithful to the original artifact.

[Marty] The primary markets where reverse engineering is used is for those markets where the shape of the product is changing yearly- primarily automotive. Market forces are making these changes needed faster and faster to keep up with the competition coming from more and more suppliers of automotive products at cheaper prices.

[Chris] Automotive, aerospace, and also to a certain extent consumer goods developers and manufacturers are currently the major investors in scanning technology for the purposes of reverse engineering and production part inspection. The main driving force behind this investment is the pressure that these companies face to be ever quicker and cheaper to market with their own innovations, in order to gain those highly coveted first-mover advantages.

[Giles] Military and Aerospace. Re-use of existing hardware for new systems.

10. What impact do these changes have on the technical requirements (specifications) for the 3D-based machine systems used in reverse engineering? And how will 3D-based machine vision systems have to change to address these more demanding requirements?

[Marty] The scanning industry is seeing more pressure for change to be easier to use and less expensive. Suppliers of the technology will have to more and more tightly integrate software and hardware to make the scanning system and output more automated and easier to use and train.

[Chris] Such systems will naturally need to respond to the needs of the customer, primarily helping them prototype and produce their own products more quickly, at a lower cost and with fewer development iterations. Automation will be critical in the future.

[Giles] Answer as # 7.

[Susan] From our perspective we have a very precise scientific instrument and can capture at the level required to meet customer demands.

11. As a supplier of 3D-based machine vision systems for reverse engineering what are some challenges you face in marketing 3D-based machine vision systems?

[Chris] There is still a degree of customer education taking place in developing markets, this lengthens the time and increases the cost of doing business.

[Giles] System prices including training etc need to be high due to the complexity of the solutions and the need for expensive software. This current high price prevents the rapid expansion of use.

[Susan] We focus our marketing to our website and key tradeshows. Our challenge is letting customers know that this type of technology is available and a viable option.

[Marty] The biggest marketing challenge for reverse engineering products is the ultimate end user, application and industry as the market is so widely varied.

12. What advice would you give to a company investigating the purchase of a 3D-based machine vision system for a reverse engineering application?

[Giles] Make sure you get your vendor to take a real job from start to finish (physical item to CAD) in a real life environment before you buy anything. See if the vendor actually knows how to do it; they might never have tried!  Be prepared to pay to have the whole job done properly by people who have the experience and know what they are doing. It will be cheaper than your investing in the wrong technology on the back of convincing but fundamentally unrealistic demos.

[Susan] Really spend the time to define exactly what outcome you want when you use the equipment. Make sure you hire staff that can not only operate the equipment but also understand the software applications you will be using.

[Marty] It is best to work with a scanning technology services company to see what systems they would use to do your specific type of applications and find the one that does it the best with the least amount of error and buy that one. If that company can provide the service for you quickly and accurately, and they can supply the technology to you as well, then you have all the ingredients you will need to be successful doing it yourself. Expert user support is the only way to quickly become an expert user.

[Chris] Try before you buy – run a full benchmark of all relevant products to ensure you are making the right decision. There is a lot of technology out there offering a wide range of capability, don’t assume that because two products appear similar on the surface that they are equal.