December 03, 2007
Laser Scanning Makes Manufacturing Inroads
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| by Jeff Rowe - Contributing Editor
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Until recently, in-process inspection hasn’t been very practical in mold production, according to Bill Berry, President and CEO Die-Tech and Engineering Inc. in Wyoming, Michigan. “You’re not mass producing molds, so you can’t use the measurements as feedback for the next product,” he explains. Like any toolmaker, the best he and his staff could do was to measure the product after the fact and rework any deviations that might fall outside the specified tolerances. Quality control remained a post-production cost, rather than a value enhancement.
Berry didn’t give up, though. He remained committed to finding a way to implement in-process inspection. It was a principle of good manufacturing – one of principles that he learned while working for one of the Big Three automakers and that had made his 40-employee company successful at producing tools for plastic injection molding and aluminum and zinc die-casting. He has introduced as many of these techniques as he could, as well as the advanced technology to support them, since establishing the business back in 1984. “This industry has become more of a science than a craft,” Berry observes. “Even though we were a small company, we started employing the
most advanced production and computer technologies we could afford.”
Consequently, a full complement of CAD/CAM systems, CNC machine tools, and automated electrical discharge machines (EDMs) move both digital data and physical product through the 25,000 square feet facility, from conception to delivery. His steadfastness on in-process measurement was rewarded when Berry came across the LC50 laser scanner and the supporting Focus suite of software from Metris North America Inc. in Rochester Hills, Michigan, USA. The technology gave his quality-control experts the ability to scan the contours, sharp corners, and deep narrow pockets on the molds made by his company in a fraction of the time that it would take a coordinate measuring machine (CMM) fitted with
a conventional scanning touch-probe. Finally, he had found the cost-effective method that he needed to measure these features and elicit the appropriate feedback for correcting the process and avoiding costly and time-consuming rework.
CMMs for Inspecting Cavities
Despite his willingness to invest in high technology, Berry had never considered CMMs for process control and resisted buying one much longer than others in his position did. “It would have been purely an expense with no real pay off – just a quality control cost with no benefit other than record keeping or score keeping,” he says. “Without laser scanning, there was really no cost effective way to apply CMMs.” Because he could not justify the capital outlay, he sent his molds to measurement service whenever a customer required him to validate molds on a CMM. The problem with conventional CMM technology is that the touch probes and supporting software were
simply too slow and cumbersome for getting regular process feedback from molds. Even if the probes could reach into narrow recesses and sharp corners with radii as small as 1mm, gathering the large amount of datum points with conventional touch probes, even scanning ones, would require a significant programming effort. Then, interpreting the mountain of data collected by the CMM would be time-consuming and tedious.
After all that, scans compiled by probe would contain blind spots between touches, allowing anomalies there to go unnoticed. Moreover, measuring the molds after machining contributed nothing to in-process measurement. It was still inspect after the fact. Measuring the 10 to 50 electrodes typically used by the EDMs to finish the cavities was a slightly different story with the same ending. It would solve the problem of access because they are reverse images of the holes, cavities, ribs, and contours and, so, have no walls or other obstructions around them. It also would provide a kind of in-process feedback mechanism because any corrections to the electrodes occur before actually making
the finishing cuts on the cavity. The problem of collecting and processing millions of points and thousands of surfaces quickly and economically would remain unsolved, however.
The LC 50 laser scanning head and Focus software changed the situation radically, prompting Berry to invest in a CMM equipped with the Metris technology. With help from Focus Scan, the head can collect 19200 datum points per second along any 3D surface in its line of sight. Focus Inspection then compares the cloud of points to the CAD model and generates a color-coded map of deviations from nominal. In a few days, quality control can provide production a visual analysis of an entire surface. “Laser scanning changes the economics by gathering vastly more data in an extremely compressed time frame,” says Berry. The turnaround is fast enough for the shop to use this feedback to
produce perfect electrodes between the roughing and finishing processes while the roughed block is offsite at a heat-treatment facility for hardening. Meanwhile, the CAD department designs the electrodes, the machining department cuts them, and the quality control department scans them. “By inserting laser scanning into the process, we can use the electrode measurements and setup information to perform a kind of simulation of the process,” says Berry.
This simulation using Focus Inspection validates both the electrodes and the setup instructions for the EDMs, the two primary sources of variation in electro-erosion. The CAD technicians use the setup data to put the electrode into the specified position and orientation and then compare the electrode to the corresponding parts of the CAD model of the mold. Die-Tech’s CMM uses a Metris LC50 laser scanning head to measure an electrode that an EDM in the shop will use to finish an injection mold for producing housing pivots for windshield wipers. The color-coded map of the comparison leads machinists to any minute interference and clearance caused by an imprecisely machined or
positioned electrode for correction before any cutting takes place on the mold cavity. By the time the roughed mold block returns from heat-treating, the electrodes are within tolerance and the setup instructions are ready. Feedback from the simulation has neutralized the primary sources of variation, and the electroerosion process itself is extremely accurate and repeatable. “So we have reduced the dimensional errors in the production of our molds to the tolerances of our equipment, which normally exceed the requirements of customers,” reports Berry.
Consequently, EDM operators can have the confidence to run all of their jobs untended and as fast as allowable. “In the past, there were certain complex EDM operations that they hesitated from doing without being there because they were critical and had to be just right,” explains Berry. Now, the operators have the confidence not only to run their machines untended, either overnight or while they tend other machines during the day, but also at full speed. Berry estimates that the confidence created by Metris’ software squeezes about 10% from the lead-time, helping Die-Tech to keep its three to four week lead-times well below the industry’s more typical five to
six weeks. As far as he is concerned, any scanning on the tool to prove that it adheres to customers’ specifications is free. “They might ask for 16 or so points for verification,” he says. “We can give them a million, proving overwhelmingly that the tool is incredibly accurate.” And now, that capability figures prominently in the business plan. “We don’t send anything out the door that we expect to come back for anything other than customer-paid engineering changes,” says Berry. “We haven’t budgeted for a mold’s coming back to make things right.” He also has confidence – the confidence to eliminate that line
from the budget. He knows that laser scanning has transformed measuring on the CMM from a cost into a value-added process that shortens lead-time, trims cost and guarantees quality. Chris Berry, the owner’s eldest son, uses Focus Inspection to check an electrode for finishing an injection mold for producing housing pivots for windshield wipers. He is comparing a cloud of measurement points collected by the laser scanner to the original CAD file.
Commentary By Jeffrey Rowe, Editor
Even though you have to dig a bit for it, this is actually an interesting application story about applying reverse engineering principles to inspection using the Metris LC50 laser probe and associated software.
The LC50 3D laser probe is a high-speed CMM scanner capable of scanning up to 19,200 points per second. It is mounted on a Renishaw PH10M (a motorized probe head) and transforms the 3-axis mechanical CMM into a 5-axis optical digitizing device. It is capable of quickly scanning complex forms such as turbine blades, and in this case, injection molds, for inspection and reverse engineering purposes. Non-contact CMM scanning technology such as this allows for accurately scanning flexible or fragile parts without risk of damage – more about that a bit later.
Focus Scan is the driver, data acquisition, and point cloud pre-processing software for Metris laser scanning. The software controls the Metris laser scanner on the CMM and is integrated with Focus Inspection and Focus Inspection Automation for automated CMM inspection stations. Focus Scan 5.0 now also supports indexing rotary tables increasing the application range for CMM based laser scanning to even more complex part geometries. There is also a Focus Scan Offline that module enables the user to create, modify, and prove out part programs using only 3D CAD models instead of using the actual CMM hardware and waiting for real parts.
Although I have never actually used the Metris laser scanner and its software, I do have experience with other similar devices and software. In many peoples’ minds, reverse engineering is the illegal act of copying, in effect stealing, an original design, in this case a physical object. That old perception and definition is something I wanted to help dispel with a more positive image based on my experiences.
Reverse engineering (whether used for inspecting or ultimately physically reconstructing an object) is a process for digitally reconstructing a physical part. This is significant because recent estimates are that up to 80% of new designs come from existing ones, usually from existing parts and assemblies. Reverse engineering is part of a larger scheme becoming known in some circles as digital shape sampling and processing (DSSP).
DSSP data for manufacturing purposes can be viewed as having two somewhat similar yet definitely distinct ways of describing and representing 3D forms. Reverse engineering does it by handling geometry as sets of discrete points, whereas traditional CAD does it with shapes defined by continuous curves and surfaces. Combined, reverse engineering and CAD are complementary to each other and are what transform physical objects to digital objects, and ultimately back to physical objects in a workflow. In other words, reverse engineering extracts geometric information from physical objects and CAD reconstructs it into a digital form that can be used for creating physical objects based on the
Reverse engineering is a process of examination only, the part under consideration is not modified during the scanning/digitizing stage (which would make it re-engineering), although it can be modified in downstream applications, such as CAD.
The past fifteen years have seen explosive development of many different types of 3D digitizing devices, as well as the reverse engineering software that allows the data produced by the digitizing devices to be manipulated into a useful form.
There are two parts to data-related portion of the reverse engineering process – scanning and data manipulation. Scanning, also called digitizing, is the process of gathering geometric point data from an object. Several different contact and non-contact technologies are used to collect three dimensional data. Each technology has its advantages and disadvantages, and their applications and specifications overlap. What eventually comes out of each of these data collection devices is a description of the physical object in 3D space called a point cloud.
There is usually too much data in the point cloud collected from a scanner/digitizer, and some of it may be unwanted “noise.” Without further processing, the data cannot be used by downstream applications such as CAD/CAM software or in rapid prototyping. Reverse engineering software is used to edit point cloud data, establish the connections of the cloud points, and translate it into useful formats such as surface and solid models or STL files. It also allows several different scans of an object to be combined so that the data describing the object can be defined completely from all sides.
Usually, collecting an objects data is the shortest and easiest part of any RE procedure. Normally, most scanning only requires a few seconds or a few minutes. On the other extreme, manipulating that scanned data can be quite time-consuming and labor-intensive, but like RE in general, this scanned data manipulation techniques are rapidly improving and becoming much more time and cost effective.
Although there are several digitizing technologies available today each has its own distinct advantages and disadvantages.
Feature-based scanning is a method where features of an object are scanned by physical contact. A mechanical touch probe, also known as a contacting digitizer, is a physical part contact device and method well-suited for prismatic parts, such as an automotive transmission housing. The touch probe is actually a pretty basic device that is connected to a computer and simply lets you know when and where in space contact is made with an object.
Touch probes, are usually very accurate over a wide measurement volume. There are contact digitizers that are positioned manually to yield a single measurement at a time, or may be scanned across a surface to produce a series of measurements. There are also touch probe instruments available which can automatically scan an object using a variety of mechanical drives. Contact instruments usually employ an articulated arm that allows for multiple degrees of freedom of movement.
In feature-based scanning, basically, you can randomly scan sections of a part that are automatically turned into lines and splines for creating a digital surfaces and solids.
A couple of disadvantages of contacting devices include the fact that they can distort soft objects. They also can be too slow for digitizing organically-shaped parts, because they usually require too much time and labor for scanning complex curved surfaces, although there are work-arounds. On the other hand, they are not affected by the color, transparency, or reflectivity of a surface the way laser systems can be. And while they can be relatively slow, contacting devices are often the fastest way to digitize simple surfaces where just a relatively few data points are required.
Point Cloud Scanning
Point cloud scanning is performed using a laser scanner that is a physical part non-contact device and method well-suited for organic, freeform, artistic parts, such as statues. It is also well-suited for scanning soft objects with surfaces that could be distorted by a touch probe. Point cloud scanning is not as well-suited, however, for prismatic or sharply faceted parts as is feature-based scanning because too many points are captured that need to be dealt with.
Laser scanners most often use relatively simple geometric triangulation to determine the surface coordinates of objects. A laser line is scanned on a target object and integrated sensors, such as CCD arrays, image the line, usually simultaneously from each side of the line. Where the laser line's image falls on each sensor is determined as trigonometry is applied to calculate the position of the target surface at each point on the laser line.
The relative simplicity of the laser technique and its ability to quickly digitize a large object accurately with good resolution have made laser scanners increasingly popular for reverse engineering purposes. Laser scanner products are available as complete systems, and as self-contained measuring heads for mounting to standard touch-probe arms or in other ways, including customized mechanical fixtures.
A significant challenge for point cloud scanning is that there is often more clean up required of the scanned data because of the number of points captured, but this is being addressed on different levels by several vendors.
Reverse engineering is a fascinating field that is really starting to take off from several different perspectives – hardware and software – largely because there are an increasing number of legitimate applications for it. Because more companies in more industries are starting to realize its benefits, I expect reverse engineering to continue to grow at an impressive rate for both potential users and hardware and software vendors servicing those users.
The Week’s Top 5
At MCADCafé we track many things, including the stories that have attracted the most interest from our subscribers. Below are the five news items that were the most viewed during last week.
SpaceClaim Corp. announced the availability of SpaceClaim Professional 2007+ and the Explore SpaceClaim 30-Day Trial program. SpaceClaim Professional 2007+ is a complementary 3D design solution that enables users to originate concepts, make better use of existing models and freely modify mechanical designs. The release includes the ability to create sheet metal parts, as well as open and modify sheet metal parts originating in other CAD systems. Additionally designers can work with lightweight assemblies, drive 3D modifications via any 2D section, add and modify driving dimensions and integrate with CAD-neutral partner applications. SpaceClaim is also introducing a trial program. The
Explore SpaceClaim Trial program enables participants to download and use SpaceClaim Professional 2007+ for 30-days.
The Explore SpaceClaim 30-Day Trial program includes:
SpaceClaim Professional 2007+ software
3D Data Exchange Package, which includes PARASOLID, ACIS, Rhino data exchange and import of CATIA v4, Pro/ENGINEER, NX, Inventor and SolidWorks files
Access to on-line, live training classes
Access to Technical Support
The Sheet Metal Module, ECAD Integration Module, standard parts library, CATIA V5 and JT data exchange packages are not included with the trial program.
Geometric Ltd., a leader in Product Lifecycle Management (PLM) services and technologies, today announced the release of eDrawings Professional for CATIA V5. Major enhancements in this release of eDrawings Professional for CATIA V5 include support for:
3D Functional Tolerancing & Annotations (FTA)
With eDrawings Publishers users can:
Generate ultra compact eDrawings with up to 95% compression, compared to the original CAD file
Share and receive feedback on product designs with review-enabled eDrawings and collaborate with an unlimited number of recipients
Manage, track and merge comments from different team members
Share design data with password protected and self-extracting eDrawings
Measure the geometry in part, assembly and drawing files when dimensions are absent
Disable measurement feature to protect sensitive design data
Examine internal details of parts and assemblies with dynamic cross sectioning
Hide/Show/Move components to better understand assembly structure
eDrawings Publishers are available on CATIA V5, NX, Pro/ENGINEER, Autodesk Inventor, Solid Edge, and Google SketchUp.
OPEN MIND Technologies AG has completed the development of hyperMILL V9.7. With this product release OPEN MIND is now offering the users SolidWorks integration. hyperMILL’s integrations with Pro/ENGINEER Wildfire, Autodesk Inventor, thinkdesign, and hyperCAD 2007.1 have also been updated in this release.
Alongside added functionality, the newest version of the CAM software program hyperMILL brings users of hyperMILL’s CAD integrations up to date. Users of these versions can access all of the software’s functional benefits in an integrated manner, including the new millTURN module. hyperMILL offers users an array of strategies for 2D, 3D, HSC and 5-axis machining, as well as milling and turning, in one user interface. Programming efforts are reduced with sophisticated feature technology, including feature recognition, automatic mapping of hole and pocket features, feature list, feature browser, macro technology and macro database. The postprocessors, tailored to specific
machines, controllers and manufacturing processes, ensure that the CAM programs are processed on the machine. With new workspace monitoring the user can check in advance whether the machining job can be performed within the given workspace or whether limit switches will be crossed. The best fit’ function automatically optimizes machining with a view to the available work space and also allows optimal space usage when small or limited machines are used.
Datakit has acquired the engineering data interoperability business of Ingetech and will be distributing the CADIQ, CADfix, and DEXcenter products from ITI TranscenData.
CADIQ - the 3D CAD model comparison and product data quality product
CADfix - the multi-CAD exchange, repair and defeaturing solution for downstream CAx
DEXcenter - the data exchange automation and supplier CAD data collaboration portal
The services and solutions offered by Datakit are designed for manufacturers, their first-tier suppliers, and all players in the supply chain. Users are particularly concerned with the ability to effectively receive part files and complete assemblies, supply them to their partners, check the quality of incoming models, reliably and automatically demonstrate compliance with design specifications, and implementing long-term solutions for data archiving.
TekSoft, Inc. has been renamed Geometric Technologies, Inc. This follows the decision to adopt the “Geometric” brand across all operating companies by its holding company - Geometric Limited (formerly Geometric Software Solutions Company Limited). Geometric specializes in several aspects of engineering solutions, services, and technologies. Its portfolio of global engineering services and digital technology solutions for PLM, enable companies to formulate, implement, and execute global engineering and manufacturing strategies aimed at achieving greater efficiencies. The end-user products from Geometric include CAMWorks, eDrawings Publisher, DFMPro, and GeomCaliper. eDrawings
Publisher is a lightweight collaboration tool for 3D models that enables publishing of 3D model from all major CAD systems. DFMPro is an automated intuitive tool for designers to accurately predict the manufacturability of models. GeomCaliper is an integrated, automated thickness checker for 3D CAD models. The key technologies from Geometric are NestLib, Feature Recognition (FR), GeomDiff, and 3DSearchIT. Geometric licenses these technologies to OEM partners and also designs and implements customized process solutions using these technologies for industrial customers.
Jeffrey Rowe is the editor of
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-- Jeff Rowe, MCADCafe.com Contributing Editor.