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Automotive to Wire, Vision Systems Monitor Dispensing Applications
by Winn Hardin, Contributing Editor - AIA Posted 05/06/2009
Vision systems have inspected discreet manufacturing of parts for years, but they also have found use in process control systems, such as the dispensing of material or product. Dispensing applications can be found in many manufacturing industries including automotive, medical, semiconductor, and wire insulation, just to name a few.
Today’s cutting edge vision systems are using a combination of 2D and 3D vision along with new processing techniques and algorithms to provide just the right amount of process control and inspection without adding undo cost or complexity to the customer, helping manufactures avoid bulges, neck downs, and other defects that negatively impact the look or function of the product.
Dispensing Grows in Automotive
Automobile manufacturing has progressed from manual assembly, to factory line assembly with manual welding, to robotic, automated welding and assembly. Each improvement in the manufacturing process has resulted in better quality and value for the customer. Today, this manufacturing evolution continues as automotive manufacturers use new adhesives and sealants to reduce the weight, time, and cost of building cars.
“We probably see 25% of all our vision guided robot applications involved in dispensing applications,” says Steve Mleczewski, Project Engineer at Pepperl+Fuchs-VMT (Ann Arbor, Michigan).
According to Christopher Brewster and Scott Burr of Dow Automotive, “Adhesives offer a more durable solution to the mating of two metal surfaces than do traditional riveting and metal mating…there is greater corrosion resistance and subsequently an increased life in bonded joints over that of traditional welding or riveting seen in metallic substrates such as aluminum and steel. The use of adhesives can now be involved in the bonding of non-traditional engineering materials as well. The use of adhesives to fasten non-traditional engineering materials for use as structural components allows for far superior performance in harsh environments over traditional metallic substrates. This makes the use of non-traditional engineering materials an attractive alternative to those more traditional materials such as metallic substrates for certain applications. The result is a more durable method of joining materials of construction in automotive applications through the use of adhesives.”
In the past, U.S. carmakers used vision systems to monitor the dispensing of underbody sealants, rust inhibitors, paint and similar “wide area” materials, according to Kevin Taylor, Vice President of the Business Unit Automotive at ISRA VISION SYSTEMS (Lansing, Michigan). For these sealant applications, a gap in the sealant didn’t represent a safety hazard, or a defect that would immediately lower the value of the car. Today, U.S. manufacturers are following Europe’s lead by increasing adhesive applications in cars for everything from mating car door panels, to gaskets for engine parts, to installing windshields. A leaky oil pan, defective engine gasket, or missing window sealant poses an immediate safety threat to the product and customer, requiring new vision solutions to monitor number of characteristics.
“Glue used in body shops adds structural integrity to the vehicle, so you have to be sure its where its supposed to be in and in the right amount,” explains ISRA’s Taylor. “Today, we’re typically talking about presence/absence, but also skips, width, and location. A big question becomes do you do it in process or post process. Manufacturing lines can’t always afford the extra cycle time to lay the bead, and then inspect it, so we focus a lot on in-process vision systems where 3 camera surround the dispensing tool with views slightly larger than 120 degrees to constantly view the presence, width, and location of a bead regardless of the position of the dispensing tool or camera.”
Wiring the Electric Grid
Extrusion machines are another growing area for vision-enabled dispensing machines. The tread and walls of tires, for instance, are extruded in long strips that have to be measured for accurate cross section profiles. Now, instead of merely checking the width of the extruded material, the vision system must determine the full 3D shape of the product to make sure the dispensing system is working as expected. In other applications, cables used to distribute electrical power across large-area electrical grids are insulated using rubber extrusion, an application that may benefit from recent U.S. stimulus plans to upgrade the national electrical grid.
“Solar has certainly been a hot market for vision systems, but they’ve got to get that electricity from where it’s generated to where it’s needed,” explains Jim Anderson, Machine Vision Product Manager at SICK (Minneapolis, Minnesota). “Wire comes out the machine at about 1000 feet per second, and we need to verify that all aspects of the jackets are correct. Any bulges in the jacket can indicate a sub-surface defect – perhaps a broken strand of copper. Narrow jackets can mean insufficient insulation for these high-voltage power cables, which would pose physical threat to whoever comes into contact with the cable.”
Environmental initiatives could lift other industries as well, such as thermally-resistant windows for homes that are made from injecting inert gas between two window panes that must then be sealed against gas loss. Significant stimulus money, as well as investment capital, also continues to go into medical research and technology. Scientists at Merck and Kalypsys recently developed a dispensing system to monitor microtiter samples in well plates used for drug testing using a pair of Cognex cameras and VisiApp and Cognex’ InSight Explorer software. Within the semiconductor market, Asymtek uses DALSA Genie cameras and Sapera software to guide the placement of fluid dispensing heads for under fill and IC encapsulation.
While many manufacturing industries are waiting for economic clarity for new capital investment projects, not all automation projects can wait. New industries, such as the solar industry, need to take advantage of government backing to build market share even when the economy is down. Even the automotive industry must adapt to a new emphasis on smaller, efficient cars, new electric vehicles, and the need for improved efficiency and productivity.
“These days, there’s a lot of call for reuse and refurbish of manufacturing systems,” explains ISRA’s Taylor. “We’re seeing major equipment, such as dispensing machines and robots, being retasked in automotive. The difficulty arises when you have a high-tech product, like machine vision. These systems are installed in harsh environments, and when a plant is decommissioned and equipment moved to another location, it is not always handled with the greatest care. The question becomes how do you get the equipment back into pristine condition, and what are the warranty needs after you do.”
One way to get around these cost concerns is to develop systems that are extremely cost effective and deliver exactly the amount of functionality the customer needs. SICK’s new AT20E and AT20D line array sensors are such systems, designed to use white LED light lines and CMOS sensors rather than lasers and expensive CCDs to monitor the width and position of almost anything, from glue beads to the edge of a manufactured web. “We put out an analog signal that gives position information. With the AT20E, it gives an output relative to the amount of the light line that is covered, and with the AT20D, you get a single analog value relative to the width of the dispensed product, such as the diameter of a glue bead. New chip designs have made it possible for us to do this quickly, using less expensive lighting, and simple sensors rather than dual cameras, and still deliver better than 100 micron repeatability.”
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