Smart camera inspects metal sprinkler parts
Metal inserts, critical components of fire-suppression sprinklers, are manufactured in a variety of shapes, surface finishes, and diameters.
Metal inserts, critical components of fire-suppression sprinklers, are manufactured in a variety of shapes, surface finishes, and diameters. Before assembly into sprinklers, these inserts must be inspected for correct part type, diameter, shoulder radius size and shape, presence of metal shavings, and drill slip-surface damage. "With diameters ranging from 0.088 to 0.145 in., the metal components must be measured to 0.001-in. accuracy," says Richard Ross, president of Ross Microsystems Inc. (RMI; Nanuet, NY; www.rossmicro.com), an integrator and manufacturer of application-specific, machine-vision-based, automated inspection systems.
"Although the assembly machine used can intermix various part types, the inspection system had to accommodate all part types with a single camera/light configuration and make any necessary algorithm modifications to accommodate different part types automatically," he says. "In the past," adds Ross, "our customer had worked with cameras and lighting devices from several vendors. Unfortunately, these products did not prove suitable for this particular application."
Detailed analyses of the edge contours and surface finishes of both good and bad metal parts led to a system-inspection design that describes the various angles the light needs to strike the critical parts surfaces to create a high contrast image. The system design uses a combination of light-emitting-diode lighting devices, Fresnel lenses, and holographic diffusers.
To capture images, RMI chose a VC-38 SmartCam camera from Vision Components (Ettlingen, Germany; www.vision-components.de), which provided an open environment for the development of specific algorithms. Though this approach resulted in longer development times and required skilled developers, the resulting inspection system proved accurate and reliable. In addition, the low price of the VC-38 mitigated the higher development costs via the lower cost and ease of adaptation of follow-on systems. Using this camera's VGA output, a serial port, and a programmable logic controller (PLC) I/O port, RMI created a standalone system that essentially consisted of the camera and a standard VGA monitor. For adjusting inspection parameters, a standard mouse was connected to the camera's serial port to interact with an RMI-developed Windows-based graphical user interface.
Interestingly, other developers using Vision Component's camera line have cited similar development times and resulting low-cost benefits. One company, Billows Protocol (Wolverton, Milton Keynes, England; www.billowsprotocol.co.uk), experienced the same software issues in the development of a low-cost computer-to-plate (CTP) punch (see "CTP punch speeds prepress production," p. 28).
Similarly, a third-party company, Vision Systems Engineering (Kenmore, WA; www.vseltd.com), has developed Intelicount, a machine-vision software package for Vision Components' VC M30, M40, and VC38 cameras. Developers can use a point-and-click setup feature to select image parameters such as percent coverage, square millimeters, and pixel coverage.
"Inspection tools including circles, annulus, rectangles, line tools, and a combination of these tools can be used at one time," says David Baker, president of Vision Systems Engineering. Features include the setup of a built-in ring light, trigger input, and pass/fail outputs. Developers who want to evaluate the software can download an evaluation copy from the company's Web site.