issue: May 2009 APPLIANCE Magazine
Expanded Online: A Quick Look
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Video imaging puts high-speed production line/automation faultfinding into tiny camera heads.
From an engineering standpoint, there is “no worse word
associated with faultfinding than ‘intermittent’,” says Andrew Bridges,
director of sales and marketing, and Nils Lassiter, application
engineer, for Photron Inc. (San Diego, CA, U.S.; www.photron.com). “The
Fastcam MC2 has several trigger methods that make it a straight-forward
matter to have the camera record when the problem occurs, be it
minutes, hours, or even days after the system is armed.”
The cameras can also be used in destructive testing, in which a part is subjected to extreme stresses, and packaging drop tests.
light-sensitive, CMOS (Bayer system color), 10-µm pixel, single-sensor
camera is available in three models. All three feature 512 × 512-pixel
resolution; Model 500 features frame rates up to 500 frames per second
(fps), Model 2K offers frame rates up to 2000 fps, and Model 10K
operates at frame rates from 60 to 2000 fps at full resolution and up
to 10,000 fps at reduced resolution.
appliance manufacturing engineer’s biggest benefit may come in the
ability to record synchronized high-speed video, with a small camera
head. “When it comes to camera size, the smaller the better,” Bridges
and Lassiter say. They note that the tiny camera heads share many
components with those engineered for use in vehicle crash work with the
company’s Fastcam MH4 camera system. “The small size enables engineers
to mount the high-G cameras on top of, under, or even inside of just
about any component they wish to study under the worst real-life
conditions they will ever encounter.”
The camera can work with two camera heads, connected for opposing views, for true 3-D motion analysis.
with any high-speed video camera, the sensor is the critical element,”
Bridges and Lassiter tell APPLIANCE magazine. “The Fastcam MC2 uses a
proprietary CMOS sensor designed specifically to Photron’s
requirements. Once photons have been converted to electrons through the
pixel’s light-sensitive area, this voltage is transported from the
sensor through multiple channels, or taps, to adjacent buffers. This
analog voltage is digitized by on-chip analog-to-digital convertors
(ADC) prior to communication from the camera heads for storage in the
processor’s digital memory. The sensor can be globally ‘gated’ or
shuttered, independent of the frame rate, with exposures ranging from
1/60th of a second to six microseconds (6 µs). This ensures that every
pixel is exposed at the same time to provide crisp imagery that is free
of motion blur.”
The precision digital camera
system has clock accuracies (oscillator frequency stability at ± 50
ppm) in excess of several parts per million. “The CMOS sensor features
an array of 512 horizontal pixels by 512 vertical pixels, each of them
10 µm square,” Bridges and Lassiter explain. “This combination of
precision timing, and attention to the sensors’ physical build, means
we can achieve extreme accuracies both spatially and temporally. Modern
motion-analysis software can track a point’s motion to roughly
one-tenth of a pixel’s physical size, enabling engineers to measure
exactly where a point is at any precise point in time, at what speed it
is moving, how fast it is accelerating or decelerating, the frequency
it is vibrating, and whether it came into contact with any other parts
throughout its motion.”
What does this mean for the end-user? “Accuracy, and the ability to see exactly what happened.”
Fastcam MC2 camera heads are just 35 mm on a side and weigh only 3.2 oz, making them easy to mount for close, high-speed inspection.
Appliance Testing Applications
Bridges and Lassiter pose a scenario in which an engineer needs to identify the cause of intermittent failures in a washing machine motor mounts. Two cameras could be mounted on either side of the bracket, along with dc-powered, high-intensity LEDs for illumination. If required, accelerometers could be used to precisely measure the vibration levels experienced. With the camera fitted with maximum memory and recording at 1000 fps, the washing machine would then repeatedly cycle through typical usage patterns until a failure occurs. When the failure occurs, a trigger signal, or alarm, is sent to the camera’s processor unit, resulting in the previous eight seconds of video and accompanying vibration data, to be saved to the Gig-E networked laptop in the engineer’s office.
Other potential testing applications include the following:
Observing what happens when a dishwasher’s rotating jet clips a plate that is too tall for the rack.
Observing how a waste disposal unit deals with metal cutlery inadvertently dropped inside.
Watching during a mandated three-foot drop test when thinner-ply packaging is introduced as a cost-saving measure, to see whether the enclosed appliance would survive.
Appliance Production Applications
“Photron high-speed systems have also seen plenty of use in production faultfinding situations, e.g., as a line that stamps out parts from sheet steel, [in which] there is an unidentified roller, upstream from the stamp that occasionally causes a tear in the edge sheet metal roll,” Bridges and Lassiter tell APPLIANCE. “When this tear reaches the stamping machine it causes a web break and the entire line must be shut down, rethreaded, and restarted. The MC2 event-capture system could be pointed at the suspicious rolls and operated in the endless record mode where it would continue to record high-speed video until it received a stop trigger from a tension sensor, indicating a web break.
The last few seconds of video from the camera system would then be viewed from any computer in the plant and the production engineer could evaluate it frame by frame and identify the offending roller.”
In the same way the video system could also help the production engineer evaluate welding or high-speed pick-and-place operations using the same mode of operation.
The unit is made to be quite easy to add on the manufacturing line. The power supply that comes with the camera requires 110 V ac power, or the camera can be connected directly to an available 18 to 36-V dc power supply. Installation also requires a place to bolt the camera and, if required, an illumination. This easy installation means the camera can be moved from one part of the line to another as needed. The camera can be mounted on any axis as the software allows the user to easily rotate the image.
A key issue for an installation is field of view, which dictates what lens may be required.
A good zoom lens may solve some installation concerns.
Another key factor is lighting, as high-speed cameras require additional lighting due to their short exposure times. Bridges notes that there are many third-party lighting solutions on the market, from simple dc-powered LEDs to complex and more-expensive flicker-free illuminators. Flicker can be an issue, as many domestic lights turn on and off with the frequency of the ac supply. This appears as fluctuating light intensities when recordings are made at speeds not synchronized with the 50-Hz supply.
The camera maker also offers its own optional LED illumination source, specifically made for use with the camera system.
“This illumination can be operated continuously or synchronized with the high-speed video capture,” Bridges and Lassiter explain.
A Quick Look—read more online:
- Appliance Testing Applications
- Appliance Production Applications
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The Rise of Rapid Manufacturing