Quality Measurement: Select the Right Video System
But how can operators ensure video will work for them? Like any system, video measurement has to be applied correctly, says Mark Arenal, president of Kinemetric Engineering LLC (Laguna Hills, CA). Certain applications work well with video or vision, while others are better suited to a coordinate measuring machine-style application. In general, with features that are mainly microscopic, or with flat parts where operators cannot physically touch an edge, such as 2-D, it is best to use a vision system. Vision is strong in these areas, and yields faster throughput than tactile measuring systems. When looking at a 2-D part, such as a thin gasket, video systems can grab many features in the field of view. Speed is an advantage, particularly with microscopic features, because the cameras can quickly capture all of the detail.
Arenal says video measurement may be the answer if the application requires the ability to resolve very small features. “Video lends itself very nicely to parts that are soft or pliable because you can’t always touch them,” Arenal says.
An advantage of some video measurement systems is the ability to use multiple sensors, such as a touch probe or laser, on a single machine. A multisensor video machine can measure hundreds of data points, while a touch probe can reach areas not accessible with video. Also, a laser can scan surface contours. Video is fast and capable, and when other sensors are used, there are few dimensions that cannot be measured.
Often application-specific, optical systems can help filter out irregularities. Manufacturers may want video measurement because parts were rejected or because they were unable to measure certain parts with their current equipment.
Sometimes optical measurement is not enough, such as when measuring the taper or squareness of a hole, and a probe is needed, but multisensor systems can take care of that, Bibee says.
With optical measurement, a common fallacy is that people think color is good, Bibee says. The system reduces it to grayscale value. “Vision measurement should be made in black and white. Color adds nothing to accuracy,” Bibee says. “It’s a lot sexier but it doesn’t help you measure accurately.”
Selecting a SystemWhether vision is incorporated into shop-floor operations depends on the shop and the staff. Some companies have relied on vision for many years and have it well integrated into their shop, while others have standalone units. However it is organized, it is important to have a setup that operators can use effectively.
“It’s all about applying the product,” Arenal says. “Getting a machine in is one thing, but properly applying it is another.” Many times manufacturers do not know exactly what they need-they just want the correct system for their application, without overspending or buying unnecessary equipment.
Several things drive purchases: budget, staff capability and application. “Sometimes somebody will buy just on price, and that’s a mistake,” Arenal says. Price may obscure other key factors in selecting a system, and the cheaper system may not deliver the needed efficiency or throughput.
Sometimes manufacturers will purchase a manual-type machine instead of a motor-driven one that can be programmed and run automatically; the motor-driven machine may cost more at the start but save money over time.
On the other hand, a more sophisticated machine may seem too complicated, and a cheaper, basic machine would suffice. Therefore, Arenal says the role of sales engineers is important. They can determine what type of system will work best for the application. The sale is not the end of the deal, Arenal says, and the company should help the customers use the technology.
Greg Hollows, vision integration partners coordinator at Edmund Optics (Barrington, NJ), has specialized in video measurement for eight years and has some pointers on selecting a video measurement system. He suggests that customers make two columns: needs and wants.
Hollows compares this process to car shopping: “The customer may want a BMW SUV, but they only need something that runs reliably.” For example, the operator needs to measure a part to a certain tolerance or accuracy, but he may want to measure five parts at a time. There should not be a gray area between the columns, Hollows says, and customers should not let the wants list cloud their judgment.
Then after manufacturers decide to implement vision into their system, they should consider location and space restrictions. System location is important in metrology and inline quality inspection, so operators should examine where it will go and what it will do. Manufacturers can have the machines brought to their facilities, so they can see benefits of the technology right on their shop floor. This allows them to easily find out if the technology fits their application.
Finally, customers should consider the budget and determine how much money they have to spend. Operators should consider if machine vision is a customer requirement, or if it can reduce costs for their customers.
If manufacturers have done a thorough assessment of their needs, a vision integrator can provide a quick budget number, Hollows says, but before selecting a system provider, manufacturers should pay attention to who has the better support and knowledge. Customers should be sure to get various quotes on a package, and ask the reasons for the price. Then they should take all that information, stack it up, make a decision against it, he says.
Also listen to the questions from the sellers about the application. Hollows says manufacturers should look for experts; if companies are slightly more expensive, this may indicate a strong engineering staff.
Customers should ask why they need this and how to make it work. Operators should ask about long-term guarantees and the support level after the purchase. Getting a system up and running is one thing, but ensuring that the production line is running at 3 a.m. is another, Hollows says.
After a company has selected a video measurement system, they should get a detailed proposal. It is important to state expectations up-front to prevent the list from getting longer and more complicated, which can lead to a difficult application.
Selecting a System• Make two columns: needs and wants.
• Consider the location and space restrictions for the video measurement system.
• Determine how much money is available for the project.
• Listen to the questions from the sellers about the application. Customers should ask why they need this and how to make it work.
• Finally, get a detailed proposal.
Choose WiselyWhen choosing a system, manufacturers should be sure that the machine performance specifications suit their application, Flynn says. Most customers come to OGP with a specific application, part in hand, he says, and they want the fastest, most efficient way to measure the part accurately. Some customers want to do batch sampling, while others do 100% inspection. Some measure lots of the same part, while others measure a variety of different parts. This is why the flexibility of video measurement is a key selling point. Choosing a system designed for flexibility allows customers to dictate their needs and the system to meet those needs.
Video measurement technology is widely accepted, though many people have not stayed current with the latest advances, sensors and software. For those not up-to-date, they may not be aware of the greater measurement capabilities and larger work envelopes that accommodate large parts. “Back in the early 1980s, if you had a large, prismatic part, you couldn’t measure it with video,” Flynn says. “Now, because of multisensor technology, you can.”
While technology has dramatically improved, measurement basics have not. “Sound metrology is always important,” Arenal says. “You can’t make up for poor metrology and mechanical platforms.” Q
For more information on the companies mentioned in this article, visit their Web sites:
Edmund Optics Inc., www.edmundoptics.com
Kinemetric Engineering, www.kinemetric.com
Werth Inc., www.werthinc.com
Tech Tips• Video measurement provides noncontact dimensional measurements with speed, accuracy and flexibility.
• Video measurement can be used with consumer products, aerospace, automotive, medical, plastics, metals and rubber.
• Buy the correct system for the application, without overspending or buying unnecessary features.