The Many Faces of Machine Vision Maintenance
| By: Winn Hardin, Contributing Editor
Across industry, preventive maintenance is seen as a way to avoid unexpected downtime. Electrical motors are regularly tested for vibration, while thermal imagers track hot spots in housings and electrical loads. Human machine interfaces (HMI) are mined to see how electrical loads compare to production schedules and speeds to develop qualitative data indicative of overall equipment health. Trends in this data are then used to schedule preventative maintenance downtime – a brief break in production that hedges against longer, unplanned outages – and to make sure that necessary spare parts are on hand.
When it comes to high-technology industrial solutions, such as machine vision quality assurance, material handling, and assembly systems, customers need to adopt similar approaches. And like the best conditioned-based maintenance (CBM) processes, risk analysis and other factors should guide engineers when they consider their machine vision maintenance needs.
Maintenance As a Training Tool
“There are really two types of maintenance: preventative and repairs,” says Brian Durand, President of machine vision integrator i4 Solutions (St. Paul, Minnesota). “It’s our experience that short of a hardware failure, vision systems work for a long time. Usually, the only issues that come up are related to material handling systems, which affect how the part is presented to the vision system, or changes to the product itself, which would then require some reprogramming.”
Most machine vision equipment is all solid state, which means few, if any, moving parts and few points of failure. “We see cameras in use for eight to10 years after they were manufactured,” adds Scott Smith, Director, Application Engineering at Allied Vision Technologies Inc. (Newburyport, Massachusetts). “We put new cameras through rigorous temperature and burn-in cycles. Like all electronics, if something is going to fail, it usually fails at the beginning. So when a camera survives the manufacturing stress tests, it’s usually good for a number of years as long as it’s used under temperature and environmental conditions set by the manufacturer. User error is also a rare source of camera failure, since most users and integrators know these are sensitive electronics, and so they don’t place them in positions where they would be damaged by impact or inappropriate conditions.”
Repurposing and Reprogramming
The longevity of machine vision technology actually contributes to the need for maintenance programs – just not as one would imagine due to mechanical or electrical failure. The systems tend to last much longer than product designs they inspect, which means changes in product, packaging, and the like need to be programmed into the machine vision system.
“Reprogramming a system is one of the primary reasons we suggest a maintenance contract to our customers,” explains Nicholas Tebeau, Manager of Vision Solutions at Leoni (Lake Orion, Michigan). “We spend a lot of time during the design of the system and through the development of comprehensive documentation and reference documents as well as on-site training to avoid the normal causes of preventative maintenance such as calibration, software upgrades, SPC [statistical process control] data review, and so on. We really want to design the system so the customer can maintain it themselves, which is what most of our customers want regardless of whether they are a large outfit with a big engineering department or a smaller operation. We design our software modules to help guide the user through replacing a broken camera and finding the right field of view, for example.
“Where we do maintenance contracts,” Tebeau continues, “is when the customer has large numbers of parts going through the system. In these cases, we often use remote access to assist the system owner with programming the system to inspect the new part. Usually, the customer can do it without our help, but when they get stuck, that’s when a maintenance contract is good to have.”
i4 Solutions’ Durand prefers to use regular site visits for both preventative maintenance and reprogramming to help reinforce the relationship as well as the technical training for the system owner. “The frequency of the visits depends heavily on the number of systems the customer has on site,” he says. “If they have dozens of systems, then a monthly site visit to review SPC makes sense because we can identify small problems before they become big problems. A lot of our customers have a problem with allowing anyone remote access to their production floor because of security reasons. Also, troubleshooting a material handling problem isn’t really possible without being on site. Finally, the most valuable part of the service contract is knowledge that the customer’s personnel gain by looking over our shoulder as we reprogram systems and perform other maintenance. We provide documentation and some training, but if the customer doesn’t have to mess with the system for months, chances are they won’t remember most of the training.”
Site visits also force the customer to plan and prepare for the visit from i4 Solutions’ technicians. “It makes the customer take a minute and think about any conveyor changes that may be affecting the system, even slightly, or other changes to the product or packaging,” concludes Durand. “Sometimes this is the only time the customer really focuses on the machine vision system because they keep doing what they’re programmed to do day after day.”
While integrators are happy to respond to any and all service requests, customers often ask how to get the most out of their spare parts and maintenance contracts. A key factor in this calculation is the cost to production of having the machine vision system go down.
“If a customer has one or two machine vision systems, keeping another one or two cameras can double their component costs,” says AVT’s Smith. “But if you have a hundred cameras on your production floor, it’s reasonable and wise to self-insure through on-site spares. It largely comes back to the economic risks of downtime.”
The same criterion applies to integrator engineering support when it comes to the decision to sign a maintenance contract or not. “For simplicity’s sake, you have to ask yourself as a customer: How long does my company take to issue a PO when I need the service right now?” concludes Leoni’s Tebeau. “If you need service in five hours, and your company takes two days to issue a PO, then the system engineer or internal champion needs to get that PO in advance and put it into a maintenance contract so they’re not left waiting for repair services. Response time can be everything to a customer’s operation. If you expect that you’ll only need a small amount of support time, then it makes sense to go with a flat-rate contract. But if you think it may be more than that, then time and materials may be the best way to go.”