By Mike Bacidore, Managing Editor
Recently, we asked our readers to answer some questions about motion control and presented those results as part of a Market Intelligence Report video.
As many of you may remember, our Market Intelligence Report videos used to feature the field operatives from our own Control Intelligence Agency, who then reached out to our Virtual Brigade of agents—qualified controls engineers like you who volunteered to contribute to and participate in our intelligence-gathering missions.
I had an opportunity to run some of the findings from our recent survey on motion control by a Virtual Brigade member and, as always, was intrigued by his comments.
Bob Mack is a controls engineer, electrical engineering services, at Steel Warehouse in South Bend, Ind. More importantly, he’s one of our original Control Intelligence Agency Virtual Brigade members.
Mike: In a recent reader survey we conducted, only 20% of respondents said they purchase motors and drives that are already integrated. Do you buy separate or integrated motors and drives?
Bob: We only purchase separate components.
Bob: Price, accurate application, more flexibility. Integrated systems are very targeted to a specific application that keeps the cost down but that is a very small market in my opinion.
Mike: To control their many motors and servos, respondents in that same survey said they use a variety of methods. More than 40% use a PLC along with one or more motion controllers, while almost 23% use a PC or PLC with variable frequency drives, and 19% use standalone motion controllers. Meanwhile, close to 10% use PCs plus motion controller cards. Are you seeing a trend toward using PC-based control for more applications?
Bob: We use PLC with the occasional motion control card in the PLC rack. We are not using PC-based applications for motor control and never will. Where current PC technology is today, reliability is too complex and requires too much management. It isn’t cost-effective, and I doubt that it ever will be. PC stands for “personal computer,” and that is what it is, nothing more, nothing less. Using a PC can only be equated to ”experimental.” It is just a PC. We also use embedded drives technology with a DSP. Not all PCs are equal, and calling a PC part of an integrated drive control system is a contradiction. Does that PC run your tax program while controlling that drive?
Mike: Electronic components and software designs seem to have taken a larger role than mechanical components. Is it possible now for you to improve machine performance simply by adding software features?
Bob: No. It requires new sensor feedback technology.
Mike: How much of an impact do mechanical components still have in your machines and processes?
Bob: If the mechanical components or systems are not reliable and are not engineered to fit the exact end use, then they have a big impact. Otherwise, they have no impact.
Mike: Update rates continue to get faster, in step with increasing machine operating parameters. A quarter of the respondents in the survey said they need cycle times in the microsecond range, and 61% need rates faster than 100 msec. But how much more speed or capacity is an end user actually using without being choked by bottlenecks in other areas of production?
Bob: Very insightful question. Too bad management people do not understand it. They look at it from an upfront cost perspective. The problem then becomes, when you do a upgrade, you double your price because you are not “fast enough” and have to upgrade everything instead of just what is needed. All processes have bottlenecks, and sometimes management just overlooks them because they are making too much money. Then the tide changes. Faster processors affect everything from finished product volume, required manufacturing space, what to automate and reliability to creating bottlenecks that never existed before. “Slow” is diminished capacity in all things, and that costs lots of money when you relate it to a machine or process.
Mike: To move the data signals at these speeds, the survey’s respondents reported that more than two-thirds use a digital bus for motion control communications. Of those that do use digital buses, the options are many, but EtherNet/IP is the dominant choice and about a quarter use SERCOS or SERCOS III. How important is it for drive and motor suppliers’ interfaces to be compatible with open standards in fieldbus technology? What are you using and why?
Bob: We use all technologies on our integrated systems—Ethernet, ControlNet, SERCOS, VME. Would it not be more cost-effective to have just one that does it all? Why are human beings so efficient? One Brain and one hard communication system, extremely well-integrated with all its components, fit the environment with almost limitless possibilities. Time to development: only nine months and evolves all by itself. Not keeping standards open to everyone is having a dictatorship, and only the owner reaps the rewards.