Staying Error-Proof with Ballbar Testing
Smart, wireless ballbars keep a wide range of businesses competitive.
Ballbar technology that auto-diagnoses machine tool performance has been a cornerstone of precision machining operations for more than two decades. In 2009, Renishaw introduced the QC20-W wireless ballbar system; and today, companies that one might not think of as using ballbars are now utilizing the technology in new and exciting ways.
Furthermore, companion software that has been “smart” from the beginning holds inherent potential for the future of Big Data and the automation age, says Michael Wilm, business manager of calibration products at Renishaw.
Wired vs. Wireless
With the old, wired ballbars, Wilm says the wiring itself was the main problem.
“The ballbar could go into shop environment with a heavy-duty cable on it and live for five to 10 years without an issue—and that was the wired version,” Wilm says. “It’s a really durable piece of equipment, but it’d wear out the wires from being wound up so many times.”
Renishaw’s QC20-W system also resulted in several new capabilities, Wilm says.
“One is that it gave us the ability to take more data per second; we took about five times the data per second than the wired version when we went to the wireless,” he continues. “Basically, it allowed us to capture what we couldn’t capture before and at a better rate.”
Transitioning to wireless also enabled Renishaw to move into the five-axis world, with two rotary axes and three linear axes all moving at the same time. Plus, the QC20-W allowed for easier checking of the machine’s kinematic capability; in other words, where the center of rotation is relative to the linear axis on a CNC machine tool. This would have been very difficult with the wired system, Wilm says, as the cord would have become tangled in some of the axes by the way they move and contort with each other.
“With the wireless version, you can get quite a bit of information about the velocities of the different axes and their relationships to each other, which was just not possible with the older version,” Wilm says. “By taking more points, you can get a better look at the moves you’re making; so you can actually run faster and get more information, and it’s not going to skip any points.”
Wilm uses the the second hand on a clock as an example: the further the graduations are apart, the less resolution you have.
“That’s exactly what we’re doing with the ballbar,” Wilm says. “As you’re going around in a circle, the ballbar is collecting data. The faster it goes, the more data you need to collect per second; otherwise, you’re going to miss something.”
Craig D’Ambroiso, general manager of the measurement equipment sales and service company A-Tech Authority, also has been using ballbars for about 25 years. In his opinion, Renishaw’s QC20-W wireless ballbar system is “leaps and bounds” better than its wired predecessor for two crucial reasons.
“One is that, with the increased safety requirements of manufacturing nowadays, you can’t run a machine with the doors open,” he says. “Instead of spending a lot of time having to bypass the safety for the doors in order to allow the machine to move with the doors open [to make room for the wire], we can now run the ballbar with the doors closed. It’s safer for our people and it’s a lot more convenient.”
The second reason, he says, lies in the ballbar’s redesign.
“The ball end is now tapered down to a point, which allows us to do a full 220-degree Z axis motion, instead of a 110-degree motion,” D’Ambrosio explains. “So we’re able to collect a lot more data on partial arc circles than we could before, which makes the results a lot more accurate.”
Companies that make inexpensive 3D printers—the kind that the average consumer can buy off the shelf and use in their home—are increasingly buying wireless ballbars, Wilm says. After all, these companies have two-axis or three-axis machines, and want to measure the relationship between those axes very quickly and cheaply.
“The 3D printer industry is a perfect and new industry for the telescoping ballbar, because its product is just like a CNC machine tool: it’s programmed to move to a position and complete a task,” Wilm says. “When you put something down on a surface, it’s got to be in the right place; if it’s not, it’s not going to look very good when it’s finished, even to the user. So there’s a degree of accuracy required in this, even in the [consumer-focused] plastic 3D printing industry.”
Medical companies also are buying more ballbars, as a way to faster and more accurately move materials and drop them into exact locations.
“Whether they’re moving vials or pieces of paper, they’re using two or three axes to get them there,” Wilm says. “They’re using the ballbar to determine whether the axes are square to each other, whether they’re positioned correctly, or whether one drive is faster than the other.”
One example is Nemcomed, a division of Avalign Technologies and full-service supplier of implants, instruments, cutting tools, specialty instruments, cases. and trays for medical device OEMs. Nemcomed uses Renishaw’s QC20-W wireless ballbar system to do fast capability checks on small machines and also establish a benchmark on their machines’ volumetric capacity.
But no matter the industry, the overarching goal is the same.
“All of these companies realize that they need a quick and easy way to identify whether the axes are relative to each other—because every single moving axis has six degrees of freedom, and they need to reduce those degrees of freedom or otherwise cause errors in their equipment and errors in their products,” Wilm says. And that’s where the ballbar comes in.
“The diagnostic capability of the ballbar is the key to its success,” he says. “It’s sold itself in that regard, because time is money; people cannot afford to be down. And in just a couple of minutes, the ballbar system runs a test that can identify the source of the problem and give you all the information you need to fix it—often before the problem even happens.”
Smart Software, Smart Business Model
Around the year 2000, Renishaw released auto-diagnosis software for its wired ballbar system, which D’Ambrosio says was way ahead of its time.
“It was intelligent then, and they’ve only made it better,” he says. “And it’s extremely easy to use; it takes longer to load the programs into the control than it does to run the test.”
D’Ambrosio says that he can train any one of his employees on how to run a ballbar, because the process is so intuitive.
“Initially, after data collection, the software takes you to the first analysis screen, which ranks the top five contributing issues, from one to five” he says. “So, even just a basic maintenance person can run a quick ballbar test and go, ‘Oh, my number one issue here is squareness; let me fix that. My number two issue is backlash; let me fix that.’ It literally walks you through attacking the most prominent errors and working your way down.”
“The talent comes from learning how to interpret the data, and that’s what sets us apart from everybody else,” D’Ambrosio continues. “We’ve had so much history with it that we know how to interpret the data based on the way the ballbar looks, before the software even gets a hold of it.”
Besides rapid diagnosis and ease of use for newcomers, Wilm says that customization and the ability to prioritize inventory are inherent in the software as well.
“If a company has 100 CNC machine tools, they could benchmark each of them when they arrive, whether they bought them used or from a factory; and if they measure them again in two or three weeks’ time and they see a change, then they know something’s wrong with the machine, or with the foundation of the machine,” Wilm explains. “And from there, they can do predictive maintenance on the machines and prioritize which ones need to be worked on first by looking at the degree of error.”
Wilm adds that small and large shops benefit from this benchmarking system in different ways.
“A smaller company has to make better use of their assets, as they’re more likely to repurpose their machines for other tasks,” Wilm says. “So it’s very important for a smaller company to be able to know what their errors are and to be predictive about those errors, because they may be making different items on one machine—and what may not affect one item may affect the other item.”
“With the larger shops, they’re going to lose a lot of money if they have a lot of machines with errors and they don’t know it, or they don’t know which ones to prioritize, or they don’t fix them until they break,” Wilm continues. “If you don’t put a priority on which machine needs to be fixed, you’re going to be chasing fires rather than preventing fires.”