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Fixturing Help is Within Your Grasp

Jul 25, 2023

The latest workholding offerings are designed for all the facets and demands of modern machining

Those who think of workholding as a static area would have trouble holding on to that view if they took a good look at the latest offerings from leading workholding manufacturers. They’d find a variety of products aimed at helping shops meet current machining challenges. In addition to advanced off-the-shelf options, skeptics would discover suppliers willing to help compensate for shop shortcomings tied to the current labor market with special workholding products and helpful guidance.

A major advantage of some of the latest workholding options is how they fit in with the trend toward increased automation in machining operations. Take hydraulic vises, which are operated by a pump with a control valve connected to the machine control. Hydraulic workholding is chosen for many metal-cutting operations because it provides high cutting forces with smaller pistons than a pneumatic workholding system would need to generate the same amount of force, according to Chuck Milam, industrial products sales manager at Minneapolis-based Kurt Manufacturing Co., which sells hydraulic fixturing systems.

In addition, hydraulic workholding is a good choice for those interested in more automated production. Consider, for example, what Milam describes as a semi-automated manufacturing system, in which picking and placing is done by humans rather than a robot but the vises in the system operate automatically. "You might have 10 vises on a bed and you just hit a button and everything clamps automatically with very controllable clamping force," he noted. As a result, the process doesn't change when shop personnel change.

According to Milam, experienced machinists develop a "feel" that allows them to clamp parts with just the right amount of force so that they’re firmly in place but aren't deformed by the process. But manual clamping can go very wrong when those doing the job haven't yet developed such touch and feel.

The latter situation is fairly common, noted David Simpson, Kurt's product marketing manager. In fact, he said many shop owners at last year's IMTS reported that less experienced operators were damaging parts by manually clamping them with excessive amounts of force. "With manually clamping, everybody has their different idea of ‘tight’—it's a strength thing," Simpson explained. "Automated clamping can help to eliminate some of those idiosyncrasies of people's strength. So even at a base level of automation, operator-triggered automated clamping can help create better parts and prevent wrecking parts."

In machining operations with robots, workholding products can also help facilitate automated pick-and-place operations. For example, some of the vises sold by Lang Technovation Co. in Hartland, Wis., are designed with clasps or indents that make it easier for robot end-effectors to grab and move them, noted Jon Dobosenski, the company's general manager.

Lang specializes in flexible vises that allow users to meet the requirements of various jobs. "It's a lot cheaper to just change the jaws instead of having to change out the entire vise," Dobosenski said. "So we have a lot of different jaw options that can be utilized in a standard vise base."

These vises are just one example of an industrywide move toward more flexible workholding. In the past, shops typically used workholding designed specifically for the manufacturing of specific parts. But the same equipment couldn't be used when it came time to move onto the project, lamented Larry Robbins, president of the commercial division of SMW Autoblok Corp., Wheeling, Illinois.

"All of a sudden, this $500,000 in specialty workholding they bought is now sitting on a shelf or in a scrap pile somewhere," Robbins said. "So, all of the product we’re developing now is with flexibility in mind to meet the customer's needs not only for the (current) job, but for every job moving forward."

Autoblok's latest workholding products consist of changeable front-end components that come in contact with parts and an actuation back end that doesn't change. With the company's CCS chuck-switching system, for example, users can turn a workholding device into a variety of different solutions. "It could be a three-jaw chuck, a four-jaw chuck, a collet chuck, a mandrel, or a simple fixture just by changing your front end," Robbins said.

What's more, he added, changes can be made in less than a minute with 10-µm positional repeatability. This is in stark contrast to a typical workholding changeover, which Robbins described as a more arduous and labor-intensive process that can take as long as 30 minutes, even for an adept operator.

Another advantage of Autoblok's CCS tech, according to Robbins, is that the system can be adapted to workholding from other companies. This requires the use of an adapter that puts space between the workholding and the face of a spindle. But Robbins noted that the distance is negligible and doesn't make the setup less rigid.

Although CCS is more expensive than conventional workholding, Robbins said customers are more concerned about value. "The more functionality you build into your workholding, the more people seem to accept spending additional funds to get that extra bit of flexibility," he said.

To make its workholding more flexible, Lang Technovation focuses on modularity. One example is the Makro-Grip Ultra, a new modular workholding system for machining plates and large components. Able to incorporate different base bodies, jaws, spindles, and other accessories, the system offers a wide range of possible configurations that can be changed quickly and easily, according to Lang. In addition, the company points out that the system's expandable modules allow workholding setups with different heights and clamping parts longer than 800 mm.

Lang also makes vises with tapered bodies that allow more movement in applications involving five-axis machines. The taper allows the workpieces to be tilted enough that machining can be done on the undersides, Dobosenski explained. On the downside, however, he noted that the jaws on these vises are a little smaller than normal.

Though five-axis machining was uncommon in the United States in the past, Dobosenski said it is becoming much more commonplace. "So we sell quite a few vises with the taper."

The emergence of five-axis and mill-turn machines, both of which are capable of producing many different part types, has also increased demand for flexible workholding, added Michael Gaunce, vice president of sales for tooling and workholding at Schunk USA in Raleigh, N.C. One workholding product aimed at these applications is Schunk's Vero-S quick-change pallet system. As the name suggests, the Schunk system allows fast pallet changes on machine tables. A centering cone in the middle allows positional repeatability within 5 µm, according to Gaunce.

He added that the workholding changeover time saved by this system can be particularly valuable for users of mill-turn machines. These machines "are higher-cost investments, but you’ll have a lot faster return on your investment if you invest in a quick-change pallet system," he asserted.

The rise of five-axis machines may give a boost to magnetic workholding. "If you have a magnet that's just holding a part on the bottom side, it means that you have access to (the other) five sides of that part," Gaunce said, noting "which is good for five-axis machining."

In addition, he pointed out that the trend toward automated manufacturing processes and connected devices in those processes may create additional demand for magnetic workholding. The reason, he explained, is that magnets are operated electronically, making them suitable for automated production environments and connection with other equipment.

Rather than employing a vise, magnetic workholding systems hold parts in place entirely with magnetic force. Because the force acts on an entire part surface, magnetic workholding provides good vibration reduction.

In order for magnetic workholding to be a viable option, workpieces must be made of a ferrous material. Another good rule of thumb, according to Gaunce: If a workpiece is at least the size of a sheet of letter paper and half an inch thick, there will be enough magnetic force holding that workpiece in place for traditional machining.

One common use cited by Gaunce for magnetic workholding is to help secure large pieces of metal in large machines. "When I say large, I’m talking two meters wide by six meters long and larger. You can't just put multiple 6" (152 mm) vises on that machine to clamp a huge piece of steel," he said. "So a lot of times people just cobble together some supports and some toe clamps around these workpieces wherever they can put them."

However, the clamping process can take three to six hours, which Gaunce points out is unproductive time during which the machine spindle isn't running.

For situations like this, Schunk developed an extra-large clamping kit that includes magnets, as well as risers, vises, and the company's Vero-S system.

These items can be used in a modular way to clamp parts in large machines, with the magnets placed in strategic locations to reduce vibration.

For a big part on a gantry machine, for example, Gaunce said, "You can clamp it in a couple of places with very large vises that we have designed specifically for clamping large parts. And in the middle, you can place a couple magnets on risers to reduce vibration of the workpiece there."

The magnetic force can cause chips to stick to a magnet or workpiece, which could potentially interfere with the machining process, Gaunce cautioned. But, he said, this problem is easily avoided when operators are properly trained on how to use a magnet.

Another significant workholding development is the recent entry of a new competitor into the field. In the summer of 2021, a workholding line that includes manually actuated, self-centering vises and bases was introduced by Mate Precision Technologies, Anoka, Minn. "We applied the 60 years of experience we have in making precision products out of alloy materials—mostly A2, D2, M2, H13, and S7," said Frank Baeumler, Mate's vice president of workholding. "These high-alloy tool steels are not the cheapest things on the market. But that's how we know how to build product, and we applied that to this workholding family."

The result, Baeumler said, was a line of "very robust" products that provided users with more rigid, stable, and predictable workholding than what they were using before. "The combination of design and materials that we selected and the way we execute in building the product has been really well received," he reported. "That would be an indicator that there's a market segment of high-end need that maybe was not being served so well in this space."

So far, Mate's workholding products have mainly found a home in the medical and firearms industries. According to Baeumler, the vises feature accuracy of 0.0006" (0.015 mm) and repeatability of 0.0004" (0.01 mm), while the bases offer accuracy of 0.0005" (0.013 mm) and repeatability of 0.0002" (0.005 mm). Also notable, he said, is the design of the vise lead screw. Featuring a trapezoidal thread that makes more surface contact with the female side than a rolled thread, the lead screw produces high output force with relatively low input torque, he noted. Made of heat-treated H13 steel, the lead screw has a hard TiCN coating that prevents chips from embedding in the screw, extending the life of the workholding devices, Baeumler said.

When even high-end standard workholding products don't fit the bill, shops must seek out custom solutions. One workholding supplier that has been fielding an increasing number of inquiries about custom products is Cleveland-based Jergens Inc. In response, the company is bolstering its capability to design and build such products, according to Mike Antos, the company's workholding product manager.

Besides specialized products, Antos said customers are asking for additional support from the workholding supplier. "A customer will say, ‘I don't just need the product, I need a recommendation on my whole process and how I can improve that,’" he noted, adding that the types of information customers are looking for include advice on the best way to fixture their parts and whether or not they need quick-change workholding.

Antos attributed the upsurge in requests for these services, in part, to the growing shortage of skilled and experienced personnel in the machining industry. "You may have a company that's trying to become more efficient, but they might not have the people with the experience or expertise to do that," he said. "And not just on the engineering side to implement it, but maybe you also have a less skilled workforce on the machine. So now you might need a more thoughtful or engineered fixturing solution on your machine. And a lot of times that will necessitate a custom design and build solution."

At Jergens, a custom workholding solution could simply be a modified version of an off-the-shelf product—for example, a stock plate with added mounting holes so the plate fits onto a customer's machine table. Or it could be a complex fixturing build that's made from scratch.

Of course, there are downsides to customized workholding. Antos said it could cost 50% more than an off-the-shelf product, and the time it takes to complete a custom product can range from a week to a few months, depending on the size and complexity of the project. Typically, the extra cost of custom workholding is far less of a concern to a customer than the time it takes to get the product into the shop, Antos pointed out. The reason is summed up by the familiar axiom: time is money.

"You’re seeing people that are under the gun to get production ramped up," Antos said. "They might have a machine on the floor that's not making any parts, so a lot of times the weeks it takes to get that (workholding) are more costly than the actual dollars it costs."

Whatever type of workholding solution customers opt for, Jergens can help them look past the price tag by quantifying their cost savings over time. For example, Antos cited a situation where a potential customer spending a couple of hours a day changing fixtures is considering quick-change workholding. "If we can take that two hours down to a few minutes, we have tools to help customers see how that saving adds up over a week, a month, a year," he said. "So the initial cost might be expensive, but with what you’re going to save, you might pay it off in a couple of months."

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SME Media Staff The latest workholding offerings are designed for all the facets and demands of modern machining