Still building fixtures from scratch? Modular workholding is a faster, easier, more cost-effective solution
For as long as people have been machining parts, they’ve been devising ever-more ingenious ways to grip them. Hydraulic and pneumatic-powered chucks and vises, zero-point clamping systems, quick-change jaws and collets—these are just a few of the modern workholding options available to anyone looking to reduce machining costs and enhance flexibility. What’s more, these systems are increasingly modular—easily moved from machine to machine or job to job with minimal modification— further increasing their owner’s bottom line.
And yet, too many shops are still stuck in the past, designing and building homemade jigs, fixtures, and other workholding that add cost and lead-time to their projects. Assuming these one-time tooling woes don’t push a shop out of the running during the quoting process, this dedicated hardware must be stored on a shelf when the job is complete, awaiting the next production run. And when the job goes away for good? Time to toss the fixture in the scrap bin.
Workholding in Kits
The term modular workholding means different things to different people, but any investment in tooling able to eliminate the scenario just described is money well spent. Consider the pre-configured kits offered by some tooling providers, each containing an assortment of clamps, risers, studs, blocks, and rails. The $10,000 or more (often way more) spent for one of these general-purpose solutions might seem excessive at first until you consider that the kit will replace dozens or perhaps hundreds of dedicated fixtures. Countless hours in the toolroom are avoided. Changing customer demands are more easily met. Payback is often measured in weeks.
EROWA Technology Inc., Arlington Heights, Illinois, is one company known for such kits in use on wire EDMs. Regional Manager Fred Holzmacher explained that the company has expanded well beyond its initial focus and now sells a broad range of workholding products for CNC machining centers, especially those with five axes of motion.
“Everybody wants to palletize and automate their five-axis machines,” he said. “When you’re spending several hundred thousand dollars on a mill, you don’t want it sitting idle while someone is bolting down a vise or indicating a fixture. Setup time is everything, and once the machine is running, you need the ability to get parts in and out quickly.”
Plates, Knobs, and Clamps
But what does the term “modular” actually mean? Here again, each provider has its own definition, although most would agree that modularity starts with a standard locating system. For CNC machining centers, this is often a baseplate that mounts directly to the machine bed and is equipped with a standardized series of holes, some or all of which are threaded to accept various adapters, pallets, or clamping devices.
In EROWA’s case, this might be the MTS (Modular Tooling System), although Holzmacher is quick to point out that the company offers several similar workholding solutions, among them the EROWA UPC (Universal Power Chuck), CleverClamp, and PowerChuck P systems. “The MTS is the newest of these and is typically for larger production work on five-axis machining centers. The UPC is also quite popular, depending on the required level of accuracy,” he said.
In addition to universal baseplates, zero-point systems like these are growing more common. As with EROWA, most workholding companies now offer some form of pull-down, retention knob-like clamping hardware and accessories. One of these is SCHUNK Inc. in Morrisville, N.C., where Brad Evans, stationary workholding team lead, noted that the newest of these—the WDM-5X—is a manually-activated system that combines the toolmaker’s VERO-S technology with a series of stackable modules, providing more than 1,000 clamping possibilities.
“The WDP-5X is a pneumatic version of the same system,” he said. Both are modular, but are designed for quick-change clamping as opposed to palletizing. “A mold and die shop, for example, might stack up various components to support and position a mold base, then use a pair of VERO-S modules with the clamping pins attached directly to the workpiece to secure it in place. Or the whole thing could be set up offline on a grid plate and dropped onto those same VERO-S modules,” said Evans. “Either way, it’s far faster and more accurate than straps and toe clamps and everything is easily reconfigured to whatever comes in the door next, significantly reducing the need for custom fixturing.”
Evans pointed to several other components of the WDM-5X system, among them a line of telescoping, five-axis stabilizers designed to reduce vibration when machining tall workpieces. SCHUNK also offers the KSP-BWM series of pneumatic vises with quick-change jaws, all of which work with the VERO-S platform.
“Automation is growing by leaps and bounds, and these types of modular systems support that need,” he said. “Where robots were once limited to relatively simple load/unload operations, a modern, five-axis robot is able to service multiple machining centers, changing pallets, parts, and even grippers. It represents an entirely new approach to manufacturing.”
Edging into Success
Carr Lane Manufacturing Co., St. Louis, Mo., sees similar trends. Chief Operating Officer Colin Frost agreed that modular workholding of all kinds is growing in popularity, but particularly that designed for five-axis machines. “Workholding for these applications must provide as much access to the workpiece as possible, which requires different strategies than traditional workholding,” he said. “For example, we recently developed a line of low-profile edge clamps that are equipped with slotted bases for easy adjustment during mounting.” These devices are also convertible from mechanical to hydraulic, allowing for basic automation.
Also new at Carr Lane are mechanical zero-point systems that attach directly to the workpiece. Frost explained that the DropZero system provides for clamping and locating in a single device, and are designed for use with the company’s modular sub-plates and blocks. “They can also be mounted to one another to support uniquely shaped workpieces,” he said.
Whatever the system, the initial investment in modular workholding may be significant, but the ability to deploy it on job after job ensures that ROI is positive, even if specific to each application, Frost added. “That said, scalability is critical. It is rarely possible or practical to invest in a complete solution at one time, which is why shops should select a manufacturer offering systems that are expandable in the future. We also recommend using manufacturer-provided CAD solid models to preplan the clamping and, whenever possible, loading the clamping data into the CAM software to ensure clear toolpaths.”
One or One Thousand
Frost noted that virtually any part is a candidate for modular workholding, but it’s those with unique shapes not well-suited to a vise that make the best candidates. And even in these situations, dedicated fixtures often remain the first choice for jobs that are expected to repeat, or where very complex machining and/or tight tolerances are involved.
EROWA’s Holzmacher pushed back on at least some of that idea, suggesting that today’s product lifecycles are far shorter than in the past, forcing machine shops to do whatever is necessary to reduce dedicated tooling costs. “Years ago, people would design a part and it would run for five years,” he said. “Now, the life expectancy of a product is often a year or less, so instead of producing hundreds or thousands of something, you might make only a handful before the job goes away.”
This argument goes far beyond the cost of designing, machining, and storing jigs and fixtures. These costs are, in fact, secondary to that of the machine downtime associated with more frequent setups. And the best way to reduce this lost time, Holzmacher said, is to palletize wherever possible.
“It’s a common misconception that pallet systems require large job quantities to justify,” Holzmacher said. “The reality is, it’s the exact opposite. By using modular workholding together with a zero-point system, you get the best of both worlds—shortened setup times and lower tooling costs, regardless of the job quantity.”
Workholding in Lathes
All of this is good news for the milling and EDM departments. How about CNC lathes? Changing out top jaws, switching from a three-jaw to a collet chuck or arbor—these are just a few of the time-wasters that any lathe operator must deal with, often on a routine basis. What kinds of modular workholding options do they have? Michael Larson, marketing director for Hainbuch America Corp., Germantown, Wis., has a few ideas, starting with the company’s centroteX chuck quick-changeover system.
“An operator can switch from one workholding device to another in five minutes or less, and our new mini version—the centroteX S—is even faster, providing changeovers of less than one minute thanks to a single radial locking screw,” said Larson. “Perhaps best of all, it works with a shop’s existing chucks—all that’s needed is an adapter. It provides a lot of flexibility and greatly decreases machine downtime.”
Larson said the company recently expanded these capabilities with the Hainbuch modular system, which includes TOPlus and SPANNTOP chucks and mini chucks, the TOROK manual chuck, and the HYDROK hydraulic stationary chuck. Each is available with various “adaptations” such as OD clamping heads (collets), ID mandrels, two-jaw and three-jaw modules, face drivers, and magnetic chucks.
“There are ten different workholding devices in our modular system, giving users around 65 different combinations,” he added. “The system also works on a milling machine, so again, there’s a great deal of flexibility. And for shops using one of our collet chucks, changeover within 10 seconds or so is possible. And with a properly-equipped robot, it’s possible to automate much of this changeover.”
SMW Autoblok Corp. is another well-known name in turning solutions, offering a broad line of lathe accessories, among them its KNCS-series quick jaw change chucks, steady rests, collet chucks and mandrels, and the CCS chuck switching system. Yet Larry Robbins, president of the company’s commercial division, noted that the Wheeling, Illinois-based company recently moved into stationary workholding, and like most manufacturers with new products to promote, had planned to unveil them at last fall’s IMTS.
Had that event occurred, visitors would have had an opportunity to kick the tires on SMW Autoblok’s APS zero-point clamping system, said to reduce setup times by up to 90 percent in milling, turning, and grinding applications. Other stationary products include the ZeroAct, a zero-point clamping module that supports manual actuation of up to three units simultaneously, the WPS (workpiece positioning system) for direct workpiece clamping, and a variety of five-axis vises, chucks, and similar workholding accessories, most of which are modular.
Yet it’s SMW Autoblok’s contactless inductive coupler system that has Robbins the most excited. Capable of transmitting both electrical power and data across an air gap of up to 4 mm, the technology promises to simplify workholding installations while providing greater control of clamping pressures, positioning, and status.
With SMW’s MM electromechanical four-jaw chuck, for example, each jaw can be individually controlled and monitored, providing “an enormous increase in flexibility, quality, and operational safety. There’s more to it than closing a chuck or vise, because while I’m doing that, I can also transmit instructions,” he said. “For instance, I might tell clamp number three to move two microns to the left and clamp number five to move six microns to the right, and the system will provide feedback when those actions are complete. The system will store all this information and send you a report when it’s all over—what values were changed, what clamping pressures you used, torque and rotational forces. Everything. All from a standard interface.
“It’s going to have a huge impact on workholding, but also robotics, positioning systems, material handling—basically any industrial application that can make use of inductive energy and data transmission in a single coupling,” Robbins concluded. “This is why we recently started another company, called SMW-Electronics, and have hired 35 people dedicated to developing and supporting this new technology. It’s a game-changer, that’s for sure.”