Agility Delivers Workholding Dollars
Setting targets leads to finding the best solutions
By Jim Lorincz
Quick change (QC), zero point clamping, modular vises and clamping devices are just some of the buzzwords one hears in the workholding world. Typically stated objectives are reduction in setup time and downtime, increased spindle utilization, and flexibility to match requirements of automation and increasingly popular five-axis machining. No industry is exempt. The return on investment can often be measured in hundreds of hours of production time gained over a year, leading to gains measured in the hundreds of thousands of dollars and more. So important are the benefits, suppliers of workholding believe, that if only end users can be brought into a meaningful dialogue about their production needs and challenges, decisions to tool up new machines, or retool existing production machines would become self-evident.
"What we are seeing is a trend toward quick change and the ability to change from part to part within families with little or no setup, especially for a rejuvenated auto industry," said Jeff Estes, director, Partners in THINC (Charlotte, NC). "We’ve been adamant in telling people that workholding is one of the essential components that they have to consider in automating a process, along with good tooling, good chip control, and some feedback mechanism that provides real time feedback for automatic compensation."
Okuma, like other machine tool builders and their distributors, has embraced the need for intelligent systems that enable communication of data in real time from their processes. As a result, third-party supplied devices of everything from workholding, in-process measuring devices, software and chip management systems are readily integrated into machine tool processes that feature open architecture control.
"Those solutions come from our Partners in THINC and the ability of their products to be integrated into the machine tool system. It’s a universal trend across machine tools to try to get intelligent systems to talk to each other," said Estes. "All of this relates to the trend toward automation and the workholding required to make the automated systems work. Workholding must be automation-friendly and agile, able to be used with a bar feeder, an FMS or a simple or complicated robotic system. Workholding is becoming a component of a larger automation package. So people are looking at it differently today," said Estes.
Increasingly popular five-axis machining, for example, poses its own set of challenges to the agility of workholding and its ability to allow access to all five of the machining planes of the workpiece. "There are a number of ways of accomplishing this with quick change devices and even magnetic workholding devices," said Estes. Choosing a multifunction machine is another way. "Small parts can be bar fed and processed on our Multus multifunction lathe that allows access to five sides of the part using simple workholding consisting of three-jaw chucks and collets. The Multus has the advantage of having a large ATC like machining centers to accommodate redundant tooling for multiple jobs," said Estes.
Set a Goal to Challenge Workholding Solutions
"What we bring to helping our customers with their workholding solutions is knowhow and the ability to troubleshoot their applications," said Tim Winard, COO, Kitagawa (Schaumburg, IL). "The best way for us to evaluate the customer’s needs and current situation is for them to share with us what improvement they would like to see realized and then for us to be held responsible for the results. For example, "we’re presently producing ten parts per hour, but we need to get to fifteen parts per hour." We can show them what the result of the right solution would mean to their business, to their productivity and most importantly… their profitability" said Winard.
Winard believes that the market of workholding ideas and solutions needs clarity which begins with opening a dialogue with customers, each of whom has their own unique challenges. "Frequently the solution is vetted out after an in-depth discussion has taken place, where all needs and expectations are fully understood. The correct solution should address not just today’s immediate problem, but those smaller fires (i.e. problems) that are being accepted rather than dealt with. The best dialog uncovers opportunities that were not apparent prior to the discussion. One such example involved a customer who was primarily concerned with the expense of chuck grease and chuck parts," said Winard. "In this case, saving $10~15,000/ year was pennies compared to the $1,200,000/ yr in added profit that came about when the dialog broadened to include reduced downtime (planned & un-planned) and cycle time. Without the customer having been growth oriented, open and candid about his business we never could have structured this solution as we did," said Winard.
A workholding provider should also be a good mediator in balancing the many requirements/interests put forth by customers. "In one case, a production engineer wanted to reduce cycle time and the maintenance engineer wanted a reduction of both planned and unplanned downtime. To align both members, I suggested that we define the best solution which would provide the greatest amount of production throughput. From there it was a matter of consideration the path with the greatest potential" said Winard.
New from Kitagawa is the new TP530 NC Rotary Table, which is well-suited for machining large workpieces such as oil pipe. This rotary table features a compact design that is significantly smaller than a conventional rotary table, weighing 440 lb (200 kg) more. "The result is that the end user doesn’t have to buy as large a machine to handle heavy-duty machining of large workpieces," said Winard. For five-axis machining, Kitagawa’s VAX125 compact vise features versatile clamping with 40-kN maximum clamping torque by built-in toggle joint mechanism that allows clamping many kinds of materials from hard to soft.
Look for Cost Savings Under the Spindle
"Customers traditionally have programs in place and generally don’t change tooling on the spindle without some cost savings associated with the change," said Paul Kieta, national sales manager, Jergens Workholding (Cleveland, OH). "Larger customers even have formal programs or utilize the cost saving forms from cutting tool suppliers when they’re looking at making a change in tooling. It’s a widely accepted practice in industry to do that." Jergens calls its approach, Savings Under the Spindle. "We are taking a similar approach to document setup time reduction. What we deliver to the customer is additional machining time by keeping the spindle running and, in many cases, by putting more parts on the machine table for horizontal, vertical and five-axis machining."
Jergens looks at a customers’ operations and applications and chooses from four different quick change classes of solution that reduce setup time, reduce the number of tool changes, and increase spindle uptime. The four include the Bock quick change grid system, Ball Lock universal mounting system, the Jergens ZPS zero point clamping system and the Fixture-Pro system for five-axis machining. The Fixture-Pro Drop&Lock Pallet can also be used for first article inspection on a coordinate measuring machine or on a secondary operation. "These are modular systems allowing interchange between systems so that they can be standardized throughout the shop. What we are trying to do for our customer is reduce setup time, as much as up to 90% or more depending on the operation," said Kieta.
Zero point systems, which are popular in Europe and are beginning to gain a following in the US, are accurate and repeatable to 2 tenths (0.0002"). Kieta said that the zero point system comprises a receiver module that is mounted to the machine table or mounted in a subplate. Studs can be mounted into the fixture plate or directly in workpiece. Studs locate into the receiver module and are clamped through mechanical spring clamping force so they are securely clamped in place during the machining process. "To release we can use air or hydraulic pressure that is used to release the mechanical clamp. In cases where you are looking to do automation you can link the control to the air or hydraulic actuation or you can do that manually through a valve or a quick disconnect," said Kieta.
Check Out this Catalog to See What’s New
"When we go to trade shows, we get a lot of interest from customers who want to see our catalog, because they know that they’re going to see what’s new in workholding," said Justin Gordon, general manager, Fixtureworks (Fraser, MI). "Our quick change manual clamps, for example, offer a wide range of solutions for holding from overhead, underneath, and side clamping for accurate and quick change clamping and unclamping. The One Touch Imao manual clamps are designed for high-volume production and feature high repeatability in continuous use. Sizes range from 250 to 1300 lb (113-590 kg) clamping force for workpieces small to medium in size."
To meet the need for gripping finished workpieces that can’t be gripped with a lot of force, Fixtureworks has introduced Sof-Top grippers for delicate work surfaces and Abrasive Diamond Surface Grippers for smooth or slippery surface with minimal clamping force and surface marking. Sof-Top grippers have a urethane surface to grab onto a painted or finished surface that won’t distort, deform or mark a thin wall or softer material. The diamond surface gripper has a surface comparable to 100-grit sandpaper bonded permanently to a stainless steel pad to provide non-slip gripping and offers a very high coefficient of friction. The diamond surface produces a good grip without having to apply a lot of force. "When customers tell us they can’t apply 20–30 lb [9-14 kg] of force on a part before it starts to distort, or a serrated gripper leaves a mark on the part or slips on the part, we have a solution," said Gordon.
"One of Fixtureworks’ newest clamps is the OD Holding Clamp. "It is a table mounted clamp that is machined out to fit the shape of irregularly shaped workpieces. When the workpiece is clamped, force is applied evenly from all sides of the part," said Gordon.
Vises Designed for Specific Machining Processes
Kurt Manufacturing Co. (Minneapolis, MN) has introduced three new vises, each aimed at addressing a specific machining need. "The two new five-axis self-centering MaxLock vises simplify programming for five-axis machining," said Steve Kane, global sales and marketing manager. The new smaller models have 2 ½" (63-mm) and 4 ½" (114-mm) jaw widths, in addition to the present 4" (102-mm) jaw width model. "The self-centering design along with Kurt’s Anglock feature aligns parts in the vise and reduces part lift to a minimum by pulling parts down and holding them with maximum rigidity for close tolerance repeatability in all axes," said Kane. For every pound of force forward, there is a half pound of force pulling down with the Anglock feature.
The new smaller MaxLock models are designed for precision small part machining. They are well-suited for clamping parts for continuous five-axis cutting motion of complex pockets, sculptured and contoured surfaces, and intricate 3D features with repeatable high precision. The MaxLock vises are able to hold parts up to 6 ½" (165-mm) in length with machined jaws and clamp both OD and ID. They feature an adjustable centerline, and their tall jaws provide increased spindle clearance and are machinable to include a step for eliminating the need for parallels.
"A major benefit of the zero point clamping system is its ability to reduce setup time and deliver high quality part finishes without scrap. The DockLock zero point system is able to reduce setup time for a typical workholding setup change requiring 20 minutes using standard methods to less than 2 minutes," said Kane. "For a mold company, for example, the pull studs can be put right into the mold itself. When the mold comes back for rework, they put pull studs back into the machine and it’s already placed for machining," said Kane.
"The big challenge of five-axis workholding are the variables in part size and shape," said Andy Popky, applications engineer, Tombstone City (Stuart, FL). "People want simple solutions to holding parts on five-axis machining centers. You always have to deal with the possibility of interference with the spindle head which tilts from vertical, where there is less chance of interference, to horizontal where interference with the vise, the workpiece or the machine table can occur."
Tombstone City offers the VB 5AX 100 five-axis vise in 4, 5, 6, and 7" (100, 125, 150, 175-mm) heights that are designed to avoid interference issues when the head is tilted to the horizontal or the spindle is larger. "The larger the spindle, the more chance of interference," said Mr. Popky. "Our tall vises from 4 to 7" [100-175 mm] are designed to eliminate the problem. We also offer adapters that you can add into the vise to make the vise grow from the standard 4.7" to 12.5" capacity, up to 24" or more [610-mm] capacity. The adapter kit allows you to hold a 12" [305-mm] or larger part using the same vise."
"In our five-axis vise, we offer a variety of features that can be used on many different table designs, including T slotted, drilled and tapped. The vises fit most standard different T slots and you don’t have to buy a lot of extra components to mount your vise."
One way to become more productive is getting more innovative with fixturing, especially with modular vises. "We offer a modular vise system which can hold multiple parts from one to a dozen in a single vise depending on the part size. For companies with medium production runs, the system is easily customizable. In that way that can modify jaws for special jobs and hold more parts in the workzone with their vises," said Popky. ME
This article was first published in the February 2013 edition of Manufacturing Engineering magazine. Click here for PDF.