by Kip Hanson
What are you waiting for? It’s time to transform your shop with zero-point workholding
With production quantities falling and the machine shop landscape growing just a bit more competitive every day, wouldn’t it be great if you could set up a new job in less time than it takes to eat a ham sandwich? It’s not as crazy as it sounds. Many workholding suppliers offer tooling that does exactly that–all it takes is a little planning, some slight modifications to your existing tooling, and a lot less money than you might think.
How does it work? You start by attaching several studs not unlike the retention knob found on the end of any CAT or BT-flange toolholder to a vise, fixture, or even the workpiece itself. The non-threaded end of each stud fits into a mating zero-point retainer or chuck, which is in turn mounted to a sub-plate or sometimes directly to the machine table. Depending on the manufacturer, air, hydraulic, or mechanical pressure is then applied, drawing the workholding device down and holding it securely against a locating surface.
This is the essence of zero-point workholding. It’s fast, rigid, extremely accurate (within “a tenth or two”) and can be used on virtually any machine tool, with average payback times of six months to as little as a few weeks. The question is, why aren’t more shops doing it?
“From what I’ve observed, only 10 to 20 per cent of the shops in North America are using any sort of quick-change workholding system,” says Michael Gaunce, stationary workholding group manager for Schunk, maker of the Vero-S zero-point system. “We see a very different story in Europe, where even small to medium sized shops are constantly investing in new technology; they understand the value that those investments bring to their throughput and profitability. Over here, you’ll certainly find shops that are very successful with this technology, but they are definitely in the minority.”
Maybe you’re thinking, “we only set up a couple times a month. It’s not worth the hassle and expense to save just a few hours here and there.” Maybe not, but it’s important to recognize that the benefits of any zero-point system extend well beyond setup time reduction:
If your customer calls with a rush job that she absolutely must have by tomorrow, there’s no need to tear down an existing setup–take the old job off, pop a new vise or fixture in its place, and you’re making chips within minutes.
With zero-point, there’s no tramming or dial indicating. Establish the work coordinate one time, record it in the part program with a G10 command, and the job always returns to the same location. No more worries about fat-fingering an offset.
Carry that thought one step further—by modeling your workholding and zero-point locating dimensions directly within your CAM system, touching off a new job can be eliminated entirely. Program the job, simulate the toolpaths, drop the tooling in, and hit cycle start. That should be the goal.
Have a tight geometric position between part features that must be machined in different operations? Zero-point means the part can be clamped one time and moved from the machining centre, the lathe, the EDM, and elsewhere without repositioning.
Need to move the rotary table bolted to the side of your machining centre but dread the downtime? Not anymore. Simply loosen your zero-point clamps and pull the thing off. The next time an indexing job rolls around, just set it back in place and get to work.
Don’t have a rotary table on your vertical machining centre but need to machine multiple sides of a manifold or similar orthogonal workpiece? Set up an angle plate with a series of zero-point chucks and tumble the part by hand to whatever orientation is needed. Problem solved.
The same goes for parts that need to be moved from a the machine table to a rotary table. Put a zero-point chuck on each so that the fixture can be placed at either location with ease.
Don’t forget about inspection. Put the same zero-point system on the CMM and you can measure the part without relocating, without building another fixture, and with much less machine downtime while waiting on the inspector for first-piece approval.
I’m sure there are more examples out there, but the bottom line is clear: shops can not only set up more jobs more quickly with zero-point, but do so more safely, accurately, and with greater flexibility to meet changing customer demands.
Just get rolling
Convinced? Jack Burley, vice president of sales and engineering at BIG Kaiser Precision Tooling says it’s easy to get started. “A lot of times customers are leery about diving in, and just want to see how it might fit in to their operation. I tell them to start with a single vise. Attach a pair of Unilock knobs to the bottom, toe-clamp a pair of chucks to the table, and you’re up and running for a few thousand dollars. You can build on it from there by adding knobs to your other fixtures, your indexer, that sort of thing. If you’re doing even a few setups a week, it’s a no-brainer.”
Lino Libertella agrees. The president of Machine Tool Solutions and exclusive Canadian distributor of the Lang-Technik workholding line, Libertella says his zero-point systems are popular with companies such as General Electric and other aerospace companies, as well as various automotive suppliers, claiming that the Lang Zero-Point system is one of the lowest in the market with a height of 27 mm and a clamping force of 6,000 kg.
Where does this leave the small to mid-sized job shops? Libertella says he sees plenty of interest there also, and like BIG Kaiser’s Burley, suggests that shops start small. “I have some people who put my zero-point system on a single lathe or a mill and see how it works for them. It doesn’t take long before there’s zero-point everywhere in the shop. It’s that beneficial.”
Ask the right questions
If you’re ready to give it a try, ask yourself some questions first: where will zero-point be used? For example, if there’s a wire EDM in your shop (or think you might have one some day), you’d best buy a system made of stainless steel. Do you need to tool up a five axis machining centre? A mill-turn lathe? How about the tombstones on a horizontal machining centre? Some zero-point systems have more pieces than a Ravensburger jigsaw puzzle–others, not so much. Make sure your chosen system has what’s needed before you start modifying fixtures or writing checks.
Also, no one likes routine maintenance, so be sure to investigate which zero-point systems are the most hassle free. Which activation method–air, hydraulic, or mechanical–is best for you? Finally, return on investment with a zero-point implementation is excellent, but these systems aren’t free. Shop around and find out which fits within your budget (even if you don’t currently have a budget). Whatever you do, do something. Quick-change workholding is some of the lowest hanging fruit around. It’s time to get picking. SMT