Cutting Infinity: Ultraprecision machining delivers unprecedented accuracy

When I was a kid, I wore glasses that looked like Coke bottles and cost more than a Schwinn 10-speed. Thanks to ultraprecision machining, I now wear disposable contact lenses and spend less to replace them than I would for a cup of coffee at Starbucks.

As the grandchild of single-point-diamond turning, the same 1970s technology that made 14″ computer hard drives possible, today’s ultraprecision machining, or UPM, is responsible for making parts for everything from smartphone cameras to telescopes that can see back to the beginning of time.

Most shops are holding tight tolerances these days. What makes UPM parts different than those aircraft components you shipped last week?

“I think it depends on who it is you’re talking to—and how old the guy is,” said Thomas Sowden, owner of Contour Metrological & Manufacturing Inc., a job shop in Troy, Mich.

Sowden was making chips when the Nixon Administration thought it would be a great idea to bug the Watergate hotel. Since then, the accuracy of machined parts has progressed to levels unimaginable during the days of Flower Power and free love. “When I started machining, if you held a half-thousandth, it was pretty good. Today, we hold tolerances under a micron and impart finishes down to 30 to 50 angstrom RMS.”

Read the rest: http://www.micromanufacturing.com/content/cutting-infinity-ultraprecision-machining-delivers-unprecedented-accuracy

Machining tiny electrodes can be a big challenge

Figuring out micro-sinker-EDMing is no easy task. As electrodes shrink, challenges grow, including maintaining the proper spark gap, minimizing electrode wear and determining the correct power settings. Plus, experienced EDMers know that using graphite electrodes can turn your hands black.

This wire EDMed electrode is for reverse burning the punch. For a burn like this, cavity spacing must be precise so that each burn can be made in succession without repositioning the workpiece. Running out of cavities before completing the final burn is a big problem, so too many cavities is better than too few.

But the challenges are worth it because micro-sinker-EDMing has a really big upside: “The whole point of sinker-EDMing is to machine parts you can’t get any other way—that means parts with features requiring crazy aspect ratios, steep-angled walls or sharp internal corners,” said Marcus Carius, proprietor of Implant-Mechanix Inc., Vancouver, British Columbia. “Any time that cutting the electrode would be far easier than machining the part itself, that’s the [deciding] factor for EDM.”

But, as Carius noted, burning parts with a sinker-EDM is often only half the battle. Just making a series of electrodes to produce a mold cavity or tooling component is an art. This is especially true when making electrodes for microparts.

Choosing the right electrode material—such as graphite, brass, copper or tungsten, among others—can mitigate some of those challenges, but the selection process itself can be a guessing game. While the guidelines for applying macroscale electrodes are well known, the rules for micro-EDM are a bit like predicting the next World Series winner.

Read the rest: http://www.micromanufacturing.com/content/machining-tiny-%E2%80%99trodes-can-be-big-challenge

Buying Time – Quick Change Tooling

It’s the 47th lap of the Indianapolis 500. You’ve been leading the pack all morning but the left rear tire is getting a bit squishy. After signaling the crew to get ready, you barrel down pit lane and slide to a stop before the garage, just as the tire changers come running out equipped with … monkey wrenches?

To a racecar driver, quick changeover means the difference between victory and defeat. But it seems machine shop owners and manufacturing engineers aren’t getting the message. Talk to most any machine tool expert and you’ll hear the same thing: fewer than 10 percent of all 2-axis lathes are equipped with quick-change tooling.

That Stuff Ain’t Cheap!

“A lot of people don’t see the benefit of quick change,” said Michael Minton, national application engineering manager for Methods Machine Tools Inc., Sudbury, Mass. “People are looking for ways to reduce setup time, but the perception of high cost gets in the way of the benefit of quick change. Machine and tooling suppliers need to do a better job of explaining the technology to end users. Given the proper application, the benefits clearly outweigh the cost.”

Quick change toolholders cost several hundred dollars each. The blocks to mount them to the turret could be more expensive than a Caribbean cruise. Adding insult to injury, lead times can be long. Once you’ve purchased a new CNC machine, you might wait 8 to 10 weeks for delivery of a quick change tooling package and spend another 20 percent over the machine’s $150,000 price tag. “It is very hard to convince a guy who just bought a 2-axis lathe that it’s a viable solution,” Minton said.

Read the rest: http://www.ctemag.com/aa_pages/2013/130403-Turning.html

Trending Toward Productivity

The U.S. economy appears to be on the mend. In January, the Manufacturers Alliance for Productivity and Innovation gave a tentative thumbs up to sustained business expansion through the first half of 2013. And the Institute for Supply Management’s manufacturing index rose again in January, painting an optimistic picture. Maybe it’s time to buy that machining center you’ve been thinking about.

Before you whip out your checkbook, though, some homework is in order. There’s a lot more to machining centers than spindle speeds and rapid traverse rates. Sure, you’ve had good results over the years buying machines based on that, but that might be the wrong criteria in this brave new manufacturing world. You’re facing growing competition from overseas and down the street, so you owe it to yourself to take a look at what’s changed in the years since you bought your tried and true 20 “×40 ” vertical machining center.

Most everyone’s seen them at trade shows—5-axis wonder machines whittling away at intricate shapes such as motorcycle helmets, jet turbine blades and titanium knee implants. Recently, 5-axis machining centers have redefined many shops’ definition of complexity. But maybe you don’t do complex aerospace work, or you simply can’t afford to spend $500,000 on a machine tool. And 5-axis programming is way too complicated, right?

Read the rest: http://www.ctemag.com/aa_pages/2013/130303-MachiningCenters.html

Micro-Endmills – not the same old grind

Endmilling is a mainstay of micromachining. And while micro and macro milling operations share certain similarities, there are several key differences—and surprises.

One eye opener when shopping for micro-endmills is their cost—as the size goes down, the price goes up. Sometimes way up. Where a commodity 1/8” endmill might cost $6, a micro version 1/10th that size can cost five times as much or more. Adding insult to injury, you’ll likely go through a lot of them compared to their larger cousins. These things are fragile. Why the price difference?

There are several challenges to making micro-endmills, starting with the grinder. “It sounds obvious, but the machine must be designed to grind small tools,” said Mike Wochna, president of Cleveland-based Melin Tool Co. “There are a number of things required for this, including thermal stability, vibration control and extreme accuracy.”

As the tool diameter decreases and its features shrink, the grit size of the grinding wheel must be reduced as well, according to Wochna. And as grit size goes down, complications increase. With tools smaller than 1mm in diameter, it becomes increasingly difficult to accurately see and measure features, so you’ll need special inspection equipment and trained personnel to operate the equipment.

Read the rest: http://www.micromanufacturing.com/content/not-same-old-grind

Micro Scopes – Making Endoscopes Smaller

Once-revolutionary microdevices that allow doctors to examine internal parts of the human body are now commonplace. One of the most commonly used of these devices is the endoscope, and its use is growing.

The U.S. endoscopy market was valued at more than $9.87 billion in 2011, according to Sara Whitmore, analyst manager at iData Research Inc., a market research and consulting group based in Vancouver, B.C. “We expect it to exceed $16 billion by 2018,” Whitmore said. And a report by the market-forecasting firm BCC Research predicts global endoscopy sales will reach $33.7 billion by 2016.

That’s a lot of endoscopes.

Surprisingly, this growth has occurred despite a relative dry spell in technical advancements.The last big thing in endogadgets to gain market share, according to Whitmore, was capsule-type endoscopy, introduced in 2001. That’s not for lack of trying. Whitmore explained that new product development can cost more than a star NFL player’s contract and take years for approval by the U.S. Food and Drug Administration.

“Even if a company perseveres and makes it through all the required steps, there’s still no guarantee that physicians and patients will accept the new technology,” she said.

However, that doesn’t mean that existing technology isn’t being improved. Today’s endoscopes ride on the shoulders of better (and cheaper) electronics, improvements in micromanufacturing techniques, stronger, lighter materials and the engineering know-how to put it all together—the same sort of elbow grease that gave us smartphones and high-resolution televisions.

Read the rest: http://www.micromanufacturing.com/content/micro-scopes

Why so cross? Cross-hole drilling can test a machinist’s mettle

Drilling cross-holes in some parts is no big deal. These are often simple parts, such as aluminum valve bodies, where the holes aren’t too deep and meet on-center, and the customer can live with a small burr at the intersection.

On the other end of the spectrum are P-2 tool steel injection molds for complex medical devices, with more holes than a block of Swiss cheese and tolerances that make even veteran machinists weep.

Even simple cross-hole drilling presents challenges, including high tool wear, poor chip evacuation, difficult-to-remove burrs and tool deflection that can snap the toughest of drills. But there are ways to turn the bane of holemaking into a more bearable task.

According to Dan Habben, applications engineer at Sumitomo Electric Carbide Inc., Mt. Prospect, Ill., cross-holes are always a problem child. “Probably the best tip I can give is this: don’t do it!” laughed Habben, who works with automotive suppliers and sees cross-holes in everything from transmission housings to hydraulic valves for diesel engines. “Our customers cut a lot of die-cast aluminum and gray cast iron, and one of the main problems we see, especially with aluminum, is burrs. In hydraulic systems, it’s important to get a clean hole. Any chips or hanging chads left in the workpiece might pass into the hydraulics, damaging a valve or pump.”

One possible cure is effective edge preparation on the drill, together with appropriate feed and speed modifications. “We usually recommend a corner clip in this case,” Habben said, “meaning a 45° chamfer on the outer margin of the drill, together with a small edge prep, say, a light T-land or a hone of around 0.003 ” to 0.004 ” on the cutting edge. And it’s especially important to use a sharp tool.”

Read the rest: http://www.ctemag.com/aa_pages/2013/130201-Holemaking.html

Finding a 5-axis Solution

Tim St. Martin knew there had to be a better way of fixturing parts on his company’s 5-axis machine tools. “We’d visited some of our suppliers and saw how they were holding parts on their 5-axis machines,” said the senior manager of manufacturing engineering for Carlsbad, Calif.-based orthopedic implant manufacturer Alphatec Spine Inc. “They were mounting the blanks into a ‘picture frame’ and then screwing that frame to a tombstone-mounted fixture. This basically limited access to one side of the workpiece per operation. Many in our company thought we should hold them the same way.”

Management charged St. Martin with finding the most effective way to produce a family of titanium spine plates. Alphatec had purchased a pair of 42,000-rpm Mikron HSM 400U LP 5-axis machining centers to bring machining of its Trestle-Luxe anterior cervical plating system in-house.

In particular, Alphatec needed an optimal way to fixture the parts because it would be making a family of 33 different part numbers with production volumes of more than 1,700 pieces per month. While the company considered making its own fixtures, contacts at GF AgieCharmilles, builder of the Mikron machines, suggested Alphatec look at workholding from 5th Axis Fixtures Inc., San Diego, which specializes in workholders for 5-axis machines.

Read the rest: http://www.ctemag.com/aa_pages/2013/130215-Workholding.html

Ultrafast Lasers Quicken the Pulse

In the 1964 movie of the same name, the evil Goldfinger spoke fondly of industrial lasers. “You can put a spot on the moon or cut through solid metal with one,” he said to James Bond, strapped to a gold table and about to be laser-beamed in two. Luckily for Bond, the laser wasn’t very efficient. Just look at the spatters of molten metal, the recast on both sides of the beam. Goldfinger would have made a cleaner cut if he’d used an ultrafast-pulse laser (UFPL).

What makes a laser “ultrafast,” and how is it better than the one used by the diabolical gold smuggler? The answer depends on which industry expert you ask. But most would agree that UFPLs are lasers with pulse widths shorter than 10 picoseconds—about the time it takes for light to travel halfway across the “e” at the end of this sentence.

In layman’s terms, ultrafast lasers are to evil- villain lasers what modern CNC machining centers are to drill presses.

Read the rest: http://www.micromanufacturing.com/content/quickening-pulse

Thread Whirling Boosts Productivity

Ever since British machine inventor Henry Maudslay introduced the first modern screw-cutting lathe towards the end of the 18th century, machinists have been cussing him. True, the world as we know it couldn’t exist without screw threads, but that doesn’t make cutting them any easier.

Compared to other turning operations, single-point threading is slow, requiring a number of passes to remove a relatively small amount of material. In addition, those threading tools are prone to chipping and premature failure because of the high cutting pressures involved, and programming must produce a synchronized dance of spindle rotation and movement of the X and Z axes.

When it comes to making orthopedic bone screws, single-point threading is about as difficult as it comes. Their unique thread forms are often much wider than their V-thread cousins, leading to chatter during machining. Length-to-diameter ratios can be up to 10:1 or higher, making deflection and taper a problem. In short, bone screws are a challenge to produce.

Read the rest: http://www.micromanufacturing.com/content/thread-whirling-boosts-productivity

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