GT Metal Products (Edmonton, Alberta, Canada) is a custom metal fabrication job shop that manufactures power distribution panels, grain hopper bottoms and aeration tubes, stair cases, hand rails and steel structures, computer module consoles, and complete communication and electrical cabinets.

The shop has a wide range of capabilities that include CNC forming, plasma and laser cutting, robotic welding, rolling, shearing, punching and drilling, as well as drafting and engineering design. Their extensive fabrication capabilities range from the design, build and delivery of a single custom part to large scale mass production that requires multi-process manufacturing.

GT Metal Products found that, to be competitive in the market, the pressure was on to supply a far higher level of precision cutting than had previously been required. The shop was looking for ways to ensure the proper angularity of cuts and accuracy of parts to customer drawings. They had to maintain required tolerances and make sure parts were straight and smooth, with few customer rejects.

OUT WITH THE OLD PLASMA SYSTEM
In response to customer demand for more precise cutting than could be obtained with their older plasma system, the company replaced the old system with two Mazak STX510 MkII 2.5 kW CO₂ lasers a few years ago. They originally ran two CAM systems to drive the lasers, but experienced problems that made them consider alternative solutions.

“Previously we could only specify one cut condition per thickness, which gave us quality issues,” explains production manager Dustin Sim. “We were also looking to find a faster way to nest parts and reduce material waste. Based on our previous CAM experience and the ability for the software to allow for multiple cut conditions per thickness, we selected JETCAM (Monte Carlo, Monaco) and opted for their High Performance Nesting module from to maximize efficiency and material usage.”

Two licenses of JETCAM Expert were installed in May 2009, one with the High Performance Nesting module. This configuration allowed two programmers to design parts and one machine to be used for generating highly optimized nests. The staff was initially trained, but were then able to learn the system independently due to the additional training material that was provided.

After installation a number of benefits immediately came to light. Programming time was halved as processes took much less time than the previous systems due to many of the processes becoming automated. Once profiling information is applied to each part it is immediately available for each machine, with any updates reflected automatically on any nests.

Nesting time was reduced an astounding 90 percent as users began to simply queue up all parts to be nested for a given material and thickness, and specify an amount of time that the nester can run for (which can be overnight to allow the system to consider the most optimized nesting options) and generate NC code. Machine cycle time also saw a 20 percent improvement due to optimized lead-ins, common line cutting, path optimization and finishing cut sequences all playing a part.

Material utilization improved by 25 percent, not only because of the newly optimized nests, but from the ability to store and re-use remnant sheets efficiently. “We can quickly queue up multiple jobs and nest them together for efficiency,” notes Sim. “When you add up all of the savings from these process gains, we paid for the software system in just two months.”

Support requirements had previously taken up more staff time because one of the older CAM nesting systems took considerably more time than the other one. The company converted their two licenses to a server-based floating setup that allows several PCs to have the software installed and for two to run concurrently. “The JETCAM software is faster and much more flexible than all of the previous systems we’ve used. It excels in material utilization and generating optimized NC code.”

But unfortunately, while the new CO₂ lasers were indeed able to deliver on their high precision claims, their slower cut speeds seriously disrupted production flow and limited business growth. Operating and maintenance costs for the lasers were also higher and the thickness range was affected. The CO₂ lasers reached their limit of effectiveness at thicknesses up to ¾ in, so the plant was faced with the need to turn away customer requests for cutting of over ¾ in mild steel.

In addition, the shop found that the laser tables, which measured 5 ft by 10 ft, resulted in plate size limitations because demand was increasing for cutting 6 ft by 24 ft plate. Since increased cutting time was crucial to its continued growth and success, the company went looking for a cutting solution that would offer the fast cutting speeds and low maintenance costs typically associated with plasma, combined with a cut quality comparable to laser.

Their goal was to find a tool that could handle the backlog that had been building up on the lasers,  ensure parts flow to their seven full-time welders, and provide more quoting and business growth opportunities.

IN WITH HIGH DEFINITION PLASMA CUTTING
The shop owner worked with Pinnacle Industrial Automation Inc. (Mississauga, ON), the OEM that originally sold the company the CO₂ lasers, to find a plasma cutting solution that would offer the necessary productivity improvements along with a cut quality comparable to laser.

The integrated plasma cutting system that was recommended features an ultra-precise table motion capable of providing a near laser quality cut. This system, built by Hypertherm, Inc. (Hanover, NH), expands GT Metal Products’ already extensive offerings beyond the limitations of the lasers and enables greater flexibility in quoting, materials use, and production, with lower operating and maintenance costs.

The plasma cutting system uses a HyPerformance® Plasma HPR130XD® to deliver near laser cut quality with minimized operating and maintenance costs. An EDGE®Pro CNC and ArcGlide THC create Rapid Part technology that significantly improves productivity without operator intervention. It has increased the plasma cut speed up to three times over the CO₂ laser.

The programmer uses ProNest2010 nesting and process optimization software to more easily monitor material usage and minimize scrap. The system applies True Hole™ technology to minimize drilling and secondary operations by automatically delivering bolt-quality holes. “HyPerformance Plasma cuts at lower cost, at higher speeds, with greater quality,” comments Dennis Berreth, the owner of GT Metal Products. “We have gone from cutting at 26 ipm with the lasers to 80 ipm with the plasma, and drilling has been minimized due to this technology.”

The addition of this cutting machine immediately allowed the shop to reduce their operating expenses by eliminating the second shift and returning to the one-shift model that decreased heating and cooling, supervision, and overtime costs.

The nesting software helps their programmer monitor material usage and minimize scrap, giving the shop greater flexibility with quoting projects because they can offer both laser and plasma pricing. “With quotes 30 percent less than laser quotes for the same job, plasma is often better than the job requires, so we are able to give our customers the choice, as well as the option to save money,” explains Berreth.

Reduced maintenance costs have proven to be a benefit as well. “The plasma system is much easier to maintain and requires less than half the time,” notes Berreth. The material range of the HPR130XD has also expanded the services the company offers by allowing them to cut A516 (PVQ 516-70) steel plate, abrasion resistant (AR) steel, and quenched and tempered (QT) steel plate. Any material with scale or rust now automatically goes to the plasma. “We don’t cut a lot of it, but to keep our customers happy we can cut it when we need to, and that is important,” smiles Berreth.

TWO BETTER THAN ONE
Now the company uses both technologies to give customers the full range of thickness with the level of detail needed for the particular project or application. They offer laser cutting for fine features and extra detail on thinner materials used for precision parts with tight tolerances, very thin (less than 10 ga) stainless steel, or for parts with lots of holes that are very close together.

For the larger, thicker or longer pieces, like those for drilling rigs, construction or agricultural installations, the plasma cutting tool is ideal. Since the high definition plasma offers excellent cut accuracy at about 30 percent less cost, some customers who originally requested laser cutting may opt for plasma when they see the results.

Having both technologies in-house avoids the problems frequently associated with subcontracting out jobs. GT Metal Products can control the quality and doesn’t have to deal with labor costs and safety risks of loading, unloading, and inspecting material. Transportation of parts slows down turnaround time, and fuel and shipping costs can mount up. Having both cutting tools in-house removes all of these variables and allows the shop to turn around work more quickly and avoid being at the mercy of a subcontractor’s schedule.

“Our integrated plasma cutting solution delivers increased productivity with up to three times improvement in cut speed over CO₂ lasers,” states Berreth. “We can now offer more cutting time and provide what our customers need at the quality and price they need it.”

GT Metal Products, 5616-103 Street (Gateway Boulevard), Edmonton, Alberta, T6H 2H5 Canada, 780.-434.-8721, Fax: 780-437-5960, sales@gtmetal.com, www.gtmetal.com.

JETCAM International s.a.r.l., “Millenium” 9C, 9 Boulevard Charles III, Monaco, Monte Carlo 98000, +44 (0) 870 760 6469, www.jetcam.com.

Hypertherm, Inc., PO Box 5010, Hanover, NH 03755, (603) 643-3441, Fax: (603) 643-5352, technical.service@hypertherm.com, www.hypertherm.com.

Pinnacle Industrial Automation Inc., 39-5359 Timberlea Boulevard, Mississauga, ON L4W 4N5, 905-212-1096, Fax: 905-212-1097, www.pinnacle-ia.com.

Only solar and wind plants don’t need them. Driven by an unprecedented demand for more efficient energy sources, most providers of heat exchangers are playing catch-up. But in response, several alert fabricators of familiar shell-and-tube heat exchangers have debottlenecked one of the most time consuming and repetitive operations in heat exchanger fabrication: tube sheet grooving.

The result is that the grooves – literally hundreds of them in every heat exchanger – are completed in one half to one third the time, so the finished units can be shipped days or even weeks sooner. “A two-thirds reduction in grooving cycle time can boost the effective capacity of a typical heat exchanger shop by 25 percent,” says Mike Dieken of Ingersoll Cutting Tools (Rockford, IL), whose team developed the milling cutter that enabled such gains.

HEAT EXCHANGER ANATOMY
In a typical shell and tube heat exchanger (see Figure 1) the process fluid flows in one end of the pressure vessel, through the tubes and out the other end, while the coolant circulates around the outside of the tubes between the two sheets. The tube sheets – huge steel discs at either end, riddled with holes to accommodate the tubes – seal off the process fluids from each other.

To forestall any leakage, every hole in the tubesheet must be of precise diameter and include two machined grooves, into which the tubes are “rolled in” or swaged.  “Rolling in”, also covered by industry codes, is preferable to soldering or welding because it facilitates maintenance and tube replacement later on.

DOUBLE GROOVER: 3-TO-1 IMPROVEMENT
The key to the new tubesheet grooving tool is that it machines both grooves in one step. The previous best practice was to mill them one at a time. One early user reports reducing cycle time per hole from 18 seconds to 5 seconds while eliminating all post-deburring. These are the times for grooving a two-inch thick carbon steel tubesheet with ¾ in holes. The user also reported that previously, burrs became a problem as soon as the single tool began to wear even the slightest.

Their previous tool of choice was a solid carbide single slotting cutter. Because of the rising cost of carbide, they tried to get more life out of each tool by gradually increasing the toolpath radius to offset the wear. This is what caused the burring. It became a matter of balancing deburring costs against tool-replacement costs.

“Burring is eliminated with this new double slotter because it uses a more durable carbide grade and also includes a deburring radius on one corner of the cutting edge,” explains Dieken. “Even if you expand the toolpath for wear compensation, the tool itself takes care of the burr.” One Gulf Coast user reports 30 percent longer tool life than before, with no deburring required.

The new grooving tool is essentially a very sophisticated ChipSurfer double form-slotting mill. With basically one orbiting radial plunge action, the cutter simultaneously produces two identical code-compliant grooves. For a ¾ in hole, for example, a 5/8 in milling cutter carves out two 0.125 in flat-bottomed grooves spaced with a 0.250 in gap and 0.030 in maximum depth.

This cutter uses a replaceable solid carbide tip that screws onto a shank, either carbide or alloy steel. Repeatability with tip replacement is 0.0005 in, which eliminates dead cycle time for “touching off” or offsetting after each tip change.

Because of the tight quarters – only 1/8 in of clearance between a 5/8 in tool working in a deep ¾ in ID hole, “doubling up” wasn’t as simple as it may seem. “It is a long-reach operation in a high-aspect hole, which generates chips twice as fast as a single slotter and can double the lateral forces,” states Dieken. In response, he settled on a four-flute design that balances chip evacuation space with chip load per tooth, and a high-positive  presentation geometry to minimize cutting forces.

PRICE CUSHION ON COSTLY CARBIDE
This new replaceable-tip design also helps cushion the rising cost of carbide. “A short tip uses less high-priced tungsten than a long carbide tool,” notes Dieken. “When the tool is worn, you replace the tip only, not the entire tip and shank.” He adds that the 0.0005 in repeatability tip to tip, a recent refinement, simply enhances the value of replaceable-tip tooling in today’s shop environment. One shop cites the tip costing 75 percent less than their solid carbide single tooth end mills, running 30 percent longer and reducing cycle time by more than 60 percent.

For two reasons specific to tubesheet grooving, Dieken recommends a carbide shank, with its extra rigidity, over its lower-cost alloy counterpart. “First, a tubesheet with a hundred holes is definitely a high added-value component. You can’t risk an out of tolerance condition on the hundredth hole and ruin the whole thing – or put it into service and risk a leak. Second, a double cutter doing twice the work will inherently encounter higher lateral forces than a single cutter, so users will benefit from the more rigid carbide shank.”

As a practical matter, most early users are backing off about 30 percent from the recommended MRR, adds Dieken. “But even when they do, they come out ahead, because that reported 3-to-1 productivity improvement at one shop was achieved despite a very large easing off from standard recommendations. With more experience, I have a hunch they’ll ramp it up, but gradually.”

Ingersoll Cutting Tools, 845 S. Lyford Road, Rockford, IL 61108-2749, 815-387-6600, Fax : 815-387-6968, info@ingersoll-imc.com, www.ingersoll-imc.com.

When we sat down to write this article we set out to identify a handful of sawing mistakes – and we came up with almost 60. And for each problem, there are as many as ten causes. Mistakes are common and predictable, but they’re also preventable. With the economy recovering and factories coming back to life, this is no time for slip-ups, so let’s sink our teeth into the top five sawing mistakes that waste material, time and destroy blades.

Saws are very much like the people who use them: they don’t react well to heat, shock, abrasion, stress, and tension. Here are some tips and advice to extend blade life, make better cuts and improve productivity.

(1) FEELING PRESSURE TO PERFORM?
We all feel the need for speed, but your blades can really feel the heat when you run them too hard or fast. Excessive feed rate, pressure and speed can damage or destroy your blades. Running a blade too fast or pushing material too hard can dull blades, break teeth, snap welds or crack the blade’s back edge. Chip welding can also be a problem.

A blade works by removing chips from the material being cut; if the blade runs too hard, heat from friction welds those chips into blade gullets, filling the indented space between blade teeth. When the gullets circle back around, there is no place for the chips to go and that leads to bad cuts, stripped teeth and cracked gullets.

SOLUTION: Know the material you’re cutting and set your machine to the correct blade speed and cut rate. As a general rule, slow the blade for tough material and increase speed for softer material. Check your operator’s manual or the feed rate chart on your machine for specific information. Ask your bandsaw blade sales representative if the company they work for offers free, online educational resources and calculators that can help determine correct cutting procedures.

(2) KEEP YOUR COOL
When a blade overheats its teeth wear faster, material chips weld into blade gullets and this all leads to worn out bandsaw blades and poor cuts. Cutting fluid is a critical part of the operation because it cools the blade, lubricates the teeth and washes away chips. Cutting fluid needs to be mixed with water, and it has its own special formula when you use it for sawing versus grinding and general machining. You’ll need a richer cutting fluid mix when you use it on bandsaws; a rich solution does a better job coating and lubricating the blade throughout the entire cut.

SOLUTION: Coolant should wash over the blade as the bandsaw blade enters and exits the cut. Coolant is recirculated and used continuously throughout the cutting process, but be sure to replace water that evaporates from the mixed solution. You should also be on guard for chips that fly into the system and block coolant flow. Watch for system leaks, which can also be a problem.

(3) GIVE YOUR BLADE THE BRUSHOFF
Most machines have a rotating wire brush that sweeps material chips out of blade gullets while the bandsaw blade is making its cut. These chips could get welded into the gullets if the blade runs too hard, hot or fast. The brush should be positioned close to the drive wheel so it can continually whisk away debris. When we make shop visits, quite often we see poorly adjusted brushes that are set too far from the blade to do any good; the brush tips don’t reach far enough into the gullet. We’ve also seen machines with no brushes at all, which is a big and all-too-common problem.

SOLUTION: The brush needs to be close enough to the blade for the filaments to effectively remove chips from gullets. But don’t set the brush too close to the blade because the hard-hitting filaments could prematurely dull bandsaw teeth. A brush set too close to the blade could also wear itself out and quickly become useless. The brush should reach in and touch, but not go beyond the deepest part of gullets.

Manufacturers today realize that feature location in part design and production is crucial. In order to produce interchangeable parts in a manufacturing environment, care must be taken that the design is sound enough to allow mating parts to work correctly.

Furthermore, the industrial process must be robust enough to produce parts called out in design in an efficient and predictable manner. Likewise, measurement of the final parts must be done easily and with confidence in order to verify the in-process or final products.

For example, inspection of a bore in an open setup often requires multiple measurement steps and mathematical calculations. Portable CMM technology can alleviate much of this work by allowing the user to fix the part in one spot, take several points to create an alignment of X- and Y-axes, and measure the bore. Software is then able to determine the position of the bore and its deviation from the called out position.

Traditionally, to find the deviation from true position (sometimes simply called the position) of a feature, the “open setup” is used. This process involves the use of calipers, height gauges, micrometers, and other hand tools used in conjunction with an inspection plate to take measurements and compare the feature’s position to datums.

Following the appropriate measurements, the true position diametrical deviation, D, must then be calculated via the following mathematical formula (Equation 1): D = 2{(Δx)2 + (Δy)2}1/2 where Δx = the deviation from the true position along the X-axis and Δy = the deviation from the true position along the y-axis.¹

Consider the following situation (shown in Figure 1), which is one of the simplest examples using the open setup method. In order to determine the true position of this hole, the block must be fixed in place. At this point, several measurements must be made, perhaps with a pair of calipers.

First, the diameter of the hole must be determined. To do this properly, several different measurements should be taken in order to verify the diameter and, at least in a qualitative way, the circularity of the hole. (Little can be said of the actual cylindricity of the hole, however. The diameter’s uncertainty combined with the lack of data on cylindricity often means expensive go/no-go gauges must be used as well.)

Next, measurements should be taken of the hole’s closest and farthest points to the x-axis (defined by the datum “L”) and the Y-axis (defined by the datum “N”). In this way the position of the centerline of the hole can be calculated in Cartesian coordinates. This (X,Y) position can then be compared to the position called out in the drawing (1.889,0.947) and the deviation can be calculated according to Equation 1.

This cumbersome procedure representing one of the simplest measurement scenarios can take twenty minutes or more and is subject to relatively large amounts of error due to the difficulty of determining the hole’s closest and farthest points from the X- and Y-axes. The procedure becomes even more complex when MMC conditions are applied or when the geometry of the part deviates from the simple part under consideration.

Now consider the use of a portable CMM that records positions of a probe via encoders and translates these positions into a coordinate system useful to the user. First, the user clamps the part in place using simple tools such as toe clamps. Then the operator takes several data points along datum “L” by merely using the device’s probe to touch the points in question and pushing a green button each time contact is made to record the data.

When all of the appropriate points are taken, the user pulls away from the part and touches the red button to terminate the measurement process. The software then best fits the line and allows the user to define the resulting line as datum “L”. The process is then repeated for datum “N” and the hole (cylinder). The user then inputs the nominal values for the cylinder, tells the software to dimension the position of the cylinder, and the result is returned (including cylindricity).

The entire process, including setup, is less than five minutes in most cases.

The advent of portable CMM technology has greatly reduced the difficulty of measuring GD&T properties, including the deviation from true position of features. The combination of hardware and software allows the user to take points easily and quickly and the software uses best fit algorithms to give the user accurate, virtually instantaneous, results.

The portable CMM also eliminates other issues associated with the traditional open setup method such as the need for go/no-go gages and a lack of three dimensional form results. This technology provides manufacturers accurate and convenient measurements where deviations from true position can be found and corrected quickly.

References
1. James D. Meadows, Geometric Dimensioning and Tolerancing: Applications and Techniques for Use (CRC Press, LLC, 1995), p. 441.
2. Robert A. Ochs: Positional Tolerancing Presentation, http://www.isixsigma.com/offsite.asp?A=Fr&Url=http://faculty-staff.ou.edu/O/Robert.A.Ochs-1/Notes/PositionalTolerancingPres.ppt.

FARO Technologies Inc., 250 Technology Park, Lake Mary, FL 32746, (407) 562-5036, Fax: (407) 333-9911,  www.faro.com.

Connecticut Spring and Stamping (CSS; Farmington, CT) manufactures springs, metal stampings and assemblies from both wire and sheet metal. After winding, bending, stamping, and grinding operations, many of the products must be cleaned and degreased before a final finish is applied.

By the mid-1990s, parts degreasing operations had become a financial and environmental burden on CSS. The 1960s-era vapor degreasers necessitated the purchase of huge quantities of expensive virgin tetrachloroethylene (perc), new regulations tightened permissible air emissions and made waste perc disposal much more costly, and concerns about the health implications of worker’s exposure to perc meant reducing emissions or installing a venting system.

Facing tightening air emission regulations, CSS made a serious effort to find alternatives, eventually deciding to purchase two state-of-the-art Pero Model 2501A batch vacuum degreasers with an in-line still to recover valuable perc from the unit’s waste. The new units’ improved design halved virgin perc purchases and cut perc vapor emissions by 70 percent. The fully-contained unit discharges no water, producing only a very small chemical residue that is processed in accordance with hazardous waste disposal regulations.

The new turnkey system allowed CSS to change its hazardous waste generator status from large quantity generator to small quantity generator, which came with very welcome reductions in overhead and regulatory requirements. Reduced tetrachloroethylene purchases netted savings of nearly $40,000 a year and hazardous waste disposal costs were reduced by $7,500. In addition, CSS virtually eliminated air emissions from the prior system. Finally, dramatically reduced odors removed the need for personal protective equipment or an exhaust system.

The results of the new system far exceeded their expectations and are seen by Chuck Thomas, the company’s vice president of operations and environmental officer, as the single most significant factor that shifted the factory’s thinking and set it on its current path of going above and beyond requirements to doing what is best from an environmental point of view.

“We knew our old equipment needed to be replaced and we had a variety of lower cost options, but we decided to go for this top of the line system for the sake of our employees, the environment, and to set us up for improved manufacturing processes to keep up with the times,” notes Thomas. “The results opened up our eyes to the extended benefits of environmental compliance.”

In a final testament to the importance of the achievement, the Connecticut Department of Environmental Protection wrote a Pollution Prevention Study about the system in 1998, making CSS a veritable poster child for investing in environmental excellence.

After gaining success with its foray into cutting edge environmental equipment, CSS has now moved to a situation where it goes over and above every existing state requirement, actively looking for an environmentally preferable alternative for every chemical or substance used in the plant. It has been cited in numerous customer audits as well ahead of other similar vendors in environmental compliance.

The need for the “elevator speech” seems obvious since hordes of salespeople fumble and stumble when asked what they do. Even though they may have adequate knowledge of what they sell and the company they represent, they’re unable to verbalize the message clearly and succinctly. As someone said, “If you don’t have an elevator speech, people won’t know what you really do.” It’s no wonder that sales managers make it a top priority to motivate their people to prepare and practice mini-messages.

If all this is true, then why knock it? Why challenge something that’s needed and useful to a salesperson? To put it bluntly, an “elevator speech” is damaging because it’s a one-way, robotic “conversation” that defeats sales. It “tells” but doesn’t “sell.”

To better understand the “elevator speech” problem, consider one of the most common complaints of sales managers: salespeople talk too much. Silence seems to drive them crazy, so they fill “the empty space” with a constant flow of patter about anything and everything. But there’s more to the story. Customers also complain that salespeople turn them off by talking constantly and failing to listen. All of this becomes a vicious circle: they’re poor listeners because they won’t shut up. On and on they go babbling about their product, service and the company they represent and don’t stop long enough for customers to ask questions.

“Many salespeople feel compelled to recite their canned pitch regardless of the customer’s actual interest,” comments Steve W. Martin of USC’s Marshall School of Business. In other words, they spin their spiel rather than interacting with customers and prospects.

Of course many salespeople talk too much –– and it’s always about themselves and their company. That’s what they know. It’s drilled into them day-after-day. And they simply regurgitate the words because that’s what they’re told to do. So why should anyone expect them to change or do otherwise?

Salespeople go to lead generation groups, stand up and talk about themselves. No one listens, particularly when they’ve heard the same words week-after-week. In such situations, salespeople should be asking themselves this question: “Why should the people sitting round the table recommend me?” But they don’t because they’ve been taught to mouth an “elevator speech.”

They show up at networking meetings and say (a dozen times over), “Hi, I’m Susan from Gotcha International and . . .” Susan is doing what she has been told to do and she leaves with a handful of business cards. Back at the office, she tells her boss that it was a good day for Gotcha.

When making cold calls, salespeople invariably start out by saying, “Hi, I’m Roscoe and my company . . .” Whether it’s in person, on the phone or in emails, it’s time to slam the door, hang up or hit delete. It’s time salespeople got the Special Memo: no one cares who you are or what you’re selling.

There are 11,000 companies that currently compete in the $85 billion medical manufacturing market in the U.S.¹ Without exception, every one of them demands more reliable, faster and more cost effective manufacturing solutions to stay competitive in the tightening global marketplace, and they are all looking to advanced technology to meet their needs.

For example, there is heavy demand for the precision cutting of thin metal tubular structures used in instruments such as rigid endoscopic and arthroscopic devices, biopsy tools, needles and cannulas. The most common materials used in these and other surgical and implantable medical devices are stainless steel, cobalt chrome alloys, nickel alloys, titanium and Nitinol. In the dental sector, there is heavy demand for high-precision bridges, crowns and implants that also use titanium as well as prosthetics materials such as chromium cobalt, zirconia, ceramic, and plastic.

Several methods have been developed within the industry to cut these exotic materials, including laser, EDM, waterjet, chemical machining, milling and grinding. This series takes a closer look at the latest developments in two of these technologies: fine laser cutting and micro-milling.

FINE LASER CUTTING
New laser technology offers the surgical precision needed for medical tools.

Geoff Shannon, Miyachi Unitek Corporation

Over the past 20 years, laser cutting has been used in an increasing number of manufacturing applications in the medical, automotive, electronics, aerospace and other industries. Many of the pioneer laser cutting applications were performed with high power carbon dioxide (CO2) gas lasers, but CO2 was eventually found to be unsuitable for fine laser cutting due to lack of heat input control and focus spot size.

As a result, solid state lasers emitting a shorter wavelength – typically near one micron – emerged as the best choice for precision cutting applications and, over time, became the preferred choice for many thin wall metal tube cutting or machining applications, particularly when superior edge quality, tight dimensional tolerances and/or high volume production is required.

Now conventional solid state lasers are being replaced by fiber lasers that offer a reliable, stable energy source, have exceptional beam quality, high repetition rates and are easy to integrate into production manufacturing machines. In fact, fiber laser cutting is most effectively used in the “surgical precision” cutting of thin wall metal tube materials, such as those used in endoscopic and arthroscopic medical instruments.

The term “surgical precision” aptly applies to the need for clean sharp edges, contours, and patterns found in the tools and devices being introduced into this burgeoning field. From surgical instruments used in cutting and biopsy, to needles containing unusual tips and side wall openings, to puzzle chain linkages for flexible endoscopes, fine laser cutting provides higher precision, quality, and speed than traditional cutting techniques.

Integrated fine laser cutting technologies are advancing quickly into the market, including 5-axis motion packages that give the designer freedom to cut more challenging geometries in one pass. This advanced machine configuration integrates a more powerful fiber laser with increased speed and material thickness capability into a turnkey system with multi-axis motion capabilities that gives the medical device designer the freedom to create more challenging geometries with superior “as cut” edge quality.

Integrated fine laser cutting is ideal for the specialized cutting requirements found in medical tube tools and components. The key to successfully using this technology is properly integrating the system’s components into a process flow that works. The motion, laser, software, and tooling must all work together to get the desired end product.

The Small of It All
Fine laser cutting is ideal for working on small tubes that must be cut to high dimensional accuracy because the laser light used does not have any physical presence and makes no contact with the material. It does not push, drag, or impart force that might bend a part or cause flex that would have a negative impact on process control. Laser light also offers minimal thermal input, with fine control over how hot the work area gets. This is important since small parts heat up quickly and might otherwise overheat or deform.

Fine laser cutting is highly focusable to about 25 microns, or about one-quarter of the width of a strand of human hair. This makes it feasible to remove the minimum amount of material to make the cut, resulting in extremely high precision and high accuracy. This laser cutting technology uses an extremely fine control of pulse width, power, and focus spot size. Because the laser cutting tool does not rely on touching the part, it can be oriented to make any shape or form. Not limited by physical cutting geometry, laser cutting can be used to make unique shapes. Table 1 lists the technology’s key benefits.

How It Works
The technology most frequently used to make medical tubes and components is fiber laser cutting with gas assist, which means the laser is “assisted” with a coaxial gas, typically oxygen (O2). While O2 is usually the gas of choice, occasionally shop air can be used after oil filtering, usually when the tube thickness is less than 0.010 in or when the cut quality required is not very high.

This gas assist is used for stainless steels (300 and 400 series, 17-4, 17-7), MP35N (cobalt-chrome steel alloy) and Nitinol. The method can also be used for both on-axis (90 deg to surface) and off-axis (angled to surface) cutting.

In this process, a highly focused laser is used to melt a thin sliver of material. While the material is still molten, a 0.020 in diameter gas jet nozzle that is coaxial with the laser blows away the molten material. The desired features are produced using this continual cycle of melt, then melt ejection. The distance between the laser and the material must be maintained precisely.

The O2 serves two purposes: (1) it blows away the molten material and (2) serves as a heating element, because the heated material reacts with it and heats up. The heat reaction caused by the presence of O2 adds about 30 percent to 50 percent more heating energy to the cutting area. The gas assist is a key factor in increasing cut speed and cut quality. Figure 1 illustrates a basic fiber laser cutter with gas assist. Figure 2 shows a close-up of an actual laser cutter at the work piece.

Fine laser cutting with gas assist produces the highest cut quality and high resolution cut paths, a key objective of the makers of medical tube tools and components. Dimensional accuracy is paramount to measuring cut quality – does the part match the print? Other considerations include surface roughness (better than 12 micro inches) and the absence of thermal damage.

Cut width can be extremely small with laser cutting, less than 0.001 in, and dimensional accuracy is extremely precise, at about ±0.0005 in. This accuracy is very useful for producing the jagged teeth used in some cutting tools. Dross or burr left on the underside of the cut (which can become attached and re-solidified) is minimized or eliminated to significantly reduce the amount of post-processing needed.

The recast level layer (a small amount of material that doesn’t get blown away during the process) is less than 0.0005 in. Figure 3 illustrates the typical cut quality with no post processing of features and edges when cutting 0.010 in thick stainless steel (304SS) tubing, showing the excellent quality of laser cut faces.

How It Compares
Fine laser cutting speed and precision compares favorably with that of its chief competitive technology, electro discharge machining (EDM). To obtain the same high quality cut as a laser cutting machine, EDM requires up to four passes, which slows down processes considerably. But on the plus side, EDM allows multiple parts to be processed all at once.

The width of cuts produced by a fine laser cutter is as small as 0.001 in, while that of EDM is around 0.004 in. Feature sizes are limited with EDM and sharpness is not as good, compromising cut resolution. The EDM process is also limited by the fact that it works best with certain geometries, such as tubes with a symmetrical profile. Problems arise if there is a hole in a tube that does not go through both sides. In other words, EDM is like the ubiquitous cheese cutter that uses a wire to slice through a block of cheese. All is well with a symmetrical, solid shape, but the wire cannot handle any complex geometries.

A final issue is floor space, especially for factories where space is at a premium. A typical EDM machine can be as large as 10 sq ft to 12 sq ft, while a fine laser cutting system is only five sq ft to six sq ft.

Another competing technology is electro chemical grinding (ECM), which removes electrically conductive material by grinding with a negatively charged abrasive grinding wheel, an electrolyte fluid, and a positively charged work piece. ECM is a fast cutting method that gets quality similar to EDM. With ECM, the electrolyte being used must be disposed in accordance with OSHA as hazardous waste, and some electrolytes produce hexavalent chrome when cutting steels. Finally, this sort of use of hard tooling makes it much less flexible than laser cutting.

A third competitor is waterjet cutting, which slices into the metal using a jet of water at high velocity and pressure, or a mixture of water and an abrasive substance. Waterjet cutters offer restricted cut geometry. Only symmetrical through-features or end cuts are possible using this technology. Figure 4 compares the cut quality of EDM and laser. Note the smooth sharp edges in the cut made by the fiber laser equipment.

Whole Integration
The explosion of new non-invasive surgery tools has introduced some unique and innovative shapes. This, in turn, requires motion packages that offer a new level of cutting geometry. The ability to keep a part in a machine and make intricate cuts gives designers the objective of cutting more challenging geometries in one pass.

This objective is accomplished in 5-axis laser cutting systems that use control software to command the laser and the motion together. The integration of these two functions provides a rigid structure, free from vibration. The 5-axis motion consists of 3 linear axes and 2 rotary axes in a unique set-up that allows system engineers great flexibility to choose the best axis configuration for a particular cut because they are no longer limited to where they are on the part.

Engineers can mix and match and set combinations to create a more efficient process. For example, designers might place four axes on the part and one on the focus head, or switch them around according to the best solution for the application. This is significant, because even though fine laser cutting for medical tube tools and components has many benefits, actually achieving them depends in no small part on successful system integration. The entire system must integrate the motion, laser, software, and tooling into a whole that works properly and supports the desired process flow. Putting these pieces together can be a challenge.

That challenge is exacerbated by the fact that many integrators do not have a good understanding of the laser cutting tool, which may tempt them to rely on the manufacturer of the laser cutter to integrate the system. Then, when or if there is a problem with the laser or if changes are needed to adjust to a new product, the integrator is in no position to fix the system.

To prevent this problem, users should assess the in-house laser cutting capabilities and knowledge of the cutting process of the integrator that is being considered. Though the integrator may not be a cutting laser manufacturer, they do purchase the laser from an OEM and should integrate it into a complete system with motion, software and tooling.

Any integrator that can add fine laser cutting to other related capabilities, such as laser welding and marking/engraving, should be able to provide designers with a one-stop shop for system integration, including running samples of the entire process in-house to ensure that it does the entire job as specified, and answering in-depth application questions.

References
1. Society of Manufacturing Engineers market research data, Dearborn, MI, January 2012.

Geoff Shannon is the laser technology manager for Miyachi Unitek Corporation, 1820 South Myrtle Avenue, Monrovia, CA 91016, 626-303-5676, info@muc.miyachi.com, www.miyachiunitek.com.

THE NECESSARY “BITE” FOR DENTAL MILLING TOOLS
Micro-milling takes center stage in the surgical machining of dental parts.

Bridges, crowns, implants and other dental parts are complex high-precision components with rigid quality demands in medical manufacturing. To meet these tight specifications, successful dental laboratories are turning to micro-milling technology from machine tool distributors such as ARO-tec GmbH (Rheda-Wiedenbrück, Germany) that combines a high-speed machining process with advanced interior tool clamping techniques.

ARO-tec, a German distribution and service partner of Haas Automation (Oxnard, CA), has combined Haas machinery with an innovative Swiss toolholder from Rego-Fix (Tenniken, Switzerland) to develop customized “dental packages” based around the micro-milling capabilities of the combined system.

For example, OM2A Dental micro-milling machines from Haas Automation perform extremely precise and economical machining of dental components made from ceramic, plastic and metal. They accomplish complex chipping tasks used in mass production or the quick turnaround of prototypes of small, high-precision 2D or 3D medical parts by expanding from a standard three-axis structure up to five axes using a rotary table or rotary/swiveling table, thereby allowing five-axis simultaneous machining.

ARO-tec combines this 5-axis multitasking capability with a special ISO 20 ERM toolholder from Rego-Fix that ensures a required precision run-out with 100 percent dimensional accuracy, even with small tool diameters, a function that is crucial in elevating the productivity of the multitasking equipment. “A tool can provide absolute machining precision, with top surface quality in high-speed machining, but only if it is optimally clamped and can positively impact the entire system with its precise run-out,” explains Oliver Stabenow, a sales engineer at ARO-tec.

Rego-Fix developed the ISO 20 ERM toolholder system specifically for Haas Office Mill machining centers such as those used in medical manufacturing. “The system is 100 percent precision balanced at 40,000 min^-1 in 2.5G. Combined with a high rigidity and very good run-out with figures of under 3 µm, this innovative tool clamping system ensures the best processing results,” explains Martin Brönnimann, the head of product development at Rego-Fix.

This system is perfectly demonstrated when machining dental implants with the filigree milling of chrome cobalt. A 1 mm ball cutter is used at 30,000 rpm, with feed rates of up to 2,000 mm/min. Despite the hard load, the mini-milling tool must show a high level of run-out precision in view of the extremely close tolerances specified. This is the only way to provide the necessary surface quality.

Quiet and vibration-free running also significantly increases the service life of the tools. The same holds true of the process when machining other difficult materials that are commonly used in dental technology, such as titanium and zirconium. In all cases, the dental implants have a perfect precision surface quality, which means expensive and time-consuming manual reworking is not necessary.

“Using the OM2A Dental with the ISO 20 ERM toolholder, dental technicians can overcome these special challenges quickly and economically,” notes Stabenow. “Productivity increases significantly through the precise run-out. The ease of use and the quality of the milling results, even with materials that are difficult to machine, such as plastic, zircon and metal alloys, speak for themselves. Manual reworking is no longer necessary. On balance, it is no surprise that customer satisfaction is very high and that demand for our dental packages is rising steadily.”

The original source of this article was Meditec INTERNATIONAL, www.meditec-international.com.

ARO-tec GmbH, Siemensstr. 12, 33342 Rheda-Wiedenbrück, Germany, +49 (5242) 9649-0, Fax: +49 (5242) 9649-19, www.aro-tec.org.

Haas Automation, Inc., 2800 Sturgis Road, Oxnard, CA 93030, 805-278-1800, Fax: 805-278-2255, www.haascnc.com.

Rego-Fix AG, Obermattweg 60, CH-4456 Tenniken, Switzerland, +41 61/976-1466, Fax: +41 61/976-1414, rego-fix@rego-fix.ch, www.rego-fix.ch.

The goal of every fabricator is to maximize productivity in order to generate as much revenue as possible. You want to get the job done quickly, accurately and inexpensively. Using auto racing as an analogy, we might say that the fastest machine on the shop floor wins. Correct?

Well, theoretically, yes. However, let me raise the yellow flag because there is a caveat to share – and it’s an important one: It is not just speed that makes the sport. And it is not only speed that wins on the shop floor. In auto racing, there are other factors, such as setup, where adjustments have to be made to the vehicle’s suspension, brakes and transmission.

Also, the time it takes to service/pit stop the car with regard to new tires, air pressure, and minor adjustments contributes to success. And when you’re on the racetrack, you may find that you need to actually slow down in order to negotiate obstacles faster. These same principles hold true for sheet metal processing, and fabricators need to recognize that factors in addition to laser power and speed contribute to productivity.

Some other aspects to help increase your productivity include (1) finding ways to reduce non-productive times, such as set-up times, and (2) reducing down times by improving reliability of the machine process. In this column, we’ll focus on ways to expand your productivity by increasing speed and improving process reliability. And to that end, here are some basic, and maybe not-so-basic, tenets for sheet metal fabricators to consider:

INCREASING YOUR SPEED
When processed with nitrogen as an assist gas, stainless steel and aluminum, as well as heavy plate, will see an increase in power. Light gauge steels also benefit from this increase in power by using nitrogen as an assist gas instead of oxygen. The use of oxygen as an assist in light gauge material limits the amount of power that can be applied to the material. The oxygen will actually do 70 percent of the work. This limits the cutting speed independent of the maximum laser power of the machine.

The use of nitrogen allows the laser to use the full power of the machine as this process is based on the laser power doing the majority of the work. An increase in power can lead into 50 percent to 60 percent increases in cutting speeds.

In addition to the speed, the use of nitrogen will provide a superior cut quality to oxygen and ensure proper weld surfaces and paint adhesion—and it will also eliminate secondary operations. The drawback, however, will be in gas consumption. Using nitrogen as an assist gas will result in 10 to 15 times the consumption rate of gas to oxygen. While there is an increase in cost due to the greater consumption, nitrogen should still be strongly considered. The higher processing speeds will produce more parts per hour at a higher quality with no secondary operations required.

A lower cost solution would be to consider the use of compressed air as an assist gas. Compressed air is comprised of approximately 80 percent nitrogen and 20 percent oxygen. This gas allows the operator to use the full power of the machine and have the added boost of the burning process of the oxygen. This can result in a 60 percent to 70 percent increase in processing speed, but the drawback would be in a maximum thickness of 14 gauge material and the possible requirement of secondary operations depending on the application.

IMPROVING PROCESS RELIABILITY
Another parameter to consider for increasing productivity in laser cutting is process reliability. This involves employing sound techniques when choosing your material and doing programming.

The first consideration related to process reliability that I would like to discuss is the piercing method. The two most common methods are a peck or slow pierce, and the second is a blast pierce. Each of these methods has their benefits. The blast style pierce is a more violent style of pierce. It will provide the quickest overall process time, but it will produce a larger hole.

The peck pierce is a controlled pierce, which, in general, will take more time than a blast pierce but will produce a much smaller pierce hole. The peck pierce will, in most cases, be the desired method of producing holes equal to or less than material thickness in steels 5/8 in thick and less. In thicker material the key is to create a small pierce hole quickly, as a peck style pierce can take more time as well as potentially apply more heat to the area. This additional heat can at times affect the consistency of the quality of the hole.

If smaller holes are required, an effective method would be the use of a pre-pierce. In this process a blast style pierce would be used along with a smaller nozzle orifice in order to create a pierce hole smaller than the desired hole. The entire sheet would be pierced and then the nozzle would be changed back to the proper size for cutting. This method would add some additional time but it will ensure a very consistent process.

MATERIAL QUALITY
In addition to piercing, material quality plays a role, especially if the material has a layer of scale on the surface. This scale will have a significant impact on the cutting quality and consistency, as during the cutting process this scale will affect the flow of assist gas to the cut, resulting in poor cut quality. In this circumstance the scale could be removed prior to the material being placed on the machine, and a light film of oil applied to the surface or the part geometry can be etched on the surface of the material to remove the scale. Afterward, the part can be cut normally. This will generally eliminate the issues of poor or inconsistent quality.

A second consideration should be a stress relieved material. In some cases a material with an abundance of stress can actually bow from the thermal process and collide with the cutting head, causing an interruption in the production process.

PROGRAMMING
A further consideration should be in programming. Many programming systems can provide an effective nest utilizing the best material usage and providing the least amount of scrap. But this is only the first step in the process. The system should also utilize proper tool paths that avoid possible collisions and allow the laser head to stay close to the material to ensure the most effective processing time and reliable process.

Also, the use of scrap cuts, particularly in heavy plate cutting, allow for the removal of the parts and the skeleton by an operator in a non-automated system done quickly and effectively. This is especially important in thicker material.

At the end of the day, a solid understanding of your laser machine’s capabilities, as well as having processes in place that employ reliable practices, may initially appear to slow the overall process of laser cutting. But just the opposite is true. In fact, taking the time to fine tune your processes will actually result in greater productivity.

The job that safety professionals will be doing ten years from now probably doesn’t even exist today. This, understandably, creates a quandary for educators and employers alike. The field of safety has drifted away from its roots in enforcement in interesting, exciting and creative ways. How can students prepare for the careers of the future? By studying some disciplines that may not be part of their present core curricula.

A SECOND (OR THIRD) LANGUAGE
Safety professionals are increasingly expected to work in a global workplace and it would seem logical that the individual not just be conversant, but fluent in the language of the people with whom he or she is charged with protecting. It’s tempting to pick a language based on today’s trends (say Spanish in the U.S., or Cantonese) but today’s savvy student will look at the languages spoken in emerging economies and consider mastering one or more of these languages.

STATISTICS
Disciplines such as six sigma, lean, and Quality Operating System (QOS) lie in statistics, and a working knowledge of this branch of mathematics is an important foundation on which these methodologies are built. But beyond that, a deep understanding of statistics is always crucial to the safety professional because statistics is the language of safety. In the U.S. safety is characterized in terms of statistical calculations, which means safety professionals who don’t understand statistics are incapable of understanding what these figures tell them about their organizations’ performance.

A keen understanding of statistics can also allow safety professionals to identify areas where the organization is at greatest risk of injury, pinpoint the most dangerous jobs and the most dangerous activities, and even determine the demographics that are most at risk. With such knowledge, safety professionals can outline how substantial changes will affect the way the operation functions and considerably improve its workplace safety. If safety is an estimation of the probability of an individual being injured, then a mastery level knowledge of probability, and by association statistics, is substantial.

PROJECT MANAGEMENT
A crucial skill that is rarely taught in academic settings – but that is nearly universally expected by employers – is project management. Project management is actually a collection of skills that is essential to safety. One such skill is planning; solid planning is vital in safety. Project planning can help safety professionals to reduce waste and free up valuable time and resources. From scoping a project to resource leveling, safety professionals need a complete understanding of planning skills.

Another useful project management skill is budgeting. Even a safety professional who doesn’t aspire to a management position should be able to prepare and interpret a budget. Such knowledge will better equip the safety professional to better align the safety function with the strategies of Operations.

Perhaps the most important project management skill is the ability to effectively manage meetings. This seldom taught but frequently expected safety skill can make the difference between the success and failure of the function. Probably the biggest drain on the safety professional’s day is the disproportionately huge amount of time wasted in unproductive meetings. In addition to studying the traditional skills associated with effective meetings, students should learn how to determine when a meeting is actually needed.

Commercial light-water nuclear reactors built in the U.S. are required by Title 10 Code of Federal Regulations Part 50 (10CFR50) to be designed to incorporate fracture toughness considerations. Presented in Appendix G of 10CFR50, the concept of a reference nil-ductility temperature (RTNDT) was created roughly three decades ago to ensure that a minimum level of toughness is present in a ferritic steel and weld metal, especially after being irradiated.

The ASME Boiler and Pressure Vessel Code, Section III, outlines the determination of RTNDT at a temperature above the ductile to brittle transition temperature, as formulated through the use of the nil-ductility transition temperature (NDTT) and Charpy V-notch (CVN) toughness tests.

In order to begin a discussion of the determination of the RTNDT, it is necessary to discuss just exactly what the NDTT is and the manner in which it is established. The NDTT is defined as the temperature above which a steel will fracture in a ductile mode and exhibit plastic deformation at nominal stresses beyond its yield strength. Below this temperature, the steel will fail in a brittle fashion when loaded to its yield strength.

A value for the NDTT in ferritic steel at least 5/8 in thick is generated through the ASTM E208 drop-weight test. This test was developed in the early 1950s by the U.S. Naval Research Laboratory and was used to examine the conditions that lead to brittle fractures in structural steels. Since then, the drop-weight test has become commonplace in the testing of ferritic steel and weld metal used in several types of components in nuclear reactor pressure vessels.

For those readers who are not familiar with the drop-weight test, a brief summary will now be provided. The test is conducted upon a steel specimen (more like a block) fabricated from the material to be used in service. As shown in Figure 1, a 1in thick test specimen is to be 14 in long by 3.5 in wide, and a one-pass crack starter weld a few inches in length is deposited on one side. If it is weld metal for which the NDTT is to be ascertained, the starter weld is oriented perpendicular to the direction of the weld joint. Into this weld is machined a groove, and the bottom surface of the groove is 0.07 in to 0.08 in above the surface of the block of material being tested.

Now the “cracked” side of the block is placed face down on top of an “anvil” that supports the end of the specimen in place. Also included as part of the anvil assembly is a “stop” that limits the deflection of the specimen.

And finally, as the name of the test implies, a guided, free-falling weight is dropped onto the side of the block opposite from the crack starter weld from a predetermined height. The weight striking the surface possesses a cylindrical shape, and can vary from 50 lb to 300 lb (and is selected based upon the yield strength of the material being tested). The mass of the weight and the distance of the drop used produce an impact energy, which is selected based upon the yield strength of the material.

The qualitative nature of the crack resulting from the drop-weight test is the criterion that provides an estimate of the NDTT. For example, in order for a sample to be deemed as showing a “break” condition, the crack produced from the test generally must touch at least one edge of the specimen. If it does not, the test may be considered exhibiting a “no-break” condition.

The selection of the temperature at which the drop-weight test must be conducted can appropriately be described as a trial-and-error process. As one would expect, a testing operator would naturally want to conduct the test in as few tests as possible – ideally in as few as three tests. A NDTT would be confirmed when one specimen at a lower temperature would exhibit a “break” condition, while two tests at the same temperature above the first would both show “no-break” result. Upon achievement of two no-breaks at this higher testing temperature, an estimate of the nil-ductility transition temperature defined as TNDT has now been attained.

On several occasions, we have received a considerable number of requests from nuclear constructors to utilize a TNDT acquired in the drop-weight test in the “determination” of an RTNDT for our filler metals. To make this connection between TNDT and RTNDT, a set of three CVN tests are conducted at a temperature of TNDT + 60 deg F. If, at this temperature, the average impact toughness obtained from three CVN breaks is greater than 50 ft-lb and the average lateral expansion is greater than 35 mils (.035 in, not to be confused with 35 mm), then the RTNDT is determined to be equal to or greater than the TNDT.