Shop Solutions: Attacking Reaming's Hidden Costs
Though reaming may represent just a tiny slice of total machining cycle time on a part, you may be surprised at how much time is wasted servicing that reamer.
Dave Roberts, process engineer at Kirby Risk Precision Machining (KRPM; Lafayette, IN), discovered just how much and, more important, a way to cut reaming cycle time on a 8 lb (3.6-kg) cast-iron housing by a factor of 7 to 1, extend tool life by 100 to 1, and reduce toolchanging time from an hour to just 2 min.
"Most important, we improved the capacity of the entire machine, because we no longer need to stop a 20-step CNC process for an hour each time a reamer needs servicing," Roberts says. "And it costs us nothing. The money we spend on the new tool comes from not spending it on the old one."
KRPM is a 96-man contract-machining company that runs 16/5, specializing in machining housings and attachments for off-road diesel equipment. Their 21-machine inventory includes CNC lathes, mills, and five-axis machines. The part that triggered the retooling has an annual volume of 5000 pieces, which KRPM typically runs in 200-piece lots every two weeks.
The changeover was made in August 2008, when an order increase for the castings sent him and his Black Belt Process Improvement Team looking for added capacity without any outlays for additional machinery. They quickly zeroed in on the bottleneck reamed hole, which measures 0.998" (25.3 mm) in diam and 1.85" (47 mm) deep.
The switch was from a conventional indexable reamer to a Qwik-Ream replaceable-tip reamer in a Qwik Adjust collet chuck from Ingersoll Cutting Tools (Rockford, IL).
They were reaming the hole with an adjustable-blade tool at 150 fpm/0.003 ipr, giving a 54-sec cycle time. It's part of a milling, drilling, and reaming sequence of operations that KRPM runs on a Mazak.
"We just looked at the problem differently," says Denny Matson, process engineer. "It wasn't the chipmaking cycle time itself that was holding us back, rather the tool-servicing time and the baggage associated with it. With all the adjustments needed to keep an adjustable-blade reamer running within tolerance, we were losing an hour of machine time and a couple of trial parts every one hundred pieces."
Roberts asked Brad Wolf of GL Technologies, one of their tool distributors, for ideas. He suggested testing the Ingersoll Qwik-Ream and adding Tim Prickett, Ingersoll field engineer, to the Black Belt team.
"The operation was more challenging than typical reaming for a couple of reasons," says Wolf. "For one thing, the hole has a 2:1 aspect ratio with an interrupted cut at the bottom. For another, tolerance requirements remain at 0.0005" [0.013 mm]/125 rms all the way right through the interrupted-cut region. Fine finishes and interrupted cuts don't mix well. The interruptions can set up vibrations and impact loads that can cause chatter."
Because of the interrupted-cut aspect, Prickett and Craig Bastian, Ingersoll product manager, suggested an Ingersoll Qwik Adjust collet chuck, which allows any spindle misalignment to be corrected. The two-piece collet chuck features axial and radial adjusting screws. When clamped in the spindle and used with a dial indicator, the Qwik Adjust holder can reconcile spindle-to-workpiece alignment.
The biggest difference between the two tools is that the Qwik-Ream is a replaceable-tip tool. Prickett explains: "At toolchange time, you simply twist out a single worn tip and twist in a new one without upsetting any datum references. Repeatability is within 0.0002" (0.061 mm) on diameter and datum references, eliminating the time spent on adjustments and scrapping of trial parts."
The net result for KRPM was gaining nearly an hour of machine capacity every one hundred parts.
The trial was run right on the production floor. Prickett and Wolf tried various settings, finally settling in on 300 fpm/0.040 ipr. This yielded a cycle time of just 8 sec—which was 14 times faster than before.
The news got better the longer the trial continued. While the original reamer needed blade adjustment or replacement every 100 pieces, the first tip on Qwik-Ream kept going until they called off the trial at 1000 pieces. On the thousandth piece, surface finish checked out at a very smooth 35 rms. With the previous cutter, by contrast, surface finish—often the trigger for stopping the operation—deteriorated to around 125 rms after 100 hits.
Roberts quickly standardized on the Qwik-Ream, using the same machining parameters as in the test. Its original tip lasted through 2000 hits, with tip replacement taking just 2 min while the reamer was lying idle in the tool magazine. "Servicing the Qwik-Ream takes zero machine downtime, because we do it off-line and very little labor time is required for the tip change itself. The biggest part of the 2-min tip change cycle goes to walking around the machine to access the tool magazine," Roberts says.
Greg McGowen, owner of GL Technologies, brings a different take to the retooling. "Recommending a tool that lasts 200 times longer certainly cuts into our resale business in this particular case. But we must always recommend what's best for the customer, or they'll find someone who will."
For more information on Ingersoll Cutting Tools, go to www.ingersoll-imc.com or phone 815.387.6600.
Robotics Prototyping Comes In-House
CAM software has been instrumental in bringing prototype robotics part manufacturing in-house on a solid business basis at a major engineering center.
In 2008, the National Robotics Engineering Center (NREC) decided that it would be useful to have its own prototype-part manufacturing capabilities to reduce leadtimes and establish greater control of manufacturing processes for critical parts.
The NREC is an operating unit within Carnegie Mellon University's Robotics Institute (RI), the world's largest robotics research and development organization. The NREC frequently adapts and refines technology developed at the Robotics Institute for industrial or government use.
A typical NREC project includes a rapid proof-of-concept demonstration, followed by an in-depth development and testing phase that produces a robust prototype with intellectual property for licensing and commercialization. Throughout the process, NREC applies best practices for software development, system integration, and field testing.
To get the shop up and running, Eric Meyhofer, senior NREC commercialization specialist, found 3000 ft2 (279 m2) of nearby manufacturing space, recruited a shop manager and welder, and purchased some CNC equipment.
The manager selected was Jeremy Puhlman, a 28-year-old engineer who was previously employed at the Veterans Administration's and University of Pittsburgh's Human Engineering Research Laboratories' Wheel Chair Mobility Lab, which is located at the VA Hospital in Pittsburgh. Puhlman brought to the job his experience with manufacturing equipment like robots, experience with a rudimentary CAM software, proficiency with SolidWorks CAD software, and a willingness to tackle challenging assignments.
His immediate task was to select CAM software. His goal for the year was to start manufacturing parts for eight to ten groups of robotic systems design teams, and to run the shop as if it were a lean manufacturing business—showing a profit in a simulated business model. If he couldn't do that, the operation would not be viable for the long term.
When Puhlman first arrived at his job, the equipment, a VF3SX Super Speed Mill and an XL30 lathe from Haas Automation (Oxnard, CA), had already been purchased and delivered to the shop. His first task was to install and quickly acquaint himself with the machines, and then research the market for a CAM system that would support these machines and future growth.
"After researching tooling, I started talking to vendors and users about CAM software options. We narrowed it down to a couple of choices and compared them by attending tool shows and dealer demonstration events," says Puhlman. "After two months of careful deliberation, we chose Mastercam from CNC Software Inc. (Tolland, CT), because it was highly compatible with Solid-Works, and offered the broadest range of capabilities."
At present, Puhlman divides most of his time between running the manufacturing equipment and programming the machines in Mastercam. He does have some part-time machine operators, but he is the only one who does CAM programming.
When he started working at the NREC, he had no experience with Mastercam. He had used a more limited CAM package with a different interface. This was not a problem, however, because he found Mastercam's interface to be similar to that of Solid- Works, with which he was familiar.
Puhlman says it took him about 5 hr to program his first part—a plastic battery cover—in Mastercam. Then it took another 4 hr to machine it on the mill. Fast forward 10 months, and those timeframes are radically shorter.
In the intervening months, he had received training by his local Mastercam reseller. He learned how to position the part to reduce the number of setups, and how to select high-speed toolpaths that remove material faster without spending a lot of time cutting air. Over time, he learned that once he had developed a strategy for cutting a certain type of geometry, he could map the toolpaths that were used previously into the new job, and not have to do much manual programming. He says: "Now this recurring category of parts takes about 30 min to program, and a similar amount of time to manufacture on the CNC mill."
One of the things Puhlman spent a lot of time on during his first months on the job was selecting the tools he would be using on his equipment, and establishing dimensional values for them within Mastercam. Today, all those tools and related parameters reside in his Mastercam tool library, and the associated data are entered automatically every time he selects a tool.
He spends almost no time assigning parameters to tooling, unless the tool is a specialized tool he is using for the first time. Even in this case, he can almost always find a comparable tool in Mastercam's standard tool crib, which can be quickly modified to meet the special circumstances.
Of course, there is always some new challenge. Recently, Puhlman has spent a considerable amount of time learning the best way to machine ultra-hard tool steels frequently used in load-bearing robotic components. Often these parts have radii, thin walls, and other design features to make them both lightweight and strong. He notes that the CAM software he used at his previous job would not have given him enough flexibility to tailor machining to these difficult materials and geometries.
With Mastercam, Puhlman can experiment with different cutters and toolpaths to optimize machining results. Then he sometimes uses the software's simulation feature as a communication tool for working with design engineers. This approach has facilitated concurrent engineering of processes for manufacturing these load-bearing components accurately and efficiently, without creating a significant amount of tool breakage or wear.
Where does this start-up prototyping operation stand after its first full year? Puhlman wanted to know, so he asked his boss, Eric Meyhofer, who gave this assessment: "The shop really helps the engineers improve by seeing how every decision impacts the cost and complexity of a part."
After a year of operation, the shop had kept pace with part-manufacturing requirements for numerous simultaneous robotics projects—doing everything except five-axis machining, which was outsourced. Based on its own internal accounting, enough money was earned to pay for the CNC equipment, shop overhead, and manpower, including Puhlman's own salary. Better still, the shop has been more responsive to the robot design groups' needs, reducing both lead times and rework requirements.
"And, being able to come over to the shop and see how the various components are programmed and machined has provided the designers with insights that allow them to do their own jobs even better," Puhlman concludes.
Now the shop is looking forward to a new growth phase that is likely to include the acquisition of a turning center with live tooling and a larger three or four-axis mill. The shop's output is expected to increase by 25-50%, and the transition is expected to go smoothly, because the CAM software and manufacturing processes for using them effectively are already in place.
For more information on Mastercam/CNC Software Inc. visit www.mastercam.com or phone: 860.875.5006.
Oscillation Welds Prevent Pipeline Failure
A dramatic technological shift has taken place in oilfield drilling in the 21st century, as most of the easily accessible oil has been tapped. As a result, producers are forced to drill deeper to access crude oil that may often be highly corrosive and contaminated with hydrogen sulfide (H2S).
Sour crude oil is a sulfurous mixture that corrodes the iron in carbon steel pipe in drill strings. The petroleum industry has sought to develop drilling technology that can resist the corrosive effects of the sour crude. To provide protection from pipeline failure and allow production of oil in new deep-water oilfields, ARC Specialities Inc. (Houston) has developed a cladding technology that controls this corrosion.
ARC Specialties is a leading manufacturer of custom automated and robotic equipment. Founded in 1983 by President Dan Allford, the company has grown to become a 50-person shop occupying a 40,000 ft2 (3716- m2) facility. The company relies on three basic control platforms: PLCs, CNC machine controls, and six-axis articulated-arm robots. Typical projects have included high-current density-welding system for aluminum troop carrier hulls, automated plasma overlay welding for hardfacing rock bit shirt tails, a plasma welding-based stereolithography system, and an ultrasonic-welding ink-jet cartridge filling system.
For sour crude-oil production, Arc Specialties has developed technology that reduces oxide inclusions and iron dilution in the cladding process, mitigating the corrosive effects of H2S. The technology combines its Kladarc advanced TriPulse hot-wire gas tungsten arc welding (GTWA) system with oscillation welding. A metallurgically lined (or clad) two-layer corrosionresistant alloy (CRA/Alloy 625) overlay is deposited on clad pipe up to 20' (6-m) long with IDs up to 30" (762 mm). Nominal thickness is 3.5 mm, with a guaranteed thickness of 3 mm.
A key to the five-axis cladding machine's capability is the ability to oscillate the arc inside the pipe. This requires a durable and efficient means of converting rotary motion to linear motion on the dual-torch oscillation X and Y axes of the machine. Oscillation is driven by precision ballscrews manufactured by Nook Industries Precision Screw Group (Cleveland) as part of its Power-Trac line.
Dual-torch oscillation simultaneously overlays two layers of CRA onto the pipe's inner surface, and provides a molten puddle with longer residence time to bond, and to eliminate some common problems of overlay welding. Leaving holes that penetrate through the overlay will expose the outer steel pipe to corrosive sour crude.
The dual-torch oscillation process involves feeding CRA wire into a 20' (6-m) long torch that welds circumferentially along the inner wall of the steel pipe. The circumferential weld is created as Nook's ballscrews wiggle the torch into the pipe back and forth about 1" (25 mm) per second, while motorized pipe rollers steadily turn the pipe. After the first 20' (6 m) of pipe is coated, the pipe is flipped 180°, and the torch is put back to coat the other half of the pipe's ID.
Each oscillation places a heavy load on the ballscrew, with the 20' torch decelerated, stopped, and reversed 120 times/min with loads running just under 1000 lb (454 kg) during acceleration. The accel/decel rate is a harsh and rapid speed/load oscillation of 0.8" (20 mm) at about 1 Hz. The oscillation process also moves the weld puddle side-by-side, which generates about 2x the weld yield. In addition, this single-pass circumferential weld ensures that the CRA overlay is seamless, and also allows the pipe to undergo long-radius bending after the overlay process.
"The oscillation process is a harsh application, since it runs and repeats without stopping for hours at a time," says Allford. "Therefore, the reliability and performance of Nook's ballscrews is vital, and a key basis for our patent-pending process."
Nook ballscrew assemblies are available in a wide range of materials including alloy, stainless, titanium, and other exotic materials. Nook provided ARC with ballscrews customized to meet the demanding requirements of the application. ARC has produced two of its advanced TriPulse GTWA systems that are currently active in the Gulf Coast region, with two more scheduled for delivery.
"Oscillation welding really sets our clad quality apart from the traditional methods of cladding, and produces a long-life coating that prevents pipeline failure," says Allford.
For more information on Nook Ind. go to www.nookindustries.com or phone: 800.321.7800.
Insert Grinding to the Micron
The US branch of UK-based Rigibore Inc. (Mukwonago, WI) is a precision boring tool producer that has recently developed a special capability.
"Our boring tools can be adjusted to the micron, so we wanted to be able to create very high accuracy inserts for them," explains Anthony Bassett, Rigibore Inc. president. "The closer tolerance the inserts can be, the less adjustment that is necessary—it's almost like having a brazed tool."
Rigibore's customers include second-tier automotive suppliers, small engine producers, and builders of large engines for off-road applications. "For the larger users, we produce special shapes and forms to do very specific things," Anthony says.
"We needed a machine that can produce small quantities quickly, and which can operate untended for larger batches. We approached ANCA Inc. [Wixom, MI] for this project because the software is user friendly," Anthony says. And that's saying a lot because Rigibore develops much of its own software for manufacturing.
"We thought we could grind inserts in a different way than they had been ground before. We had developed a range of inserts for the North American market, the production of which we had been outsourcing," Anthony explains. "With the ANCA grinder, we could bring the work in-house and assure ourselves that we could market ISO standard H tolerance [±13 ìm] inserts, one of the highest tolerances that can be ground.
"Today, with ANCA's application assistance, we are grinding consistently within 1–2 µm with our ANCA RX7 and its iPunch software," says Anthony. "It's amazing how the machine is holding that tolerance around the center of the piece." With superabrasive roughing and finishing wheels, the company grinds the periphery of the piece and the chipbreakers for specific applications on its boring tools.
The RX7 is robot-loaded, providing Rigibore the ability to operate untended. "During the course of the process development, we and ANCA learned quite a bit about automating the production of very small pieces, from fixturing to robot handling," Anthony points out.
Originally developed by ANCA for grinding punches used in metalworking and tablet production, iPunch intelligently handles multiple steps by knowing the material already removed from the previous operation. By spiraling in from the initial shape to the final shape, iPunch ensures the wheel is always in contact with the part, which eliminates any wasted time spent grinding air. Reversal marks are eliminated during finishing. Different back tapers are easily produced by using the C axis to pivot the wheel position.
"The iPunch software can grind in three axes so we can grind any shape we need," says Ken Kasten, Rigibore precision grinding specialist, "and we can control it within 1 µm. That was it for us. Plus, the software was easy to learn," he adds. "iPunch software moves the wheel in and out, and up and down, and it controls the C axis. This gives us a flatter edge, Kasten says.
"Most customer parts come in as drawings," Kasten says. "We design the parts in SolidWorks, and then save it as a CAD file and import directly into iPunch. From there we can tweak it and simulate the process to be sure we will produce what the customer asks for," he adds.
With the implementation of iPunch, Rigibore has reduced cycle times 30–40%. iPunch operations can be integrated into iGrind applications, offering Rigibore complete flexibility in grinding its inserts.
"The closer tolerance the inserts can be, the less adjustment that is necessary—it's almost like having a brazed tool."
For Rigibore, iPunch opened the door to production of extreme-tolerance inserts that other sources simply can't touch.
"Our goal is to do more special inserts, and we feel we can do that with the RX7, iPunch and our special fixtures," Anthony says. "The machine has opened up new possibilities for us in grinding inserts. Any insert we have on our shelf, whether it is CBN, diamond, or carbide, is ground to H tolerance. And we can do it confidently with the RX7 and iPunch software. The combination gets us where we want to be, grinding special forms on inserts. Going outside for this kind of service would be unacceptable in terms of time and quality," he concludes.
For more information on ANCA Inc., go to www.anca.com, or phone: 248.926.4466.
This article was first published in the April 2010 edition of Manufacturing Engineering magazine.