Shop Solutions: Full Speed Ahead to Measured Savings
"From the manufacturer's point of view, each part is a single copy," says Michael Kiehl, production manager of Zelter GmbH (Rhenish Hennef, Germany), slowly moving his thumb along the contour of a 500-mm long turbocharger housing. "Nevertheless, in the end they are two of a kind—at least with regard to their critical dimensions. For the bearings of rotor blades rotating at up to 300,000 rpm, a precision of ± 0.05 mm must be guaranteed." Keeping such tolerances concerning form and position is the daily routine at Zelter. Here production metrology by Blum-Novotest GmbH (Germany; Blum LMT, Erlanger, KY) makes all the difference.
Established in 1923, Zelter GmbH is a major sub-supplier to the automotive industry. The company supplies series of parts, batches of exhaust manifolds, hubs, parts for steering gears, brakes, and belt pulleys or even housings for turbochargers.
Though Michael Kiehl's production department is working in three shifts of 7.5 hr each, Zelter is working to full capacity. Every week up to 20,000 parts are produced. On average, two trailer trucks per day supply the semifinished cast components that are necessary for such high output.
"Usually the dimensions of these cast parts vary by 2 mm," explains Kiehl, "each one is different from the following one." Therefore, the position of the surfaces, bores, and channels that must be machined vary when they are clamped into the machine tool. At present, Zelter is working with 34 machining centers with travel distances up to 800 mm. Half of the machines are equipped with TC51-20 touch-probe systems from Blum-Novotest; the other half with Blum Z-Nano and Z-Nano IR tool-breakage-control type systems.
Until the end of the 1990s, Zelter first milled orientation surfaces on the gas inlet and outlet of the semi-finished products within the tolerance of the material allowance. The disadvantage was that machining was done on a separate machine, one that did the roughing. Reference points could be lost as the part was transferred to the production machine. By the end of the '90s, Kiehl equipped his machines for the first time with Blum probe systems. "At that time it was the best you could get on the market, and this still hasn't changed today," he says.
Blum measuring technology is credited with generating the conditions for the economical serial cutting of these cast parts of varying dimensions.
The touch probe TC51-20 is set into the toolholder of the CNC machine to detect single points of the geometry of the parts—the actual data—and send them by infrared transmission to the machining center's controller. The CNC compares these data with the coordinates in the part drawing—the set data—and calculates the position of each zero point. If the feature is a bore, for example, each workpiece of the series has its own reference point. Or, you can say, by detection of the reference points of the semifinished tool, the machine tool "knows" where to start.
Zelter roughs and finishes parts on two different machines. The remaining tolerance is between 0.4 and 0.5 mm. The reason for using two machines, however, has nothing to do with the Blum measuring technology, but rather with the craggy geometry of the housings and the resulting interrupted cuts. Theoretically, savings potential would be considerably greater if the semifinished products were set, measured, and then finished on the same machine—something that is at present just a theoretical possibility.
When roughing and finishing on different machines, Zelter uses the TC51-20 to detect each workpiece's zero point on the corresponding machining center. The savings are substantial compared with the former handling of parts. Today, the TC51-20 with its acceleration of up to 100 m/sec2 is preferred. What pays off is the rapid probing speed of 5 m/min. Depending on the complexity, the TC51-20 is able to detect within 5–10 sec the reference points of parts with a length up to 500 mm, a considerable distance from one to another. So, essentially capacity increases.
Coolant and pollution are no problem, as the probe's enclosure corresponds to IP 68. Handling is simple; the TC51-20 has a standard ABS-50-interface. It is placed in the ATC like any tool, and changed into the working zone for measurement by the CNC. The probe system works bidirectionally, enabling Zelter to carry out all necessary measuring operations. Besides the usual measurement into the beam, measurement out of the beam is also possible with the TC51-20. This is an advantage for Zelter as the probe system can exactly detect the spiral insides of the turbine housings. Data transmission is wireless and transferred by infrared to an IC 55 Blum receiver in the working area. Its enclosure is also to IP 68 standards. This receiver then forwards the data to the CNC of the machine tool.
With a standard 9-volt-battery, the TC51-20 works independently from external current sources. In practice, up to 235,000 measuring operations are carried out with one battery. According to Kiehl, his colleagues have been, by and large, entirely "unconcerned" about the system. In a case where the battery might fail early, the probe sends a warning signal to the machine control. Furthermore, the LED gives information about the actual operating conditions.
The probe system can be used at high speed on machine tools and machining centers without any deflection of the measuring system. There are no undesired trigger signals or mechanical damages on acceleration or deceleration. Despite measuring-value resolution in the range of thousandths of millimeters, the TC51-20 is said to be almost indestructible under harsh production conditions.
For years, Zelter has used the Blum Z-Nano IR probe systems for measuring the length of their tools and for tool-breakage detection with the TC series completing the company's inprocess reliability. Both types—the TC as well as the Z-Nano IR series—can be used "in duo." It is possible to use two TC systems, two Z-Nano IR Duo each, or one TC system and one Z-Nano IR Duo on one machine tool in parallel with another. Detected data will be transferred to the machine control via the IC55 receiver in the working area.
Like the TC probe system, the ZNano IR is also protected according to IP 68. This system enables wireless data transfer and works without external current supply. Therefore the probe can be installed into the working area, and it can be set between the workpieces without restriction, so that the tool to be checked can reach and contact it easily.
The Z-Nano IR works with an internal light barrier. The trigger signal is generated without any mechanical switching, avoiding the wear of mechanical switching devices. Canting of the measuring surface of the Z-Nano is reportedly impossible. The functional principle with linear guides enables very small, fine and filigree tools to be measured.
Consequently, for the standard design of the Z-Nano IR, diameters of less than 0.5 mm are normal, and in the "high precision" arena, diameters even smaller than 0.1 mm are possible. The reset, which is set by spring force, is the only mechanically operated feature of the Blum design.
For more information on Blum LMT, go to www.blumlmt.com, or phone 859.344.6789.
UMC Brings Large Parts Back In-House
One way to get leaner is to acquire new equipment to streamline production. That's exactly what Messer Cutting Systems (Menomonee Falls, WI), a manufacturer of thermal cutting systems, did to gain greater control of processes and lead times and bring outsourced work back in-house.
Messer Cutting's plasma and oxyfuel cutting systems are used by heavyequipment manufacturers, metal-service centers, shipyards, the military, and fabricators to cut shapes from mild steel, aluminum, and stainless plate. The company engineers, manufactures, and assembles all of its thermal-cutting gantry machines at its Menomonee Falls, WI, plant.
Prior to purchasing a U5 universal machining center from MAG (Cincinnati), Messer outsourced production of its machine rails due to their size and varying material hardness. "The rails are made of high-carbon steel and are very difficult to machine to spec," explains Michael Steger, machine shop supervisor. "With this new machining center, not only is this work back in-house, but we're also using fewer hours to machine the parts, and that's helping us shorten lead times and control our delivery process better."
The rail-type U5 UMC is used to machine about 30% of the company's critical, large-sized components for its gantry-cutting systems. The oversize parts had previously been farmed out due to accuracy requirements and machining complexity of the material. The gantry-style MAG U5 features 4.3-m X-axis and 3.6-m Y-axis travels, and the power and accuracy for largepart machining and contouring operations. As a result, Messer has gained the capability needed to manufacture the larger components of its cutting systems—including some as large as 10.5-m long and 1.5-m wide, and weighing more than 2630 kg. The parts include beam assemblies, end trucks, rotator housings, and machine rails. Parts are fixtured with a combination of pedestals, vises, and grid boxes. Besides the high-carbon steel of the rails, materials machined on the U5 include cast aluminum and mild steel.
Engineered for aerospace applications, the U5 is equipped to handle the range of materials required by Messer, with the torque and stiffness required for cutting titanium and other hard metals, as well as the speed and agility to machine aluminum. The U5 was designed using FEA, allowing engineers to select the optimum materials and construction to produce high static and dynamic stiffness for the machine tool. The X-axis drive system on the U5 has a heavyduty rack and pinion mechanism with dual-drive motors on each X-axis rail for high-power performance.
Messer's large-part accuracy, productivity, and part quality all improved with the acquisition of the U5 machining center. The net result is a 25% improvement in productivity, gaining greater control of production cycles, quality, and delivery times in the process. "Our old machining center didn't have the rigidity or accuracy we required," says Operator Dan Stujenske. Tolerance on Messer’s machine rails is 0.002" (50.8 µm) over a length of 10' for parallelism, and 0.0015" (38.1 µm) concentric to bore for the rotator housings.
"We're getting a 50% increase in speeds and feeds, and we're tapping at 50 fpm [15 m/min], which is about two-and-a-half times faster than before," says Stujenske. Engineered to cut titanium, the U5's rigidity is established on hardened and precisionground box ways. This provides chatter-free machining with feed rates of 20 m/min in X, Y, and Z axes, an asset in Messer's work. "Because of reduced vibration, we're getting a better finish with fewer passes," Stujenske adds.
Messer selected the standard vertical and horizontal head spindles for its U5, both providing 30 kW continuous duty at 6000 rpm and 854 Nm at 333 rpm. Switching the heads takes less than 2 min with an optional automatic head changer, further reducing out-of-cut time. A five-axis contouring head is also available for the machine that can add 190° A axis and 360° continuous C-axis capability.
While satisfied with the initial performance of its new machining center, Messer envisions the U5 providing even greater production advantages down the road. "The advantages of bringing work back in-house, increased productivity, and controlling delivery times are becoming even more critical as the economy recovers and orders increase," says Gary Wierzbinski, plant manager. "Customers placing orders want machines ASAP so they can meet demand on their end."
Wierzbinski adds, "Having just received this machine in 2009, we're still a little new to it, and as we improve our programs and setups, we should increase our untended operation and multiple-part setups. This will allow our machinists to be more productive, handling deburring and inspections while the machine cuts parts."
For more information on MAG, go to www.mag-ias.com, or phone 859.534.4600.
HOG Does Optical Shaft Inspection
The family of turbocharger shafts produced at Cummins Turbo Technologies (Palmetto, SC), have up to 11 diameters and are produced in various lengths. They are complex parts that must be inspected consistently and at rates that keep up with production. Clayton Butler, metrology technician, has a solution that has been working on the Cummins shop floor alongside the grinding machines for several years. He calls it his HOG—the Hommel Optical Gage.
Machine operators use the Opticline from Hommel-Etamic America (Rochester Hills, MI) to measure a shaft and turbine impeller wheel assembly for the turbochargers it produces—diameter, runout, straightness, and length. The staff also uses the gage on the shop floor to measure an impeller mounted on an arbor. Each part is measured between centers.
Cummins began investing in the optical measuring technology nearly 10 years ago and now operates nine machines of various capacities. It has five of the model 314 Opticline, capable of inspecting parts 300-mm long and 140 mm in diam.
"We measure diameters to 4µm with a gage R&R of 5%," reports Clay. "You can't touch that anywhere. We just need to have the part extremely clean as it's an extremely fine measuring device, yet it operates beautifully alongside the grinders."
Hommel-Etamic's Opticline noncontact CNC shaft gaging system measures form, dimensional, and positional tolerances of shaft-type parts in submicron detail with a two-camera system, recording results instantly. The optical machines are well-suited for measuring complex parts such as bearings or turbine blades on the shop floor, in the metrology lab, or within a production system.
The flexible shaft-gaging systems accommodate shaft type part sizes from 0.2 to 480 mm diameter, 1–2500-mm long with measuring accuracies to ±1 µm, and provide a powerful alternative to conventional shaft measuring techniques that is faster, more accurate, and more complete.
Contour, diameters, length, roundness, concentricity, cones, angles, flatness, parallelism, eccentricity, stroke, and threads, among other characteristics, can be recorded during a single pass of the optical measuring head. Measurements are easily completed within a production cycle for 100% quality control.
"The versatility of the machine is a big help as we are always improving shaft and wheel designs, and the Opticline keeps up with that easily," Clay says. "With air gaging or hard gaging, there is a lot of setup and time-consuming changeover, but with the Opticline, I can change programs in about 15 sec, and be ready for the new part number. Flexible chucking helps also."
To create a program, Clay scans the part with the Opticline cameras, establishes a length of scan, and then starts a measurement cycle. "Previously, we would use touch-probe gages and compare that to a master," Clay points out. "To accomplish the shaft measurements with air gages or ring gages, you would have multiple gages, which require setup, mastering, and maintenance. This adds up to greater cost over 3-4 shaft designs with a couple of sizes of each."
Most important, the accuracy for the optical gage is superior to that of the ring-gage approach. With the Opticline, the machine compares the profile of the part to a nominal profile of the part.
As for the quality of the parts, the grinding machine operators like Opticline. They put the parts between centers, start the measuring cycle, and in less than a minute have complete measurement results while they continue to monitor the cylindrical grinding machines. Because the cycle is so fast, operators are more likely to check parts and report any changes in the shape of the part due to breakdown of the grinding wheel.
On the shop floor, the profile grinder operator produces three diameters, measures the profile, then moves the workpiece to another grinder that creates a groove in the shaft. The operator then measures the profile form, location, diameter, lead direction, and runout.
"How many parts of a run are checked depends on the capability of the process" Clay says, "but the operators typically check 100%—because with the Opticline, they can. And there is a lot of capability for measuring different features that we have not yet begun to explore," Clay concludes.
For more information on Hommel-Etamic America, go to http://www.hommel-etamic.com or phone: 248.853.5888.
Waterjet Stimulates Wells Downhole
Centura Oil Inc. (Minnetonka, MN) specializes in stimulating gas and oil wells through the use of waterjet technology in its well recompletion and production-enhancement services.
Established in 2001, Centura Oil powers its CenJet 90 downhole 90° waterjet-cutting process with a portable diesel-powered waterjet intensifier pump from Jet Edge (St. Michael, MN). The system stimulates gas and oil-well production by increasing a well's penetration into the surrounding payzone.
The CenJet 90 utilizes ultra-high pressure waterjet cutting technology capable of piercing the well casing and cement in seconds. It horizontally drills multiple 8–10' (2.4—3-m) long lateral perforations up to 10" (254 mm) in diameter into the surrounding payzone, a coal seam for methane, or an oil or gas formation. This process eliminates conventional perforating and acidization, both of which create problems for optimum gas production.
"This waterjetting process can increase a coalbed methane well's production up to 300% by expanding its area of influence by 16–20' [4.9–6 m] in diameter at multiple depths," explains Centura Oil President Michael Uthe, who notes that the process typically pays for itself within a year.
The CenJet 90 consists of a modified 55 kpsi (379-MPa) Jet Edge Permalign II abrasive jet cutting head that is coupled to coiled-steel tubing and lowered down the wellbore. The cutting head is oriented at 90° to the well casing and is brought up to pressure at precise depths to perforate the casing and surrounding formation. The abrasive waterjet, which is capable of cutting 15" (381-mm) thick titanium, cuts a single perforation in the casing wall. During operation, the tool never leaves the wellbore.
Two coal seams in New Mexico's San Juan Basin were successfully "shot" by the process, demonstrating its effectiveness:
- San Juan 30-6 Unit #463S well was completed in October 2004. Peak production of 160 Mft3/d (4.5 Mm3/d) occurred in December 2004 and declined to 70 Mft3/d 1.9 Mm3/d) by October 2006. CenJet 90 shot this well in November 2006 and increased production to 165 Mft3/d (4.7 M3/d).
- San Juan 30-6 Unit #450S well was originally drilled and completed in November 2004. Production peaked at 160 Mft3/d (4.5 Mm3/d) in April 2005 and declined to 90 Mft3/d (2.6 Mm3/d) by May 2007. The Cen-Jet 90 shot the well in June 2007 and increased production to 180 Mft3/d (5.1 Mm3/d).
Centura Oil's waterjet well-stimulation process is said to be more cost-effective and environmentally friendly than conventional coalbed methanewell completion and rehabilitation methods. "Conventional perforation operations are typically performed using a shaped charge. The formation can experience damage due to the violent nature of the explosive charge. The CenJet 90, by comparison, washes and cleans as it is cutting, eliminating near-well-bore damage, and increasing perforation depth by as much as three times when compared to conventional perforations," Uthe explains.
"Conventional well completion and rehabilitation projects also typically require costly hydraulic fracturing to keep fractures open. The hydraulic-fracturing process involves pumping chemical fluids and proppants, such as sand or ceramic beads, into the formation. To date, none of the coalbed methane wells stimulated by Centura Oil's waterjetting system have needed to be fracture-stimulated."
Environmental benefits of the CenJet 90 waterjet well-stimulation process include extending the lives of existing wells, increasing their productivity, and reducing the need to drill new wells. Because wells stimulated by the CenJet 90 have not required hydraulic fracturing, their owners have avoided those costs and potential damage to the formation. The CenJet 90 uses only 4 gpm (15 L/min) of water and 1 lb/min (0.45 kg/min) of garnet abrasive. Garnet is a natural stone that can be disposed of in a landfill. The effluent created by the waterjet cutting process consists of coal cuttings, garnet, and water. It is flushed out of the well and discharged into a lined holding pond.
Uthe says that he decided to equip the CenJet 90 with a Jet Edge intensifier pump and to use a modified version of Jet Edge's waterjet cutting head because he needed dependable equipment that could stand up to a harsh remote environment.
"If I have 3000' [914-m] of hose downhole, and something breaks, I stand to lose a lot of money. I bought the Jet Edge waterjet intensifier pump after meeting with Jet Edge management and getting several referrals from people who told me that Jet Edge was the most reliable pump on the market. The Jet Edge waterjet pump has been extremely dependable and Jet Edge's support has been excellent. I know that when I need to call Jet Edge, someone will answer. Even on Saturdays, I can get through to someone on Jet Edge's 24-hr emergency cell phone."
Centura Oil plans to expand into new-well completions with its Cenjet 90 process, and also sells its CenJet 90 waterjetting systems under a licensing agreement.
For more information from Jet Edge, go to: www.jetedge.com, or phone 800.538.3343.
This article was first published in the July 2010 edition of Manufacturing Engineering magazine.