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Shop Solutions: CNC Threading the String in the Oilfield


The Gulf of Mexico is one of the richest oil-producing regions in the western hemisphere. Over the years, the region has generated a tremendous amount of work for Gulf State machine shops dedicated to oilfield work.

Today, those shops are busier than ever.

One of these shops, Gulf Coast Machine Inc. (Broussard, LA), sits among Louisiana's coastal bayous, about 100 miles (161 km) west-northwest of New Orleans. The family-run shop produces a common, but essential, oilfield commodity: threaded drill pipe.

 Big and awkward to handle, drill-stem pipe varies in hardness for steep-taper threading and re-threading using the latest CNC technology at Gulf Coast Machine.

Traditional oilfield machining may seem highly specialized to the uninitiated. It's different from the kind of work most shops encounter, often involving a mix of new production and old-part refurbishment, in materials with extreme variations of hardness. Parts are generally big, loading is usually awkward, and jobs are frequently dominated by threading or rethreading operations. The work doesn't quite fit into the normal CNC-production category, so a lot of shops still do it manually.

"There's definitely nothing delicate about it," Gulf Coast's owner Brad Stutes says. "Manual threading on a hollow-spindle machine is tough work. After turning handles all day on a job this demanding, you're done! It's hard on the machinist, and it's hard on us—just finding experienced people to do the job."

Screwed together end-to-end, this pipe forms the long drill shaft, or string, that is used to drill for oil. The indispensable threaded part looks simple enough, but Gulf Coast knows better, and the company is using the newest large-bore CNC turning technology from Haas Automation Inc. (Oxnard, CA) to change the way it's made.

Brad's son, director of operations Kyle Stutes, explains: "Actually, we don't call it simple drill pipe anymore. We lump it into a category called drill-stem tools. We turn out a whole range of different tubular drilling tools, but threads are a crucial part of almost everything that goes downhole."

Kyle Stutes cites the example of a big offshore find that Chevron has made in the Gulf. "This one discovery may increase North America's known reserves by an incredible 50%, but they have to go through 7000' (2134-m) deep water just to start drilling. Whenever their drill crew has to make a trip (periodically pull out the drill string to change the worn drill bit), that mile-and-a-half of pipe has to come out of the hole—one joint at a time. Nothing but a set of threads is holding together everything hanging below it."

A clean shear due to thread failure anywhere along the string could strand millions of dollars worth of tools down the hole. Naturally, the potential liability is staggering. To reduce these risks, the industry demands that each threaded piece is controlled and traceable (similar to aerospace parts), with a complete inspection and documentation paper trail back to the foundry.

At the drill rig, an independent third-party inspector performs another critical ball-gage check to certify, again, that the lead, pitch, taper, and diam of the threads are in spec. This independent inspection validates the shop's work, and ensures there hasn't been any damage during transit. Precision is essential, and with stakes so high, nothing is left to chance.

"My dad's been in the oilfield machining and tool-rental businesses for 28 years. He tells me he can't remember a time when there's been this much activity," Kyle Stutes says.

"Oil is getting much harder to find," Brad Stutes points out, "so the technology has stepped up to allow much deeper wells. That means a lot more tools are put into each drill hole, and that helps our industry. As the holes get deeper, the inspections get tougher. There's more manufacturing and a lot more repairs to do. It's a crunch at times to keep up with what's coming in."

 AsUsing large-bore TL-4 CNC Toolroom Lathes with 10.81 inch (275-mm) diam through-bore and Intuitive Programming enables Gulf Coast Machine's inexperienced machinists to outperform traditional manual machining in quality and volume. problems go, too much work is a nice one to have. With business booming, father and son are tackling their situation head-on. They've invested in a pair of large-bore Haas TL-4 CNC Toolroom Lathes. Featuring a 10.81" (274.5-mm) diam through-bore, front and rear chuck capability, and a 35 x 80" (889 x 2032-mm) maximum cutting capacity, the machines are especially suited for oilfield operations. Gulf Coast purchased two of the first TL-4s to come off the Haas production line in California.

"These machines have changed everything," says Kyle Stutes.

Oilfield shops have been adopting NC equipment since the late 1970s. Gulf Coast installed its first CNC machine, a Haas SL-30 lathe, back in 2001, but the large-bore TL-4 machines have stepped things up to a new level. They're not only sized and powered for heavy oilfield work, they're also equipped with Haas Automation's latest Intuitive Programming System, which has builtin thread-repair and re-cutting cycles that make oilfield threading precise and, above all, easy.

"This is a real breakthrough," says Kyle Stutes. "Specialty CNC machines for our industry have never been this affordable, or anywhere near this easy to use."

"We're using Haas TL-4s to cut all our rotary shoulder connections," he explains. "One machine is set up to cut the box [the inside threaded part], and the other is set up to cut the pin [the outside threaded end of the part]. These are large, tapered threads with a heavy shoulder machined at the end. They're called rotary shoulder connections, because Drill-stem materials machined at Gulf Coast Machine range from 4140 steel to Monel to nonmagnetic stainless.the drilling crew joins the tubes by rotating the thread until the connection finally shoulders-up tight."

This happens repeatedly during drilling, and the parts are re-inspected each time a joint is broken apart. The crew may re-assemble connections three or four times, or sometimes use them only once.

"We continuously get damaged tools back from the field for reworking," Kyle Stutes points out. "Training an inexperienced person to re-cut threads of consistently high quality on a manual machine can take a year or more. The trainee needs perfect timing and perfect hand-eye coordination, or he'll destroy your machine just trying to learn. A split-second hesitation getting out of that course thread at the end will break an expensive insert—at the very least," he says.

"This is where the TL-4s have changed everything; they're being run very successfully by green workers," Kyle says. "I've got machinists who've been doing this work for eight or nine years on manual lathes, but the new guys on the Haas machines, who have less than a year's experience, are turning out three to four times the work—and it's 100% perfect. The TL-4s Intuitive Programming System makes threading just unbelievably easier. Some of my manual guys would kill to get on these new Haas machines. I honestly don't know where we'd be without them."

Kyle Stutes is excited about his shop's prospects. "Our business has grown 400% in the last two years," he says. "We want to get another TL-4 right away. We've got stuff happening."

Brad Stutes, with long years in the business, views the new technology from a slightly broader perspective: "This machine is going to end up replacing the old dinosaur machinists in our industry. We all have a lot of respect for those guys, but it's time—their breed is going away. This is absolutely the right machine, at the right time, to really help our industry."


CNC Carving Shapes Medical Devices

Advanced CNC machine technology is enabling Otto Bock Healthcare, a manufacturer of prosthetic and orthotic devices, to make substantial improvements to its production of prostheses and seat cushions at its Plymouth, MN, facility. From this location, Otto Bock markets these devices to prosthetists and orthotists throughout North America.

Otto Bock, a leading German supplier of medical devices, worked in cooperation with the CNC carving machine builder, Bornemann-Werkzeugtechnik (Delligsen, Germany), to produce a series of five-axis robotic milling machines for manufacturing its medical products. The majority of devices made at this facility are custom, one-off productions, which creates operational challenges at every turn.

"Otto Bock has operated in Minneapolis since 1958, acting as a sales and distribution location for the company's many product lines. In the case of the prosthetic and orthotic devices, we quickly realized the need to manufacture here, so we've constantly evaluated the available technologies for machining," explains Otto Bock Vice President Bill Clover. "Our biggest challenge is how to remain flexible in our manufacturing, given the constant flow of one-off work. We knew something was needed."

 What once took hours is now done in minutes using a five-axis milling machine that uses Siemens Sinumerik 840D CNC with Simodrive 611U drive package for precision carving/milling of prosthetic, orthotic, and custom seating systems at Otto Bock Heathcare.

Product lines at Otto Bock run the gamut from orthotic support seating to various prosthetic shapes, cosmetic covers, and neck-to-pelvis body jackets. Products are often made from very large blanks of specially formulated and costly material, making it critical to have machines that will not only run efficiently, but also have the flexibility for fast changeover and interpolation of large data files.

The Bornemann machine alliance led to the development of carving technology, utilizing the latest CNC protocols. The Bornemann carvers, each of which is equipped with Siemens Sinumerik 840D CNC technology, are used to cut proprietary rigid and flexible polyurethane foams into the seat cushions used to support spinal injuries, as well as various upper and lower-limb prosthetic devices and supports.

Software provided by Otto Bock's facility in England is used to capture the patient's particular physical characteristics, such as limb length, circumference, and degrees of soft-tissue containment. Once the prosthetist or orthotist collects the data, Otto Bock's fabrication software support engineering supervisor, Dennis Miller, enters the picture. "It's critical to have the data accurately interpolated into the toolpath for cutting these blocks of foam and rigid materials," Miller explains. "You might draw some analogy to the aerospace industry and the contours of a wing. The human body has no straight lines, so the movements of the cutting tool require extremely complex machine programs."

The previous carving method for the seating systems produced at Otto Bock involved making a plaster cast that would be reverse-engineered for determining the cutting path on a router. "It was a very slow and imprecise method," says Clover. "We can now model the end-user [patient] and directly carve the product from the material blank using Bornemann's robotic five-axis milling machine."

The process is called the Otto Bock Shape System, or OBSS. The patient is seated in something similar to a bean bag chair. The bag is then evacuated and the bag surface is digitized, using Otto Bock proprietary software, developed in cooperation with Polhemus (Colchester, VT), originators of the FasTrack 3-D contact scanning system.

Polhemus is a global supplier of 3-D position tracking systems motion tracking, and digitizing systems for various industries including medical, military training and simulation, computer-aided design, and virtual reality. Through the use of this advanced, clean, and non-invasive laser-scanning technology, an accurate image can be made of the patient's torso from the impression left in the seat bag surface that is used to initiate the design process.

The software is then manipulated from CAD to ProfiCAM, and finally to the CNC on the machine, through the proprietary OBSS system. Otto Bock recently upgraded the NCU/PCU for its Siemens Sinumerik CNCs to accept the most advanced version of this translation.

"Compared to the old toolpath generation method, the path that took 2–3 hr now takes perhaps 10 min," says software engineer Dennis Miller. A wheelchair cushion that used to take 90 min to manufacture on the old system takes Otto Bock less than 20 min. to produce. In terms of overall productivity, both Miller and Clover say that a typical month's seat-cushion output was once about 20, but is now averaging about 250. Clover further states, "We could never have achThree-axis milling of hard foam creates a positive model of the patient's limb to be used in the thermoforming process at Otto Bock. The patient wears this plastic check socket during the initial stages of prosthetic limb fabrication.ieved these levels without the Bornemann machines and Siemens CNC technology."

In a typical manufacturing operation for a seat cushion, a 26 x 26 x 14" (660 x 660 x 355-mm) "H" block of material is secured in the vacuum bed on the Bornemann machine. A probe determines the zero offsets on the blank. For a prosthetic device, a rotary-axis, two-ribbed, cone-shaped arbor is mounted on the machine. A predetermined coordinate fixture is used to verify the offsets and rotation angles. For foam cutting, a 12" (304-mm) long hollow tube of tool steel and a 40-mm ball-end rasp are used. On the rigid polyurethane blanks, the same design of cutting tool, only 7" (178-mm) long with a ball end mill, is utilized.

In the work envelope of the machine, one axis is used to move the seat cushion; two axes are used to move the tool. A 0° rotation achieves most material removal with a 30° undercut typical. On the prosthetics, three axes rotate the material in a vertical helical pattern.

Once it's made, a prosthetic device is checked using a specific diam check ring, as well as digital calipers, to verify the contour surfaces as accurately as possible.

The machine operators at Otto Bock generally do not require extensive G-code programming skill. The program is directly downloaded to the NCU on board the Siemens CNC. Since the part programs are usually quite large, they run directly from the NCU on the machine.

A service contract on the machines has proven effective with phone support quickly provided to troubleshoot both the Bornemann machines and the CNCs. This support is especially critical, Clover says, as there are currently only seven such machines in operation worldwide. Training on the machines was done at the Otto Bock world headquarters factory in Duderstadt, Germany.


One-Platform Processing of Chips and Coolant

The switch to common platform conveyor/coolant handling units has reduced and eliminated downtime resulting from filter changes, overflows, and low volumes in heavy-duty machining at Team Industries (Bagley, MN).

For more than 40 years, the midwestern manufacturer has been a leader in research, engineering, prototyping, and manufacturing of drive-train and chassis components for snowmobiles, ATVs, utility vehicles, and golf carts, as well as turf, garden, agricultural, and construction vehicles.

Typical parts produced for the applications include transmissions or gearboxes, axle housings or differentials, continuous variable transmissions, and transaxles. All must meet rigid specifications for low noise levels and be able to handle severe shock loads, to fit in tight spaces, and to provide long service and durability.

For Team Industries, the pressure to provide the highest quality products in the face of price and timeline constraints is a constant factor of doing business, just as it is for virtually every worldwide supplier to OEMs today.

 Team Industries has equipped four new machining centers with Mayfran ConSep high-pressure chip/coolant handling systems. Any new machines will most likely be specified to include ConSep units.

Until a short time ago, the plant's through-the-spindle machine-tool high-pressure coolant systems at its Cambridge, MN, machining facility created problems that prevented machines from running smoothly and producing parts at optimum output levels. Production-interrupting culprits were the ever-present need for filter bag changeouts and the likely potential for overflows and shutdowns due to low coolant volume.

Steve Buchholz, then engineering manager at the Cambridge plant, and Ron Boudreau, maintenance manager, were challenged with the task of reducing downtime and maintenance/labor costs while enhancing coolant recovery efforts and chip-handling operations.

Team's Cambridge facility is wellequipped for heavy-duty machining of steel components and those made from cast ductile and gray irons. Among the various operations performed on components such as pump housings, differential cases, transmission housings, and hydraulic motor housings are face milling, boring, drill and tap, and deep-hole drilling for oil passages.

"These operations require that machines be outfitted with through-the-spindle, high-pressure systems, in particular for the deep-hole drilling tasks, to help cool and protect the tools and to efficiently flush chips from the hole," Buchholz explains. "Our previous machining systems included a chip conveyor and coolant tank from one supplier; while the separate high-pressure pump and filter system were sourced from a different supplier."

This configuration of coolant and chip-handling systems resulted in several problems. Boudreau explains: "One was that the cast-iron components produced both chips and small fines that created a grinder-like sludge that quickly clogged the bag-type filters."

As a result there were many times when a filter would require changing or cleaning every week with one to two hours of downtime. If this maintenance was not done, low-coolant alarms or shut downs could occur, and worse, filter backups could result in overflows and cleanups.

"Clean filters are critical to the operation. Keeping coolant lines clear and flowing is necessary to eliminate the grit that wears on machines, tools, and pump parts, and helps make sure that the coolant's cooling effect is not undermined," Boudreau says.

Another complication arose as coolant levels dropped in the "clean" reservoir. "The high-pressure pump would start suctioning air, resulting in foaming with an eventual drop in coolant performance and protection. Because the coolant tank was from one manufacturer and the high-pressure unit from another, the tank never seemed to have the right capacity for our needs, and would often require refilling and topping off to keep the machines running," says Boudreau.

"There were also the challenges of integrating the different systems—the machine tool, the conveyor, and the high-pressure unit—so all would be on the same page as to alarms, emergency shut downs and such," says Buchholz. "A condition might be critical to one piece of machinery, but not to another, so we had to devise our own wiring schemes to provide the warnings and procedures best for our application."

Messrs Buchholz and Boudreau were introduced to the ConSep chip-removal conveyor and coolant-filtration/separation unit from Mayfran International (Cleveland) by Hegman Machine Tool Inc. (Maple Grove, MN).

"One of Team's other machining facilities ordered a new machining center and specified a Mayfran ConSep conveyor/separator," Buchholz, who is now new business development engineer, recalls. "The machine was initially set up in our plant for trials and runoffs. Ron and I saw the ConSep in operation and were impressed."

Team Industries has since included four of the Mayfran ConSep systems with its new machines, two HMCs and two VMCs. "From the day the very first unit was put in operation, the results have been outstanding. We have gone for three and more months with no problems whatsoever, and no downtime due to filtration blockage issues, changeover requirements, foaming, or overflows," says Buchholz. "It has been a win-win environment for the operators facing fewer problems. For Team, productivity has improved while costs have decreased."

The ConSep 2000 chip conveyor/coolant separator represents the latest generation design of the Mayfran's single-platform systems. Offering a different approach to chip handling and coolant processing methodology, it's designed with a minimum number of components and has a low profile to fit with a wide range of both domestic and imported machine tools. This equipment interfaces with international machine system controls, and its construction standards meet the specifications and requirements of machine tool builders and users worldwide.

Designed to process all types and sizes of chips, including long strings and expansive nests, the ConSep 2000 unit's design features a hinged steel belt conveyor system for larger chips and strings. A patented inner chip-handling system with spiral conveyor underneath the belt is designed to carry and discharge smaller chips and contaminates removed by the integral drum filter.

An onboard drum filter uses a poly fiber fine-mesh filter cloth with a backwash system and a flowthrough venturi nozzle to clean the filter media. The pressurized wash system requires no downtime for manual cleaning, and the process can be viewed through a clear access panel for visual inspection and verification of the cleaning action.

The filtered coolant is held in a clean coolant holding tank for return to the machine tool. The removal of fines and sediments to 50 µm size from the fluid produces a less abrasive, gritty coolant flowing back into the machining process. Machine component and tool wear are reduced, minimizing maintenance required and improving the ability to hold part tolerances.

Various high-pressure systems are available with up to 8 gpm (30 L/min) flow rates and pressures ratings to 1000 psi (6894 kPa). The high-pressure system with filter can be linked to the conveyor system, and typically includes controls that provide connectivity to the machine tool's CNC for program-embedded operational instructions.

Mayfran offers an AT-Cleaner based high-pressure package that is integral to the main ConSep providing 50 µm nominal clean coolant. The ATCleaner delivers 10–15 µm clean coolant to an ultraclean tank to which the high-pressure pump is mounted.

"With the ease of integration along with zero downtime for filter media replacement or accidents, and no more media handling or disposal costs, the ConSep 2000 units are just what we needed at Team.

"Given the performance of our four existing ConSep systems and how they've improved the overall operations of the machine tools they're working with, any new machines ordered will most likely be specified to include Mayfran's ConSep units," Buchholz concludes.


This article was first published in the February 2008 edition of Manufacturing Engineering magazine. 

Published Date : 2/1/2008

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