Shop Solutions: Case Histories of Manufacturing Problem Solving
Shop Solutions is edited by Senior Editor Jim Lorincz
Precision Machining Hydro Impellers
Canyon Hydro (Deming, WA) is the country’s leading supplier of large hydropower generating systems, located west of the Mississippi right in the heart of the hydropower market. The company builds hydroelectric systems to the rigid specifications of public and independent power producers. Using state-of-the-art CNC machining technology, Canyon Hydro manufactures Pelton, Francis, and Crossflow-type hydroelectric turbines in a highly automated CNC machining facility it has built specifically for that purpose.
Turbine rotors, called "runners" in the hydropower industry, convert water flow to the rotary motion that drives the generators. The principal machining challenge is to contour-mill the runner buckets, which are essentially paddles on a sophisticated paddle wheel where every machined surface has a hydrodynamically correct curvature. A typical runner, made from a stainless casting, weighs 10 tons (9.07 t) measures 11' (3.35 m) across, and has 22 carefully contoured double buckets. Runners can take months of continuous five-axis, long-reach milling to complete, removing a ton and half of stainless chips in the process. Although virtually all milling involves long 19" (482-mm) shank lengths, as-machined surfaces must be smoother than 32 µm and geometrically correct within 0.010" (0.25 mm), in order to prevent turbulent flow while in service.
Advanced tooling and customer support from Ingersoll Cutting Tools (Rockford, IL) have helped Canyon Hydro complete the runners in one-third the time with accuracy and surface finish required for higher efficiency over the runners’ projected 30–40 year service life. "It’s like a large-scale cavity milling job," says Ingersoll’s Chris Murray, who devised the tooling solution.
Previously, Canyon Hydro finished the buckets by manual grinding, using CAD/CAM templates to check dimensions and contours. Typical cycle time for an 11' diam runner was six months, involving 100% attendance by skilled operators. Typical tolerances were 0.035–0.040" (0.89–1 mm).
Anticipating greater demand for alternate energy sources including hydropower, the company made the strategic decision in 2009 to change its process by automating runner machining. The company built a CNC facility in nearby Sumas, WA, with the centerpiece machine, a FPT five-axis CNC floor-type horizontal mill from FPT North America Inc. (Livonia, MI). The mill is equipped with a two-axis rotary table, 80-station ATC, and two interchangeable heads: a 360° universal 3 + 2 bi-rotational head and a 29" (736.6-mm) extension head. A skeleton crew of two to four CNC machinists works 8-hr shifts to handle support functions as the machine runs largely untended, sometimes overnight as needed to maintain delivery schedules. "Chipmaking itself is essentially hands-off," says Mike Hansen, Canyon Hydro manufacturing engineer.
To find the needed tooling solutions, the company invited proposals from all mainline vendors. "Cycle-time savings were really secondary to repeatable accuracy and smooth finish," says Hansen. "We knew the business would become more efficiency-competitive, and standard tooling was essential to eliminate all the uncertainties and expenses inherent in special tooling."
Only Ingersoll offered full application support free of charge, and found a standard tool able to do most of the job and a modified-standard to handle the rest. "It was their up-front helpful attitude that led to our choice," Hansen says. "Sure we would test each of Chris Murray’s ideas in trials later on, but only to verify recommendations and optimize parameters, not to pick a vendor. We were looking for a marriage, not just a first date."
The company started up by automating the smaller runners, diameters down to 4 ½' (1.37 m), gradually working up to the larger parts. The smaller runners were handled by a standard 1" (25.4-mm) Ingersoll FormMaster Pro specially suited for long-reach roughing and finishing. To defeat harmonic vibration, the three-flute tool features circular, serrated inserts in a timed array. Each insert is turned 5 min from the other, so its edges engage a different area of the cut, and the whole toolpath is covered progressively with every full cutter revolution. Close mating between the seat pocket and corners keep the insert in exact position.
The operation ran smoothly with no chatter, reducing cycle time on average by 50% vs. manual grinding. Tool life was more than enough for lights-out operation when needed. It wasn’t until February 2011 that Mike Hansen converted the larger runners over to the automated process and had to scale up the tool sizes. Principal model in this class is 11' (3.35-m) diam with an average annual volume of 12 pieces.
Geometry of the runner buckets includes six-axis contours, mostly long reaches, and some undercuts, calling for use of ball mills for the most part. Sheer size of the workpieces called out for a tool much larger than most standard models. "To do a 3' [0.9-m] contoured cavity with a 1" [25.4-mm] ball mill or FormMaster would take forever," Hansen says. "Besides, in stainless steel the insert would wear out too quickly for secure lights-out operation."
Chris Murray recommended a 2" (51-mm) Ingersoll ProBall indexable ballnose for the bulk of the work, and a modified standard Form Master button cutter to handle the undercuts. "The button cutter works like a standard contour mill for most of the pass, then like a T-slotter when it reaches the undercut portion along the outer edge of the bucket," Murray explains.
Hansen and Murray worked together, right at machine-side, to establish machining parameters for the 10 ton (9.07-t) 410 NM stainless casting. The undercut portions required the modified button cutter and involved the longest reaches: 20.5" (520.7 mm) from spindle to face. Hansen uses these parameters during the day when the machine is tended, backing down the feed rate about 10% as a precaution for lights-out operations. In all cases, the inserts last long enough for absolute process security over 12 to 15 hr; some last 45 hr per edge.
The big two-flute ProBall ball mill features serrated inserts at the ball end plus heavy-duty side cutting inserts farther up the active length for larger diameters and deeper cuts. "Visitors to our shop floor are amazed that such a large ball mill is available as a standard," Hansen adds. A screw-on style coupling enables in-spindle tip-shuttling to 0.005" (0.13-mm) repeatability so there’s virtually no dead time for tool servicing.
More a modified standard than a special, the button cutter is needed to access one portion of the cut which involves undercutting much like slotting. The backside of the tool must be effective upon withdrawal to create the top of the slot. The tool uses standard inserts with the cutter shank extended and insert seats repositioned to present cutting edges on both the front and backsides. Mike Hansen gave Chris Murray the CAD file on the starting and finishing geometry of the outer lip of the bucket, which was handed off to Ingersoll product specialist Mark Teno and his team back at Rockford.
Working together on the shop floor, Hansen, Murray, and lead CNC machinist Ken Neal have bumped up the parameters about 15% overall since February, always paying attention to accuracy, surface quality, and process security in a chatter-prone operation. "It’s as much a matter of listening as anything else," says Murray.
Not surprisingly, all Canyon Hydro’s runners are completed much faster and with much less operator attention as a result of the company’s strategic move to CNC automation and advanced tooling. Cycle time averages are down by 50%, and labor costs are virtually nil. The mainstream eleven footer runs even better: 500 vs. 1500 hr previously, and tool life is reliably long enough to enable lights-out operation as needed.
"What’s most important is the improvement in repeatable accuracy and surface finish quality, which will pay off for hydropower developers whose bottom line hinges on efficiency of these runners. Holding 0.005–0.010" [0.13–0.25 mm] on geometry and near-mirror 32-µm finishes at our end will make a measurable difference at theirs," Hansen concludes. ME
For more information on Ingersoll Cutting Tools, go to www.ingeroll-ims.com, or telephone 815-387-6600.
CNC Monitors Aerospace Turning
Monogram Aerospace Fasteners (MAF; Commerce, CA) is a leading producer of high-strength blind bolts for aircraft assembly, temporary fasteners for fixturing and alignment, as well as installation, finishing, and removal tools. With manufacturing expertise of more than 120 years, the company has pioneered a number of fastener innovations. Its Visu-Lok, Composi-Lok, Radial-Lok, and OSI-Bolt brands are well known throughout aerospace manufacturing. Likewise, the company’s fastener designs have evolved with the times and technology to incorporate various features required for semi-automatic or totally automated assembly operations, as well as to meet the unique fastening requirements of today’s composite aerospace structures. The company boasts numerous industry certifications (AS9100, ISO9001 and NADCAP), plus supplier awards for quality, delivery, and technology.
Founded in 1889 as the National Screw & Tack Company in Cleveland, OH, MAF opened its California facility in 1949 to serve the growing needs of West Coast industry and commerce and, in the 1970s, became completely dedicated to the aerospace business. Today, the company occupies 130,000 ft² (12,077 m²) and employs over 250 people. MAF supplies total fastening solutions for the commercial, military, and business aircraft platforms of most major airframe manufacturers and their sub-tier contractors.
MAF runs a complete machine tool department with rotary transfer, lathe, screw machine, headers, grinders, punch presses, and robotic handling devices. Heat-treat services are also provided to other fastener manufacturers, while plating and specialty coating processes are performed in-house as well. As part of its green initiative, MAF maintains a comprehensive waste control and treatment operation, plus a systematic energy management program.
The materials run at MAF typically include 6AL4V titanium, A286 stainless, Inconel, plus various alloy steels and 300 Series stainless. The core products at MAF are high-tensile strength blind bolts, used as structural fasteners on airframes, primarily on control surfaces such as rudders, flaps, ailerons, and both horizontal and vertical tail sections.
MAF purchased four new S6 CNC turning machines from Eubama USA Inc. (Elkhart, IN) for high-volume production of its fastener families. The S6 design features a centerline clamping, two-jaw chucking system that allows fast diameter changeovers for the rapid production of families of workpieces. After the S6’s fast tool and clamp jaw change, the Sinumerik 840D CNC from Siemens (Elk Grove Village, IL) permits nearly immediate restart of the cutting cycle with the proper feed speed and rapid traverse.
The Sinumerik CNC was considered a critical step up from the conventional hydraulic or hydromechanical control typically found on such machines by MAF, and a definite solution to the small and medium batch production needs at the fastener manufacturer. There was also some consideration given to a further enhancement, namely, an ongoing condition monitoring system offered by Siemens that would substantially improve the predictive maintenance capabilities at MAF.
While at an IMTS trade show, a team of MAF company engineers, led by industrial technologist Karl Haffner, saw a demonstration of a remote access, condition-monitoring system from Siemens, part of the CNC manufacturer’s Electronic Production Services (ePS) suite. Without interruption in production whatsoever, the ePS protocol could be set up on each machine, monitoring every keystroke and machine action taken, storing them on a secure cloud server.
"Monogram was seeking a total service solution, where the basic service contract they received would be extended in functionality by giving our service department the ability to look into their Eubama machines on very short notice," explains Daniel Martinez from the Siemens Aerospace Center of Competence. In the end, Karl convinced his management that the enhanced service and remote access capabilities of our ePS were a less costly investment, compared to the increase in service and inside maintenance needed."
Specifically, after a lengthy needs assessment by Valerie Biester, the business developer for Siemens, and her team, working with Haffner and other MAF personnel, it was determined the Condition Monitoring System would track five key conditions (called triggers) with SMS/e-mail notification. In addition, production part count would be plotted graphically, for easy access by the production team.
Brad Cornell, engineer from Siemens technical support side, describes the benefits of access: "By accessing the Eubama machines at MAF with our ePS, we eliminated additional calls to identify part numbers and software versions. I could look into the error log, versions display and machine data instantly to get actual values. By utilizing ePS remote viewing, we minimized time spent on the diagnosis of a failure."
With the remote access and condition-monitoring services installation, setup, and MAF operator training completed in less than one day, the impact on production was minimal. Haffner says the improvements in the maintenance efficiencies have been substantial at his company. As an example of the functionality of the system, MAF recently contacted the Siemens Technical Center in Elk Grove Village, regarding a fault on one of the Eubama S6 turning centers. The remote access session was initiated by the MAF operator directly on the machine’s CNC. Technical support was able to see the alarm log directly onscreen to diagnose the issue. It was immediately determined that an on-site field service call was needed. However, prior to the use of ePS, this incident would likely have required three to four additional calls and as much as 300% more time to resolve. The obvious savings to the MAF production scenario were substantial.
Through ePS, all HMI action logs, machine data, and CNC status data are captured in real time. A PLC trace enables the prior actions to be taken as a snapshot for instant analysis of alarms.
Trigger determinations can vary substantially with the customer, according to Val Biester: "This is definitely not a one-size-fits-all proposition, because the production variables monitored are driven by customer and machine needs." She also notes that condition-monitoring services are not designed only for large production departments. She also cites the benefits to the machine tool builder: "Although a shop might not wish to access all the data the system can collect, a builder might find it useful to have such comparative real-world information." ME
For more information on Siemens Industry Inc. Drive Technologies, go to www.usa.siemens.com/cnc, or telephone 847-640-1595.
Software Inserts GD&T Symbols
STD Precision Gear & Instrument Inc. (West Bridgewater, MA) is a leading manufacturer of high-precision (AGMA Q14), tightly toleranced gears, splines and other related mechanical transmission components, primarily for the aerospace, medical, commercial, and military aircraft industries. STD takes solutions from prototype through production employing a full spectrum of in-house capabilities including saw cutting, CNC turning and milling, Swiss machining, wire and ram (die sinker) EDM, surface grinding, internal/external cylindrical grinding, broaching, honing, CNC marking, heat treating, passivation, isotropic superfinishing, and tool design and tool making.
STD Precision Gear has provided solutions for such critical applications as NASA’s International Space Station, the Hubble Telescope, commercial and military aircraft, as well as for various defense products. The company turned to DISCUS Software (Columbus, OH) to maintain a high level of attention to precision and accuracy in first article inspections while serving its growing portfolio of customers. Soon after implementing DISCUS software, STD realized significant savings in both time and labor savings. STD Precision Gear has been business for 26 years. "A constant drive to refine our processes and enhance efficiency has been an essential component to our growth," says James Manning, president.
Paul Gomes, the quality engineering manager for STD, recognized an opportunity while using DISCUS software to provide an automated process to insert Geometric Dimensioning and Tolerancing (GD&T) symbols into drawings that could significantly cut down on the time spent manually placing the symbols in drawings. Gomes, who had a background as a machinist at Texas Instruments where he also worked in the drafting department for eight years, had taught seminars on using GD&T as a way to standardize communication from design to manufacturing the end product.
Although various evolutions of GD&T symbolic language have been present for more than 100 years, the engineering language started to grow in widespread use during World War II. Since that time, GD&T has been adopted by many manufacturers across a spectrum of industries in an effort to describe geometric parts completely and unambiguously. Today, two major GD&T version standards have emerged: ASME Y14.5M and ISO/TC 213. Though not yet adopted by all quality engineers, proponents of GD&T see its benefits in precisely locating holes and size dimensions, and the language is expected to grow in use as it streamlines global industry communication. Reasons for this include:
-- Dependability to explicitly describe tolerances,
-- Emphasis on the intent of the design,
-- Reliance on definition by math and numbers, and
-- Easy translation into other languages
Gomes knew what other quality engineers and design drafters who are skilled in GD&T understand: consistent and effective usage of the symbolic language can thrive when a method to automate the encoding and decoding process is in place. "When I started working with STD Precision Gear, I saw the ability of this software to take customer drawings and make our markups using its built-in optical character recognition (OCR) feature. I recognized immediately how the software functionality fills the role of an entire drafting department. We use this software to run the whole shop. Nothing hits the shop floor without a DISCUS marked-up drawing."
Because GD&T software capabilities are typically only an option in drafting-specific software packages, Gomes was unsure whether DISCUS would be responsive to his suggestion to integrate GD&T functionality into their software suite, which is designed to manage the whole Technical Data Package. Gomes explained how the added functionality would allow STD to create superior drawings and differentiate the company from its competitors. DISCUS responded by working with Gomes to understand his needs. As a result, the software development company introduced GD&T capability in its next software update, and Gomes was one of the first to realize the benefits.
Manning estimates that DISCUS software now eliminates more than 5 hours of work in the shop each day. When he first recognized how much time just one of his shop technicians was forced to spend manually writing out inspection reports, he sought out a software product to manage the Technical Data Package. The decision to move forward with a software product was obvious when he extrapolated that time by the number of employees and the number of times each day that process was required. When Gomes joined the STD team, he was impressed with the efficiencies DISCUS allowed and took on the role of coordinating quality management for STD, implementing even more time-savings measures with the software’s functionality, including GD&T integration.
Gomes is responsible for guiding quality management throughout the life of a project at STD. When a part order comes in, a shop-floor quality inspection plan drawing is created. Then at the end of the project, an FAI package is assembled to send out to the customer. Each drawing set requires STD to include precise dimensions and GD&T markups. Before STD implemented the software, both of these drawing sets were completed manually.
The software tools are a one-stop shop to manage the intelligent Technical Data Package. "The software takes care of all of our needs as far as production documentation, instructions for the operators, inspection criteria, and inspection documentation," says Gomes. He separates the dimensions and balloon characteristics by job centers, according to the type of machine that requires those dimensions to make the part. Custom shop-floor drawings are distributed to every operator using balloons and token tags to create a customized set of characteristics that each operator needs to check on.
Depending on how many characteristics are present in a drawing, Gomes estimates that he previously spent anywhere from 10 to 30 min drawing in GD&T symbols manually. When he conveyed his desire to see GD&T integration with DISCUS, the company was intrigued. Gomes and the software development company shared screenshots and discussed how the symbolic language could be integrated into the software interface. "To say that DISCUS implemented a GD&T solution quickly is an understatement. They thoroughly understood what I wanted to see and matched it excellently," says Gomes.
Now an extra panel on one of the software pages opens a full selection of GD&T symbols. Fifteen main symbols can combine with modifiers to create 30–40 unique marks to control characteristic types, orientation, location, runouts, part profiles, and other refinements. "I’m not used to a software company providing such valuable two-way communication," says Gomes. "The result has been an added capability that provides a significant advantage for our business."
Manning notes that that time savings have not been the only benefit the new functionality provides. "The high quality documentation we can deliver to our customers with clean ballooned drawings sets us apart from our competitors and gives us an edge in our industry," says Manning.
According to Manning, STD will soon begin using the DISCUS Planner and CMM modules to create in-process inspection plans and manufacturing process plans and to import results from CMM Reports. "The ways that we’ve been able to adjust DISCUS software for our own unique needs has reaped tremendous benefits, says Manning. "As the president of a company, I’m all about numbers. What we’ve done here in terms of productivity allows us to save significant shop time while delivering a 97% on-time delivery rate and excellent precision to our customers." ME
For more information on DISCUS Software, go to www.discussoftware.com, or telephone 614-360-2424.
This article was first published in the January 2012 edition of Manufacturing Engineering magazine. Click here for PDF.