Shop Solutions: Drill Switch Pumps Up Holemaking Productivity
DC Fabricators Inc. (DCF) manufactures heat-transfer components for the United States military and other users. The company's exacting standards have resulted in it being chosen as the exclusive supplier of critical heat-transfer components to the military for more than three decades.
DC Fabricators is always looking for improvements to its manufacturing processes, and recently a tooling switch improved productivity and quality in holemaking operations. An operations review undertaken by DCF manufacturing engineer David Honea with a local distributor and a representative of cutting tool supplier Iscar Metals (Arlington, TX) revealed the possibility of improving drilling of several hundred holes in large superalloy and stainless steel plates. Materials and workpiece hardness vary from job to job depending on the end use of the product.
During the review, the Iscar ChamDrill caught Honea's attention. Aimed at replacing both high-speed steel and solid carbide drills, the insert tools combine carbide's toughness and wear resistance with the forgiveness of a steel body.
DCF's original drilling process required one hour of setup time per workpiece, including several tool changes with adjustments to tool lengths. The ChamDrills allow operators to change the cutting edge in a few seconds right at the machine, essentially eliminating tool change time. The one hour per workpiece savings was a critical factor in the decision to switch tools.
A test of the ChamDrills and several competitors revealed the Iscar tools could produce almost double the number of holes-425--before a tool change was needed. Cost per hole was less than 25% of the existing method. Cost savings were also achieved against the normally less expensive reground solid carbide drills.
CNCs Control 77 Axes for Riveting Work
At the Boeing Co. facility in Macon, GA, they push the envelope on the term "multiaxis."
The plant uses two Broetje Automation Integrated Panel Assembly Cells (IPACs) to produce fuselage panel subassemblies for Boeing's C-17 Globemaster III cargo planes. The CNC riveters incorporate four controls, handling a total of 77 servo axes on each machine.
Macon produces major subassemblies for both the C-17 and the US Army's AH-64D Apache helicopter. The plant operated CNC-controlled Gemcor multiaxis riveters for a number of years, but recently switched to the IPACs to meet cost, quality, and delivery demands.
The IPACs use multiple CNCs to control all axis movements from a single operator station. One benefit of this newer system is reduced setup time. Boeing also maintains a full part program library on its own server, and can instantaneously call up any program needed via the control software.
On the riveters, the four main machine controls are Sinumerik 840D CNCs from Siemens (Elk Grove Village, IL). The CNCs are interfaced to a central operator station through PROFIBUS fieldbus communications protocol. The machines' Siemens SinDNC links to the captive Boeing servers to access part programs. In addition, the riveters incorporate Siemens Simodrive 611U drive packages and Simatic PLC/HMI terminals.
Each of the riveters has four CNCs to control a total of 77 servo axes in normal operation. The entire sequence of rivet selection, position, and completed actions is monitored from a central operator station, which also includes video monitors for visual inspection. Additionally, a modular optical system (MOS) camera is used to fine-tune positioning, allowing removal of temporary fasteners and improving the automation process.
The previous machines used two CNCs, but the older hardware was cumbersome to operate. The IPACs integrate multiple CNCs on the machine to allow improved ease of use and maintenance.
The Siemens controls are used for X, X1, Y, Y1, Z, W, A, A1 and E-axis movements. Each control, through separate channels, manipulates the universal panel holding fixture portion of the machine, which holds the part during processing. Typically, it runs about 16 rivets per minute on the C-17 fuselage panels. And, owing to a variable spindle speed range from 500 to 24,000 rpm, the machines have the ability to handle both aluminum and titanium alloy parts.
Macon operators say the controls are easy to use compared to older CNCs. Instructors from both Siemens and Broetje conduct training on-site. Boeing technicians are completely familiarized with every aspect of the machines, and the company has used Siemens training specialists for assistance on enhancing screens, developing specialized tables for troubleshooting, and implementing process counters for use on the machines.
Additional benefits of the new system involve increased efficiencies in both programming and machine performance. All programming for the IPACs is accomplished off-line with full simulation capabilities, resulting in programming time reductions of up to 50%. The system also allows the same programs to run on both machines, saving programming effort and reducing program maintenance.
Combining programming and operational efficiencies has given the Macon facility a truly competitive advantage. Machine run-time is up, and setup time is greatly reduced. Because all machine axes are operated by the Siemens CNCs, changing from one C-17 panel to the next is as simple as loading a new program and pushing a button. No manual intervention is required, as with the older machines.
New Machine, New Drills
Cemline Corp. (Cheswick, PA) manufactures heat exchangers for commercial and industrial hydronic heating systems. The company purchased a new vertical machining center in late 2002, and the production team soon realized that maximum feed rates, essential in optimizing cost savings and increased throughput, could not be achieved with the tooling used on the original machining center.
To reach their goal, engineers for the 50-person company began exploring alternative drills for applications on stainless steel, brass, and premachined plate steel heat exchanger covers. The tubesheets, which anchor the heat exchangers' copper tube bundles, range in diameter from 4 to 24" (100 - 610 mm) and are 1 - 3" (25 - 76-mm) thick.
After considering a number of possible replacements for the modular drills that ran in the previous machine, Cemline began to use Dynapoint SE211HP solid carbide drills from Kennametal (Latrobe, PA).
"The improved feed rates and tool life that we have experienced since making the switch are amazing, and the process of changing over to new tooling was much smoother than I thought it would be," says Cemline owner/president Lindsay Chappell.
The drills have allowed a 2.5 X increase in feed rate, from 2 to 5 ipm (50 - 127 mm/min), and a similar jump in spindle speed, from 1000 to 2500 rpm. The increased performance results from the tools' KC7515 submicron carbide substrate; a patent-pending point geometry that reduces heat and thrust, and improves hole quality by cutting from the center; and a patented multilayer PVD coating with excellent hot hardness. The drills run at surface speeds of 700 sfpm (215 m/min) in low-carbon steel and 270 sfpm (82 m/min) in type 304 stainless steel. Surface finish and hole accuracy make reaming unnecessary. Cemline uses an aluminum support plate on the underside of the exchanger covers to prevent flexing and dampen vibration caused by the increased speeds and feeds. The increased cover rigidity allowed accurate holes in a single pass.
Cemline also benefits from up to 4 X the tool life versus the competitive modular drill with replaceable drill points. The modular drill produced 200 - 300 holes before the carbide drill point needed to be replaced. Cemline can now drill 800 - 1000 holes with one drill, maximizing time in the cut.
The net result of all the improvements is a 70 - 80% reduction in manufacturing time. Response time in fulfilling orders for replacement tube bundles also improved, and a 57% reduction in cost per part ($26.02 versus $61.08) has strengthened Cemline's competitive edge.
Rather than regrinding, Cemline uses Kennametal's Blue Box program, which reconditions drills to "like new." The process uses the same kind of CNC grinding equipment on which the original drills were manufactured, and incorporates patented edge preparation processes and Kennametal coatings.
"Before switching to Kennametal, we were unable to use reground drills for holemaking in stainless steel and other tough-to-machine materials," explains Cemline production manager Jason Chappell. "After six months of using Dynapoint drills, I look at our holemaking productivity and quality reports, and I am still amazed by the dramatic improvements we have experienced with the product."
Digital Indicators Boost Tube Quality
Dial indicators aren't the newest or most exciting measuring instruments around. But for a manufacturer of tubing used in end-products such as automotive drive shafts, shock absorbers, and washer agitator shafts, a new Swiss-made digital version of this old measuring tool is providing unsurpassed repeatability.
Oil City Tube Div., Webco Industries Inc. (Oil City, PA) makes tubing that must meet rigid quality specifications for customers such as General Motors, DaimlerChrysler, Ford Motor Co., and Whirlpool. The new instrument plays a critical part in its daily production of more than 15,000 tubular parts, which must be cut into precise lengths and formed to exact straightness. The parts are processed at two separate but nearby plants in Oil City and Titusville, PA, the latter where shorter tubular pieces must be within a ±0.006" (0.15 mm) tolerance.
"Our target for these shorter parts is total indicator reading [TIR] tolerances of 2.994 - 3.006" [76.05 - 76.35 mm]," explains director of quality assurance Andrew Dailey. "A simple digital readout assures us of being on-target, so the new indicator avoids the errors formerly caused by our old manual dial indicators which inevitably were subject to human error."
All measurements performed in the plants are done directly on the tubing production line. At Oil City, coiled steel is converted to tubing lengths from 20 to 40' (6 - 12 m), while Titusville produces finished tubes in lengths from 2 to 60" (51 mm - 1.5 m).
For straightness measurements, the indicator is fixed in the center of two rollers upon which the tubes are spun. Typical measurements are less than 0.10" (2.5 mm) TIR--comparable to the straightness specifications of special-order arrow shafts for archery.
Quality checks for straightness and length are done periodically during each 12-hr shift using Ultra-Digit Mark V Sylvac indicators, distributed in North America by Fred V. Fowler Co. (Newton, MA). To measure length after tube spinning, the indicators are set up horizontally, thus giving Webco dual measuring capability. "The actual length of the part is critical, and this is programmed directly into the indicator," Dailey explains.
The indicators incorporate tolerance signal lights, selectable resolution, and bidirectional RS-232 output. The display face on the instruments rotates 270º for easy viewing, and their ability to output data facilitates Webco's statistical process control (SPC) efforts.
"It's no secret that manufacturers are increasingly sensitive to the absolute need for zero-defect, error-proof quality, particularly in assembling parts that have rigid specifications so that they mesh perfectly with other parts," Dailey says. "The fact that we get double duty from this digital indicator, which is extremely easy to use on the line, is helpful and saves us considerable time.
"What used to take 20 seconds per inspection now takes 5 seconds. Considering the number of parts we produce, that's a big saving in time and improvement in our quality. It's also reassuring to know that we can measure everything we have to."
Five-Axis Opens Market Doors
"We call our five-axis capabilities a solution and evolution in part machining, especially for high-tolerance, high-volume, intricate parts that require tolerances of 0.0002" [0.005 mm] or better," says Al Mustardo, VP of Phelps, NY shop Magnus Precision.
Launched in 1982 as a mold and die shop, Magnus has developed a niche in cutting high-volume, precision parts, often in tough materials like titanium. Now most of the shop's products, for medical, aerospace, and sports equipment applications, easily fit in the palm of a hand.
"We went into production machining because we thought we could get a better return on our investment," Mustardo explains. "We felt there was a void in small- to high-volume, close-tolerance parts, and we thought we could really fill this need using EDM, CNC turning, and multiaxis milling."
Initially, Magnus bought VMCs and HMCs to produce prismatic parts. Complex workpieces that required multiaxis machining were placed on different machines or completed using a rotary table setup. But as part tolerances became tighter, Mustardo realized he needed something more.
Magnus purchased its first DMU eVolution five-axis machining center from DMG America (Schaumburg, IL) a few years ago. Within three years, the company added four more; now, Mustardo is looking at adding another five.
The machines boosted productivity and precision by machining the part in one fixturing. According to Mustardo, they also allowed Magnus to sell parts for less money by reducing labor costs. "We are more productive with the people we have," he says. "We have one person running three or four of these five-axis machines."
Magnus' biggest five-axis machine is a DMU 70 eVolution with a 30 X 24 X 21" (800 X 600 X 500 mm) work envelope. One of the five-axis centers uses robotic load/unload; one is paired with a 30-pallet changer and uses laser and touch-probe tool monitoring and part probing.
According to Mustardo, Magnus investigated machines from four builders before purchasing from DMG. "Five-axis machines weren't that common three-and-a-half years ago," he says. "DMG had the best all-around accuracy and organizational support. It's been a good choice. That's why we bought four more."
This article was first published in the March 2004 edition of Manufacturing Engineering magazine.