Shop Solutions: Five-Axis Programming Keeps Bottle Molds Flowing
The Sidel Group is a large manufacturer of rotary blow-molding machines and equipment for filling and capping the final product. The company's equipment is used to produce containers for such products as water, mayonnaise, ketchup, fruit juices, tea, milk, and cooking oils.
In 1988, Sidel started a moldmaking division in Norcross, GA. This would allow the company to offer turnkey blow-molding packages, including design, development, mold build, and prove-out of the complete process. Sidel started mold production as primarily a repair and support operation with limited production capabilities. When the company needed to increase output, managers purchased two FJV vertical machining centers from Mazak Corp. (Florence, KY).
Molds are produced from either aircraft-grade aluminum alloys or stainless steel. "I'd say 80% of the molds are aluminum, and the other 20% are stainless," Production Manager Jay Lowry says. Aluminum is used because rotary blow-molding machines use centrifugal force, and light molds produce less centrifugal force and offer quicker cycle times. A complete mold set generally means from six to 25 molds.
The VMCs served Sidel's needs, but engineers found that five-axis technology offered a more productive way to machine their complex molds. Sidel purchased two Mazak five-axis Variaxis 630 VMCs in 2002, largely because of the machines' Mazatrol conversational control. "With this control we can do a lot of the programming at the machine, whereas most five-axis machines have to be programmed offline," says Lowry.
Lowry believes in empowering operators and training all employees in the implementation of advanced technologies to keep the company's competitive edge. Programmers and machinists are cross-trained in-house, and the Mazak CNC allows a significant portion of programming to be accomplished on the shop floor, reserving CAD/CAM programming for complex mold cavities.
Lowry says five-sided machining capability was the second factor for moving to the five-axis Variaxis. "Most of our molds are cylindrical, around six inches in diameter," he explains. "We also have an older type of mold for large bottles, such as a 1-gal [3.8-L] mold that can be made from either stainless steel or aluminum. The mold is made from two halves that make a 180-mm square. We're able to machine the back of each mold half, then mount it to a fixture and finish machining the other five sides in one setup."
Sidel also found that accuracy of basic operations, such as squaring the piece, improved dramatically in a single-setup environment. Lowry can keep the molds on one machine, reducing or eliminating transfers between machines and stack-up of machining variables. This benefits the rest of the processes. Tolerances are in the range of ±0.0004" (0.01 mm).
Five-axis capability facilitates production of vents in the molds that allow air to escape. "We have 600-psi [4-MPa] air that blows into the molds to form the bottle," Lowry explains. "Air has to be removed between the pre-form and the cavity wall. We need escape vents for the air, and the five-axis gives us the capability to do this."
Sidel also benefits from the machines' pallet-changing system. One pallet is in the machine holding parts while the other is being loaded by an operator. To further increase flexibility and spindle utilization, Sidel is adding a Mazak Palletech material-handling system with 12 pallets that can be automatically shuttled between the two machines.
The setup will allow untended production, a capability that wasn't really factored into the initial purchase decision for the two machines. "But it was in the back of our minds; eventually we really want to step up our untended production time," Lowry says. "We figure we can get another 15 - 20% out of the Variaxis machines just by adding the Palletech system. We have two shifts, and we want the third shift to be untended from 10 pm to 6 am."
Since 1998, production has ramped up from 35 molds per month to about 250, with no increase in manpower (15 operators on the floor). The five-axis machining centers helped by enabling Sidel to reduce lead times from 8 - 10 weeks to 3 - 5 weeks. The machines also eliminate practically all EDM functions, including engraving, and reduce hand polishing on mold surfaces to only about an hour per mold.
Welding Switch Cuts Rework
A switch to a new welding process and a programmable power source helped the Polaris Industries Inc. plant in Roseau, MN increase productivity by reducing post-weld cleanup operations by more than 1/3 in one application.
The plant was using a conventional constant-voltage (CV) MIG welding process to fabricate chassis, steering, and suspension components for Polaris snowmobiles, all-terrain vehicles, and Ranger utility vehicles. Craig Cerminara, welding engineer at the 1900-employee facility, says the main goal was to increase productivity and profitability by reducing weld spatter, distortion, and rework.
Pulsed MIG welding using Lincoln programmable power sources paid off in multiple benefits at Polaris Industries' Roseau, MN, plant.
"With the CV MIG process, our operators were using various modes of metal transfer depending on the particular preference of each operator," Cerminara recalls. "We were lacking repeatability from one operator to the next. One operator might use a spray transfer method, while his neighbor was using a globular transfer method."
Further complicating things were limited weld lengths--2" (50 mm) or less on most parts. Limited length means the arc is only on for a brief period of time for each weld, and thus has limited time to establish itself. So, Polaris was looking for a power source that could provide rapid arc stability.
To find the right technology for the job, Cerminara and his colleagues put power sources from a couple of possible suppliers head to head. The winner was the Power Wave 355M from Lincoln Electric Co. (Cleveland, OH). The machine's proprietary Waveform Control Technology made an immediate impact on arc quality and consistency compared with the competitive unit.
"With the Power Wave 355M units, we provide a set range for our operators and then they have the ability to fine tune for their particular welding style," explains Cerminara.
The units' high travel speed and low-spatter, pulsed spray transfer improved arc consistency, reduced weld spatter loss, and achieved higher travel speeds. Benefits included increased throughput and reduced welding-related distortion, and, in the first application where Polaris used the power sources, the company experienced a 35% increase in productivity, attributed to the reduction of post-weld clean-up operations.
"Using a pulsed MIG process, it doesn't matter what wire feed speed the operator sets, he or she will always run the same process and we will always get consistency in the welds," says Cerminara. "Pulsed MIG reduces the amount of heat input into the weld and therefore decreases distortion. Spatter has also been reduced, translating into a huge cost savings in labor and rework time."
Initially, Polaris purchased 16 Power Wave units, but the company has since added another 12 systems and plans to add more in the future.
The Power Wave 355M comes standard with more than 60 factory-programmed waveforms optimized for specific wire types and sizes. Custom waveforms also can be shaped digitally using software, and Polaris used waveforms developed by Lincoln applications engineers to create tight, crisp arcs. "We were looking for a specific type of pulsed MIG arc that was forgiving and one that could consistently handle gaps," Cerminara explains. "With Lincoln's help, we developed five custom waveforms. Eventually we will pare those down to three for even better consistency."
At Polaris, the custom programs and increased arc travel speeds resulted in lower shielding gas usage and, because it was easier to achieve the desired weld size, less over-welding. These added benefits translated into a significant welding cost reduction.
Plasma Cutting Boosts Armor Production
O'Gara-Hess & Eisenhardt (OHE; Cincinnati, OH) first made a name for itself in 1948, when it engineered a bullet-resistant limousine for US President Harry S. Truman. Since then, more than 60 international heads of state and a long list of diplomats have been customers. Part of the Mobile Security Division of Armor Holdings Inc., the company today is the world's largest provider of wheeled vehicle armor.
The armor plate OHE installs ranges from 1/4 to 3/4" (6.4 - 19-mm) thick. Because the company retrofits armor to existing vehicles, pieces must sometimes be cut to fit into very tight places with tolerances in the range of ±0.015" (0.38 mm).
Keith Kilpatrick, director of manufacturing engineering at OHE's Fairfield, OH, plant, needed to boost cutting capacity to support the company's increasing business. He had his eye on a plasma cutting system he had seen in a sister plant in Germany, and contacted a representative of ESAB Cutting Systems (Florence, SC).
Developed by a team of US and German engineers, ESAB's Acer 2 plasma cutting system featured high-speed dual side drives, a precision linear rail cross axis guidance system, the company's Precision Plasmarc plasma system, and a Windows-based CNC. It can provide good cut quality on carbon steel, aluminum, and stainless steel workpieces.
Precision Plasmarc is a proprietary arc constriction technology that results in very low cut edge bevel angle and minimal dross, and requires little or no clean-up. It allows cutting and plasma marking with the same torch when used with an optional integrated flow control and PC. This eliminates the need for a dedicated marking station, improves accuracy by eliminating the need for tool offsets, and speeds cycles by cutting out machine motion between offsets.
The Fairfield facility has grown into two separate production buildings, both using a cellular assembly line process to produce military and commercial vehicles. In both cases, the vehicles are first disassembled and gutted, then the armor package is applied and the vehicles are reassembled.
Armor packages include ballistic-grade steels welded throughout the passenger compartment, transparent armor consisting of multi-layered ballistic glass, battery protection to ensure continued power supply, and Runflat wheels to help the vehicle reach safety in the event of an attack. Suspension upgrades are also included if required.
The machine's integrated flow control uses CNC-controlled proportional valves to control cut, start, and shield gases. Process parameters are selected and stored in the control, but can be manually adjusted and saved for future use, giving the operator flexibility.
Installed in November 2003, the initial Acer machine was so successful a second unit was added in June 2004. The machines have been instrumental in meeting OHE's demanding production schedules, including 350 Up-Armored Humvees per month for the US Army.
Centerless Belt Grinders Speed Finishing
Milark Industries Inc. (Mansfield, OH) saves time and reduces finishing operations on plated motorcycle accessories by polishing the steel rod from which they are formed with a centerless abrasive belt grinder before forming and plating.
A privately owned, third-generation company with more than 150 employees, Milark specializes in metal stampings, tube bending, welded parts, and subassemblies, as well as related finishing operations. It lists customers in the automobile, motorcycle, and appliance industries, among others.
Major portions of many of the company's motorcycle accessories are formed from either cold-rolled steel or chrome/moly steel in various diameters. In some cases, plates, gussets, and other stamped or formed components are welded to the formed rods to make the final product.
To achieve smooth, flaw-free plated surfaces, the company polishes the rod stock before it is bent to shape using two CF-8082 OD cylindrical finishers supplied by Grinding & Polishing Machinery Corp. (G&P; Indianapolis). The grinders feature dual abrasive belts with rubber contact wheels set at a slight angle to feed the parts through without operator contact. In production, the operator simply lays a rod on the workpiece rest to the left of the first belt, and it feeds through the process automatically. Production Planner Brian Reich says the entire cycle takes about 10 sec.
Depending on the material and the finish required, belts with two different abrasive grades can be used. Typically, the first belt, on the left, will not be as fine as the finish belt on the right. Because the parts makes contact with the abrasive belt on an unsupported area of the belt, it is possible to polish tapered parts as well as straight workpieces.
The machines can handle stock diameters ranging from 1/2 to 3" (12.7 - 76 mm). Powered by 5-hp (3.7-kW), three-phase motors, the grinders use 5 X 73" (125 mm X 1.9-m) abrasive belts that run at a speed of 3500 sfm (1066 m/min). Belt changeover takes only minutes, according to Reich.
Before getting the machines, Milark had the stock ground by an outside source. Bringing the work in-house has given the company better control of quality and delivery, Reich says.
Laser Trackers Help Develop New F1 Car
The new Renault R25 race vehicle lies at the heart of the Mild Seven/Renault F1 team's plans to challenge rivals Ferrari for the 2005-2006 World Championship title.
The team uses two LTD800 laser trackers from Leica Geosystems (Norcross, GA) to measure components, set up the cars for wind tunnel testing, and perform other tasks, according to wind tunnel facility manager Mickey Nolan.
One laser tracker is used to set up the car in the wind tunnel test facility. The other Leica tracker is primarily used to measure large manufactured components and complete legality checks on the finished R25 race vehicle.
"In the high-demand environment of F1 wind tunnel testing, this system provides the Renault F1 Team with a cutting-edge tool for improvements in efficiency and accuracy," he says. According to Nolan, the laser tracker reduces setup times by 55% and enables improved repeatability.
"With commonality of CAD packages and real-time CAD comparisons, our engineers can measure and verify any part in any geometrical position around our model," he concludes.
The Leica LTD800 laser tracker and wireless T-Probe and T-Scan products enable engineers to capture measurements with precision, speed, and flexibility in a variety of industrial environments. The T-Probe is shock-resistant and insensitive to temperature changes, and can be used for rapid, hand-held rapid measurements within a 30-m volume. The T-Scan can be used for rapid, noncontact digitization of large objects at a rate of 7000 points per second.
Development of an all-new race platform is already paying off for the team. Giancarlo Fisichella won the season-opening Australian GP, while team-mate Fernando Alonso took victory two weeks later at the next race in Malaysia.
Training Maximizes CAD/CAM investment
Stihl, a family-owned manufacturer of chain saws and other lawn and garden equipment, continues to expand its Virginia Beach, VA, plant, the only one in the United States. Over the years, production has doubled and is still growing.
The plant switched to Mastercam CAD/CAM software from CNC Software (Tolland, CT) for its machining three years ago. Productivity has since doubled, says Tool Room Supervisor Todd Blanton.
According to Blanton, Stihl also chose to adopt Mastercam's Certification Program. Originally meant to create a benchmark for technical schools and other academic programs, the certification could be tailored to Stihl's requirements to meet internal quality standards and further its commitment to ongoing workforce training.
The first step was training and trainer certification from Mastercam's Educational Division. The program includes a detailed curriculum that gives students a comprehensive understanding of machining and programming, from how a computer works to how a toolpath is made.
Stihl already had an apprentice program, and ten people were chosen for the certification program. They began taking classes at the plant in August, and finished training in December. In February, nine out of ten students received certification after a test. Students also received college credit from Tidewater Community College.
"We like to train our own employees right here," says Blanton. "We have our own systems in place."
One employee who took the class summed up the benefits. "Everyone who took the class is pretty fluent now," he says. "They can analyze and think for themselves."
This article was first published in the May 2005 edition of Manufacturing Engineering magazine.