Shop Solutions: CNC Multispindle Hits All Targets
Trafimet (Vicenza, Italy), a leading manufacturer of MIG, TIG, and plasma welding torch tips and sockets, produces millions of plugs and sockets per year, much of which is manufactured from brass. That has required three shifts per day. Although the production is relatively high, the company seeks to keep inventory to a minimum and produces according to a just-in-time schedule.
The company is continually looking for ways to improve its precision machining operations and get things done faster, while carrying the minimum amount of inventory. Trafimet management has carefully analyzed the activities that affect the production process, including when processing time was unavailable because of tool breakage, programming changes, maintenance, bar loading and loader downtime, tool grinding, and other factors.
A substantial increase in demand for its plugs and sockets of four million pieces annually in 2006 led the company to investigate production options. Initially, its engineers considered an eight-spindle automatic lathe for socket production, but they were concerned about the ability to change over quickly to another product.
In addition to requiring the ability to produce precision parts in volume, they determined that what was needed was production flexibility. They looked at a CNC multispindle from Milan-based machine tool builder Tajmac ZPS (Milan; ZPS America, Indianapolis) as a way to achieve the optimum lot size and product mix: 10,000–50,000 parts with minimum setup time. This, it was felt, would provide the needed flexibility and would help to reduce the cost of the sockets and plugs.
In view of the amount of investment needed for such a choice, it was clear to engineers at Trafimet that such a machine would have to guarantee a high degree of flexibility in the following:
- Differentiation of products (high mix),
- Lot flexibility,
- Reduction in tooling time,
- Containment of production costs.
"Tajmac had proved to be a reliable supplier over the years for both products and technical assistance, both of which are of enormous importance to a production unit," explains Ugo Simioni, industrial engineer at Trafimet. Choosing the ZPS CNC Mori-Say TMZ 642 multispindle in 2006 meant being among the first to test the innovative CNC product. As promising as it seemed, however, it required some further confirmation, especially in those fast processes used by Trafimet, where the cycle time is usually faster than 10 sec per part.
Once the decision was made to partner with Tajmac, the companies cooperated closely in training Trafimet personnel from machine prototyping and process prove-out to machine building. In September 2006, the project began when a Trafimet technician was sent to Tajmac for training with Tajmac technicians. This included:
- Four months training at Tajmac during the testing of the TMZ machine for in-depth knowledge of multispindles and numerical controls;
- Three months of training at the ZPS factory in Zlìn, Czech Republic, helping to build the Trafimet machine and gain detailed product knowledge; and
- Participation in start-up, testing, and run-off of the machine.
The two companies also cooperated in the definition and development of new tools to solve any problems which might occur in the field, and to set up a training course for operators so that they would both benefit from better start-up and product management and development.
Trafimet operators knew very well how to get the most capability from the TMZ CNC multispindle production center. The return on investment, therefore, was accomplished quickly, so quickly that the six-spindle multispindle effectively rivaled the cost-effectiveness for a single-spindle turning center the company was also using.
"Tajmac helped us to think differently about our processes and thus to reach better results," says Simioni. "Mechanically, the TMZ machine is revolutionary."
It features a double Siemens CNC and more than 70 CNC axes. Standard features of the versatile TMZ multispindle include six independently driven CNC spindles, six independent compound slides (X and Z), six independent tool carriers with driven tools, three backworking tool carriers (two driven), and standard presettable VDI tooling.
Each of its six spindles is linked by a composite shaft to its own motor located away from the spindle drum, which employs a Hirth coupling. This makes it unnecessary to reverse-index the drum at the end of each 360° cycle, connect, and disconnect the motors to the spindles with each indexing, cool the drum to dissipate the heat generated by the spindles, or to supply power to the spindles through rotating, slip-ring connectors. The mechanical stability of the machine is achieved without the use of refrigerant or spindle compensation.
The absolute independence of each spindle makes it possible to perform any type of machining, including machining operations requiring spindle stopping or C-axis spindle orienting, making the TMZ a complete turning and milling center.
The Trafimet goal of 70% improvement in efficiency was achieved in three months.
In July 2007, the machine was installed at Trafimet. The ramp-up of the project lasted only two months.
"In the third month, the system had already achieved a degree of efficiency close to the 70% parameter set by the contract. This was an excellent result compared to the usual time previously needed for the start-up of machines of similar complexity and with the same approach problems," Simioni says.
With efficiency now up around 90%, the company is considering moving additional production to the multispindle from other machines in the shop, while working to further reduce setup time. Although very efficient, set up is an important issue when running a variety of parts across the machine.
"In tough times, we find we can move some products to the TMZ multispindle and handle lower lot sizes while reducing cycle times per part," Simioni says. "One of our parts had been running on a single-spindle turning center with a cycle time of about 1 min. With a little planning, we found that it could do the same part economically in batches of 5000—12-sec cycle times—with three changeovers per week on the TMZ." The Trafimet engineers had already determined that a 15-sec cycle time would permit the machine to produce lots of 10—20,000 pieces economically.
"Thanks to the development and use of newly designed equipment from Tajmac, it was possible to reduce cycle times both in the products covered in our contract, and in the new 'complicated' products which had migrated from single-spindle CNC to the multispindle TMZ 642 CNC," Simioni says. "The independent spindle drives and advanced drive system, the use of extra axes, and other improvements made the machine extremely versatile, and also enabled us to find new ways of reducing product costs."
The difference between the fine-tuning of the TMZ machine compared to that of a traditional mechanical machine or a single-spindle three-turret CNC is significant. One year later, Trafimet has two specialized technicians who can tool and operate the TMZ machine.
Through the use of SMED (single minute exchange of die) techniques, films, and joint analysis of the recorded data by machine builder and customer, it was also possible to shorten targeted machine setup times by 30% in some cases.
Tooling Takes Checkered Flag for Gibbs Racing
In the world of sports, it's often said that defense wins championships, but in the world of the NASCAR Sprint Cup Series, the name of the game is consistency. That's not too different from the performance excellence expected in team sports, exemplified by winning Super Bowls in the National Football League.
To find success at the pinnacle of American motorsports, it takes teamwork. Just like the NFL. Not only does it take a talented person who can drive the wheels off his car and a crew chief who can plot weekly top-10 finishes, it takes the support of a team of machinists operating the most advanced machine tools to produce the parts that go into the highly engineered race cars.
Long before the green flag drops, machinists lay the foundations for their team's success by producing consistently flawless parts with lead times ranging from hours to days. Their ability to machine a variety of parts can spell the difference between finishing first and taking the checkered flag, or even not finishing at all.
No team knows that better than Joe Gibbs Racing (JGR; Huntersville, NC), which entered NASCAR in 1992. JGR is owned by Hall of Fame and Super Bowl winning former Washington Redskins coach, Joe Gibbs, and his son, J.D.
JGR is one of the premier organizations in the sport. The team has amassed more than 100 victories, which include three Sprint Cup Championships, the 2008 Nationwide Owners Championship, three Brickyard 400s, and the 1993 Daytona 500. JGR currently fields Toyota Camrys for three NASCAR Sprint Cup Series teams and two NASCAR Nationwide Series teams, which are driven by Joey Lagano (#20), Kyle Busch (#18), and Denny Hamlin (#11).
Soon after JGR won the 2000 Sprint Cup Championship with driver Bobby Labonte, the racing team began looking for a new tooling supplier. Mark Bringle, JGR technical sponsorship manager, hoped to maintain and improve its competitive edge by bringing all proprietary manufacturing in house. Bringle chose Sandvik Coromant (Sandviken, Sweden; Fair Lawn, NJ).
"Though the improvement of cycle and lead times was imperative, we wanted a tooling supplier that could also help us improve speeds, feeds, and depths of cut in materials like 4130, 4340, and stainless steels without suffering a reduction in tool life," Bringle explains. "Sandvik Coromant offered an extensive product line that suited those needs." Cutting tool solutions cover the broad range of processes including turning, parting, grooving, milling, and drilling.
The first tool recommended by Sandvik Coromant for JGR was the CoroMill 390, a high-precision indexable end mill that is designed to improve productivity in long-edge and square-shoulder milling. The integrated dampening of the Coro-Mill 390 provided JGR with more efficient, vibration-free machining for improved performance in deep cavities and pockets. This reduction in vibration also enabled an increase in cutting parameters without compromising workpiece quality.
"The CoroMill 390 allowed us to reduce cycle times on some parts from 4.5 to 3 hr without the use of coolant," says Bringle. "We were not only saving costs through increased dry machining, but we were also able to define the proper inserts and cutters for maximum material removal due to the variety of tools available. This flexibility provided an instant boost to our Concept to Car system."
Concept to Car is a key ingredient in JGR's recipe for success on race day. Thirty-five engineers have the job of finding new ways to make each car faster. After concepts are developed, they go through a series of prototypes, and test and failure analyses. Once approved, parts go into immediate production. No longer forced to wait 4–6 weeks for the return of outsourced parts, JGR has a typical lead time of about two weeks. But due to the nature of NASCAR's grueling 38-race Cup schedule, lead times often shrink to as little as two days.
One Tuesday before a race at the Las Vegas Motor Speedway, a new concept emerged that could, with quick machining turnaround, make it to the speedway in time to be implemented that weekend. After locating the necessary materials in a Pennsylvania warehouse, JGR had the material shipped to North Carolina overnight. Upon receiving material the following morning, the new parts were manufactured and then shipped overnight to the track in Las Vegas. Though the JGR haulers, which carry two race cars and enough parts, spares, and equipment to build another car, had already left for Las Vegas, the newly machined parts made it to the track before the trucks.
"Ten years ago, it would have been impossible to get a concept to a car under that scenario," says Bringle. "With Sandvik Coromant's tooling solutions, we are able to overcome adversity in production and translate that to wins on Saturdays and Sundays."
Sandvik Coromant tools are used exclusively on all JGR's machine tools. Equipment includes 18 Doosan Infracore mills and lathes with box way construction for high-accuracy parts production. As a result of the total implementation, the 20 machinists in JGR's 25,000 ft2 (2323-m2) state-of-the art Advance Technology Center produce roughly 950 proprietary parts for six internal customers: the motor shop, the Nationwide division, and the fabrication, shock, chassis, and parts rooms.
JGR can also call on Eric Gerringer and Bo Shomaker, local Sandvik Coromant representatives, to work with machinists to identify and capitalize on areas displaying a potential for improvement.
"Most of our machinists were lead men and supervisors at other shops," says Bringle. "They are the experts at what they do, but Bo and Eric still visit twice per month to advise them on everything from the ideal products to choose from the catalog to ways to machine parts faster and more efficiently."
Recently, Gerringer helped JGR make programming improvements and tooling changes that shaved the cycle time for a part by more than 4 min. After seven years of this partnership, the longest cycle time for any part in the shop is a motor plate made of aluminum alloy that clocks in at 3.5 hr. Unsatisfied, Sandvik Coromant representatives worked with Joe Gibbs Racing throughout the off-season to reduce that time, along with others, in preparation for the 2009 NASCAR season.
"When we went looking for a tooling supplier, we didn't want to have to re-invent the wheel," Bringle says. "Sandvik Coromant are experts at what they do, and we wanted that expertise to be a part of what we're doing. They have a complete product line that they are constantly working to improve, and that is why we consider them to be a major player in the core of our business."
Training Powers Husky Productivity
Skills shortages, even among the current manufacturing workforce, are having a widespread impact on the ability of manufacturers to achieve required production levels, increase productivity, and meet customer demands.
With few qualified people prepared to replace the retiring "baby boomer" generation of skilled workers, the situation is approaching crisis proportions in an economy that continues to grow more constrictive in the face of tightening credit and intensifying domestic and international competition.
Husky Injection Molding Systems (Bolton, ON, Canada) recognized the situation and has taken action to remedy the skills gap. A leader in the design and manufacture of injection-molding machines and components for the global plastics industry, Husky has plants, technical centers, and parts distribution centers around the world, supporting customers in more than 100 countries.
Each Husky manufacturing plant is responsible for its own training plan. The company's plant in Milton, VT, employs about 370 people, including a small team of manufacturing engineers and continuous-improvement technicians to manufacture hot runners for mold making. A hot runner system often consists of a heated manifold and a number of heated nozzles. The system's main task is to distribute resin to various nozzles, which then meter it precisely to the injection points in the mold cavities.
A principal training objective is to grow the confidence of machine tool operators. A typical example where confidence needed to be reinforced would involve a new technology that was supposed to result in faster machining speeds. The operators' first reaction might be to turn things down, because they didn't understand the technology. Through training, management felt, different levels of skills could be introduced across the shop floor that would put decision-making in the operators' hands, and give them the knowledge to back it up.
To acquire that knowledge, Husky manufacturing engineers signed up for the Comprehensive Application Engineering Course offered by Kennametal Inc.'s Knowledge Center (KC; Latrobe, PA). Since its inception in 1998, the Kennametal Knowledge Center has grown from delivering a few courses per year to delivering more than 40 face-to-face courses per year globally.
The company recognized the need for educating internal and external customers in the metalworking field early on. This thinking was spurred on by new workpiece materials, more advanced machine tools, new tooling advances, and the requirement that companies find ways to stay competitive. The KC operates under the principle that metalworking is a science and not an art, so it uses a noncommercial, tuition-based delivery to teach and discuss engineering principles and facts, no matter what manufacturer's products students plan to use.
"The Comprehensive Application Engineering Course is designed to be an intensive four-day metalcutting overview," explains Ron Davis, KC global manager. "There's a day of materials, covering carbides, ceramics, PCDs, and PCBNs; a lathe day covering turning, threading, grooving, and cutoff; a milling day; and a holemaking day. Spread throughout are applications, process optimization, removing bottlenecks, and other lean applications."
Husky had attempted to partner with local technical schools, but found that all they offered was shop math, or maybe some GD&T. That's when the company began looking at other companies around the area, including the technology vendor base. The company found that it wasn't surrounded either by a lot of young people or by good industrial technology education programs that could produce highly motivated trainees or update its employees with the latest technology.
Once the Husky team experienced the Comprehensive Application Engineering Course at Kennametal, they contracted with the company to tailor a three-day on-site course at the Milton plant. "Everyone from management and manufacturing engineering to the shop-floor guys has a different set of priorities, but everyone wants to get parts out the door," says Davis. "While productivity gains are important, we saw a real opportunity to improve communications throughout the workforce—among operators, programmers, MEs, and purchasing."
Where operator feedback used to be hard to get, Husky personnel are now able to diagnose and fix problems a lot faster with operator input.
There are many common metalworking processes employed in making hot runners, including milling, turning, holemaking, and finishing. Focusing on process improvement and operator feedback, as well as exploring the latest tooling technology, resulted in improvements in many applications.
The new ideas and techniques that were implemented led to significant cost savings and productivity gains that could be documented and data that could be captured. This led to the Husky manufacturing engineering team signing up for Kennametal's Certified Metalcutting Professional training, which comprises 15 courses in engineering principles, turning center processes, and machining center processes, all delivered on-line, so students can stay at their jobs and still take the classes.
The company had plenty of management-development tools available to manufacturing engineers, but not a lot on the technology side. Typically, the MEs and the higher-level technicians were the ones with the knowledge. The training regimen has enabled Husky to capture baseline information on its different manufacturing processes, including deep-hole drilling, turning, milling, and surface grinding.
"This is tribal knowledge that can now be spread around the company," says Davis.
Like other manufacturers, Husky is constantly solving the problems at hand. The KC training, has enabled the company to put a process in place for gaining new information, documenting processes, measuring results, and capturing knowledge about its operations, all with participation of its whole workforce.
This article was first published in the March 2009 edition of Manufacturing Engineering magazine.