What kind of mold shop would you create if you could start from scratch, with a clean sheet? Able to pick from the entire marketplace of mold making technologies, what would you choose - and, just as importantly, why? How might technologies shape and change your business and production strategies?
American Mold Technologies (AMT) is one of the few shops to have that opportunity - particularly on a large scale. One of the biggest mold making business start-ups ever created in the U.S., AMT began operations in September 1993 with all new equipment in a new 50,000 sq. ft. (4,645 sq. m.) facility designed for around-the-clock operation. Within six months, staffing had grown to 50 employees and by the first anniversary had increased to 65.
Located in Mt. Clemens, Michigan, about 20 miles (32 km) north of Detroit, AMT concentrates on medium-size injection molds in the 500-2,000 lb. (227-907 kg) range, primarily for the automotive market, says Tom Stanciu, vice president and general manager. By aiming at the center of the market, AMT found, first, the volume and stability needed to support its capital investment. Second, the molds have sufficient size, complexity and lengthy production times that advanced technologies and methods could be applied to decisive advantage, AMT felt.
“We’re definitely winning business with our lead times and CNC capabilities,” states Stanciu.
CNC Strategy
AMT created the shop around a strategy of CNC production, he stresses. “We saw this giving us the greatest control over quality, lead time and labor utilization, plus the critical ability - as software and data systems evolve - to readily adapt to change and enhance our proficiency.”
The company made a thorough evaluation of equipment from all the leading makers of mold making machine tools, including several Swiss and German lines. “It was a wide open competition - we had no preconceived notions going in,” says Stanciu.
At the conclusion of the comprehensive process, AMT selected Makino. Two major factors swung the selection, says Stanciu:
First, Makino provided a process concept. Besides applying CNC throughout the process from first cut to EDM, the company showed how it engineers its equipment to optimize and integrate the various functions, take time out of a job, and shorten the overall production cycle.
Second, Makino was able to provide a “total solution” to mold manufacturing, a single source for equipment, installation, integration, training and service.
Single-Source Capability
“We bought the whole tool room, the whole process—7 machines in one order,” says Stanciu. Makino’s single-source capability was especially critical for AMT, as a new company with new equipment, new people and a new mold making concept to learn, he stresses.
Makino got the equipment up and running to specification while helping to train AMT’s employees. This enabled transition to commercial operations by AMT with minimal “teething” problems, especially avoiding the kind of incidents that might damage its credibility out of the box as a quality mold builder.
CNC capability allows machine operators to concentrate mainly on setup. The reduced staffing allowed AMT to create a unique four-shift schedule of 12-12-12-6 hours per day for seven-day, around-the-clock operation. Even day shifts are lightly attended compared to traditional practice. For example, Stanciu notes, one operator typically runs all three CNC vertical machining centers. Similarly, AMT runs all the EDM machines with just one operator per shift.
Fine Finishers
“We’re able to machine a piece to so fine a finish, we’re seeing 40-50% reductions in benching time,” states Stanciu. “We came in with the usual mindsets from past practices. It took a while to re-educate us to using higher spindle speeds and feeds, but it does make a big difference. We can make many more passes and get a much finer finish, in the same amount of time as on a conventional machine at traditional feedrates.”
Taking shallow cuts at faster feeds with less step-over leaves extremely small, fine scallops, he explains, making for faster, easier benching.
“The Geometric Intelligence control on the machines is really something,” says Jim Miller, plant manager. “We can run spindle speeds and feeds well beyond traditional mold machining, without violation of the surface from things like dwell gouging, trailing error, and corner round-off. We can even do a tool change in the middle of a routine without leaving a difference in cusp height that has to be blended out. The accuracy of the work is really excellent. Wall thicknesses, for example, are dead on.”
Using conventional cutters, AMT machines contours at feeds from 30 ipm (762 mm/min) for roughing to 70-80 ipm (1,778-2,032 mm/min) for finish machining. “We try to run as fast as we can,” says Miller. “We want to see those blue chips.” On test cuts with special tools provided by Makino, AMT has achieved 3D contouring feeds of 125 ipm (3,175 mm/min).
Variations on a Theme
The three Makino vertical machining centers are all built on the same basic machine platform, share the same overall dimensions, and feature 25-hp (19 kW) #50 taper spindles, allowing interchange of work and programs. However, each is configured slightly different by AMT to increase its mold processing versatility:
The VMCs can be used for roughing, semi-finishing, or finishing to optimize machine versatility and production planning.
EDM Strategies
On the EDM side of its operations, AMT also looked to machine capabilities to reduce the labor burden and streamline mold processing.
As part of that strategy, AMT ordered CNC machines with automated capabilities:
These features allow operators to concentrate mainly on setup, leaving machines to then run unattended.
AMT also achieves processing efficiencies by creating full-form electrodes where possible. These capture the complete part shape to allow greater feature accuracy, particularly on complex geometries, while eliminating time-consuming setups and alignments. By reducing electrode changes, full-form electrodes support unattended processing. The shop has machined electrodes from graphite blocks up to 2 ft. (0.6 m) square.
Created specifically for graphite milling, the SNC106 utilizes high spindle speeds (15,000 rpm) to reduce cutting force, while Geometric Intelligence Control looks ahead for toolpath changes and compensates on the fly for dynamic effects and machine errors. These capabilities make the SNC106 superb at creating complex and delicate shapes, such as ribs, says Stanciu. Minimal benching - if any - is required on electrodes after machining.
The SNC106’s totally enclosed cutting zone and powerful vacuum/collection system allow capture of graphite dust and chips as fast as they’re created. The built-in system eliminates the need for a special room or dedicated air systems to keep abrasive graphite dust from invading and damaging other machines. The dust collection system allowed the SNC106 to be located near the EDM machines where it best fit the flow of work through the shop.
AMT uses a common tooling system for both the SNC graphite and the EDNC machines. A common toolholder and reference plates allow quick transfer of work from one machine to the other with positioning accuracy of ±0.000080" (0.002 mm). The precision reference plates - one on the toolholder, one on the machine - mate and interlock, similar to a Lego system.
AMT ordered the EDNC ram EDMs with two high-performance options that put more power into the process at critical points to support its high-efficiency, unattended production objectives.
A 240-amp power booster enables aggressive, high-speed metal removal, while Makino’s exclusive SL (smokeless) System vacuums away the heavy volume of sludge, gas and chips being generated. The powerful SL system prevents workpiece damage and secondary discharge. It is especially effective at clearing away the sandy sludge generated during large-current machining, allowing continuous operation without stops to remove sludge. It even eliminates jump motions typically used to clear sludge from cuts, shortening machining time.
An EDM operator recalled his surprise on one of the first molds to be EDMed after the shop opened. “Going by usual experience, I figured it would take three days, maybe four. We finished that burn in 10 hours.”
He praised the ability of the machine’s adaptive controls to correct and compensate for adverse conditions, enabling high burn rates and outstanding finishes even in unattended operations.
The Process Works
Open and out-spoken, Stanciu admits that AMT was aware of the risks, as well as the benefits, of deciding to go with a single supplier.
“We were placing a big bet on one horse and had some natural anxieties. I’ve got to say, though, Makino’s mold making process works for us,” he states. “It’s a sound concept, thoroughly engineered and executed. And if it wasn’t, I’d damned sure say so.”