Fine choice: Medical Manufacturing

How moldmakers select the right cutting tools, toolholders and machine tools.

In the mold manufacturing business, lead times are becoming far more critical than other factors—even price. Several plastic-injection mold and mold base making company owners and managers told Cutting Tool Engineering that faster delivery times are pressuring them to shorten lead times and possibly even operate 24/7 to meet customers’ demands.

Consequently, the choice of machine tools and the equipment needed to optimize moldmaking operations—such as toolholders and cutting tools—is critical to meeting these abbreviated lead times. Good machines are key, said the moldmakers interviewed for this article. They need to be rigid with minimal vibration to get consistent, repeatable results.

Chase is On

Tim Roth, shop supervisor for Craftsman Tool & Mold Co., Aurora, Ill., noted that machine tool builders and cutting tool manufacturers are constantly playing a game of catch-up with each other. Craftsman is currently installing the last machines in a $1 million, multiple-machine investment the company made over the past year to expand capacity, upgrade equipment and shorten lead times to handle a growing volume of orders. One machine is a Mitsubishi MV15-20 bridge-type vertical machining center with a 160 ” X-axis travel and 80 ” Y-axis travel. “It has a much larger work area than our other equipment,” Roth said.

Courtesy of Industrial Molds

Mark Hastings, HSM department manager at Industrial Molds, monitors a work cell that includes a Makino S-56 vertical machining center (left), an Erowa robot/pallet changer (middle) and a Makino F-5 VMC (right, behind enclosure).

With a 30 ‘×60 ‘ footprint, the MV15-20’s pallet system has two tables, which allows Craftsman to set up on one while the other is operating. Craftsman also added two Kuraki boring mills. The KBT-13 has 118 ” of X-axis travel, 78 ” of Y-axis travel and a 63 “×73 ” full rotational turntable, and the KBM-11 has a 39-sq.-in. table.

“Machine and cutter technology bounce back and forth,” Roth said. “The cutters catch up with the machine capabilities, then the machines surpass cutter capabilities. A lot of the newest cutters exceed the machines’ capabilities due to their stronger coatings. Better toolholders provide superior balance, allowing the tools to be run at speeds faster than some machines are capable of.”

Lights-Out Capability

Improvements in cutting tools—and in toolholders and machine tools—have also enabled many moldmakers to run “lights out” without worrying about destroying the workpiece or making “junk.”

Dennis Nord, supervisor for the EDM department at Industrial Molds Group, a Rockford, Ill.-based mold manufacturer that has won awards for its complex automotive molds, commented that extended cutter life is “a real gain” for Industrial Molds. “When cutting graphite electrodes, we use diamond-coated tools to get more cutter life so we can run overnight and over weekends,” he said.

Courtesy of Craftsman Tool & Mold

Craftsman Tool & Mold uses this 1 ” high-feed mill for achieving high metal-removal rates when machining mold bases.

These are primarily endmills from Preferred Tooling Supply and other sources, such as Crystallume, Leading Edge and GAR.

Nord continued: “If we can get three times the life out of our endmills, that’s a big advantage for us. We can run up to 20 tools in one electrode milling machine and not have to worry about the accuracy of our cuts being compromised. It may take a number of different tools to run these setups due to the different details on the parts. If we plan for a 60- to 70-hour run over a weekend, tool life becomes critical because we have such a varied array of electrodes to cut [for use in our EDMs].”

Craftsman specializes in large, tight-tolerance, custom mold bases for moldmakers. Its primary concern is quickly removing large volumes of material. Roth purchases cutting tools for the company and is impressed with the advances over the past 4 to 5 years, particularly with high-feed mills and button cutters.

Button cutters are optimal for mold pocketing and die/mold roughing in applications such as Craftsman’s that require aggressive machining. Roth added that while button cutters are not new, recent improvements, such as advanced coatings, allow the tools to cut more effectively and hold tighter tolerances at higher speeds. These coatings also help extend tool life when cutting hardened steel and milling electrodes, which has enabled more lights-out machining.

“We’re comfortable with lights-out machining because insert wear is predictable. Knowing we can get 8 hours of run time out of the inserts as we walk out the door at night is really helpful,” Roth added.

Right Tool for the Job

Moldmaking requires a variety of operations, from small, detailed core and cavity work to hogging material in a mold base. In addition, plastic-injection molds are also manufactured from a variety of metals, ranging from aluminum and soft steel (annealed or prehardened before heat treatment such as P-20) to hardened steel (such as H-13) and stainless steel.

Courtesy of Tech Mold

This mold, made by Tech Mold, is used to produce a housing that is part of a medical device that inflates stents.

Cutting tools used in moldmaking tend to be specific to the steels used, such as soft and hardened, which tend to cause tools to wear faster than when cutting aluminum.

Molds are built to accommodate the type of part being molded, the process being employed (such as injection molding, thermoforming and blow molding), and the useful-life requirements of the mold.

For example, high-volume, multicavity (64 to 196) molds for injection-molded components, such as medical disposable products (syringes, vials and intravenous set assemblies) and packaging (caps and closures), have volumes in the millions per year. Because these molds tend to run 24/7 year-round and require less maintenance, they generally are machined from steel mold bases with hardened steel core/cavity inserts.