In the early 1980s, the toy industry quickly and suddenly moved most of its mold work overseas, taking with it nearly 90 percent of Grand Die’s business in just two years. During this “offshore migration,” Grand Die applied its expertise in intricate, complex molds to customers in the automotive, computer, medical and appliance industries.
“This transition was possible due to our focus on quality,” says Grand Die’s president, Rod DeBoer. “Our reputation for making extremely detailed molds created enough word-of-mouth to replace our toy business. In fact, Grand Die is now larger than it was prior to this customer shift.”
THE IMPELLER PUZZLE
One mold recently put the shop’s expertise to the test: a fan impeller for a ventilation system on a medical mask. “The two-piece cavity has several complex ribs that constantly change shape,” says Jim Camfferman, Grand Die’s general manager. “And we wanted to eliminate as much benching as possible. We knew it would be a difficult mold to bench, taking up to 40 hours of work after conventional burning.”
Grand Die enlisted its two newest machines, a Makino V55 high-speed vertical machining center and a Makino EDNC43S RAM EDM machine, for the challenge. “It took a few weeks to install the machines and run two test jobs through each one,” says Camfferman. “The impeller was the first paying job to go through these machines and it went better than expected.”
According to Camfferman, the V55 roughs and finishes the P20 tool steel mold at speeds as high as 12,000 rpm. Using a 3/4 inch ball endmill, machine feedrates climb as high 300 ipm. “The rigidity of the machine allows for a smoother cut and surface finish,” explains Camfferman, “which impacts the amount of EDM time needed on the impeller.”
BENCH-FREE FINISH
Using the EDNC43S, Grand Die completely eliminates the need for benchwork on the impeller with Makino’s new High Quality Surface Finish (HQSFTM) technology. “From EDM to shooting parts, the impeller mold requires no benchwork whatsoever,” says Bill Spurrier, Grand Die’s EDM operator.
HQSFTM combines micro-discharge pulse control and high response servo technology with the use of an additive that is highly stable in the dielectric fluid. This powder additive improves electrical conductivity in the fluid for more consistent discharging and spark diffusion. In turn, this diffusion provides a smaller crater for superior finish without sacrificing metal removal rates. (See the cover story for a more in-depth look at HQSFTM).
“We’re still optimizing the process,” says Spurrier. “But cycle times have already improved by 25 percent using HQSFTM over conventional EDM. That helps us focus on getting molds to our customers and increases our mold quality and capacity at the same time.”
ONE IMPORTANT ELECTRODE
Spurrier notes that bench-free molds make the electrode more crucial than ever to an application’s success. “The burn must create a mold that the customer can shoot parts into almost immediately,” he says. “Once we burn the impeller, the superior surface finish and accuracy must be there. Any imperfections in that electrode are transferred into the part, so we inspect the electrodes for any cutter marks or flaws that can be benched out. Given a choice, we prefer benching graphite over steel—it is much easier.
“HQSFTM also allows us to achieve higher polish surface finishes without using a copper electrode. This is faster, since graphite is easier to machine, holds high levels of accuracy and is less expensive than copper.”
The mold’s toughest feature, its ribs, are overburned to ensure greater material removal. “Overburning the electrode helps,” says Spurrier. “And to ensure flushing is not a problem we orbit the electrode and circulate dielectric fluid in the work tank.”
KEEPING A QUALITY REPUTATION
Camfferman also sees the benefits this technology has brought. “We used to trade off between either longer burns or more benchwork,” he says. “Now superior surface finishes and faster cycle times are both possible.”
While this new technology has already solved Grand Die’s impeller puzzle, Camfferman looks to the impact these machines will have on other jobs.
As Grand Die Engravers supports its expertise and reputation for quality molds with the latest technology, it would appear to have found the formula for success—regardless of what the changing competitive landscape might bring.
Source: Competitive Mold Maker, Volume 4, Number 2
Copyright © 1999 Makino Inc. All rights reserved.