From Mold Making To Mold Manufacturing
A visitor to Pro Mold & Die in Roselle, Illinois (a suburb of Chicago) would discover a mold shop that knows how to machine to zero, although the shop usually refers to the process as “net machining.” All of the right technology is in place: the appropriate machine tools, shrink-fit tooling, HSK toolholders, an integrated workholding pallet system, premium cutting tools and capable CAM programming software. On the shop floor, you would see some molds in which cutting to zero has clearly streamlined production and improved quality.
What a visitor couldn’t easily detect is that, for this shop, achieving that competence has not been an entirely smooth and seamless transition. “We lost some good people along the way,” admits Dave Long, who founded Pro Mold along with Walter Schaub in 1973.
“It hasn’t been easy, but we’re producing better molds today, and the higher level of service that we give to customers makes us indispensable. We had to make the change,” says Mr. Schaub.
Their experiences with the transition have given them good advice to share with other mold shops. In fact, their comments and observations about managing change should be useful to any shop manager.
How This Shop Machines To Zero
Pro Mold has 45 employees, including 8 designer/programmers and 30 in shopfloor production. The company builds about 55 molds a year for customers in the automotive, medical and appliance industries. One of the shop’s specialties is two- and three-shot molds for automotive lighting systems.
Pro Mold machines larger mold components on two machining centers from OKK (Glendale Heights, Illinois). Smaller inserts and components are machined on a VMC from Creative Evolution (Schaumburg, Illinois). All of these machines are equipped with scales for positioning feedback in increments of 0.5 micron. A chiller at each machine maintains a constant spindle temperature and prevents thermal growth.
Shrink-fit tooling is used on these machines for cutting to zero. The Creative Evolution VMC is designed for HSK-A63 toolholders. This machine has a 24,000-rpm direct-drive spindle. The OKKs have 15,000-rpm 40-taper spindles. A number of other high speed milling machines are dedicated to producing graphite electrodes for EDM (electrical discharge machining). In larger molds, the shop relies on ram EDM to produce deep slots for ribs.
Tool paths for work that is machined to zero are prepared with software from Cimatron (Novi, Michigan). The shop has been a long-time user of software from this developer. Recently, Pro Mold installed the latest version of this software. The extensive high speed machining strategies and tighter geometric tolerances that it allows lend themselves well to machining-to-zero applications.
Total Involvement/Total Commitment
Because machining to zero affects every aspect of mold production, the transition to this approach has repercussions for every department. “Everybody has to get involved,” Mr. Long says. Top managers and shop owners have to be committed to the concept. Mold designers, programmers and shopfloor staff have to embrace it as well.
Show commitment at the top. Mr. Long points out that top managers have to lead the transition. In practical terms, that means learning everything they can about the concept, techniques and philosophy of net machining, he says. “Leaders have to have this credibility.”
The most important way managers show commitment is through their willingness to make the financial investment in equipment, cutters, toolholders, software and so on. “You can’t expect a shop to succeed without all of the tools it requires,” Mr. Long says. However, he adds that machining to zero can be introduced in stages. Outsourcing the high speed machining of hardened workpieces for 3D work is one way to start. Another is to retrofit or replace one machine at a time for high speed, high-accuracy machining.
Communicate. Top managers have to convey reasons for making changes. They have to establish clear goals. “They have to sell the new approach to the entire organization,” Mr. Long says. This will take frequent meetings to introduce and explain the concept.
“We kept everyone involved right from the start,” Mr. Long recalls. “We were as open as we could be.” There were no ultimatums, he says, but he and Mr. Schaub made it clear that there was no turning back.
Be patient. “It may take a year for guys to fully accept the new approach,” Mr. Long warns. The best way to generate support is to let the workforce see the benefits for themselves, he says. Allow for a learning curve and be sure that designers, programmers and mold makers learn from each other.
Expect some resistance. Some employees might not be willing or able to make the transition. “You’re asking workers to leave their comfort zone,” Mr. Long says. “We lost some of our most experienced mold makers as a result.” When the shop began to implement the machining-to-zero process, several of its most experienced mold makers chose to leave the company rather than give up the traditional way of building molds.
A shop also has to accept the fact that machining to zero substantially reduces the need for grinding and polishing. Some jobs may go away. At one time, Pro Mold had four people doing hand grinding and polishing, for example. Now it needs only two.
A Cultural Revolution
“Net machining forced us to change our shop culture. The old culture was based on individuality and craftsmanship,” Mr. Long explains. Machining to zero meant moving from mold building to mold manufacturing.
With the old system, each mold maker could have a different technique for building molds. However, by “replacing craftsmanship with technology,” as Mr. Long puts it, mold manufacturing yields predictable results and makes production scheduling more flexible.
Standardize procedures. “We now have a Pro Mold system for manufacturing molds,” Mr. Schaub explains. He says that, when the night shift takes over, there is no guessing about how a mold was being made during the day shift.
For example, setup procedures must follow the same “rules” regarding how work is centered on a machine, which corner is set as the zero reference point, and so on. Establishing these procedures was made easier with the Macro pallet system from System 3R (Elk Grove Village, Illinois). This integrated tooling system was first adopted in the EDM department but was mandated for the milling area about five years ago.
Look for predictable results. According to Mr. Schaub, machining to zero and following standardized procedures allow the shop to make molds in multiple setups yet still get results “dead nuts to the CAD data.” Fit and finish are not dependent on who worked on which machine. “We can also manufacture repair or replacement parts more quickly. If a customer breaks a lifter or a core, then it can be reproduced from the original geometry,” he says. The customer need not ship the mold back for fitting.
Make scheduling more flexible. Mr. Long adds that work can be moved from operator to operator. This gives him more flexibility for scheduling jobs. This flexibility has added importance because machining to zero had compressed mold production time. “We can’t have a holdup because a certain mold maker is absent or on a different shift,” he explains.
Skill Still Matters
“We don’t let all of our machine operators do net machining,” Mr. Long says. It seems that certain personality types are more suited than others to the discipline and attention to detail that it involves. The ideal operator is cautious but not “nervous” about trusting the technology.
Load it and go. Pro Mold relies on unattended machining to fully utilize the machines dedicated to zero-stock machining. “We evaluate an operator by his skill in planning for unattended operation,” Mr. Long says. He adds that good communication between programmers and machine operators is crucial for unattended machining. Unattended machining uncovers any weak links in the process.
Monitor remotely. Pro Mold has an interesting system for maximizing its unattended operation. All of the machines that run unattended are monitored by ceiling-mounted digital video cameras. This allows the machine operator to log on to the Web-based, password-protected shop network and bring up the view from one of the cameras. By zooming in on the machine, the operator can tell if work is proceeding normally. If not, the cause of the problem can often be identified.
“Our next step is to install a wireless network that will let the operator control certain machine functions remotely. For example, the operator will be able to initiate tool change if a cutting tool is worn or broken,” Mr. Long says.
Because this shop is used to moving ahead, steps such as these are sure to be taken in stride.
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