Published 6/1/2007

Milling Molds Right the First Time

Proper end mill selection is critical for one manufacturer of high-end, one-off custom molds.

McCue & Associates LLC

Pioneer in Plastics

Mar-Lee Mold, one of three Mar-Lee Companies in the Leominster area, was founded in 1972 and now employs 32 people at their 20,000-square foot facility. It is not surprising that Mar-Lee chose Leominster as their home base. Leominster was once dubbed as “The Pioneer Plastics City” due to its thriving plastics industry, which began during the early part of the twentieth century, and while slowed, continues to the present day.

Mar-Lee Mold designs and manufactures complex, high-precision injection molds for the plastics industry. Located nearby and employing about 48 people combined are Mar-Lee Packaging and Consumer Products, specializing in high-volume, quality products and Mar-Lee Medical, which manufactures low-volume, complex, high-precision components and sub-assemblies for the medical device, single-use and bio-absorbable markets.

Mar-Lee Companies has built their reputation on producing high-quality, complex, long-lasting tools in niche markets. Approximately 60 percent of the molds Mar-Lee produces are used by their consumer and medical divisions to develop components and products. Forty percent of Mar-Lee’s molds are sent to outside contract manufacturers.

In 1972, Mar-Lee began operations with a conventional EDM. At that time, a moldmaker that had an EDM was considered a pioneer of sorts. They followed up this innovative trend by adding their first CNC milling machine in the early 1980s and then fully embraced high-speed machining during its debut around 1998.

High-Speed Challenges

High-speed machining presented opportunities and challenges for moldmakers in the late 1990s. Since feeds and speeds were different for high-speed machining versus conventional CNC machining, different end mills were required. Also, Mar-Lee began their high-speed machining operations on graphite material and then broadened their capabilities to include machining steel. Milling a harder material added to their challenges.

“We put our first OKUMA high-speed machining center on the floor in 1998 with the promise of increased productivity and the potential to broaden our moldmaking capabilities,” says Lavoie. “However, we needed end mills that would be effective for our high-speed applications.”

John Gravelle, President of Mar-Lee Companies, adds “For Mar-Lee to remain competitive in a shrinking moldmaking market, we needed the very best automation to efficiently and profitably produce a high-end, custom product. In order to continue manufacturing locally (in the U.S.), we needed to create efficiencies wherever possible.”

A Tooling Mystery Solved

Around 1998, Mar-Lee invited several end mill manufacturers, including Emuge Corp. (West Boylston, MA), to demonstrate their solutions. Lavoie reported that at first he examined and tried many end mills that could not do the job. Then Emuge walked through their door with a “mysterious” kit, that upon opening, revealed end mills that offered unique designs that could do the job for Mar-Lee.

“Right away we knew they had something different that we needed. We’d never seen tools with geometry and coatings like theirs. It was clear they knew their stuff,” says Lavoie.

He continues, “Only Emuge understood our requirements and had the right solutions. When I consider end mills, it is not just based on cost. Longevity and performance of the tools is more important. Ultimately, the proof is in the application. It has to be able to run.”

Emuge offers a complete line of milling tools that are specifically designed for optimum performance in a wide range of materials and machining applications. For example, Emuge S-Hard Cut end mills are made from superior grade carbide and are capable of hard machining up to 66Rc material. In all, Emuge carbide end mills feature appropriate flute geometry, coatings and designs based on specific applications.

The Proof Is in the Application

The use of Emuge end mills in its hard milling, high-speed moldmaking operations has provided Mar-Lee with solutions that are dependable, that increase productivity and that reduce costs.

Much of the injection mold work that Mar-Lee does involves short runs in hard material on high-speed machines. The company reports that Emuge end mills provide them with 30 to 40 percent more tool life than others they have tried.

Lavoie notes, “During the process of a cycle, from toolholder to machine to the end mill, there is a notable, up to 50 percent, cycle time reduction using Emuge end mills.”

For example, a high-volume manufacturer of baby wipe con-tainers that shipped 60 million of these containers last year, relied
on Mar-Lee to produce an eight-cavity mold for this product.

The process that Mar-Lee performed for this job is called in-mold labeling (IML). IML technology allowed Mar-Lee to produce the container with a “no-label” look and a graphics quality they might not have been able to achieve with conventional label decorating methods. Mar-Lee was able to successfully implement the IML process because they have the latest in tooling and automation to perform the operation.

Gravelle notes that when a company is manufacturing millions of pieces, they must work with suppliers that are using the most dependable automation. High-volume manufacturers cannot afford an interruption in their supply. He said that Mar-Lee was able to win this IML job, actually beating a competitor in China, by reliably producing the highest quality product at a competitive price.

Lights-Out Efficiency

Emuge end mills help Mar-Lee reduce labor costs by allowing one operator to tend to three automated work cells. Mar-Lee is able to conduct several hours of unattended operation using these efficient work cells.

Scott Hastings, a CNC machinist at Mar-Lee, says, “My machine runs all night using the Emuge end mill, many times working in hardness of 48-56 Rc, and by morning the cutter is still good. We can’t do that with other end mills because we would have to set up four tools and break up the tool program. Re-tooling wastes time and money.”

Hastings continues, “When you need to take a few tenths off a mold, an Emuge end mill will do it to tolerance. It consistently removes those tenths without wear.” In one example, Mar-Lee ran the tool to mill four cavities and the dimensions on the cavity were dead-on consistent.

Mar-Lee depends on Emuge end mills to produce a superior product. Hastings notes that the difference is in the geometry and coating on the Emuge end mills. For example, using a six-flute Emuge end mill versus a traditional four-flute mill, he achieves a mold with a mirror-like finish because the end mill is removing material faster and more accurately.

Successful milling means not only the right programming, CNC machine and end mills; toolholding is also a critical element. To that end, Hastings achieves further efficiencies by using the Emuge Shrink Master induction shrink workstation. Emuge reports that the Shrink- Fit technology provides the most accurate and rigid tool mounting available.

Hasting agrees and comments that Shrink-Master provides an extremely rigid setup that eliminates run-out and helps to prolong the life of the tool. The system uses an inductive heating coil to very quickly heat the shrink fit holder (in 15-20 seconds), which causes the slight expansion of the holders’ precision bore. The tool shank is then inserted in the holder end. The resulting bond transmits torque value two to four times higher than conventional mechanical or hydraulic chucking systems.

Les Regan, a CNC machinist at Mar-Lee, notes benefits from Emuge tools as well. Regan explains, “Emuge tools complement high-speed machining to the fullest. They last longer and hold up better than other end mills we’ve tried for milling hard materials in the 48-50 Hc range. Sometimes we even go as high as 54-56 Hc. Other end mills would melt in cutting conditions like this.”

Twice the Life and More

Additionally, machinists at Mar-Lee report that Emuge end mills actually provide “twice the life and more” for which they were originally intended. At Mar-Lee, when a machinist is done using an Emuge end mill for a high-speed application, the tool is then re-used for traditional machining applications like on a Bridgeport. “All the machinists want the Emuge end mills, even the used ones from our HSMs,” states Regan.

“From the inception of our high-speed machining operations, we have been using Emuge’s tools and they perform better than other manufacturers,” says Lavoie. For a company like Mar-Lee that is competing in a narrowing moldmaking field, second tries are not an option. Milling the mold right the first time is essential.