It has long been an accepted practice in the plastics industry to maintain a 60 percent rib-to-nominal-wall ratio in injection molded parts. Any increase in this ratio can cause visible sinks on the part’s cosmetic surface. However, with a thickness differential of 40 percent, the rib and wall of the part can shrink at different rates, causing the entire part to warp and distort. So, how can you achieve a flat AND beautiful part?

External Gas Assist
Mack Tool Design Engineer, Tom Revane, has a solution. External gas-assisted (EGA) injection molding. This process allows for an increase in rib-to-wall ratio without creating sinks in the visible cosmetic surface. Here’s how.

This molding technique employs a micro-thin layer of nitrogen gas that is released to the non-cosmetic surface of the part once the mold cavity has been filled with resin. The nitrogen gas layer packs the part evenly, replacing the holding phase in traditional injection molding.

The nitrogen gas flows along the ribs, pushing them toward the surface of the wall. This causes the rib to narrow at the point of intersection with the wall, providing a flatter, more even pack with no visible sinks.

Designing for EGA
Molding using EGA is not quite as simple as adding nitrogen gas into a standard injection molding procedure. The process must be engineered into the design of the part.

“If the gas escapes from the mold, the process doesn’t work,” says Revane. “We have to design features into the mold to seal the part.” Working closely with toolmakers and design engineers is critical to ensure that elements such as shiplap joints, grooves and ribs are incorporated into the part to prevent gas leaks.

1-to-1
Using EGA, Mack can increase rib-to-wall ratio in molded parts far above the industry standard of 60 percent, which is particularly important in molding large panels and trays.

“We are able to raise the rib-to-wall ratio to one-to-one,” Revane says. This uniformity within rib and wall thickness allows parts to be more structural with less distortion. Additionally, the part shrinks uniformly, allowing for improved fit during assembly.

Mack has used EGA to increase rib thickness in several recent molding projects to mold polycarbonate, PC/ABS, ABS, nylons, polyethylene, polypropylene and even glass-filled HDPE. The process is not limited to any specific resins.

Additional Benefits
While EGA is specifically effective in creating parts with high rib-to-wall ratios, it has many additional benefits:

• no molded in stress, resulting in less warp and stress-cracking
• lower clamp force requirement, allowing for a smaller press
• reduced wear on molds due to lower operating pressure
• uniform packing pressure
• reduction, and sometimes elimination, of secondary operations
• better texture reveal on part surfaces.

Total Customer Satisfaction
Increasing rib-to-wall ratio in parts from 60 percent to one-to-one, Mack is able to produce parts that are well within customer specifications for cosmetics, flatness and dimension. Employing EGA in the injection molding process has allowed Mack to provide its customers with better quality products.

“EGA is not really well known in the industry,” Revane says. “A lot of people have never heard anything about it. Yet, for us, it’s a normal part of processing. We do it every single day.”

 

Contact:
Tom Revane, Tool Design Engineer, Tom.Revane@mack.com

 

Editor’s Note: Another Mack is ME! post, this series spotlights the people and personalities behind our services. Check back frequently or subscribe to the feed, as these profiles will be interspersed with news updates on a regular basis. We hope you’ll enjoy getting to know us!

Name: Sylvia Jarvis

Title: Leader, East Arlington Plant

Her job? Sylvia is responsible for coordinating employee activities and material movement to meet production schedules in the painting department in East Arlington. She is also the expert in silk screen training and has been taking the lead in that department for many years.

Favorite Mack project: “I’d have to say the good ole days,” she says, when questioned about her favorite times at Mack. Sylvia also enjoyed her responsibilities as a trainer and will miss guiding employees through new processes. “I really enjoy helping the new people get started,” she says.

Experience: On September 21, 1978, Sylvia began her lifelong career at Mack as a finisher at the East Arlington plant. After working in finishing for about 17 years, she moved into the painting department as a painter. In 1997, she was promoted to her current position as leader. Sylvia has maintained an impeccable attendance record, missing only a few days of work in her 35+ years at Mack.

Personal life: Sylvia has recently moved into a new home in Cambridge, N.Y.., which brings her much excitement in her retirement. Prior to her new abode, she lived in the town of Tinmouth with her husband, the late Paul Jarvis, who worked at Mack’s East Arlington and headquarters plants for over 32 years before retirement. Combined, Sylvia and her husband are responsible for more than 67 years of service to Mack! Sylvia has a grown son, Scott, who also works at the East Arlington plant, in the molding department.

Life after Mack: Having just moved, Sylvia is looking forward to the many projects she will be able to begin in her new home, once she settles in. She also plans to spend as much time as possible with her family, “the best way to enjoy free time.”

We will miss Sylvia’s skill in the training room and talent in the paint department, but are excited to wish her the very best in her retirement.

Editor’s Note: Another Mack is ME! post, this series spotlights the people and personalities behind our services. Check back frequently or subscribe to the feed, as these profiles will be interspersed with news updates on a regular basis. We hope you’ll enjoy getting to know us!

Name: Sharan Bolster

Title: Finisher, Headquarters Plant

Her job? As a finisher, Sharan builds, inspects and tests final product before it is shipped to customers. She has worked on many lines in her near-48 years at Mack, ranging from computer and business equipment to medical devices.

Favorite Mack project: Thinking back over her 4+ decades of projects at Mack, the one that shines through as her favorite was the Pitney Bowes WOW (Weigh-on-the-Way) line, a digital mailing system that weighs finished mail. Although she states that building the product was interesting, what really made it fun were the people. “The people I worked with were some of the greatest,” she recalls. “Even though the product was fun to put together, they made it an even better experience.”

Experience: Sharan began working at Mack at the age of eighteen. “Straight out of high school,” she says, “on September 26, 1966!” She launched her career in the finishing department of the East Arlington plant, the headquarters plant at that time, but when the “new building” was built and headquarters moved, Sharan moved right along with it.

Changes in Mack: The most dramatic change Sharan notices about Mack over the years is its size. She notes that not only has the company gotten physically larger and added facilities, but it has expanded into different markets and grown in personnel as well. “When I started, it was just a little company—a lot of families worked here,” says Sharan. “Now it’s a lot bigger, but it’s still a family company.”

Personal life:  Sharan lives in the Town of Sunderland, Vt., with her husband, Henry, who works at Mack in the metals department. “We met right over at the East Arlington plant!” Sharan says. They have a grown daughter, Ruth, who along with her husband, Todd, lives right next door to Sharan and Henry. “I get to have a lot of family time,” says Sharan.

When not at work: When she’s not working, Sharan is a cowgirl at heart. Growing up around animals, she now has what her daughter calls “a small farm” of chickens and goats. Her favorite summer activity is attending Saturday night rodeos in Castleton, Vt., with her family. At the urging of her sister, Sharan attended her first rodeo a few years ago and, after seeing the bull riders (her favorite event), she was hooked. “They get bucked off and keep coming back for more!” she says. “It’s so entertaining to watch!”

Her other favorite activity is spending time with her husband, daughter and son-in-law.

Life after Mack: With her new-found free time, Sharan plans to go to as many rodeos as possible! She is also looking forward to spending more time with family. “I just like to be with my family as much as possible,” she says. Sharan has enjoyed her past 47 years (and 8 months, she’s quick to add!) at Mack, and is sad to say goodbye. “It’s such a great place to work,” she says. “Everyone is so nice and easy to get along with.”

While we will miss her smile and always positive attitude, we wish Sharan many more rodeos and the best in her retirement!

Editor’s Note: Another Mack is ME! post, this series spotlights the people and personalities behind our services. Check back frequently or subscribe to the feed, as these profiles will be interspersed with news updates on a regular basis. We hope you’ll enjoy getting to know us!

Name: Elizabeth (Betty) Babbin

Title: Finishing Leader, Cavendish plant

Her job? As finishing leader, Betty is responsible for tracking production on the finishing floor. She ensures that all parts needed for assembly are on hand, including those being molded. On any given day, she is responsible for employees working on five or more product lines.

Favorite Mack project: If Betty had to choose a favorite project that she has worked on at Mack, it would be her current product lines. However, choosing a favorite is very difficult for her. “I just like my job. I like what I’m doing and I like the people I work with,” she says.

Experience: Betty began working at Mack’s Cavendish plant in June, 1968, and has been a full-time employee there ever since. At the age of 18, Betty started her first full-time job as a third-shift molder in the molding department. From molding, she quickly moved into material handling, shuttling supplies between the warehouse and finishing floor. Ultimately, she transferred into the finishing department, where she currently works. A non-traditional student, Betty began taking classes after work at Vermont Adult Learning Center (Springfield, Vt.), proudly earning a high school diploma in 2009.

Changes in Mack: Having been with the company continuously for nearly 46 years, Betty provided some insight into the changes she has seen throughout her career. “Everything has improved,” recalls Betty. “We have better jobs, a better facility and we produce higher quality products.” Mack has gained new clientele throughout those 46 years. Along with the growing customer base, the Cavendish plant has expanded, adding employees and doing more assembly work than ever before. “Being here for so long, you see a lot of new product lines come in, but there are not a lot of product lines leaving,” says Betty.

Personal life: Betty was born in Springfield and grew up in Cavendish. She has five brothers and a sister who also still live in the area. Currently, Betty resides in Ludlow, Vt., with her husband, John. She has a son, Christopher, a chef at the Putney Inn, as well as a daughter, Jessica, and two grandchildren, Skyler, 17, and Jesse, 6, who reside in N.J.

When not at work: An artist, Betty is often found capturing scenic Vermont landscapes on canvas. Originally working with graphite on paper, she switched to acrylic painting about nine years ago. “I saw my brother painting and wanted to give it a try, so I bought acrylics and  like them a lot,” says Betty. In addition to painting, Betty also enjoys exercising, which she does regularly every morning before she heads to Mack.

Life after Mack: Betty plans to make the most of her retirement by filling her time with the activities she loves. “I’d like to do more camping,” she says. She also plans to invest more time in her painting. Who knows, someday soon you might even be able to purchase a ‘Betty Babbin Original!’

Please join us in wishing Betty the very best in her retirement!