IML Enables Aesthetics, Lightweighting in Dairy Container

By Dianna Brodine, vice president, editorial, Plastics Decorating

StackTeck Systems Ltd., headquartered in Ontario, Canada, is a global provider of injection molding solutions, including engineering, prototyping and plastic part development services; injection molds, frames and quick-change technology; and automation systems. Working within the caps and closures, cosmetics, medical, PET preforms, personal care and thin-wall packaging industries, StackTeck recently put its expertise to work for Grupo LALA, with a focus on lightweighting a dairy container.

Grupo LALA, according to its website, was founded in 1949 and is the only dairy company operating nationwide in Mexico. It expanded into the United States in 2005 and began acquiring additional manufacturing plants in North America in 2009. The group’s product line includes yogurt, smoothies, sour cream and specialty milks.

As the mold provider for LALA, StackTeck saw an opportunity to lightweight the company’s 426-gram container using its proprietary thin recess injection molding (TRIM) technology. Lowering the overall part weight would result in savings in resin usage and transportation costs, while maintaining the container’s part strength and improving filling balance. In-mold labeling created opportunities to control the part weight while adding aesthetic and functional properties.

Christopher Day, general sales manager for StackTeck’s Mexico office, discussed the process of working with label printer MCC Verstraete, molder Envases Plasticos Industriales de Guadalajara SA de CV, and StackTeck’s engineers to revamp LALA’s crema packaging.

Piloting a new path within the same process parameters
“This was a pilot project for LALA, a large dairy company in Mexico that is pushing into new markets,” Day said. “We took a very typical, 426-gram round container that already was in production with an in-mold label, and we looked at how we could reduce its weight. In this particular case, once all limiting parameters of the system were accounted for, we were able to achieve a 14.8 gram weight, down from 17.3 grams.”

During the weight reduction study, the existing system parameters are taken into consideration, including press tonnage, maximum injection pressure, cavitation and resin type. Then, StackTeck’s engineering team began customizing the pattern design, altering the aggressiveness of the wall thickness reduction and its location (bottom, shoulder or sidewall).

“We start with the existing container, and that’s where we begin our work,” said Day. “We know the existing container weight, and we determine a target weight, but then we take into account injection pressure limitations, tonnage, cavitation, etc.”

An analysis is done, and each iteration provides additional information until it’s massaged into a successful matrix that is within the boundaries of all the constraints. “Then in production tests, we have to make sure what we see in theory actually matches what happens when it’s molded,” he explained. “When adding TRIM to the sidewall, the graphics must be accounted for, and that’s where the IML comes into play.”

IML adds to the aesthetics and functionality
Due to the thin wall pattern, offset printing isn’t possible when using this weight reduction technology. But, LALA already had converted this container to IML prior to the weight reduction test, so the testing was done with the existing in-mold label.

“LALA is actually new to IML,” Day said. The dairy company has seen its use of the in-mold label from MCC Verstraete increase the quality of its graphics, as well as
the clarity of the small print. IML also allows the use of hidden QR or scan codes for easy plastic separation at recycling plants.

“It’s been a process of growing through the learning curve to see the impact potential of how the package looks and
the amazing things that can be done in terms of being creative to change the looks of the brand and the product,” he continued.

A sustainability story
“We piloted the project and sent it to the customer for trials with the production robot,” Day said. “The impact of the container is quite significant, from a sustainability standpoint.”

A 14.5% part savings was achieved, within the existing injection molding capabilities, keeping maximum injection pressure in system limits, maintaining the same mold cavitation and using the original resin type. “In fact, a new mold is not required,” he said. “Instead, new core assemblies can be used that can run interchangeably on the same mold. This will allow the molder to run either the standard part or the weight-reduced part, if required.”

In this particular application, the molder has multiple systems. A nearly 15% part weight savings would potentially allow resin savings of ~190 tons/year on the given systems.

“LALA liked the samples,” Day said. “Originally, the company was worried about how the containers would compare to the standard parts’ impact-resistance capabilities, but the weight reduction didn’t affect the structural rigidity of the container in the field tests.” Day explained that there also were no changes needed on the filling lines, without changes in the diameters of the lids or destacking of parts.

Adding to the sustainability story, in-mold labels are made of the same or similar resin as the container itself, ensuring the package is fully recyclable when sent to the recycling facilities. The use of IML, along with the lightweighting success, earned recognition in the 2023 IMDA Awards Competition with an honorable mention in the Sustainable Use of In-Mold Processes category.

As LALA continues its North American expansion efforts, and as sustainability remains in the spotlight for packaging consumers, StackTeck’s efforts will give the dairy company a significant story to tell.