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The inmold phenomenon began with simple processes such as placing metal inserts into the mold and shooting plastic around them to create metal-reinforced bosses. Today, it’s inmold everything—from painting and coating to labeling, decorating, and assembly—and you can see a lot of it in action at NPE.

Clare Goldsberry

June 1, 2009

10 Min Read
Inmold everything saves time, money vs. secondary ops

The inmold phenomenon began with simple processes such as placing metal inserts into the mold and shooting plastic around them to create metal-reinforced bosses. Today, it’s inmold everything—from painting and coating to labeling, decorating, and assembly—and you can see a lot of it in action at NPE.


This injection molding system using a StackTeck mold in a Netstal press with CBW automation is a dedicated resource for IML projects.


Using TRIM technology, this 32-oz tamper-evident container shown with blue lid and label and undecorated in natural PP (r) demonstrates what can be done with IML to reduce costs.


Kuka's KR16 six-axis articulated robot maneuvers in an inmold application.


This IML container mold runs in a system developed by Waldorf Technik that performs automation in label placement and quality checks.

Automating with inmold technology offers some tremendous advantages, including higher productivity, reduced secondary operations, and fewer quality problems, which can translate to higher profit margins for the molder and moldmaker. Mold manufacturers play a critical role in this technology, often acting as the choreographer in the mold design and build, and the integrator of the mold, molding press, and automation that creates a competitive advantage.

IML has been slow to catch on in North America, helped partly by the predominant use of round containers. In Europe, containers are mostly rectangular. “The U.S. needs to go to a square container to accommodate inmold labels,” notes William Llewellyn, VP and senior consultant for AWA Alexander Watson Assoc. BV (Amsterdam, the Netherlands), a market research and consulting firm that focuses on packaging. “Increased competition in IML markets comes from heat transfer, pressure-sensitive, and shrink sleeve labels, and this will keep increasing.”

One European-based company that has addressed container shape with its automation equipment is Waldorf Technik GmbH & Co. KG, a supplier of automation equipment for IML applications that recently opened a U.S. subsidiary in St. Charles, IL to serve the IML market in North America. The company, headquartered in Engen, Germany, recently completed two IML automation systems that it will be shipping to North America. Taras Konowal, president, says that Waldorf Technik has extensive expertise in designing IML systems due to IML’s popularity in Europe.

“We’re unique in that we offer a fully flex system, which means on one system we can run a round container and a lid that can be easily switched over to a rectangular container, all by changing out what we call format parts,” says Konowal. “It’s something we’d been doing for years, but given the IML market in North America is limited with lower volumes, we’ve found there are advantages to this system.”

To help U.S. OEMs justify the use of IML, Waldorf Technik offers the ability to quickly switch out molds and the automation that accompanies an IML system to adjust for lower volumes. “As volumes grow, the system can accommodate it,” explains Konowal. “The flexibility allows you to grow as your business grows, and you can run different shapes or different labels as needed. Before, you had to run 40 million containers to justify the system, but now we can address the needs of the company that runs smaller volumes such as 1 million containers/labels or has numerous changeovers.”

Quick mold changeovers for IML mean that a molder can switch from a round container to a rectangular one with a multisided label in about 30 minutes maximum, says Konowal. “The bottleneck is generally the mold changeover, so now the automation can be changed out quickly with the mold.”

Threats to inmold

One of the primary threats to any type of multiprocess inmold operation such as assembly, decorating, coating, or painting, is the complex and extended value chain. “IML technology requires all the players, including the raw material supplier, the label maker, the printer, the moldmaker, and molder,” says AWA’s Llewllyn. “If all the players are not integrated, the failures in the market will prevail.”

Waldorf Technik’s Konowal agrees, saying that it’s best for the mold manufacturer to work closely with the press maker and the automation supplier from the outset to ensure the system is optimized. “Placement of the labels into the mold is a critical operation and there are specific things that have to be done with the mold to allow it to accept the label,” says Konowal. “Typically, we use a two-headed robot that places the label on one side and removes the part off the other side, depending on where it’s injected. The end-of-arm tooling always does both.”

Unlike in the early days of automation and robotics, when automation was considered after the mold was built, today’s mold manufacturers begin thinking about the use of robotics and automation from the outset of a program, which is key to the value proposition that inmold operations provide. Pat Duda, plastics application engineer for Kuka Robotics Corp. (Clinton Twp., MI), says that, with the evolution of injection molding, parts get more complex, processes become more sophisticated, and plastics processors are finding that more complex automation is required.

Consequently, moldmakers are often required to create increasingly complex molds and assemblies to accommodate inmold operations with robotics.  Duda notes that injection molding automation has moved forward from sprue pickers through pick-and-place robots, and on to servodriven four- and five-axis robots, and finally the new six-axis robot arms that Kuka offers. “The six-axis robot makes more difficult projects easier,” says Duda. “Others can do some complex projects, but it is very difficult because they are limited by what the robot can do. Our six-axis arm is the next step in automation because it can do complicated jobs easier than in the past. With this trend, more molders are supplying full services and complete assemblies.”

Moldmakers as IML developers

StackTeck Systems Ltd. (Brampton, ON), a manufacturer of specialty high-production molds, announced a new patent-pending technology for lightweighting injection molded parts called TRIM (thin recess injection molding). The announcement was made at last October’s IMDA/IML conference in Phoenix. Jordan Robertson, general sales manager, says TRIM uses an advanced approach to plastic part and mold design to enable thinning out the part wall section well beyond the conventional approach used for thin-wall packaging molded from polyolefins with high melt-flow indexes.

Conventional thin-wall part design assumes a maximum L/T ratio of 300:1 (i.e,. ratio of flow length to average wall thickness). Using TRIM, it has been demonstrated with a 32-oz rectangular container that large areas of the part can be thinned out, which corresponds to an L/T ratio of more than 500:1. Part weight savings of 20-40% can be achieved using this technology.

StackTeck’s president Randy Yakimishyn said in a prepared statement, “Our customers are telling us that lightweighting is more important than ever, and so we are continuing to advance the forefront of this technology. At this point, we believe that we can achieve part weights that will make injection molding much more competitive against thermoforming, while maintaining key functional features such as the tamper-evident rim on a container and high top load compression strength.”

StackTeck molded a prototype part of a 32-oz tamper-evident (TE) container with a flow length of 5.74 inches, and with the recess area covering half of the part’s side wall and bottom, a panel thickness of 0.011 inch was achieved. The injection speed and pressure used to fill the part were normal by thin-wall packaging standards, and it is expected that thin-wall molders using IML can adopt this technology using existing injection molding machines. A fill time of 0.2 second was achieved at a moderate fill pressure, using a 35-melt PP from Basell.

“Designing this part took a huge amount of flow modeling,” Robertson says. “With wall thickness that is one-half the standard thickness and covers one-half of the surface area of the part, we expected to have holes, but the model told us we wouldn’t—and we didn’t.”

TRIM technology is being showcased on StackTeck’s IML pilot cell at the company’s facility with a 330-ton press. The pilot cell is a joint effort of StackTeck, Netstal (Devens, MA), and CBW Automation (Fort Collins, CO) to provide a prototyping and pilot program vehicle to the industry for IML applications. NPE attendees can get more information from StackTeck in booth S54049.

Mold manufacturer Electroform Co. Inc. (Rockford, IL) is once again preparing a mold to exhibit at the Arburg booth (S46048) for NPE2009. Electroform’s rotating stack mold that produced an assembled toy racecar at NPE2006 drew a lot of attention with its inmold assembly and labeling. Wade Clark, president of Electroform, also notes that the most critical thing for a moldmaker is getting all the parties together so that the integration of mold, molding press, and robotics/automation comes together smoothly.

“The whole integration thing brings about some extreme complexities—automation is so critical to the success of a multiprocess mold—and you can get yourself into a lot of trouble if you don’t deal with the right people that understand the process,” he says. “The project management portion of a program involving inmold production is also critical. Because there are so many operations involved, there are a lot of different players, so you need one point of contact—a good project manager at the moldmaker’s end—to pull it all together.” Clark says that with multiprocess molds, if there are any variables in the process, every step in the process becomes “screwed up.”

Tech Mold Inc. (Tempe, AZ) has a license for Spin Stack technology, and Craig Oestreich, project manager for the company, said the process starts with a checklist containing information provided by the customer, such as what type of manufacturing cell the customer has in mind, mechanical issues with regard to inmold assembly, and even an evaluation of the cost effectiveness. “Inmold assembly costs more if you’re looking at a Spin Stack mold,” says Oestreich. “After all the evaluation, sometimes inmold assembly isn’t the way to go, which makes it difficult to come up with the numbers to justify it.”

Inmold operations are a floor space issue for many companies. “If they can combine three or four assembly operations into a mold, rather than have two or three pieces of auxiliary equipment, it allows them to optimize manufacturing space,” says Oestreich. “Inmold assembly knocks out a big part of the downstream automation equipment normally needed.”

Oestreich has a patent on an inmold assembly method used for one customer’s mold that saved more than $1 million in manufacturing costs the first year and eliminated the need for a second mold and molding press. On an inmold folding operation, a customer saved $3 million in downstream equipment, he explains.

It’s important to have a team composed of the moldmaker, machinery manufacturer, product designer, robotics supplier, and the customer’s engineering staff, Oestreich says. “With this many people working on a project, open communication is critical to the success of the program. The decision tree gets bigger with inmold multiprocess operations. Every aspect has to be discussed and the customer has to really know his product to make a program like this successful.” [email protected]

Waldorf Technik has developed a roll-flex IML system with Schober GmbH that cuts labels during the manufacturing process rather than arriving precut—a method Waldorf says is helping molders gain entry into IML.

About the Author(s)

Clare Goldsberry

Until she retired in September 2021, Clare Goldsberry reported on the plastics industry for more than 30 years. In addition to the 10,000+ articles she has written, by her own estimation, she is the author of several books, including The Business of Injection Molding: How to succeed as a custom molder and Purchasing Injection Molds: A buyers guide. Goldsberry is a member of the Plastics Pioneers Association. She reflected on her long career in "Time to Say Good-Bye."

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