Application Spotlight: Maximizing Output with Stack Molds

To stay competitive in today’s market, plastic packaging manufacturers must strive for ways to achieve higher productivity, increased flexibility and reduced costs. Our latest article shows you how Husky stack mold technology can help you leverage equipment to maximize output and meet consumer demand.

It’s no secret that to remain competitive in today’s market, plastic packaging manufacturers must constantly strive for ways to achieve higher productivity, increased flexibility and reduced costs.

Stack molds are one of the most cost-effective ways to achieve these goals, helping you increase injection molding system output by up to 100% percent with a relatively low additional investment or disruption. Here’s how.

What are stack molds and which applications are they suited to?

Compared to standard molds that have just one molding surface or parting line, a stack mold can have two, three or four parting lines. The opening, closing and remaining stages of the injection molding cycle take place in parallel for all stack mold faces, resulting in minimal cycle time increases.

While a stack mold can be used for increasing productivity on a wide range of applications, the technology is most beneficial for parts with low height that do not require large mold opening strokes. The most popular applications are closures, thinwall containers, lids and medical applications.

How does it work?

The unique design of a stack mold places particular challenges on the injection molding machine itself. As a result, the decision to use a stack mold solution must be made at the very early stages of a project. Here are some important points to consider.

What are the machine requirements?

While significantly enhancing output rates, the additional plates that stack molds require must be handled appropriately to ensure part quality and tool longevity. Firstly, the clamping unit should be capable of carrying the higher weight of the stack mold without the middle mold section sagging and with minimum platen tilting. Secondly, the press should be capable of a higher opening stroke and shut height. The injection unit should be able to support the extra output with a larger shot size and higher recovery speed and injection rate. Thirdly, the mold itself should be equipped with a hot runner system that ensures balanced flow and temperature to each cavity.

How does Husky stack mold technology stack up?

With more than 50 years of experience manufacturing stack molds, Husky offers a comprehensive range of industry-leading stack mold systems, including injection molding systems with specially designed stack mold carriers, hot runners and molds for closures, as well as medical applications.

Based on our proven Hylectric^® and HyperSync™ machines, all components of Husky stack mold solutions work in unison to deliver maximized productivity through faster cycle times, exceptional part quality, higher uptime and superior ease of use.

Hylectric and HyperSync machines are excellent platforms for maximizing both production output and tool longevity. Their stiff clamp bases enable the industry’s highest mold weight carrying capability, eliminating stack mold sagging. Trademarked Reflex platens ensure uniformly applied clamping force and reduce overall tonnage requirements. Both machine models also offer industry-leading clamp opening stroke, mold shut-height and dry cycle times.

The Husky stack mold carrier is mounted on linear bearings capable of supporting heavy loads and high speeds. The bearings typically move along rails attached to the clamp base ensuring a solid setup that alleviates shifting. A distinguishing feature of the Husky carrier is a harmonic linkage mechanism connected to the machine platens that synchronizes the opening and closing of all parting lines.

In addition to high productivity, Husky stack mold carriers also offer great flexibility. Because the carrier is integrated into the machine, it remains inside during stack mold swaps. Mold installation and removal are fast and, because carrier removal is quick and easy, the machine is also able to run conventional molds. Additionally, the carrier can incorporate localized services, such as cooling water manifolds, which streamline operation.

Based on our extensive experience, Husky stack mold solutions offer unique benefits that can help you meet customer demand and increase profitability by extracting maximum value from your capital equipment and floor space. This is all supported by the unmatched global presence of Husky experience and engaged service team.

Success stories

Chip cannister lid

Several global packaging leaders rely on the high speed and capability of Hylectric® 300- and 600-tonne machines for producing their chip cannister plastic lids. A typical Hylectric 300 machine running a 12+12 stack mold at a 5-second cycle time can produce more than 130 million lids a year. Increasing the machine size to a Hylectric 600 running a 24+24 stack mold would effectively double the annual output with just a slightly larger footprint.

Coffee creamer flip-top closure

Another popular product taking advantage of Husky stack mold technology is the flip-top closure used on coffee creamer bottles. A single Hylectric 1000 machine equipped with a 32+32 stack mold can produce more than 125 million flip-top units a year.

Multi-material medical application

Husky stack mold technology can also enable overmolding for producing complex two-material parts. An interesting example is a diaphragm check valve used in medical dispensing systems. The part combines a stiff polypropylene rim and a flexible TPE (thermoplastic elastomer) diaphragm added by an overmolding shot. A compact manufacturing system includes a dual-injection unit Hylectric 225 machine equipped with a stack mold carrier and running a two-level 16+16 Husky medical stack mold. Husky EASYcube™ technology transfers parts between the two parting lines of the stack mold. Ejection of the complete parts occurs only at the second parting line, after the overmolding shot. Despite the sophisticated process, the system is capable of running a 9-second cycle time, with an annual output of roughly 45 million parts.

Do you think a Husky stack mold system can benefit your operation? Contact Husky today to learn how we can help you turn your production and packaging ideas into reality.

Look into Husky stack molds. They are an excellent way to achieve higher productivity, increase flexibility and boost your bottom line.