You cannot truly grasp the injection molding process without diving into its beating heart: the mold itself. How did simple metal blocks transform into highly complex, precision-engineered systems, and how is Rion leveraging this cutting-edge technology today?

Ask any plastics engineer to describe the division of labor on the shop floor, and they will likely tell you that while the injection molding machine provides the raw power, it is the mold that dictates the precision, complexity, and ultimate quality of the final product. Over the past few decades, as injection molding machines have become faster and more robust, the most significant technological leap has occurred within the mold itself. This is a story of engineering evolution – a journey that transformed a basic casting tool into a sophisticated mechanical system operating under extreme pressures and temperatures.

The Early Days: Two Blocks of Steel and Minimal Sophistication

In the beginning, injection molds were incredibly simple. They consisted of two metal halves: the core and the cavity. Molten plastic was injected, cooled, and the mold opened to eject the part, often requiring manual intervention from the operator.

Cooling systems back then were elementary: straight holes drilled through the steel plates to circulate water. This resulted in uneven cooling, excessively long cycle times (making production slow and costly), and parts that frequently suffered from warpage due to poor heat dissipation. Part geometries were also severely restricted. Manufacturing any product requiring side indentations or complex internal cavities (“undercuts”) was nearly impossible without cumbersome secondary assembly processes.

Flow Systems: From Cold Runners to Hot Runners

One of the first major revolutions in mold design was the transition from cold runner to hot runner systems. In older molds, plastic flowed through metal channels until it reached the part cavity. As the mold cooled, the material in these channels also solidified, requiring it to be ejected with the part and manually trimmed—a process that generated massive material waste and required additional labor.

The development of hot runners changed the game entirely. This system uses internal heating elements to keep the plastic in a molten state inside the mold right up to the gate (the entry point to the part). This breakthrough saved enormous amounts of raw material, slashed cycle times, and enabled smooth, highly precise plastic injection into multi-cavity molds.

The Mold Becomes a Machine: Sliders, Lifters, and Internal Automation

As the design requirements for plastic products grew more complex, molds had to evolve accordingly. Side cavities, internal threads, and unusual geometries demanded creative solutions. The mold transitioned from a passive “open-close” structure into a dynamic mechanical mechanism packed with moving parts.

Engineers began integrating sliders and lifters – metal components that move diagonally or laterally as the mold opens to release “trapped” areas within the product. Simultaneously, ejection mechanisms were refined, utilizing internal pin systems to eject parts fully automatically. The mold essentially became a giant Swiss watch, where dozens of steel components move in perfect synchronization, thousands of times a day.

The Magic of the Melt-Out Core: When Standard Ejection is Impossible

Despite advanced mechanical mechanisms, certain geometries are simply impossible to eject from a standard steel mold, for instance, pipes with highly convoluted internal passages, such as automotive intake manifolds or complex pump housings.

This challenge gave birth to a fascinating technology known as “Lost Core” (or melt-out core) injection molding. In this method, the internal “cavity” of the product is pre-manufactured from a material with a low melting point, such as a special metal alloy or a soluble polymer. This core is placed inside the mold, and the plastic is injected around it. Once the part cools, it is removed from the mold and placed in a heating or washing bath. The internal core simply melts or dissolves and flows out, leaving behind a complex, seamless, and completely hollow plastic product.

The Two-Component (2K) Revolution and Multi-Cavity Scaling

Historically, if a manufacturer wanted to produce a toothbrush with a rigid plastic handle and a soft rubber grip, it required two separate molds, two machines, and a lengthy assembly process (usually manual or glued).

Over time, multi-component (2K) injection technology emerged. This advancement led to complex molds featuring rotary tables built directly into the mold or mounted on the machine. The product is injected with the first material, rotates, and is immediately injected with the second material while still hot. The result: a robust chemical bond, eliminating the need for secondary assembly, all within a single cycle.

Alongside this, the drive for mass production led to an exponential increase in the number of cavities per mold. From single-cavity tools, the industry advanced to 8, 16, 32, and even more cavities, where a fraction of a second or a single-degree temperature variance between cavities can dictate the success or failure of an entire production run.

The Race for Perfect Cooling: From Copper to 3D Printing

Cooling time accounts for the longest phase of the injection cycle, making the race to reduce it an ongoing industry obsession. Previously, to cool hard-to-reach areas where standard water channels couldn’t fit, engineers used Beryllium-Copper inserts. While this metal offers high thermal conductivity, it is prone to rapid wear and poses toxicity risks during machining.

In recent years, the advent of 3D metal printing (SLM – Selective Laser Melting) sparked the Conformal Cooling revolution. Instead of drilling bulky, straight water lines, the insert is printed layer by layer, with cooling channels intricately winding through it to precisely follow the complex contours of the part. This represents the latest step in mold evolution—total design flexibility that slashes cycle times by tens of percents.

At the Forefront of Technology: Rion’s Mold Department

Recognizing that the injection mold is the definitive factor in a project’s success, Rion has invested massive resources into developing its in-house capabilities. A major turning point occurred in 2012 with the acquisition of “Raveh Molds” (one of Israel’s leading mold makers, founded by the late Zvi Raveh), integrating it seamlessly into Rion’s operations. Dudu Leib, Rion’s CEO, aptly described this as “the best decision made in the last decade.” This synergy allowed mold designers to truly live and breathe the shop floor, aligning their engineering designs with real-world production and maintenance challenges.

Today, Rion’s Mold Department leads the industry in implementing the advanced technologies outlined above:

• Conformal Cooling: Rion extensively utilizes “hybrid inserts” – a machined steel base topped with a 3D-printed cooling zone. This integration enables the company to drastically cut cycle times and tackle products with stringent requirements and tight tolerances.
• Multi-Component (2K) Injection: Rion specializes in these advanced applications. A prime example is a project executed for Maytronics for a robotic pool cleaner brush. A product that previously required manual stitching of rubber fins was converted by Rion into a fully automated 2K injection process on dedicated ARBURG machines, vastly improving quality and eliminating significant labor costs.
• High-Cavitation Molds: Rion routinely manages mass-production projects involving dozens of cavities (currently up to 64, with infrastructure preparing for 96). To mitigate the risks associated with these massive capital investments, the company produces preliminary “prototype molds” to validate the design before scaling up to mass production.
• An Advanced Global Workflow: The Israeli mold department, comprising about 15 experts, is responsible for the meticulous design of every mold. The actual manufacturing is outsourced to strategic partners in China, India, and Europe, under the strict supervision of Rion’s local branches (such as the China office). This model ensures uncompromising quality and competitive pricing, while the Israeli workshop focuses on the highly efficient maintenance of approximately 1,000 active molds, as well as the rapid fabrication of urgent, short-lead-time molds.

The evolution of the injection mold is far from over. However, one thing is certain: mastering these engineering tools, as exemplified by Rion’s Mold Department, is the ultimate guarantee for advanced, high-quality, and globally competitive manufacturing.