Planning a new part? Do yourself a favor and read this -it might just save you a lot of headache and money on your journey to mass production

In the world of plastic product development, it’s easy to get swept up in a sleek 3D render. But the real test begins only when you try to translate those digital lines into a physical part – one that is stable, precise, measurable, and ready for mass production. This is where Rion’s “Expanded DFM” (Design for Manufacturing) process comes into play. We’ve refined this methodology over years of experience to ensure every product is perfectly aligned with the injection molding process.

The DFM process between designers and mold makers isn’t standardized; it varies significantly from one supplier to another. Sometimes it’s a limited exchange between an overseas mold designer and the customer; other times, it’s a more comprehensive collaboration. At Rion, we strive to maximize this process within the customer’s constraints, because our experience proves that the deeper we dive into DFM early on, the more time and money we save down the road.

“Most problems in these projects aren’t born on the production floor,” says Aharon Weiss from Rion’s Engineering Department. “They start at the product design stage. A trained eye can often spot immediately where design tweaks are needed to ensure optimal commercial production later on.”

To avoid late-stage surprises, Rion’s engineers analyse the model the moment we receive it. We evaluate whether the geometry allows for a stable injection process, if the part is truly manufacturable as designed, whether it requires a complex mold solution, and how the customer’s engineering choices impact production costs, cycle times, warping, and the need for secondary operations.

Not Every Tolerance is Possible in Plastic

One of the first things we examine is the fit between the drawing’s tolerances and the material’s properties. While tight tolerances are common in metal CNC machining, plastic is far more complex. The final geometry is influenced by numerous process variables: the specific shrinkage rate of the polymer, the flow direction of the melt, the temperature profile across the part, and uneven cooling. These factors dictate the final dimensions, geometry, and sometimes even the mechanical properties.

“We perform ‘tolerance analysis’ to see if injection molding technology can actually meet the drawing specifications,” Aharon explains. “We look at the ‘expected process variation,’ taking into account raw material batches, machine precision, and mold accuracy. We don’t just look at linear dimensions, but also geometric relationships like perpendicularity and parallelism. Sometimes, especially with low-shrinkage materials, we can achieve high precision. But when a requirement is unrealistic, we start a dialogue with the designer to figure out what is truly necessary and find a feasible manufacturing solution.”

Beyond tolerances, there’s a fundamental question: Is the dimension even measurable?

“Many designers don’t realize this,” he notes, “but if there’s no clear measurement datum, even advanced CMM systems won’t be able to verify the requirement. In those cases, we have to rethink how to define or indirectly measure those features. For example, if you want to measure the diameter of a trapezoidal groove with a radius at the tip, there’s no defined contact point. Yet, in CAD, a designer can easily click a point that simply doesn’t exist in reality.”

Early Simulation: Understanding the Part Before it Exists

After reviewing the drawing, we run initial simulations to evaluate how the part will behave under ideal injection conditions. This is a critical stage – it allows us to predict areas prone to warping, sink marks, or geometric deviations before a single dollar is spent on mold design.

When a simulation flags an issue, we look for ways to adjust the design without compromising functionality. “Sometimes it’s as simple as swapping a sharp corner for a radius. Other times, adding a few ribs can completely eliminate warping. The earlier we address these, the more correction cycles we save the client.”

As Aharon puts it, once mold fabrication begins, the room for maneuver shrinks dramatically. An “Expanded DFM” process is all about asking the right questions before decisions become irreversible, or prohibitively expensive to fix.

Mold Cost vs. Production Cost: The Missing Calculation

A vital insight in injection molding is that the “true cost” doesn’t end when the mold is finished. Decisions that look like cost-savers on the mold quote can lead to high operational costs down the line, especially when secondary processing is involved.

A common example is opting for a manual gate cut instead of a hot runner system. “On paper, it looks like a budget win,” Aharon explains, “but if the gate is large, you’re no longer talking about a simple trim, you’re talking about milling work. The savings evaporate, and in many cases, the total cost of ownership increases significantly compared to the alternative that was rejected upfront.”

Sometimes, the solution is to integrate operations into the mold itself. Instead of drilling and tapping holes as a secondary process, we can integrate internal mechanisms or motors to perform these tasks during the molding cycle. It’s an investment, but shifting the focus from the initial mold price to the long-term production cost almost always pays off.

Automation and Multi-Component Molding: Rethinking the Product

The Expanded DFM process isn’t just about fixing problems, it’s about reimagining the product. For instance, if a client designs two parts that are later assembled, we often suggest switching to two-component (2K) injection molding to eliminate assembly steps entirely.

“When combining materials, like rigid plastic and an elastomer, we have to determine if the bond will be chemical or mechanical, and design the parts accordingly,” Aharon says. Depending on the part structure, production volume, and equipment, we select the right mold concept, be it a rotary plate, a rotating core, or other solutions.

In one project, Rion needed to mold a tiny component onto a large part. Instead of a complex, traditional over-molding solution, we integrated a small, auxiliary injection unit directly onto the mold. “It was a creative, structural adaptation that made the entire manufacturing process significantly more efficient,” says Aharon.

The Power of Three: When Departments Talk

Ultimately, the success of a project depends on the synergy between three key players: the product designer, the mold designer, and the injection molding technologist.

“Our approach at Rion is that every part must be examined by all three professionals before we move forward,” Aharon concludes. “When one of them is left out, projects get stuck in the late stages, and that’s where the cost becomes astronomical.”

He recalls cases where expensive molds had to be scrapped because the part warped and failed to meet specs. “One customer bought a multi-cavity mold from an overseas supplier without a proper DFM process. Once we started production, we found the mold couldn’t produce compliant parts. Fixing it would have been so dramatic and costly that the mold was literally thrown in the bin. The customer had to order a new, properly engineered mold from us.”

The message is clear: The “Expanded DFM” process isn’t just a “nice-to-have” add-on; it is a critical phase that turns a conceptual design into a viable, efficient, and profitable reality.