Friday, 7 November 2025

Wombat: Not Just an Animal—A Lesson for Plastics Operations

Hello and welcome to a new blogpost. When you hear “wombat,” you might picture a sturdy little marsupial from Australia. But in the world of plastics engineering, Wombat stands for something else entirely: 

Waste of Money, Bandwidth, and Time. 

And it’s a concept every polymer professional should keep top of mind.

Wombat in the world of plastics engineering.


Why Wombat Matters in Plastics

In our fast-paced industry, it’s easy to get sidetracked by shiny new technologies, endless data, or meetings that lead nowhere. But every minute and euro spent on non-essential activities is a minute and euro not spent on what really matters: making perfect plastic parts.

Wombat is a reminder to ask ourselves:

  • Are we investing in tools and processes that actually improve quality and efficiency?
  • Is this meeting, report, or project moving us closer to our production goals?
  • Are we focusing on root causes, or just treating symptoms?

Applying Wombat Thinking to the Plastics World

Let’s look at a few practical examples:

  • Material Selection: Don’t over-specify or under-specify. Choose the right polymer for the job, not the most expensive or the one with the flashiest datasheet.
  • Process Optimization: Focus on parameters that truly impact part quality—like melt temperature, cooling time, and pressure—rather than chasing every minor variable.
  • Troubleshooting: When defects arise, use data-driven root cause analysis. Don’t waste time on guesswork or “just try it” fixes.

The Payoff: Perfect Parts, Less Waste

By keeping Wombat in mind, you’ll streamline your operations, reduce scrap, and deliver higher-quality parts—without burning through resources. It’s about working smarter, not harder.

So next time you’re faced with a decision, ask yourself: Is this a Wombat? If it is, steer clear and refocus on what truly drives success in plastics manufacturing.

Let’s leave the wombats in the wild—and keep our operations lean, focused, and efficient!

Thanks for reading & #findoutaboutplastics

Greetings,

Herwig Juster



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Monday, 3 November 2025

Ratio Projects - A Story Beyond Plastic Material Prices

Hello and welcome to a new blog post in which I want to share a story that changed the way of thinking about cost-saving in manufacturing:

Ratio projects

Not long ago, I was sitting across the table from a customer who was laser-focused on one thing: lowering material costs for an injection-moulded part. He was convinced that if we could just supply a cheaper material, his problems would be solved.

But as our technical team and I examined the part and the moulding operations together, something caught our eye. The runner and sprue—the channels that guide the molten polymer into the mould—were enormous. In fact, they were much bigger than the part itself! Imagine pouring a glass of water and spilling twice as much on the table as you actually get in the glass. That’s what was happening here.

Instead of just talking about material prices, we rolled up our sleeves and worked side by side with the customer. We reimagined the entire gating system, redesigning the part and the tooling. It was a true collaboration, blending expertise and creativity.

The result? We didn’t just shave a few cents off the material cost. We cut the total cost by 50%. Half! Not by using a cheaper material, but by using our knowledge to optimize the design and the process (Figure 1).

Figure 1: Optimizing the sprue and gating of an injection mold as part of a ratio project.

The customer was amazed. He realized that the real savings came not from squeezing suppliers for lower prices, but from looking at the bigger picture—design, tooling, and production.

This experience taught us all a powerful lesson: sometimes, the answer isn’t in the price tag of the material, but in the ingenuity we bring to the table. When we focus only on material costs, we risk missing out on much greater opportunities for improvement.

So next time you’re tempted to chase the lowest material price, remember—true value comes from partnership, innovation, and seeing the whole picture.

Thanks for reading & #findoutaboutplastics

Greetings,

Herwig Juster


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Wednesday, 22 October 2025

Stories From The Granulatefather: The Triangle Test

Stories from the Granulatefather: The Triangle Test by Herwig Juster

The hum of machines filled the air as Anna, a young design engineer, walked briskly through the plastics manufacturing plant. She clutched a sample part in her hand—a translucent connector for a medical device. It looked perfect, but Anna’s brow was furrowed. She had just received a report: several connectors had cracked during field use.

At the conference table, Anna met with her mentor, Mr. DeWitt, a seasoned materials expert. He examined the cracked part, turning it over in his hands. “Environmental stress cracking,” he murmured, almost to himself.

Anna sighed. “I thought we picked the right material. We even checked the chemical compatibility.”

Mr. DeWitt smiled gently. “Let me tell you a rule of thumb I learned early in my career. When it comes to environmental stress cracking—ESCR—think of a triangle. Three legs: environment, stress, and chemicals. If you can remove or reduce even one, you break the triangle and prevent failure.”

Anna leaned in, intrigued. “So, where do we start?”

They walked to the design lab. Mr. DeWitt pointed to the sharp corners on Anna’s part. “Stress concentrates here. Let’s round these edges and thicken the walls. That’ll help.”

Next, they reviewed the cleaning agents used in the hospital. “Some chemicals are harsher than we realized,” Anna noted. “We can recommend alternatives.”

Finally, Mr. DeWitt pulled a datasheet for PPSU, a high-performance polymer. “This material has excellent resistance to ESCR. It might cost more, but it could save us from future failures.”

A week later, Anna watched as the new connectors passed every test—no cracks, no failures. She smiled, remembering the triangle. By tweaking the design, rethinking the chemicals, and upgrading the material, they had broken the cycle of failure.

Anna’s story spread through the company, a reminder that in plastics, success isn’t just about picking a material—it’s about understanding the whole system, and knowing which leg of the triangle to break.

I hope you enjoyed the story!

Thanks for reading & #findoutaboutplastics

Greetings,

Herwig Juster


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Tuesday, 21 October 2025

Don't Mix Maximum With Optimum Plastic Material Selection & Plastic Processing I Rule of Thumb

Hello and welcome to a new Rule of Thumb post discussing why mixing maximum with optimum in polymer material selection and plastics processing is not the best thing to do. 

Understanding “Maximum” vs. “Optimum” in Plastic Material Selection

When selecting materials, it’s important to distinguish between “maximum” and “optimum.”

Maximum refers to the highest possible value of a single property (e.g., the highest tensile strength, the greatest heat resistance, or the lowest density).

Optimum means the best possible balance among several relevant properties for a specific application. The optimum is not always the maximum of any single property, but rather the material that meets all key requirements most effectively.

Why is this distinction important?

Choosing a material based solely on a maximum value (such as the strongest or most heat-resistant polymer) can lead to unnecessary costs, processing difficulties, or other trade-offs. The optimal choice is the one that delivers the best overall performance for your specific needs—even if it doesn’t have the highest value in every category.

Example: “Optimal vs Maximum” in Plastic Material Selection

When selecting a plastic material for a specific application, engineers often seek the “optimal vs maximum”—that is, the best possible balance between competing requirements, such as mechanical strength, cost, processability, and chemical resistance.

Case Study: Gear Wheel for Automotive Application

Requirements:

  • High mechanical strength and stiffness
  • Good wear resistance
  • Dimensional stability at elevated temperatures
  • Cost-effectiveness for mass production

Material Candidates:

  • Polyamide 6 (PA6)
  • Polyoxymethylene (POM)
  • Polyetheretherketone (PEEK)

Selection Process:

  1. Define Key Properties:
    The gear must withstand high loads (tensile strength), resist wear, and maintain shape at temperatures up to 120°C.

  2. Score Materials:
    Each candidate is evaluated for tensile strength, wear resistance, heat deflection temperature, and cost.

Find the “Optimal vs Maximum”:

  • PA6: Good strength and cost, but absorbs moisture (affecting dimensions).
  • POM: Excellent wear resistance and dimensional stability, moderate strength, good cost.
  • PEEK: Outstanding properties, but very high cost.

After scoring, POM emerges as the “optimal vs maximum”—it offers the best compromise between performance and cost for this application, even though PEEK has higher absolute properties.

The “optimal vs maximum” is not always the material with the highest individual property, but the one that best meets all critical requirements for the application. In this case, POM is the optimal choice, delivering reliable performance at a reasonable cost.

Takeaway:
When selecting plastics, always look for the “optimal vs maximum”—the material that provides the best overall fit for your application, not just the highest value in a single property.

Optimum vs Maximum in injection molding

For example, in injection molding, the optimum flow rate is not necessarily the fastest possible, but rather the rate that minimizes shear stress, ensures proper mold filling, and avoids defects like air traps or weld lines. Similarly, the optimum temperature profile for a molding process might balance melt temperature for flow with cooling time for cycle time, while minimizing residual stress. 

Figure 1 presents the concept of "maximum vs optimum" for plastics processing. In essence, while maximum settings define the boundaries, optimum settings represent the sweet spot within those boundaries for achieving the best possible results in plastics processing.

Figure 1: Difference between optimum and maximum in plastics processing. 

More Rule of Thumb posts can be found here.

Thanks for reading & #findoutaboutplastics

Greetings,

Herwig Juster

Literature: 

[1] https://youtube.com/shorts/q_KfChgTwdM



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