Die cutting, at its simplest, is pushing a material hard enough over a form to cut it precisely. However, to ensure precision, efficiency and maximize cost savings, experienced operators perform careful die cutting tonnage calculations to ensure that they are using enough force on the material to make the necessary cuts without wasting the energy of a more powerful machine than is required or slowing down the process itself.
This guide will help you understand how die cutters:
- Use tonnage from their very first steps on a project
- Calculate it using a combination of material strength and design patterns
- Can make or break a project by not incorporating real-world experience
- Can demonstrate their expertise in cutting disparate materials
What is Tonnage in Die Cutting?
At its core, tonnage is simply the force needed to cut through a given material during a die cutting process. Use too much force and it adds to the cutting costs and ties up machines that could be used for other, stronger materials. Use too little force and the cuts in the materials may end up incomplete or vary significantly.
From a manufacturer’s perspective when considering a die cutting vendor, seeing examples of expert calculations ensures that your product design is respected, your materials are handled correctly and used to the limit of their dimensions, and your timelines stay on track as you integrate a supplier into your production or post-production process.
How Tonnage is Calculated: A Simplified Overview
A tonnage calculator requires only three variables: the length of the edge of the material being cut, the thickness of the material being used and the shear strength of the material in pounds per square inch (PSI). With that, the formula is as follows:
While the calculation may seem to be a simple one, shear strengths are usually listed in ranges, rather than absolute figures, with upper ranges some times twice as great as the lower bounds. This requires die cutters to use their own experience with their machines and the materials, and to test out processes on small-scale runs to ensure that they work in real world applications.
How Accurate Tonnage Calculations Impact Your Process
Accurate tonnage calculations are the cornerstone of an efficient and high-quality die cutting process. When properly calculated, tonnage ensures a seamless production cycle with benefits that ripple across every aspect of the operation.
Product Quality
Precision in tonnage directly influences the quality of your final product. Too little force may result in incomplete cuts, frayed edges, or uneven finishes, especially with materials like leather or rubber that require clean, smooth edges. On the other hand, excessive force can deform the material, stretch adhesives, or damage intricate designs in foam or cardboard. A die cutter skilled in tonnage calculation guarantees consistently sharp, precise cuts that meet design specifications and client expectations.
Material Efficiency
Minimizing waste is critical in industries where margins are tight and material costs are high. Accurate tonnage calculations ensure that only the necessary amount of force is applied, reducing the chance of overcutting or tearing through materials. This precision is particularly valuable for expensive or delicate materials like custom adhesives or high-density foam, where every scrap counts toward the bottom line.
Equipment Protection
Every die cutting machine has a maximum tonnage capacity, and operating within this limit is crucial for long-term reliability. Miscalculations—especially underestimating the force required—can overburden the machine, leading to mechanical failures, downtime, and costly repairs. While this doesn’t necessarily affect manufacturers directly, knowing that a die cutting shop emphasizes improving the longevity of its own machines is a strong sign they extend quality control to every element of the process.
Cost-Effectiveness
Mistakes in tonnage calculations can lead to costly production delays, wasted materials, and damaged equipment. Beyond the immediate financial implications, errors can disrupt timelines. Accurate tonnage ensures a streamlined process, saving money by preventing rework and ensuring timely delivery of components.
By prioritizing precise tonnage calculations, experienced venors can maximize product quality and optimize resource usage, all while keeping production costs under control.
Factors That Affect Tonnage Requirements
While the word calculation is part of the phrase, understanding tonnage requires a bit of deftness and a fair amount of real-world experience both with specific cutting machines as well as a variety of materials. There are several key issues in play
| Issue | How It Affects Tonnage Calculations |
|---|---|
| Design Intricacy | Ensuring proper cuts may require higher-tonnage flat bed or rotary machines, or specially-prepared dies. |
| Volume and Scalability | There is a fine line between ensuring that all cuts are precise and that there is no excess force or time spent to create waste in a process. Experienced die cutters balance efficiency in operations with meeting the goal tolerances of their partners’ designs. |
| Material Properties | Whether working with adhesives, foams, plastics or other materials, the shear strength is never just one number, but a range that varies based on the material producer and myriad other factors. |
In fact, material strength variation is high enough that companies who work with die cutting experts need to ensure that their partners have worked with similar materials or can quickly prototype small-scale runs of a project to verify that the tonnage calculations are correct. Below are some of the key ranges for materials processed in rotary and flatbed die cutting processes by experienced vendors:
Shear Strengths of Common Die Cutting Materials
| Material | Approximate Shear Strength (psi) | Notes |
|---|---|---|
| Adhesives (general) | 300–1,000 | Depends on adhesive type (e.g., pressure-sensitive, hot-melt, or epoxy). |
| Cardboard | 300–600 | Corrugated cardboard typically requires more force; varies by thickness. |
| Foam | 50–200 | Greatly varies based on density and type (e.g., polyurethane, EVA foam). |
| Rubber (general) | 1,000–2,500 | Hardness measured in Shore A affects strength; EPDM is commonly used. |
| Leather | 1,500–2,000 | Includes natural and synthetic types; thickness significantly impacts force. |
| Plastics | ||
| Polypropylene (PP) | 3,000–4,500 | Flexible, lightweight, commonly used in packaging and automotive parts. |
| Polycarbonate (PC) | 8,000–12,000 | Strong, impact-resistant plastic often used in lenses and protective gear. |
| Acrylic (PMMA) | 6,000–8,000 | Transparent, rigid plastic commonly used in displays and signage. |
Common Challenges in Tonnage and How a Skilled Die Cutter Overcomes Them
With 75 years of experience in die cutting, Colvin-Friedman has encountered and mastered the most intricate challenges in tonnage calculations. Below are some common themes among the solutions developed over those seven decades
Challenge 1: Misjudging Material Shear Strength
Every material, from high-density rubber to delicate adhesives, has a unique shear strength.Skilled die cutters rely on decades of tested data and real-world experience to calculate precise tonnage requirements. For example, when working with multilayered corrugated cardboard or laminated materials, one must factor in not just the material’s surface strength but also how internal layers respond under pressure. This depth of understanding eliminates guesswork and ensures clean, reliable cuts every time.
Challenge 2: Managing Intricate Cuts with Tight Tolerances
Designs with intricate shapes or tight tolerances present unique challenges, as even a minor miscalculation in tonnage can compromise the precision of the cut. Using specialized dies can help reduce this risk, along with high-precision machines to handle the most complex patterns. For example, when cutting leather for luxury goods or gaskets for automotive applications, expanded quality control measures check that every detail meets the standards set by clients.
Challenge 3: Adapting to Material Variability
Materials often behave differently depending on environmental factors like temperature, humidity, or aging. For instance, adhesives may become softer in warm conditions, while rubber can harden in cold environments. These variables can significantly impact tonnage requirements. Die cutters must test materials under real-world conditions and adjust our calculations based on the pre-production data.
Final Thoughts
Tonnage calculations require an understanding of materials, machine capabilities and the ability to adapt to real-world changes in conditions. The experience that die cutters with decades of work behind them can develop enable them to quickly point to factors like temperature or humidity that could cause an issue in a future production process.
To learn more about how tonnage calculations work to ensure precise cuts for components using a variety of materials, or to get a quote based on a specific material and design, fill out our short quote form. You can also contact Vice President Josh Rodman directly at (707) 769-4488 to discuss your project.