an employee-owned company

Rigid Plastic Packaging

Stress Engineering Services has pioneered many of the rigid packaging computer simulation and testing methodologies used in the industry today. For over 25 years, our applied expertise in rigid packaging design, material selection, and performance evaluation has led to scores of technological advancements and innovations.

Non-Pressurized Bottles/Containers

Bottles and containers are required to sustain a broad spectrum of structural and thermal loads during shipping, handling, and in the consumer’s hands. At the same time, they are also required to safely store products throughout their service or shelf life.

Stress Engineering has unique capabilities in this area that couple advanced predictive analysis with testing. The result is an accelerated container design and development process aimed at balancing marketing intent with structural and cost requirements.

We routinely conduct a variety of analytical and experimental evaluations for container design, performance characterization and failure analysis including:

  • Fluid filled drop simulation
  • Top load optimization
  • Drop load simulation and testing
  • Squeeze stiffness
  • Fluid flow predictions for squeeze dispenser bottles
  • Fluid flow modeling for filling operations
  • Closure analysis
  • Capping torque prediction
  • Vacuum buckling
  • Seal performance and seal design
  • Internal pressure assessment
  • Pressure resistant base design
  • Shelf life predictions
  • Creep from imposed loads (pressure, stack load, other) under temperature conditions expected in service

We have developed a program to reduce container gram weight before tooling commitments are made. The “Container Weight Reduction Program” combines blow molding simulation with predictive non-linear structural technologies to lightweight blow molded containers.

Pressurized Bottles/Containers

Pressurized packaging is commonly used to contain beverages and aerosols at high pressures, often reaching values of ~125 psi (862 kPa), and at temperatures as high as 130-150°F (54-66°C). Under these conditions, short- and long-term mechanical properties of the resin system, material distribution, and the shape of the container are all critical in managing distortion and avoiding catastrophic creep failure.

Stress Engineering brings a unique breadth and depth of experience in the use of predictive engineering analysis and testing to design and develop pressurized containers. We have developed pressurized packaging with resin systems that include PET, nylon, polycarbonate, PEN, and others. Using virtual engineering techniques and focused material characterization, we routinely design and/or evaluate pressurized containers for:

  • Dimensional and environmental stability
  • Creep rupture
  • Feature retention under elevated temperature and pressure
  • Base stability
  • Top load under internal pressure
  • Drop impact under internal pressure
  • Stretch ratio and crystallinity optimization (PET/PEN)

Retort Packaging

With the aggressive conversion of glass to multi-layer polypropylene and other resin systems, the retort process employed to meet FDA requirements has produced new challenges in retort-package development. Applying traditional trial-and-error methods to develop container designs that will sustain the thermal loading, vacuum loading and overpressure typical to retort processes, is both difficult to apply and costly.

Stress Engineering has adapted proven analysis methodologies, originally developed for hot-fill applications, to solve design problems for retort containers. We also have developed on-line instrumentation for monitoring critical process parameters both inside the retort and the container during a typical thermal and overpressure cycle.

Stress Engineering has developed proprietary simulation methods to predict pressure and temperature within a package undergoing retort and the response of the package during retort.

Squeeze testing and analysis is often used to evaluate consumer feel, squeeze to dispense package performance, denting during conveying, and vending machine issues/performance.

In the case of consumer feel, packages may be too flimsy and feel “mushy” to the consumer. Analysis and testing can provide successful packages quicker by developing target performance criteria and iterating the package design in the computer until all key targets are met.

Hot Fill

In the hot-fill industry, bottle shape does more than establish brand identity. It also provides the critical function of resisting internal vacuum that tries to cause the bottle to buckle and distort.

Stress Engineering has developed a market niche in helping clients develop and optimize hot-filled bottle side panels and bases to effectively manage the displacements caused by this process. Our methods take into account the coupled effects of thermal loading from the fluid, changes occurring in the headspace and evolving material properties of the stretch-blown PET bottle.