The Cal Box Group is an industry-leading corrugated packaging company, supplying custom corrugated boxes & more. Contact us to learn more.

In the late 1970s, some U.S. paper companies began to mix some recovered and repulped OCC (old corrugated containers) into virgin liner. Since 2000 our paper mill supplier has run on 100% OCC. This is usually called ECT. (Most corrugated boxes ordered from catalogs are made from virgin kraft paper, not recycled paper) To insure reliable quality, we are AIB (FDA) and ISO 9001-2019 Quality Certified.

When testing for optimum strength of flute structure of corrugated boxes, it helps to be aware of potential issues before the problem becomes a reality.

In general, there are four things that all ACC corrugated boxes should have:

  1. Quality as a mindset includes sharp, clear printing with uniform print coverage, especially for bar codes and product or company identification, and exact panel dimensions with crisp scores, slits and slots.
  2. Protection for whatever is shipped or stored in the box. (Low rejection rate)
  3. Compression strength to allow the filled container to be stacked for storage or shipping without crush.
  4. Durability: the ability of the container to retain the above qualities over a desired period of time. Here, a suppliers advanced machine technology is important.

What should a corrugator or box plant test for?

Appearance is a highly subjective quality and is often judged by an expert eye. Stiffness properties are more quantifiable and the combined-board tests provide the core for improving compression at the expense of flat crush.

  • BCT (Box Compression Test)
  • ECT (Edge Crush Test)
  • Flexural Stiffness (Stacking Strength)
  • Pin Adhesion (Strength of Adhesive Bond)
  • Flat Crush (Flute damage)
  • Caliper (Thickness)
  • Burst (Mullen Test)
  • STFI or Ring Crush (at the mill)

To demonstrate the strength of bonding, perform your own pin adhesion test on several commercial boxes by peeling the liner from the medium. You may be surprised at the number of boxes that demonstrate little or no fiber pull. This is a simple boxmaker’s guide to corrugator bonding with a marginal relationship between pin adhesion strength and ECT board.

We continuely conduct test on boxes for Arizona's cyclic heat and humidity conditions. In trucks, warehouses, and outside storage, the box can be subjected to 20% relative humidity swings. Under these conditions, the box will “creep” – when the paper fibers swell and contract due to the humidity or cooling variations. This repeated swelling and contracting creates stresses within the combined board. Under these conditions, the box simply “wilts” or warps. The result is a failed corrugated box or damaged products. A test to identify paper that is more susceptible to creep should allow box-makers the ability to reduce this type of box failure. We use the quality control test for both Kraft (Mullen) and ECT.

We offer lab analysis and feedback. Most of these tests are performed for us in the professional laboratories at our mills or independent labs, with no cost to you, our customers.

So, improve your decision making: let us put our resources to work for you. Click on contact CalBox Group for more information.

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