Since the 1960s, corrugated printing requirements have grown from simple logistics to eye-catching promotional packaging with skus and tracking information. Improvements in doctor blade materials and tip configurations have played a key role in making this possible. While anilox rolls have gotten better at efficiently transporting a precise volume of ink to the plate, they are only as good as the metering blades they’re paired with: if a doctor blade leaves excess ink on the roll, a printer quickly loses control over quality and consistency.
Corrugated Doctor Blades Through the Years
1960s – Straight UHMW
About 50 years ago, corrugated printers started using doctor blades as a replacement for rubber rolls to gain control over the amount of ink transferred to the plate. (Read: “Corrugated Ink Delivery Systems: Two Roll or Doctor Blade” to learn more) UHMW offered a good solution because its dense molecular structure was ideal for printing environments that combined long runs and coarse anilox engravings. This soft, thick material was safe to handle, didn’t score anilox rolls, and was highly resistant to stress cracks and chips. It was also very abrasion-resistant which gave the blades extremely long life. UHMW products were engineered in thicknesses of .090” and .100″ which was adequate to produce the type of work being done at that time (and still in many applications today) – simple solids and lines in one to three colors.
Late 1980s – Early 1990s – Introduction of Bevels
As packaging began to take on more of a marketing role in the 1980s, the demand for higher quality graphics grew. Doctor blades became common in corrugated applications and new press technology, including ceramic anilox rolls and doctor blade chambers, came to market. Blade manufacturers focused on developing stronger, more durable materials that could be engineered into thinner products. Blade thicknesses decreased to .060″ and .080″, and 30° and 45° bevels were introduced to allow a smaller area of contact with the anilox roll.
Late 1990s – Early 2000s – Plastics and Composites with Finer Bevels
Packaging graphic requirements continued to increase in the 1990s, and there were more innovations in anilox rolls and press components. Printers began using more advanced plastic materials for a stiffer, more durable alternative to UHMW. Acetal blades were effective at metering moderate to high line screen rolls while providing great chemical resistance, good dimensional stability and a low coefficient of friction. These materials could be fortified with additives such as Teflon and manufactured into thicknesses of 020” to .040”. The material was able to accommodate finer bevels of 15° and 22° to produce difficult fine type and reverses. Tight weave fiberglass composites were also developed for screen and process work due to their extremely stiff and durable characteristics.
Mid 2000s – Next Generation UHMW
For printers using UHMW to produce low to moderate graphics, Flexo Concepts introduced a new high-density formulation UHMW, called DuraPoint, to deliver up to 25% longer blade life than traditional UHMW. This next-generation formula was capable of producing enhanced graphics for a longer wear period and is still widely used today.
Today – Next Generation Polymers
Nowadays, box makers are asked to produce packages that serve as both shipping and display vehicles. Graphics requirements are exceptionally challenging and more colors, finer plate screens, half-tones and higher anilox line counts are being used to produce attractive point of sale and point of purchase containers. Predictable ink density and color control are essential to ensure manufacturers’ brand consistency. This shift in purpose caused a gap to emerge within corrugated printing, where neither UHMW nor Steel doctor blades were ideal. In 2017, a new blade that offers the best of traditional non-metallics and steel was created to fill the gap in these applications. Flexo Concepts’ purposefully designed the TruPoint Green doctor blade to meter mid-high level graphics effectively, efficiently and safely. The TruPoint Green doctor blade is a next generation polymer designed to be stiff, durable, and resists mechanical creep, allowing for better print quality throughout the entire life of the blade. (View the Doctor Blade Mechanical Creep infographic to learn more)
Along with press builders and anilox roll manufacturers, corrugated doctor blade suppliers have done their job of “keeping up with the times.” Blade materials, formulations and technology have advanced over the past half-century along with the demands of the packaging industry. While UHMW, traditional plastics and composites are still the best choices in many low-moderate graphics applications, corrugated printers who want to avoid the mechanical creep of UHMW and short blade life and risks with using steel now have a next generation polymer blade to produce quality work of the 21st century – TruPoint Green.