Everyone knows that plastic doctor blades are safer than steel. But did you ever wonder why plastic is a safe doctor blade option? The answer is simply (and somewhat obviously) that the steel blades are harder and sharper than the plastic ones. While this is something that people just seem to “know,” the difference can be explained when you look at the molecular structures of the two materials.
What does it mean to be sharp?
Steel and plastic materials (and all matter) are comprised of small particles. As a doctor blade wears, the material is removed in “chunks” which can be no smaller than the basic particle size of the material itself. So, it stands to reason that the finest tip on a blade can only be as wide as one particle. Because plastic particles are larger than steel particles, when a plastic blade wears even to its finest point, the width of the tip will be larger than that of a steel blade. This scientific property combined with the fact that plastic is inherently softer than steel results in a plastic blade edge that is less “sharp” than steel and safer to handle.
So, if this is true, how is the edge of a plastic blade fine enough to meter ink as well as steel? The answer is that some plastics aren’t. For example, UHMW plastic – while effective for ink metering in many applications – cannot meter ink as well as steel on high line screen anilox rolls. Due to low rigidity, UHMW blades require thickness to provide stiffness, which means they can’t maintain a fine tip or small area of contact with the anilox roll. On the other hand, many next generation polymers (like Acetyl, Delrin, and Polyether ether ketone) have material compositions that are rigid enough to support a special MicroTip edge and achieve a fine contact area similar to that of steel. But, while the blade performs like a steel blade on the roll, the inherent properties of the plastic material prevent it from developing a dangerous cutting edge and injuring press operators. These properties make new polymer blades superior to steel, because, after all, doctor blades are not designed to cut – they’re designed to wipe liquid from a roll. Their cutting properties are not important (or rather they’re important in that you want them NOT to cut!).
If a printer requires steel for metering performance but would prefer plastic for its safety benefits, he should consider today’s next generation polymer doctor blades. The combination of advanced material and innovative MicroTip edge design allows this safe doctor blade to perform in highly demanding applications where steel was previously the only blade material capable. Converting to a safe doctor blade will reduce lost-time accidents and can save a printer a lot of money in terms of workman’s compensation insurance, medical bills, labor replacement expenses and press downtime.
When it comes to choosing between two blades that can produce high quality print equally well, why not choose the safer one? Substituting a next generation polymer doctor blade for steel is a simple way to maintain a productive and profitable pressroom environment while keeping employees safe.
We hope you enjoyed our In Safe Hands with Polymer Doctor Blades blog series. Click on the links below to view previous posts in the series:
Part 1: “Numbers That Add Insults to Doctor Blade Injuries“ – Read about the frequency of hand injuries in the workplace and their impact on a company’s bottom line
Part 2: “Steel Doctor Blade Risk Management” – Learn about options that reduce or eliminate the risk of injuries from steel doctor blades