Ever find yourself wondering, “What steel am I using for my doctor blades?” and “How does it affect my print quality?”
Find yourself asking, “Is that the right choice?” or “Does my selection match up to the preferred industry standard?” If you have, you’re not alone. Let’s look to offer the answers.
First-class, super refined, Swedish steel is the preferred industry option for doctor blade materials. That’s a general consensus statement—printers make it; manufacturers stand behind it. Why? Uniform and slow blade wear is virtually guaranteed. Swedish steel offers:
- A pure chemical composition
- Smaller sized carbide
- High-density/no porosity
- Lack of non-metallic inclusions
- An undifferentiated metallurgical structure
Non-Swedish steel can wear in much larger slivers and unevenly, leading to magnets having to be cleaned more frequently, as well as, a shorter doctor blade life, resulting in downtime and waste.
There are four types of steels to choose from: white carbon, high carbon, stainless (mostly in water-based applications,) and micro-alloy (tool steel). Plus, there are various profiles/tips, such as, radius/round, bevel, stepped lamella and wing lamella; and coated and Nano-treated blade options.
Points of Discussion
Certain factors will help determine the best blade for your operation and will help you to avoid common print defects and other troublesome issues. Items you should discuss with your technical representative are:
- Type of inks being used? Solvent, water based, UV, EB, coatings, adhesives, etc.
- Print output–all line work, process, expanded gamut process or a combination?
- Abrasive-prone inks and chemistries–whites, metallics and matte varnishes?
That said, let’s examine some common print defects and issues, such as color variation, dot gain, streaking, and ink spitting.
Pressure Reliever
Pressure is the enemy in the pressroom. Just like setting a “kiss” impression on a printing plate, you want your doctor blade to wipe with a minimum amount of pressure. A wing lamella tip lets you achieve just that.
Unlike a radius or round type blade that takes some time to wear in, the wing tip seats immediately and wipes cleanly with the least amount of pressure. This allows for greater color consistency and helps hold a true dot longer.
Material Strength
Streaking can occur from various sources, some of which include long wear-in periods and larger slivers that get trapped under the doctor blade when using inferior steel. These slivers can also cause scoring to costly anilox rollers, which leads to the next point.
Why choose micro-alloy over white carbon steel?
According to Al Jasper, “Before joining Provident, eight years ago, I spent 26+ years as an operator then printing superintendent, and I always chose micro-alloy steel for two main reasons:
- It provides extended doctor blade life at a middle of the road price point
- When it wears, it does so in a powder like sugar form, instead of breaking into larger slivers making it very anilox friendly.
Printers who run this type of steel reap the benefits. After all we all ascribe to the well known theory, “The anilox is the heart of the press!”
Life Savers
Ink spitting is very common in higher viscosity UV inks. A common cure is to increase the thickness of the blade, 0.010-in. and 0.012-in. blades normally will resolve this. The wing tip also helps shear and meter this viscous ink more efficiently.
Some other common issues are the short life of doctor blades when in abrasive white, metallic or varnish decks. Coated blades specifically made for titanium whites, which can destroy a doctor blade quickly, are a great solution to extending life, preventing constant changes that lead to costly downtime and excess waste. These blades also work very well in metallic inks and coatings, such as, matte varnishes. This issue is often the No. 1 problem pressroom managers and operators complain about.
Looking for a better solution? Today’s new Nano treatment blades might prove attractive. PrimeBlade-Sweden’s patented Nano process infuses the steel, while it is being made, to mimic long-life coatings, but in a way that is much more environmentally friendly than having to apply a coating.
Specifically, treatment is made deeper into the base material to create better durability and strength. Changing the time and temperature creates more carbon particles and allows them to unite with the softer areas of the steel. This process has shown longevity increases of 25-30 percent.
Treatment delivers better blade life and performance than standard blades of the past, the “PrimeBlade 900 Nano+” is an example of just that. Experience has documented that doctor blades flex or bend less, to keep the optimum contact angle against the anilox or printing cylinder. This will create the perfect and preferred wipe condition. It will also help more against common problems in flexo printing, like back doctoring and ink spitting. For UV-ink users, the blades will be less affected by heavy viscose UV-in and give a cleaner wipe. That’s a win/win!
Continuous Improvement Managers, Chief Sustainability Officers, Pressroom Managers—all will love and see definitive benefits from utilization of the Nano blades. Put succinctly, “Microstructure matters!”
About the Author
The Provident Group is a leading provider of doctor blades and end seals specifically designed for printing. From consistent ink metering to containment solutions that harvest uptime, it offers custom solutions, designed to each individual application. Full manufacturing capabilities means, “It makes what it sells!” Learn more at providentgrp.com.