[et_pb_section bb_built=”1″ admin_label=”section”][et_pb_row admin_label=”row” background_position=”top_left” background_repeat=”repeat” background_size=”initial”][et_pb_column type=”4_4″][et_pb_text background_layout=”light” _builder_version=”3.0.86″]<\/p>\n
[\/et_pb_text][et_pb_image _builder_version=”3.0.86″ src=”https:\/\/www.flxon.com\/test\/wp-content\/uploads\/2018\/02\/KEYS-01.png” show_in_lightbox=”off” url_new_window=”off” use_overlay=”off” always_center_on_mobile=”on” force_fullwidth=”off” show_bottom_space=”on” \/][et_pb_text background_layout=”light” _builder_version=”3.0.86″ text_orientation=”justified” module_alignment=”left”]<\/p>\n
The majority of you have probably seen a presentation from your ink supplier. Most are very informative and well written. If you haven\u2019t yet taken advantage of this valuable resource, I would suggest contacting your ink supplier and having your people sit through one. It\u2019s well worth the effort.\u00a0 Even though I am not a chemist and do not claim to be, I would like to cover the basics of ink construction as it relates to the effect this process element has on your product quality. Because the vast majority of rotogravure printers use solventbased ink, my comments may not relate to water-based ink.<\/p>\n
In my experience, water-based inks are not well suited to the rotogravure transfer process. I have visited most gravure printers in North America and have yet to find\u00a0a water-based gravure printer who isn\u2019t struggling with haze, streaks, and drag-outs. How can they compete with solvent based printers who run faster and run with fewer quality issues?<\/p>\n
Ink is comprised of the following primary ingredients:<\/p>\n
PIGMENT<\/strong><\/p>\n Pigment is manufactured by grinding natural rock minerals to extremely small particles. Particle sizes differ based on the mineral color. The following is an example of the initial pigment size achieved in the grinding process (25.4\u00b5 = .001\u201d):<\/p>\n Most pigments are ground in an aqueous media. Following grinding, the water is\u00a0removed in a drying process during which the small particles tend to join together to form larger particle clusters called \u201cAggregates\u201d and \u201cAgglomerates.\u201d These particles require shear to break them down into primary particles again (figure 1). Pigments are an INSOLUBLE solid. That means they will not dissolve or remain suspended in a fluid without assistance.<\/p>\n As a key ingredient, resin has two primary functions. It coats and helps to suspend or support pigment particles within the carrier, in this case solvent. Once pigment has been transferred and is positioned on the substrate, the resin coating binds the particles to the substrate.As a key ingredient, resin has two primary functions. It coats and helps to suspend or support pigment particles within the carrier, in this case solvent. Once pigment has been transferred and is positioned on the substrate, the resin coating binds the particles to the substrate.<\/p>\n Solvent (like pH-specific water) is the carrier used to transport the solid pigment particles from the ink pail through the ink delivery and metering system to the substrate. Once the pigment is in place, the solvent carrier is removed by drying. The percentages of solvent and solids as well\u00a0as the viscosity all impact the suspension, transfer, drying rate, and solvent retention.<\/p>\n The type of solvent used during the manufacturing process depends on the type of resin used (NC, polyamide, vinyl, urethane etc.). True solvents will dissolve resin, but diluents will not. Adding large amounts of diluents will kick out the ink (aggregates\/ agglomerates will form). At this point, ink may become unusable. It is extremely important to only use recommended solvents from your ink manufacturer.<\/p>\n Note:<\/strong> Ink that is not stable (too soft resin) will create an issue in printing called \u201cdry\u201d haze, which is different than \u201cwet\u201d haze. The cause of wet haze is more related to blade angles and cylinder polish. Dry haze is the result of a buildup of ink in the RZ of your chrome finish that does not solidify with each revolution through the ink bath. This unsolidified ink will continue to build until it prints. The way to distinguish between the two is whether or not the haze oscillates. Dry haze will not oscillate. Wet haze will.Note: Ink that is not stable (too soft resin) will create an issue in printing called \u201cdry\u201d haze, which is different than \u201cwet\u201d haze. The cause of wet haze is more related to blade angles and cylinder polish. Dry haze is the result of a buildup of ink in the RZ of your chrome finish that does not solidify with each revolution through the ink bath. This unsolidified ink will continue to build until it prints. The way to distinguish between the two is whether or not the haze oscillates. Dry haze will not oscillate. Wet haze will.<\/p>\n It\u2019s the clumping of pigment particles (\u201cAggregates\u201d and \u201cAgglomerates\u201d) that are an issue for the gravure printer. I have measured some clusters to be as large as several hundred microns. It is these larger particles that lodge under a blade\u2019s edge to cause print defects such as streaks and lines. These particles can also damage the blade\u2019s edge and lead to cylinder damage.<\/p>\n There are a number of things you can do to prevent these particles from becoming an issue in your process. You must first be sure your ink supplier is shearing these particles back to their primary size, refrain from using non-recommended additives, keep ink from freezing (I live in Wisconsin), use only recommended solvents, and make sure you filter inline between your ink pump and printing deck.There are a number of things you can do to prevent these particles from becoming an issue in your process. You must first be sure your ink supplier is shearing these particles back to their primary size, refrain from using non-recommended additives, keep ink from freezing (I live in Wisconsin), use only recommended solvents, and make sure you filter inline between your ink pump and printing deck.<\/p>\n As the Technical Service Manager for Flxon Inc., I have visited several hundred printers over the last few years. When the printer admits he is having printing issues\u00a0(i.e., streaks or drag-outs), the first question I have is, \u201cDo you filter?\u201d Most of the time the printer will say, \u201cYes.\u201d My next question is, \u201cDo you filter properly?\u201d This question always gets the same reaction out of the printer\u2014the deer in the headlights kind of look. Just because you have ink running through a round contraption that says \u201cFilter\u201d on it doesn\u2019t mean you\u2019re filtering adequately. Sometimes the \u201cfilter vessel\u201d doesn\u2019t contain a filter.<\/p>\n To be effective, a filter must remove all particulate that is large enough to cause print defects. This means any particle that is substantially lager than the average size of all particles should be removed. The hard particles may be pigment, resin or blade debris.<\/p>\n If most particulate in your ink are consistently less than 30\u00b5 – 40\u00b5 then a particle that is 100\u00b5 can be a problem. On the other hand, if all the particulate were consistently 400\u00b5 \u00b1 10\u00b5, you would not experience lines and other print defects.<\/p>\n However, consistent large particles will result in a gritty lay down and be more wearing to your cylinder and blades.<\/p>\n [\/et_pb_text][et_pb_text background_layout=”light” _builder_version=”3.0.86″ text_orientation=”justified” module_alignment=”left”]<\/p>\n Figure 1.<\/strong><\/p>\n <\/p>\n [\/et_pb_text][et_pb_image _builder_version=”3.0.86″ src=”https:\/\/www.flxon.com\/test\/wp-content\/uploads\/2018\/02\/particles-01.png” show_in_lightbox=”off” url_new_window=”off” use_overlay=”off” always_center_on_mobile=”on” force_fullwidth=”off” show_bottom_space=”on” \/][et_pb_text background_layout=”light” _builder_version=”3.0.86″ text_orientation=”justified” module_alignment=”left”]<\/p>\n [\/et_pb_text][et_pb_text background_layout=”light” _builder_version=”3.0.86″ text_orientation=”justified” module_alignment=”left”]<\/p>\n As shown in figure #2, if the particle is small enough, it can retreat into the cell and not create damage (75\u00b5 or smaller). However, if the particle is too large to retreat (75\u00b5 or greater), it will create damage in several ways and will cause unique printing defects.As shown in figure #2, if the particle is small enough, it can retreat into the cell and not create damage (75\u00b5 or smaller). However, if the particle is too large to retreat (75\u00b5 or greater), it will create damage in several ways and will cause unique printing defects.<\/p>\n So, my question to you is, \u201cDo you filter properly?\u201d\u00a0When I ask this question of printing managers, the response often is:<\/p>\n Here is an industry truth \u2026 if you are not filtering your \u201cin-process\u201d ink to at least 100\u00b5 (preferably to 50\u00b5), you have particulate related print issues that are costing you money, far more money than the cost of proper filtration.<\/em><\/strong><\/p>\n May I suggest trialing a 50\u00b5 filtration system? The majority of your streaks, drag-outs, lines, and comets will disappear. Other printers are doing this and reaping the gains on their bottom lines!<\/p>\n As one of the \u201cKey Elements\u201d of defectfree printing, it is important to keep your ink clean and stabilized to ensure this element does not create issues for you.<\/p>\n <\/p>\n [\/et_pb_text][et_pb_text background_layout=”light” _builder_version=”3.0.86″ text_orientation=”justified” module_alignment=”left”]<\/p>\n Figure 2.<\/strong><\/p>\n <\/p>\n [\/et_pb_text][et_pb_image _builder_version=”3.0.86″ src=”https:\/\/www.flxon.com\/test\/wp-content\/uploads\/2018\/02\/particles-2-01.png” show_in_lightbox=”off” url_new_window=”off” use_overlay=”off” always_center_on_mobile=”on” force_fullwidth=”off” show_bottom_space=”on” \/][et_pb_text background_layout=”light” _builder_version=”3.0.86″ text_orientation=”justified” module_alignment=”left”]<\/p>\n To recap what we have discussed so far in the \u201cKey Elements\u201d series:<\/p>\n If you need help with assessments or training for the best doctor blade solution, contact one of our experts for a consultative evaluation. Our team will be able to help you with solutions.<\/p>\n\n
RESIN<\/strong><\/h5>\n
SOLVENT<\/strong><\/h5>\n
BACK TO PIGMENT PARTICLES<\/strong><\/h5>\n
FILTRATION<\/b><\/h5>\n
ADEQUATE FILTRATION<\/b><\/h5>\n
Simply Stated – Size Does Matter!<\/span><\/h1>\n
\n
\n
\n
Download Technical Article<\/strong><\/h5>\n