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(800) 272-7764Good color matching can best be achieved through the use of color profiling software. This software allows for the creation of color profiles which capture the bias imposed by the substrate color and porosity, print resolution, as well as ink set limitations on printable color gamut. A color profile is generated by printing an “objective” color target made up multiple known color patches of absolute values, then reading the printed results with a spectrophotometer and calculating the differences or “Delta E”. The larger the number of patches printed and read the more accurate the profile. The underlying substrate color’s effect on accurate color ought not be underestimated as even a white undercoat beneath the CMYK ink may not fully defeat the shift in color. A good substrate-specific color profile can eliminate the need for the tedious exercise of multiple rounds of color correction using Photoshop or other photo editing software. Finally, periodic calibration should be performed in order to maintain good accurate color density and gradation.
Too little pad printing ink, often times the ink will not “flow” in the inkcup correctly giving an inconsistent fill of the etch. Additionally, the ink will tend to thicken much more quickly as the doktoring action of the cup allows for thinner to flash. In cases where hardener is used, very short pot life can be expected of the ink. We do have an “Ink Saver” device that allows for combating the first issue with companies that have short runs where it does not make sense to mix enough ink to fill the cup to the recommended ½ to ¾ full level.
Too much pad printing ink, the process can get messy. In particular when hardener is used. A byproduct of the addition of a catalyst (hardener) is off gassing. If this gas has no place to go, it tends to cause the cup to hydroplane as it pressurizes the inkcup. The ink that is left behind is then “plowed” into pools of ink usually on either end of the travel of the inkcup.
The XD070 Industrial Inkjet Printer “image direct” from computer to print. The perfect solution for short or long runs with quick changeovers and variable data. This printer is ideal for multicolor printing on flat and semi-flat surfaces on a variety of substrates and can be customized to meet your printing needs.
Now, let’s talk fixtures and print job setup! With 3-dimensional parts, proper presentation of the product to the print head is critical. The closer and more level the part can be presented relative to the face-plate, the better the quality of the print will be. Calipers and a level are tools which can make this process more simple, but the ability to actually advance the product into the machine to more precisely gauge your proximity is optimal. By employing the “Setup a Job Print Position (by Test)” standard software utility on the XD070, the Operator is able to advance the fixtured product into the printer to visually set the print head-to-product offset (print height), as well as the cross track (left to right) offset. This capability provides for faster initial job setup and decreased printer crashes saving both time and frustration for the Operator.
It is, of course, imperative that common sense and attention to moving parts be used when operating any piece of equipment. This includes pad printing equipment. More often than not, the KP-05 – KP-08 model equipment will be run as a standalone system with only the manufacturer’s supplied guarding in place. This includes the EZ-90 – EZ-160 equipment.
As the equipment gets larger … so goes the compression capability. The XP-13, for instance, is capable of producing compression forces of 1,050 lbs.. This is enough to flatten any hand. Along with the compression force there is usually some form of part conveyance. With this comes pinch points. For these machines it is mandatory that a light curtain be implemented, as supplied by the manufacturer, in order to keep an operator from inadvertently harming themselves.
Long end around, the manufacturer does all we can to guard those portions of the machine that are of interest however there is no substitute for good manufacturing processes and an operator paying attention to the task at hand.
Poor ink adhesion is most commonly a function of mismatching the ink series to the substrate. Where there are many different substrates … there are also multiple ink chemistries, pre-treatments, additives and post cure methods available to meet customer expectations. Appropriate testing should ALWAYS be performed to find a match of ink and substrate that satisfies the end user’s specification for adhesion.
Moving on to inks that have been properly qualified for a process, and “suddenly” show failed adhesion, one should look to contamination, the most common examples of which include mold release, skin oils from handling, upstream processes or blooming of a plasticizer.
One additional item of note, given the time of year, is the use and proper curing of processes that utilize a hardener or catalyst. With the quick turnaround that our customer’s expect today it is frequently forgotten that complete cross linking of a bi-component ink can range from 48 to 72 hours. If’n during this time the printed product sees temperatures in the mid to low 50’s (F) the cross linking process ceases … never to be started again.
Pad printing is known to be a method for odd form printing. Each part’s shape and topography pose its own set of complexities with getting print in the area you wish to see it and a one to one representation of the image you are attempting to print. That is to say, the curvier the part, the more likely you are to encounter distortion of the image.
As a general rule of thumb, present the print area of the part as perpendicular to the stroke of the pad (Z axis) as is possible. This will combat “skid” of the pad on initial contact. As the pad “reaches” or stretches over the part … so goes the image. The best method by which to combat the distortion is to have a pad that is as big as the machine will allow. Oversized, if you will.
Depending on whether the curve can be considered complex (the part falling off to different degrees in many angles) it may be necessary to appropriately size the image, bring it down, or pre-distort the artwork to compensate for the stretch.
The inkjet equipment is not as forgiving with parts that are not flat. The manufacturers prescribed distance of the array to the substrate is anywhere between 1mm – 3mm depending on the type of print head. The answer then … if the substrate will be any further than the prescribed distance … it is not flat enough.
That said, we have come up with work arounds to where we can jet ink up to approximately 10mm. These tricks include manipulating drive voltages and size of dot to be jetted. The image quality will certainly suffer when you start to range outside of the 1 – 3mm range but the end user is left to discern whether the quality is acceptable.
Two leading contributing factors to an etched plate folding up:
- Leaving ink in the inkcup over an extended break. Whether 8 hours, 16 hours or longer. The ink will begin to dry where it comes in contact with the outside environment. It tends to “glue” the inkcup to the surface of the cliché. If care is not taken to rotate the inkcup, manually, to break this seal and clean the residue … time to get your Polka on.
- Missing fasteners. Customer’s sometimes cut corners with making sure the cliché is firmly secured to the cliché support. If the appropriate restraints are not in place (e.g.: thumbscrews, socket head cap screws, pin screws) … roll out the barrels!
Here are the reasons why a silicone pad might split:
- Too much pressure on either the pick up or print side.
- Using chemicals to clean the pad surface, causing the print surface of the pad to dry and crack.
- Parts/Fixtures that have a raised portion that comes in contact with the pad and acts as shear point. This cuts the print surface of the pad.
- The pad is old.
Engineered Printing Solutions Case Study #1:
An automotive firm required assistance in gaining efficiencies in their molding and decorating process. They wanted to eliminate staging / moving parts around the facility, and to be able to print parts at the mold. The part required a custom machine as the print was not only multi-color, but on multiple planes. The customer also wanted a machine that would require as little human intervention as possible.
This required a machine that would fit in the constraints of their molding cell, capable of picking freshly molded parts from a conveyor, orienting and placing the parts onto custom tooling. The parts were then printed and automatically removed for post-print handling / inspection / packing.
The same parts could be used for different applications, so it was also necessary to provide an efficient way to change the images.
We provided a fully automated KP-08 with multiple heads with independent pads, plus automated loading and unloading. The unit was configured to integrate with the customer’s mold, so if one or the other components experienced a fault a “parts buffer” could accommodate any intermittent pauses, but also allowed for a full shut-down, if required.
Engineered Printing Solutions Case Study #2:
A large plastic injection molding firm asked for assistance with a change in their production requirements, based on their customer’s ordering preferences.
The facility is highly automated and parts are printed in-line. However, the customer was seeing their market shift toward multi-color images, as well as shorter print runs on the same series of molded parts. Their current technology allowed only single-color images, and required a minimum of 30-45 minutes for job changeovers, and more if the color had to change, as well.
We offered a solution based around our own industrial inkjet technology, which provide the following advantages:
- No loss in throughput
- Multi-color images
- Less ink waste
- Immediate curing
- Job changeover in seconds, not minutes
- Order entry could be done remotely, integrating with their own software
- Parts could also be counted, bagged and bags labeled automatically
Our industrial inkjet printer was able to be easily integrated with third-party provided feeding systems as well as the bagger / label unit on the back end.
This custom solution has allowed our client to be more flexible and more responsive to their customer’s wishes, while saving labor as well as reducing waste re: parts and ink.
Let us design a custom solution for you. Drop us a line today!
When comparing the differences between traditional printing methods – such as pad and screen printing – and digital inkjet printing, we like to use the analogy of comparing a 1969 Camaro to a 2014 Tesla. They’re both cars, and they can both get you where you are going, but the methods of how they work and the cost of operation are quite different. Traditional printing always has been done with direct contact of the inks via a vehicle such as a pad, screen or blanket to the product being printed. Inkjet deposition is done through a non-contact form of printing with specified offsets of the heads to the substrate being printed, thus eliminating pads, screens, plates, type set and stamps.
Traditional forms of printing always have been a mechanical process, and inkjet is a computerized process. The biggest single advantage of the digital process is the ability to change from one graphic to the next with the click of a mouse. No longer is there the need to change screens, pads, plates and registers between the colors for each individual print process. For companies printing short runs or dynamic data, the times savings are dramatic. However, there also are advantages to traditional forms of printing.
Question: How does ink adhesion differ?
Answer: Traditional forms of printing have been around for years, so there is a vast historical knowledge base. Inks have been tested on different substrates, so we know what pre-treatments, type of inks, additives and post-curing processes need to be applied for different print scenarios. By contrast, UV-curable inkjet printing is rapidly developing, but with little historical knowledge.
The main concerns when using pad or screen printing inks have always been adhesion and drying time. Certain materials, such as olefins, generally require a pre-treatment to obtain the proper surface tension for adhesion. Occasionally, static and surface contamination can warrant some adjustments to the inks.
Unlike traditional pad/screen print inks, adhesion is not the only concern with the UV-cure digital inks; wettability (dyne level) plays a big role in obtaining a quality print. The wet out of the print is what provides a clear, smooth, quality image. If the printed dots encounter surface tension, static or contamination, the dots will bead up and create a grainy image. Temperature is used to control inkjet ink viscosity versus analog inks where additives (thinners) are used. Environmental effects on all ink systems are a factor to consider, and humidity control and temperature play a vital role in print quality in both inkjet and other older technologies.
Question: Are there color limitations with digital inkjet?
Answer: When using digital CMYK Lc Lm inks, it is important to realize that there are limitations to color matching. Large brands have specifically formulated colors that represent their products. These are easily matched in traditional forms of printing by mixing inks to create a desired color. However, the use of custom colorants on digital devices is very rare because of their cost, the development time and the difficulty (if not impossibility) of changing colors and cleaning ink feed systems after use without contaminating the next color. It’s been estimated that only 30 to 40 percent of Pantone colors can be achieved using a standard digital CMYK. That leaves a significant portion of brand colors outside of the achievable gamut, whether they’re specified using Pantone or not. Most brand owners are aware of these limitations and understand that a perfect match for certain high chroma colors is unachievable and accept that close is close enough.
A so-called “HiFi” space using a larger number of colorants – such as CMYKOGV (i.e. CMYK + orange + green + violet) – greatly increases the color gamut; even this, it’s still estimated that only around 80 percent of Pantone colors can be printed accurately in this way. However, these inks are very specialized and are not universally compatible with all printheads and print processes. Commonly available UV-curable CMYK ink sets that include light magenta and light cyan can achieve 55 to 65 percent of the Pantone Matching System (PMS) spectrum, but again, a six-color printer is significantly more expensive than a four-color printer (more heads, ink management modules, electronics, etc.). There are on-board color controls as part of the RIP package on some digital printing equipment that mimic the abilities of Photoshop, allowing for quick color adjustments on the fly. Once made, these tweaks are saved and retained for all future print jobs using that image data set.
Question: What are the differences in ink curing?
Answer: Although there are UV-cured inks in other print processes such as pad and screen printing, the majority of ink curing usually is done by running the items through an oven to complete the flashing off of solvents. Pad printing inks are printed wet on wet. The solvent, depending on the ink and print substrate, usually flashes off within seconds and can be handled almost immediately after printing. Originally, the UV digital inks were designed to be cured by high-pressure arc lamps. It was a complete process with cure time measured by the time exposed under the lamp. Cooling the bulbs always was a concern.
There were many positives realized with the development of the UV-LED inks. The cost of operation went way down, extravagant lamp cooling systems were eliminated and there no longer was ozone created by the high-pressure arc lamps, thus eliminating the need for ozone deconstruct systems built into the print exhaust. With the new curing lamps, there also were challenges that had to be overcome. The UV-LED lamps remain constant, so there is no longer a concern if it is properly curing the ink. The newer lamps bring new concerns, including dialing in the correct speed with specific substrates and setting the optimum power levels of the lamps. The offset of the lamps to the product all have to be tested and formulated to ensure proper wet-out, adhesion and curing.
Question: How does substrate shapes affect print quality?
Answer: Pad printing has been the ideal solution for printing on odd-shaped items with compound curves. The transfer of the ink image with the silicone pad has been a proven method for decades. Accuracy and repeatability of the print is excellent. Even difficult images on extreme shapes can be adjusted with artwork distortions so that when the print is transferred, it adjusts the distortion created by the stretch of the pad. Opacity is usually excellent, even on dark substrates. Plates can be etched to different depths to allow for transfer of additional ink, and different durometer pads can be selected to achieve an improved image transfer.
Digital inkjet differs because there are limitations to the amount of offset the heads can be from the print surface. The further the drop of ink has to travel, the lower the print resolution will appear. The ideal offset for printing with most digital heads is a maximum 1.4 millimeters from head to print surface. The size of the dot, resolution, time of flight of the ink and travel speed are all taken into consideration when printing on a slightly curved surface. Inkjet systems originally were designed to print on a smooth flat surface. With adjustment to the speed of print, UVLED curing speeds and electronic settings and by isolating air turbulence, the ability to print on curved surfaces with greater offset distances continues to evolve.
Question: How do the consumable costs compare?
Answer: When potential customers ask us how much it costs per part for the decoration, calculations are done based on consumable costs. In pad printing, take the cost of ink used for a specific length run; factor in waste, and determine the per-piece cost for ink. The pad usage also is easily calculated by dividing cost against the realized usage life. We also can calculate the operation costs based on parts produced per hour and include setup time, average time of change over from job to job and clean up.
When calculating costs for the digital inkjet system, look mainly at ink consumption. The PC running the system automatically will calculate the ink consumption and provide a per-piece ink cost. There is virtually no changeover time involved going from print job to print job. The completed artwork can be sent to the system using a USB drive or directly via LAN. Remember, this all makes servicing via the Internet an excellent alternative to flying in a technician.
Question: What questions can be asked to help make a decision between analog and digital inkjet systems?
Answer: When faced with a decision, evaluate the pros and cons of traditional analog systems and new digital inkjet systems.
How often does graphic change?
What is the required production rate?
What are the color requirements?
What is the cost of the equipment?
What is the potential value added with the personalization and/or traceability that can be realized with new digital inkjet equipment?
What type of personnel do you have at your disposal?
How much are you spending on expensive supplies?
Tim Scully is vice president of sales at Engineered Printing Solutions. He received his BA in History & Secondary Education at SUNY Cortland. Since 2003 he has provided design build services for Pad Print Machinery of Vermont, now Engineered Printing Solutions. He enjoys assessing existing methods of decorating and providing new concepts and designs to make the process more efficient and cost effective for customers. Inkjet printing methods have created a new avenue to achieve greater production rates at lower costs. For more information, visit www.epsvt.com.