[vc_row][vc_column][vc_column_text]It is very important that whether it is an operator or maintenance that care is always taken when working with print heads. They are generally expensive and delicate. If you want to maximize the production life of print heads only trained personal should be handling them. A filtration of some sort should be used between the supply of ink and print head to filter out impurities before reaching the head. For UV curable inks with heads stray UV should be limited and take precaution to keep from over exposure and curing of the face plate.
To maximize the production life of print heads care must be taken by keeping the head and especially the face plate clean. Use the appropriate flush for the ink set being used. Not all flush is compatible so if not certain call your ink supplier. Wipe the heads prior to printing with the flush and a clean lint free head wipe. Maintenance jetting or head cleaning should be done daily/weekly to exercise all jets in the head depending on usage. While printing all nozzles may not be printing so this exercise ensures all nozzles fire. It is then best to perform a jet test. By doing so you will actually print on to a substrate to witness a pattern/image of the individual nozzles firing. Doing this routine on a daily basis ensures you see a possible problem before it become unrecoverable. Many heads are recoverable if taken care of and signs of blockage are caught early enough and no physical damage to the head. Talk to your ink/head supplier for possible head recovery procedures or service.
Check out our industrial inkjet printers at www.epsvt.comthere you can also find more information about Engineered Printing Solutions custom solutions, standard pad printers, industrial inkjet, consumables and other auxiliary equipment. Email email@example.com or call 1-800-272-7764 if you would like more information.[/vc_column_text][/vc_column][/vc_row]
[vc_row][vc_column][vc_column_text]In the traditional sense there are very few tools required to operate pad printing machines. In most cases you will find that a single M4 Allen key will be all that you put to the machine in order to get it setup and functioning.
However there are a few tools outside of formed metal that come in much more handy. Common sense, diligence and a little elbow grease. If the former two attributes are employed, from day one, the latter decreases exponentially as do the issues that impose themselves when allowing the process and machine to get a bit messy.
For instance, one of the leading causes of premature wear of Printing Plates is dried ink between the mount surface of the cliché and the cliché support. Simply wiping both surfaces prior to setup contributes greatly to maximizing the production life of the cliché. When ink infiltrates the surface between the two mating parts, the inkcup tends to work at what becomes a raised portion of the cliché. You will find that a divot will develop as the inkcup shaves away, ever so slightly, the material. The next time the cliché is used, the divot that has developed will catch ink. If near on in the image area the cliché will be rendered useless.
Tip number one imparted during all training sessions is to keep the process and equipment as clean as is feasible. Excess ink will seep into places that may seem innocuous at the time but down the road, after the ink has had a chance to dry and cure, it will act as an adhesive and beget many a cuss word as screws are stripped and adjustments made impossible due to parts sticking together.
How long should my pad printing pad last?
Depending on how “rugged” a surface you’re printing on, a pad should last between 50,000 and 100,000 impressions. Improper use, careless machine operation or stray grit however, can decrease the pad’s life.
What should i watch for when I’m pad printing?
Make sure your substrate is free of sharp particles and debris. Avoid printing on sharp edges, which can puncture the pad. Use as little pad pressure (downstroke) as you can to pick up and deposit your image. (Tip: Too light an image could be an improperly etched cliche’)
What causes the most damage to pads?
Overly aggressive solvents, mechanical damage, poor storage practices, dirt/dust/debris and careless use are the most common causes of damage to pads. Additionally, some inks have aggressive solvents as part of their mix that will be absorbed by the pad and cause the image to “spread” on the pad. This isn’t permanent, as the solvent will evaporate if warmed or left to stand.
How should I clean my pad?
The best way to remove ink and debris from your pad surface is with regular packing tape. You may also use a mild solvent, such as alcohol. Always clean your pad before starting a printing job and never use a sharp object on your pad.
What is the best way to store my pad?
If a pad arrives in a protective shell or with a protective cover, remove it and do not reuse. It could trap grit and debris that can damage the pad. Never store a pad on top of or compressed against another pad. Handle and store your pads carefully.
What’s the nest way to extend my pad’s life?
We sell 8 oz. bottles of Pad Rejuvenator (Ask for Part Number PAD OIL when you call our customer service department.) The other way we recommend extending a pad’s life is to have two pads that you alternate one shift on, one shift off, to “rest” the pad and let it restore to its uncompressed state.
How do I prevent pad wear? Correct design and tooling of fixtures will help eliminate pad wear … a major cause of image distortion.
Although a fairly straightforward process, there are a number of things that can affect the pad print process if your plate is not etched properly.
Common complaints range from edge definition to ink transfer issues. Improperly etched clichés can allow for inconsistent image opacity or even missing portions of the images in certain circumstances.
Some keys to properly etching a cliché (but not limited to), 1. Size of the components of the image, eg. are there bold areas and small copy in a given image, 2. Orientation of image on the cliché, 3. Type of material you are etching, 4. Substrate to be printed.
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.