Pros & Cons: Pad Printing in a Clean Room Environment

Pad printing is a fantastic, fast, quick-drying process allowing for adjustment to ink coverage, density and evaporation each step along the way. It is also vulnerable to the changing conditions in the environment surrounding your pad printing area. You may find it beneficial to consider setting up a clean room to protect your jobs from exposure to any sudden variables and contaminants that could impact the quality of the finished product. Today we’d like to help you evaluate the pros and cons of investing in a clean room.

PROS

  • Controlling temperature and relative humidity (RH) allows for consistent ambient climate conditions. Very helpful in a pad printing environment to guarantee the same quality over multiple runs.
  • Eliminating items with a propensity to throw off dust particles from the closed clean room keeps your operation free of dust and other airborne contaminants. Get rid of those plywood pad bases – typically standard issue for pad printing – and replace them with something cleaner, like aluminum.
  • Replacing flame pretreatment eliminates another source of soot contamination, as well as the risks of working with an open flame.
  • Producing a consistent, clean product improves your reputation in the marketplace, increases your daily production and attracts new customers.
  • Providing a stable climatic environment opens the opportunity to implement an ink maintenance program to systematize the process, a further guarantee for consistency across runs and between operators.
  • Commissioning a pad printing machine for use in a clean room allows for special procedures to be undertaken at an opportune time.  Special sterilization and validation is carried out on the equipment prior to initial use, often by expert third party providers.  Any component of the machine’s design which may be subject to dust or contaminant generation is outfitted with additional guarding to minimize this exposure.

CONS

  • Pretreatment options are somewhat limited.  Flame pretreatment is usually prohibited because of the possibility of generating soot from an open flame.
  • The use of air blowing at the pad to assist on ink transfer may not be workable.
  • Some installs are presented with no way to adjust climatic conditions.
  • Many clean rooms exhibit lots of air turbulence due to pressurization and air exchange frequency.  This can create drafts and negatively affect ink pickup, especially in cupslide machines, requiring heavy use of a retarder or more frequent thinner additions.
  • There can be a high learning curve required in making often severe adjustments to former ink working mixes once the environment is stabilized.

Summary

All in all, usually the Pros outweigh the Cons. Once a proper print process has been established, it can be used reliably every day.

Think you’re ready to come clean? PPMoVT’s engineers can help put you in a clean world of your own! Whether they help you design a new pad printer for your clean room, or design retrofits for the old one, call us at 1-800-272-7764, or use Live Chat on our Home page.  Pros & Cons: Pad Printing in a Clean Room Environment

A word of warning: You may find yourself wanting a clean room at home.

Reasons to Consider a Servo-Driven Pad Printer

While a programmable servo-driven pad printer will cost more than comparable electro-pneumatic models, they provide the highest degree of accuracy, control, adaptability and flexibility in a more compact area, and they include additional valuable features.

The improved servo-driven technology allows engineers to choose linear motion devices that:

  • provide the highest degree of accuracy
  • increase speeds while maintaining quality
  • reach the required torque in a given application
  • save and store programs for convenience and accuracy on future print runs
  • pick up and print an image wherever it needs to be and assure that the user produces more impressions with less waste and fewer errors in less time. That’s a win-win.

In the most sophisticated printers, the horizontal print head movement can be controlled and programmed at each of the two functions — ink pick-up from the cliché and print position on systems featuring independent pad actuators. You can also repeat or change the control values for each plate stage/print station, a major improvement that provides individual adjustment in a multicolor system with hair-splitting accuracy and repeatability.

Couple this with the ability to provide independent pad vertical movement using linear actuators that work independently. This eliminates pad interference when printing oversize parts, offering the convenience of using different pad shapes and heights at every position in a system. Are you starting to see what this can do for the future of your business yet?

Are you sure it will help me?

At PPMOVT, we carefully evaluate each application to engineer the best and most cost effective solution with the end user in mind. We execute them flawlessly on our own manufacturing floor. After all, when all is said and done, it is the printing system’s performance, reliability and user friendliness that really counts.

The same servo-driven actuators described above are also used on Pick-and-Place automation devices that provide part loading/unloading to/from holding fixtures, part conveyance and other movement accessories, with total precision even when variable speeds are required throughout the motion. Automatic pad changing can be included to allow the use of multiple pads in a selected routine. That’s technology. That’s what Pad Print Machinery of Vermont can do for you.

What do I do next?

Call us in for an analysis. That’s fun for us. We won’t sell you something that doesn’t make you better and stronger. Program in Pad Print at 1-800-272-7764, or use Live Chat on our Home page  https://www.epsvt.com
Please make sure the coffee’s hot!

Save on Pad Printing Ink!

Our customers have told us many times how frustrated they are with the amount of pad printing ink they have to throw out at the end of the day. Well we heard you and designed a handy little device to help utilize those small volumes of the ink mixed in the cups. Plus when the ink volume is less than 25 grams, the print quality can deteriorate – not with the new Ink Saver-Ring!

The Ink Saver-Ring fits into a sealed ink cup where it agitates the ink as the cup slides across the cliché. This is a great tool for pad printers who use bi-component inks that must be throw out at the end of the day. Plus this ring will also help prevent the ink pigments from settling in the cups. Over time, less ink waste will add up to a significant cost savings!

Available for all sealed ink cup sizes, call us for pricing and click Ceramic Ring Cups for details.

The Skinny on Plate Types

Engineered Printing Solutions reps often hear the question “what plate type should I use?” The answer is standard for pad printing:

  • What is the intended application
  • How detailed is the artwork (fine lines? large solid areas?)
  • What are the environment’s conditions (dusty? flying debris?)
  • What is the thickness or opacity of ink required?
  • What is the size of the run?

Your rep is here to help you analyze your job and narrow your choices, including plate type. There are two major image plate types:  Steel and Photopolymer. Let’s take a closer look at each.

Steel Plates

  • Thick Steel Plates. These are old-fashioned and originally used in pad printing because it was usually the only choice. There were few to no other more affordable materials. These thick steel plates were tempered and machined flat prior to acid etching. Very expensive and requiring an outside plate-maker service, their redeeming quality was longevity, often providing several-hundred-thousand print cycles.
  • Thin Steel Plates. These plates have gained in popularity due to the improved materials used. They provide excellent flatness for proper functionality and higher tempering (into the Rockwell 70’s) for long life. Their cost is much lower than thick steel plates and can be used on the same standard plate stages as polymer plates. These plates also need an outside plate-maker service – acid bath required.

Photopolymer Plates
Photopolymer plates come in a variety of types and are made of photosensitive material that changes chemical composition when exposed to ultraviolet light. Using a film positive, the image is etched into the plate, preventing the image area from being exposed to the UV-light. To control etch depth in larger color areas, a second exposure with a screen is necessary.

  • Double Exposure. These plates are available in several polymer materials depending on the etch depth and the number of impressions needed. An exposure unit is required to expose the plate and would require using a line screen. This material is available in either alcohol- or water-based development. A full list of plate materials can be found on our website – Printing Plates here.
  • Single Exposure. This special material provides a very thin photopolymer coating, clad to a very thin steel backing. The plate can only be etched to a .001” depth and requires a single exposure. This material has a shorter impression life than conventional Double Exposure plates. Since it lacks the customary screen in the artwork area, it is used only on fine line or text artwork. It is not used to print bold artwork or solid backgrounds.
  • Laser Etched. These plates are used in conjunction with a laser etching device such as our RapidFire Laser Etcher to produce plates similar to the conventional Double Exposure plates, including screened artwork areas of all types. Bringing this ability in-house eliminates the need for artwork films and provides multiple benefits in speed, turnaround, corrections and profitability.

Where do I get help?
Recommendations, troubleshooting and assistance in all areas of your production cycle are at the end of your phone or mouse! Call the trained and experienced Pad Print people at 1-800-272-7764, or use Live Chat on our Home page  https://www.epsvt.com
We’ll stop by for a cup of coffee!

Pad Print Thinners and Hardeners

Pad printing’s smooth transfer of an image from the inked cliché to the subtrates is facilitated by additives used in the ink’s mix. Pad Print thinners and hardeners are additives critical in handling ink adjustments for better adhesion and extending image life.

Thinners

Transferring pad printing inks requires that a percentage of thinner be mixed into the ink. Thinners are volatiles; that is, they evaporate quickly (“flash off”) to dry out the ink mixture so it becomes “tacky.”

This “tackiness” is what enables the silicone pad to pick up an image/ink and transfer it to the part.

Ink manufacturers provide special, chemically-formulated thinners to work with their inks. They usually provide thinners in different.” The “speeds” refers to how fast the thinner evaporates. Typically, you’ll find fast, medium and slow (sometimes referred to as “retarder”) options.

As you may know, there are different ink “series” that adhere best to specific substrates. Manufacturers will provide charts that cross-reference different substrates and which inks work best with them. Each of these inks may utilize one (or many) different thinners, depending on the application. Here is a link to the Ink & Materials Table from the website.

Another important function of a pad printing thinner is it also cross-links the ink/pigment to the surface of the part while the thinner is evaporating, also aiding adhesion. Some substrates are more porous than others, which makes it easier for ink to bond, so the cross-linking happens quickly. Other substrates require more time, so you’ll use a “slower” thinner. In any case, once the ink transfer (print cycle) is complete, the thinner continues to evaporate and perform its cross-link duties simultaneously, eventually leading up to a “cured” image.

Images pad printed with solvent-based inks are usually “dry to the touch” in a matter of seconds, which means you can handle the parts relatively quickly. However, most pad print inks don’t achieve a full cure until at least 24 hours, sometimes longer.

Hardeners

Where do hardeners fit into this, you may ask? They have very little effect on ink adhesion, but have a huge influence on image durability.

Again, ink manufacturers provide hardeners that are formulated specifically to their inks. Some hardeners work with more than one ink series. This formulation also includes different ink-to-hardener ratios. Some are 4:1 (ink-to-hardener), some are 10:1 and others as much as 20:1. Technical data sheets on inks will detail all of that for you.

Hardeners are always added for inks used on metal, glass and ceramics, as well as parts (regardless of substrate) that may face exposure to abrasives, chemicals, sterilization procedures, etc.

The good thing about hardeners is they enhance image durability. The bad thing about hardeners is that they decrease the “pot life” in an ink cup (normally 8–10 hours max). The important thing is your customer gets a quality, long-lasting image.

Join the conversation! Our dedicated ink experts can get your ink problems solved and your printer up and running in no time!

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Ink Viscosity and Seasonal Adjustments

Pad printing is a thin film process. It starts with an etch depth in the cliché of approx. 25-75 microns and only a fraction of that ink film is picked up by the pad. Of the wet ink, 50% is a solvent that evaporates leaving only a 5 micron dry ink deposit. You can easily see why such a thin ink film is so susceptible to changing temperatures, humidity levels, static charges and even variations in airflow. Listed below are the ways you can control the ink viscosity and seasonal adjustments.

Control the rate that solvents evaporate from the ink
• Solvents evaporate too slowly
– The surface of the ink may not be tacky enough to pick up or release images from the pad
• Solvents evaporate too quickly
– Ink might not pick up from the cliché because it has dried in the etched portion of the plate, or dried on the pad in transit to it’s destination.

Same for the pad
• Solvents evaporate too slowly
– Only some of the ink will release from the pad to the substrate
• Solvents evaporate too quickly
– Ink dries and stays on pad.

Tips
• Warm environments: Add solvents every 20 – 30 minutes. Always add a measured amount, use a viscospatula and don’t guess!
• Control temperatures: Keep printer out of the sun, away from drafty entrances, exits, dryers.
Keep the temperature of the substrate to room temperature.
Don’t let printed part drop below 59°F until fully cured – 4 days or longer.
• Good housekeeping: Dust and vacuum floors instead of sweeping. Avoid cardboard boxes in production area. Wipe down all surfaces using a damp cloth.
Static electricity feathers the print. Slow the down stroke and pickup.
• Too hot: Solvents in the ink will evaporate very quickly. Solvents are attracted to water vapor molecules in the air.
– Speed up the forward travel of the pad stroke.
– Thinner / retarder mix (75% Thinner to 25% Retarder)
• Too cold: Solvents won’t evaporate quickly enough. Ink won’t be tacky enough between pickup and and lay down to transfer completely to the substrate.
– Slow down the forward travel of the pad stroke
– Select a faster drying thinner
– Use a hair dryer pointed at the pad as it travels forward after ink pickup to speed up the evaporation of the solvent
– Raise ambient temperature.

Viscospatula to the Rescue!

Custom decorators and product marking professionals have some common challenges, and one of them is print run consistency. Getting their ink to perform in the same way with the same quality from job to job, regardless of who is mixing the ink, has a better chance of success with some controls in place.

Ink series’ colors and batches can vary. Heat, cold and humidity can make inks thicker or thinner (their viscosity) from one run to the next. Viscosity affects the quality of the print job through ink absorption, color strength and evaporation/drying.

  • Thick, high-viscosity inks are tacky and impede image transfer.
  • Thin, low-viscosity inks run loosely to their own determined borders, changing halftone dot dimensions and blurring the image.

Although it is difficult to control variables such as atmospheric conditions, plastics decorators typically change machine settings or use additives to overcome these challenges when they occur. For experienced ink technicians, trial-and-error troubleshooting is second nature for correcting ink adhesion. For others, following ink manufacturer’s instructions and written notes — in conjunction with the PPMOVT Viscospatula — take the guesswork out of mixing ink and achieving consistently satisfactory results.

The Viscospatula is a simple, efficient tool used to achieve consistent and accurate ink viscosity when mixing pad printing inks. This tool has precision-milled holes and slots cut into a special ink-shedding fiberglass compound. When dipped into a prepared mixture, the ink flows down the spatula from the first hole to the fifth at a measurable rate, allowing adjustments to the ink’s thickness. The rule of thumb is: the thinner the ink, the faster it moves from the first hole to the last hole.

Using this tool to measure viscosity on a properly performing ink and noting the results with the job’s ink mix provides a roadmap toward future mixing success. Click Uneven ink thickness to see the Viscospatula and read more about it. We hope you never again have to explain why a reprint looks different from the original.

Join the conversation!  Do you have a process to ensure reprint consistency?  What tools do you use? Our technical ink experts are available to answer your questions and assist you in achieving ink nirvana. We answer any pad printing question!

Pad Printing Pads: Is Pad Size Important?

Size minimizes distortion
Pad for a Pad Printing MachineAn important variable to consider in quality pad printing is the pad size, especially as it relates to the image size. In pad printing, the larger the pad size used, the less the image is likely to distort in the printing process.

  • Pad size is measured in length, width and height without the base.
  • As a general rule, your pad should measure 10% to 20% larger than the image’s length and width.
  • Remember the “throat” – or the distance between the cliché and the body of the machine – often determines the maximum pad size you can use.

 

Special pad printing pads for large images
In some situations, a large image area must be printed and the machine does not have the power to compress such a heavy pad in a smooth motion.

Cylindrical pad for Pad Printing MachinesTwo solutions to this problem are available:

  • The first is to use a pad with a hollow interior that provides the same surface hardness. The hollow interior also reduces the cost of silicone rubber used in a large pad.
  • The second option is a dual-hardness pad, where the core of the pad is made of a softer material and the outer layer is the harder rubber. Either method helps, but using dual-hardness allows for a more stable pad.
  • Of course a third option would be to use a different imaging process like screen printing.
  • There’s another unusual pad configuration that is like an inflated pig bladder. Specialized machines use hollow pads inflated with air just prior to ink pick-up. The pad stays inflated until it comes into contact with the substrate. Then the air is released. The deflated pad can conform to a wider area of the substrate, printing up to 180 degrees compared to 100 degrees with a standard pad on a cylinder or sphere.

Join the Conversation! Have you had problems with print distortion or image size? Click Cylindrical Printing Pads or call us at 800-272-7764 for our suggestions on pad size usage. We love your challenges!

All Fired Up: Pad Printing Glassware

Most glassware has some kind of discernible shape. Logically, pad printing emerges as a natural choice in glass decorating and printing. The more complex the shape, the more suitable pad printing becomes as a decorating process.

With the right tooling, multicolor prints, special-effects inks, and even 360 degree wrap-of-image-around-circumference are possible. Automated parts-handling options can further speed production rates.

There are two primary inks used in pad printing glassware: frit inks and acrylic inks.

Acrylic inks
Acrylic inks are mixed with a catalyst hardener as well as with a solvent thinner, which allows the ‘tack-up’ and transfer from cliché to pad to part. A post-print bake is usually recommended (3-5 minutes at about 200 degrees F) to improve the durability of the print. The bi-component ink mixture typically has a ‘pot life’ of 6-8 hours, after which time the ink hardens on its own, rendering it unusable for any further printing.

Acrylic inks are fairly durable, providing at least 50 wash cycles in your average home dishwasher.

Frit inks
For greater durability, a frit ink is the way to go.

Frit inks contains:

  1. Finely ground glass particles in the ink mixture (very small, only a few microns in size)
  2. A pigment (the colorant)
  3. A binder, which is a carrier used to keep the ingredients in suspension
  4. A thinner, the solvent which facilitates the silicone pad transfer process.

Different frit suppliers recommend different combinations of the above four components. There are no pot life issues to consider when using frit inks.

After printing with the frit ink, the printed ware is fired in a kiln, typically at about 1100 degrees F on average for up to 30 minutes. The ground-glass particles come very close to their melt point; the organic ingredients in the print burn off, and a physical bond is created between the print and the product. Frit inks are generally considered the most durable of all glassware prints, capable of lasting a lifetime and providing tremendous abrasion resistance.

Have you had glassware decorating challenges? Feel free to contact us for advice on the best options for all types of pad printing on glassware.

Print Pad Durometer or Hardness – Same Thing

Albert F. Shore developed the measurement device called a durometer in the 1920s to measure material hardness. As a result of the Shore ratings, the terms hardness and durometer became interchangeable. Many pad print pad manufacturers color code the standard durometers by adding pigment to the silicone itself or by coloring the pad base. The following chart shows the durometer range for each silcone material (color) we typically recommend:

Color                             Hardness
Blue                                  10 – 60
White                               20 – 65
Red                                   30 – 75

The harder the pad, the higher the Shore durometer rating. Three basic pad durometers are standard in the industry and cover most applications. Custom pad durometers are also available through most pad suppliers. We suggest you invest in a durometer gauge, valuable for all pad printers for determining pad hardness and quality control of pads in rotation. This simple tool is available through silicone-rubber suppliers and many general-service dealers in the screen printing and pad printing industries.

Choosing the proper pad hardness for a job is often a combination of experimentation and experience. As a general rule, the harder the pad, the better the performance, the longer the pad life. But hard pads may be impractical in some applications. Here are some guidelines for durometer selection and maintenance:

  • Use softer pads when printing on heavily contoured surfaces or on fragile items.
  • Use a softer pad if the power of your machine can’t compress the pad sufficiently to achieve a satisfactory rolling action.
  • Use hard pads for textured surfaces, or printing an image in a recessed area where the pad must roll over a “step”.
  • Use hard pads in a pad “nest” where a number of pads are spaced with small gaps (for example, printing computer keyboards).
  • Consider a special pad for printing on abrasive substrates and textured finishes. Example applications include automobile control arms like turn-signals and windshield-wipers, when the pad must resist the abrasive nature of the substrate.
  • Avoid using pads of different durometers on the same application. The thickness of the ink deposit will vary on the substrate.

Custom Pads – Custom Service
Confused about durometer? Need help selecting pad durometer for a custom job? We have a full pad department to help and we don’t charge for phone calls! Click Cylindrical Printing Padsor call 800-272-7764 for our undivided attention. We are here to help you!