Tech Tip Tuesdays: Frequently Asked Pad Printing Pad Questions?

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.

 

Tech Tip Tuesday: Servo-driven pad printer vs. pneumatic pad printer

There are two primary reasons why a client would opt for a servo-driven pad printer over a pneumatic one:

Speed & Flexibility

Speed is pretty simple to grasp – shorter strokes, faster movements – all lend themselves to higher productivity, especially when it comes to fully automated machines.

Flexibility is gained when a client has many different parts being run on the same machine, servo units can provide “recipes” for each part, thus reducing the setup time between jobs, saving labor = money.

In some instances, we provide a “hybrid” machine, with servo drives on one (or more) axis, while other movements may remain pneumatic.

This is why an honest exchange of information and expectations is critical in the discussions regarding machine choices for any application.

Tech Tip Tuesday: Symptoms of Having Chosen the Incorrect Pad Printing Pad

The pad is one of the most important elements in the pad printing process. The correct choice is essential in obtaining good final print results.

Symptoms of having chosen the incorrect pad printing pad:

  1. Pin holing (pad too soft or too shallow),
  2. Image distortion,
  3. Incomplete transfer (in particular near the peak of the pad),
  4. Inability to pickup entire image (pad too small),
  5. Will not fit on equipment,
  6. Equipment incapable of compressing pad sufficiently for pickup, transfer or both.

Choosing the correct pad requires some familiarity with the pad print process.  General rule of thumb:

  1. Choose as hard a pad as the process will allow.
  2. Keep the image size to no more than 80% of the print area of a given pad.
  3. When odd form printing … use a large a pad (within reason) as is possible.

Our customer service team will help you choose the proper pad for your printing application. Some of the questions we will ask (in addition to print area, shape and surface texture) are:

  1. Thickness of the base (1/2″, 3/4″, etc.);
  2. Type of base needed (wooden is standard, or specify flat aluminum or extruded aluminum dovetail);
  3. Machining or drilling needed on base (size and location of tap holes);
  4. Overall maximum pad height, including the base;
  5. Whether the pad needs to be hollow of with a helicoil insert;
  6. How hard or soft the item is being printed (to determine pad durometer);
  7. The size “T” nut needed to attach pad to machine (if needed).

Tech Tip Tuesday: Incorrect Pad Printing Ink Amounts

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.

Tech Tip Tuesday: Can You Get Hurt Operating Pad Printing Equipment?

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.

Ink Adhesion Part 3: Ink Mixing, Contamination, Blooming and Mold Release Agents

Before printing on any parts there are several factors which are of vital importance: ink mixing, product cleanliness and substrate additives. Regardless of proper ink preparation and chemistry, surface contamination, blooming and mold release agents may all interfere with your ability to achieve satisfactory adhesion.

The two most important factors that must be addressed when dealing with ink mixing are: How are you mixing the ink? What components are you using? Inks are formulated to be mixed at specific ratios, and any deviation may result in adhesion failure. You must choose the correct ink and mix it to the exact manufacturer specifications. It is a common misconception that adding hardener over manufacturing specifications will allow for better adhesion.

Surface contamination is a huge factor in whether or not the ink will adhere to any given object. The first reason contamination may occur is because people are not handling the object correctly. Oils on the handler’s hands can be transferred onto the objects. Contamination can also occur as a result of secondary processes being performed on the parts. For instance, if you choose to wash the objects with a detergent, this may leave a residue behind on the object and the ink may not adhere properly. Here at EPS we use alcohol. This is a standard solution which readily flashes off and is used to wipe the parts of any dust, oils or any contaminants before printing. With proper handling, cleaning the parts may be unnecessary, but wiping with alcohol does assure that there will be a clean surface to print on.

Blooming is a term used in the plastic industry and it denotes a plasticizer or other additive coming to the surface of a part over time. The difficulty with this contamination is that you can wipe the surface of the part free of contaminates but over time the part will re-bloom and the contaminants will interfere with the bond between the ink and the parts.

Mold release agents (also known as de-molding agent, form oil, parting agent or release) are substances used in molding and casting that aid in the separation of a mold from the material being molded and reduce imperfections in the surface. While these additives make the plastic manufacturing process simpler, they can wreak havoc on attempts to achieve adhesion.

In the end, experience is the best weapon in attaining adhesion. If you have any questions or concerns please contact Technical Service.  For more information about Engineered Printing Solutions’ custom solutions, standard pad printers, industrial digital ink jet, consumables and other auxiliary equipment, email sales@epsvt.com or call 1-800-272-7764.

Ink Adhesion Part 2: Bi Component, Pre-Treatment and Post Cure

Have you ever looked on the back of an object and seen the recycle symbol? It tells you what material the object is made of. When it comes to plastics, Polypropylene and Polyethylene are considered the two of the most difficult materials to get ink to adhere to due to their relatively low surface energy. Polypropylene is used to make a wide variety of items and low and high density Polyethylene is commonly used in food packaging. When it comes to these difficult substrates it becomes necessary to pre-treat to affect a change in surface energy to make the surface amenable to bonding with – or cross-linking – with the ink.  This causes the substrate surface to become more receptive.

The most commonly used methods of pre-treatment are:

  • Plasma and Corona: Electricity applied to the surface.
  • Flamer: Liquid propane (LP) or natural gas. With Flamer there may be variation due to cleanliness of the burn and how the flame will pre-treat any given substrate.
  • Chemical Pre-Treatment: Usually manually applied with a liquid soaked rag.

Unfortunately on any given substrate you cannot assume that you will affect an equivalent change in the surface energy from one pre-treatment to another. Finding the correct ink pre-treatment may consist of 3 different segments: cleaning, activation and surface bonding.

Plasma surface treatment is a process that raises the surface energy of various materials in order to improve the bonding characteristics when ink is applied. Plasma is used widely in the medical industry. This is because you don’t have the bi-product of the other 2 pre-treatments such as carbon from the flaming process or residual VOC’s left behind from the from the flashing process of a chemical pre-treatment. Corona treatment is commonly used on materials such as polymers, papers, films, glass and metals.

Plasma is a good option for components that require a longer treatment hold. Some of the key advantages include: surface chemistry and 3 dimensional treatments. Corona is another form of plasma that can be used with in-line processes. When working with corona the systems are easy to maintain and user friendly.

Flame pre-treatment can also be integrated into inline processes, and require careful and sometimes precise setup in order to be safe and effective. Proper air to gas ratios, flame intensity and dwell time all play into successful pre-treating. Flame plasma systems combine compressed air and a flammable gas which is combusted to create a flame. One advantage is that the material surface only has to be exposed to the flame for a brief period of time to become polarized through oxidation. One setback is the heat level required for this treatment may cause damage to the parts.

Chemical priming is yet another way to pre-treat difficult to adhere to substrates and is generally considered a last resort due to the generally manual nature of application. Essentially primers are used to chemically modify the surface by removing contaminants, adding reactive sites for bonding and increasing surface energy. One disadvantage is that these primers often contain chlorinated solvents that are considered volatile organic contents.

Many substrates will require pre-treatment to satisfy customer’s individual requirements for print longevity. But with the correct treatment and testing, our technical service technicians will test the inks and provide samples for the individual customer’s review.

For information about Engineered Printing Solutions’  custom solutions, standard pad printers, industrial digital ink jet, consumables and other auxiliary equipment, visit Ink Adhesion Part 3: Ink Mixing, Contamination, Blooming and Mold Release Agents, email sales@epsvt.com or call
1-800-272-7764.

Ink Adhesion Part 1: General Education

Have you ever looked down at a water bottle and wondered how the logo got there? Personally I know I have. Before the colors and image can get put together on the object the first question that needs to be answered is how to choose the right ink for the job. Simply put, ink adhesion is ink that sticks to any given product to a known specification. One of the most common tasks our Technical Service team are charged with is to “find me an ink that sticks to the surface of my product.” It wouldn’t be realistic if I told you that our Technical Service team has magic powers and can automatically determine the perfect ink for the material being printed on. Even though inks are produced to stick to a particular substrate; the question is which ink is best suited to adhere to your particular substrate based on your requirements?

There are many different substrates and even more sub-sets within each . Not all polypropylene’s (PP), for example, are created equal. An ink that may exhibit flawless adhesion to one PP product may not adhere at all to another. We therefore need to match the ink series with the particular substrate being presented. However if you supply our Technical Service team with the parts you wish to print on, they will be able to begin working their “magic”. They will be able to first make an educated guess as to which ink will meet the customers’ expectations based on experience, then begin testing the inks and provide samples for the individual customer’s review.

For information about Pad Print Machinery of Vermont’s custom solutions, standard pad printers, industrial digital ink jet, consumables and other auxiliary equipment, visit Engineered Printing Solutions, email sales@www.epsvt.com or call 1-800-272-7764.

The Future of Pad Printing

For the past three years Engineered Printing Solutions has been utilizing robotics to increase production, lower operator costs and improve the overall decorating process of various parts. The use of robotics has evolved from (a) pick and place systems to (b) SCARA robots loading tooling to (c) 6 axis robots with vision orienting and loading tooling. SCARA robots were then utilized as the actual printing arm with the capability of changing pad styles during the print process. A robot being used as a printing arm has been proven to be the most effective way to print on various three dimensional products that require multiple prints in different locations.  In prior designs an elaborate fixture would be designed to rotate the part to different print positions so the 4 axis SCARA robot could print down on the specific location.  The development of the smaller 6 axis articulating robots with increased power has led to advancement in our current robotic pad printer designs replacing the SCARA robot with a 6 axis Robot.  The part fixture now remains stationary because the 6 axis robot allows you to print at any angle. This eliminates the need for an elaborate multi axis servo driven fixture. The pad printing cycle is also shortened because the robot is no longer waiting for part rotations.

Features of the six axis robot printer:

  • End of arm tool to hold print pad
  • Automatic tape cleaner
  • 2 sets of independent clichés to allow set up of next part to run without stopping the current print process
  • Clichés can hold multiple artworks
  • Touch screen HMI controller display on strong arm
  • Camera vision system to detect orientation of part
  • Up to six color printing
  • Automatic pad changer with use of up to six different pads
  • In feed & out feed conveyers

Currently the Engineered Printing Solutions team includes many highly motivated individuals with full engineering, software development and tech support. Our #1 goal is Customer Satisfaction. Our company is constantly pushing the envelope, discovering more and more ways to seamlessly incorporate pad and ink jet printing into customers’ manufacturing environments.

For information about Engineered Printing Solutions custom solutions, standard pad printers, industrial digital ink jet, consumables and other auxiliary equipment, visit Ink Adhesion Part 3: Ink Mixing, Contamination, Blooming and Mold Release Agents, e-mail sales@www.epsvt.com or call 1-800-272-7764

Pad Printing in Multiples

Compared to the world of manual pad printing, the world of automation is virtually unlimited, within reason. Here at Engineered Printing Solutions we have taken a standard KP05 bench mounted printer and stripped it of the software and hardware. We then completely customized it to be able to produce 8,000 pieces per hour, all the while requiring minimal operator involvement.  How do you decide if automation is right for you? Well you need to ask yourself 3 questions: How many pieces per hour do you need to print? How many colors on the image? Finally what is the size of the image? With this machine, it all starts with the Bowl Feeder which aligns the parts all the same direction and feeds them down a track to the printer, printing the parts and finishing with the items going out under an infrared heater, ensuring that the images are dry enough to continue down the production line to other operations or to packaging. However with every innovation there are obstacles which we must work through.

Some of the technical problems that can arise are:

  • Being able to efficiently feed the parts to keep up with the printer.
  • Printing multiple images in one pad stroke can create some undesirable results. This may require custom pads.
  • Being able to efficiently process parts through the system without damaging even the most delicate part.
  • Ensuring that the printed image is dry enough to withstand downstream operations as soon as it leaves the system.

In this case we are printing 8 pieces at a time so our engineers need to make sure that the images are being placed correctly on each of the 8 parts every time.

For information about Engineered Printing Solutions custom solutions, standard pad printers, industrial digital ink jet, consumables and other auxiliary equipment, visit Ink Adhesion Part 3: Ink Mixing, Contamination, Blooming and Mold Release Agents, email sales@www.epsvt.com or call 1-800-272-7764