Archive for : June, 2016

Optimal Conditions for Pad Printing

“Does it make a difference if I do my printing in a controlled environment?” It is the one question I can depend on getting from every new pad printing equipment customer and the answer is yes. Controlling your operating conditions from day to day can make your job significantly easier.

Temperature and Relative Humidity

It is recommended that, as a minimum, at least the actual printing process be performed in an environment having a temperature between 68 and 72 degrees Fahrenheit, with relative humidity at 55 percent, plus or minus 5 percent.

For best results you want to keep all of your product, equipment and consumable materials (especially the machine, ink, pads and cliches) in a clean, climate-controlled environment. Like any printing process, pad printing is greatly affected by fluctuations in temperature and relative humidity. Extreme changes in temperature can cause condensation on substrates, cliches and pads. This condensation acts as a barrier to transfer efficiency in pad printing. High relative humidity has the same effect; low relative humidity increases the occurrence of static electricity.

In a perfect world, every pad printer would have access to such an environment. Better yet, everyone could store all their inks, pads, cliches and substrates in the same environment. Chances are that the average pad printing company doesn’t have this much control. In that case, you can only try to adhere as much as possible to a few general recommendations:

  • Keep your machine away from outside walls where temperature variations are going to be more pronounced throughout the day, or season to season.

  • Keep your machine out of direct sunlight, and out of turbulent airflow from heat and/or air conditioning ducts and fans.

  • Try to keep your humidity from varying by more than +/- 10 degrees F. within a given shift.

  • Try to keep your ink, pads, hardeners and thinners in the same temperature and humidity range as you’ll be printing in, or allow them to adjust to the production environment prior to using them. This is also important for your product to be printed.

Cleanliness

With pad printing, cleanliness is a virtue. The more care you take in mixing your inks, setting up your machines, and organizing your tools, the less time you will waste cleaning off your machine and parts after you “accidently” get ink all over them. I recommend using a plastic bin to keep the necessary wrenches readily available, as well as a roll of clear packaging tape for pad cleaning.

Keeping the room and your parts clean will help a lot, too. If your printing room is dusty and dirty, your parts will invariably show it. Use a vacuum to collect dirt when cleaning off parts instead of relocating the dirt by blowing parts off with compressed air. Avoid packaging unprinted parts in cardboard whenever possible. Cardboard is filthy, and cardboard dust is difficult to remove when static is present.

If you have to accept parts from your customer in cardboard boxes, ask them to put a plastic liner in the boxes if possible. If parts come layered in boxes, try using something other than cardboard to separate the layers.

When you do clean your printing room, do it at the end of the day’s production, not before. Particularly if you’re sweeping with a broom. Sweeping stirs up dust. Again, use a vacuum if possible.

If you area is too large to vacuum, and you have to sweep it, look in a janitorial catalog for an anti-dust agent. Sprayed on the floor with an insect spray canister, these agents dry within a few minutes and act like a magnet for airborne particles. Then, when you do sweep, the agents keep the dust on the floor, allowing you to roll it along with a broom.

Keep your machines as clean as possible. If you spill ink, clean it before it dries. It will take you twice as long to clean it after it dries. If it is a two component ink, you may never get it off the machine without using a hammer and chisel. When cleaning your machine, pay special attention to moving parts, and any surfaces that must be absolutely flat, like the platform your open ink well sits on and the areas that your cliches rest on.

Ventilation

Make sure that the air quality in your production area is acceptable. If you’re not sure, contact your heating and air conditioning company and ask them to make a recommendation as to the volume of air you should be exhausting.

If you’re unsure as to whether personnel are being exposed to levels of organic vapors that are hazardous, or are receiving complaints from employees, you can conduct an air quality test fairly inexpensively by obtaining air quality test badges from a safety or laboratory supply company. By reviewing your M.S.D.S sheets you can find out which solvents are most frequently used, and what their respective exposure limits are.

Once you know these limits, you can order badges capable of testing exposure to one or several solvents from a safety or laboratory supply company. Your personnel wear the badges for a specified amount of time, after which you return them to the suppliers, who in turn analyzes them and issues a written report. By comparing the results of the report to the exposure limits called out on the M.S.D.S, you can determine whether or not you are in compliance. Be advised that in many cases, you can be in compliance without everyone being happy with the overall “quality” of air they are breathing.

Lighting and Ergonomics

Lighting is important for efficiency. No one likes to work in the dark, or under a glaring spotlight. Lighting should be uniform and non-directional if possible. Cool, white fluorescent lighting placed about sixty inches above the work surface provides nice, even lighting. If possible, the work surfaces should be a neutral color (gray), and low in gloss to allow operators and inspectors optimal viewing conditions.

On January 1, 2001, the Occupational Safety and Health Administration implemented a new Ergonomics Program Standard (amendment to Part 19 of title 29 of the Code of Federal Regulations, Program Standards Section 1910.900) relating specifically to the elimination of repetitive motion injuries.

While the importance of making work areas safe and worker-friendly is obvious to anyone that has spent time standing on bare concrete or sitting on a wooden stool five days a week, twisting to move materials all over the place, it has now become law.

Taking a little extra time to think through process flow, then positioning machines, materials and manpower accordingly is less expensive than having to move everything around after production has commenced, or having to pay for a work related injury.

Tables should be at a height that is comfortable to work at, and chairs should be adjustable. Materials should be readily accessible so that operators don’t have to bend or twist to pick it up, print it, and place it on a rack, conveyor, or into packaging. Operators that must stand are much happier doing so if they’re standing on a mat instead of a concrete floor. Also, urge your employees to wear shoes that have sufficient cushioning and support.

If time permits, you can set up a mock work area prior to receipt of a new piece of equipment and try it out for yourself. Using the “foot-print” of your new machine, tape an area of the floor off and then arrange materials until you come up with the best possible material flow. Doing this can save you having to rewire electricity or relocate air and gas lines or light fixtures at the last minute.

For assistance in determining whether you comply with the O.S.H.A. Ergonomics Program Standard, I recommend logging on the Internet and simply searching under O.S.H.A. Ergonomics. Doing so should enable you to gain an understanding of what the new standard requires, and where to turn for help from safety and ergonomics consulting firms.

In addition to the O.S.H.A. standards for ergonomics there may also be some architectural-related regulations around the corner having to do with eliminating electrical interference in computer network and electrical wiring. Ask your architect about compliance with a pending addition to architectural codes called Division 17. To find out more, log on to www.division17.com.

While it is possible to pad print in an uncontrolled environment, in the long run, doing so will prove to be more expensive than the alternative. Controlling temperature, humidity, airborne contamination, air quality and ergonomic issues will dramatically increase the efficiency of your pad printing process while at the same time keeping your employees safer and happier.

John Kaverman is Midwest Regional Manager for Innovative Marking Systems of Lowell, MA. and is the author of the Pad Printing Technical Guidebook. For information, contact Kaverman via email at

john@padprinters.com.

Dealing with Heat & Humidity

temp

Many people consider adjusting ink for printing under conditions of extreme heat and relative humidity to be akin to “voodoo.” While it is true that high temperature and humidity can pose problems, overcoming them isn’t really that difficult.

The best way to minimize the negative effects of temperature and humidity variation is to control your printing environment. By keeping the temperature between 68 and 74 degrees Fahrenheit, the relative humidity between 40 and 60 percent, and acclimating your substrate to the controlled environment before printing, you can eliminate most problems. If you don’t have a controlled environment, you’ll probably have to adjust your ink under warmer and/or more humid conditions.

When the mercury rises, solvents evaporate more rapidly. As a result, you need to add either a higher percentage of thinner by weight, or add a “slower” evaporating thinner. Most ink manufacturers have slow, medium and fast evaporating thinners available for each ink type. When experimenting with thinners of different speeds or blends of compatible thinners, start by first setting the machine speed to the desired cycle time (if that is important). Then begin testing by adding a medium speed thinner at a percentage in the middle of the manufacturers recommended range. For example, if the range is 10 to 20% by weight, try 15%. After allowing the machine to cycle a few dozen times on a piece of scrap, stop the machine and clean the pad, then print a clean part at normal cycle speed.

If you see a problem with the image, perform the following simple test:

  1. Pick up the image at normal speed, stopping the machine before it prints. Look at the image on the pad. If the whole image is there, clean the pad and proceed to Step 2. If the image is only partially there, and particularly if areas of finer detail are missing whereas areas of higher coverage are not, it is a good indication that the ink is not thin enough. To see if a little more thinner will solve the problem, clean the pad, then place a few drops of thinner on your finger and rub it on the image area of the pad. Cycle the machine through pick-up and stop, once again observing the pad to see if the entire image is there. If it is, then you know the addition of a little thinner should solve the problem.
  2. Once you have an acceptable image on the pad, print a part. If the print is acceptable and there is no ink remaining on the pad, youre ready to begin production. If the image looks smeared or transparent, or there is still ink on the pad after transfer, it is a good indication that your ink is too thin. In that case, add some more ink (dont forget to add hardener, too, if youre using a two-component ink) and try again.

You may run into a situation where one thinner alone may not work. For example, you may find that by the time you get enough medium speed thinner in the ink to make it transfer under warm conditions, it is so thin and the print quality has deteriorated. In these cases, you can usually mix two compatible thinners together to achieve the desired speed. For example, if an application requires too much medium speed thinner, try mixing medium and slow together.

In any experiment you try using varying percentages of thinner and/or blends of thinner, make sure you keep good notes so that you can go back and recreate the desired results later on.

Humidity is a bigger problem than high temperatures. When the relative humidity is high, there is a thin, invisible layer of water on everything. The cliché, the pad even the substrate become saturated. Since oil and water dont mix, this water causes all kinds of problems. If you are printing in an enclosed area, try using a simple dehumidifier. If it can efficiently remove the excess humidity, your problem will be solved. If not, you might try an additive such as TOSH PR2 Paste that increases the cohesiveness of the ink.

Most ink manufacturers have an additive similar to PR2 for use in maintaining dots sizes when printing four-color process. Another common problem in high humidity are spider webs,those pesky little stingers of ink that stick out from the image area. This is caused by the water forming a barrier that prevents the efficient transfer of the ink near the imagesoutside edges. If you have a TOSH machine, increase the delay for on substrate,allowing the pad to compress and hold in its compressed position on the substrate momentarily before lifting away, thus giving the image more time to leave the surface of the pad in favor of the substrate. Dealing with wild fluctuations in temperature and humidity can be frustrating, but the situation is controllable.