Tag : productivity

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.

Options and Accessories for Productive Pad Printing

Pad printing is an effective method of decorating parts of all kinds; from ad-specialty items such as pens and golf balls to industrial products like faceplates and propane tanks. Numerous add-ons and custom options are available to make this already productive process even more efficient. Some are designed to enhance parts handling, while others address potential bottlenecks in the printing workflow. Let’s take a look some of these beneficial technologies.

Multiple colors

Most manufacturers offer standard vertical machines in one through four or six-color configurations. Multicolor open systems can have multiple cliches, or one cliche in a split inkwell. Independently adjustable cliches are more desirable than having all of the colors on a single cliche. The benefit of independent cliches is simply the ability to more easily absorb potential image-to-image and/or image-to-part-location problems.

Multicolor closed systems can also have single or multiple cliches. A few manufacturers offer small (60-mm) multicolor ink cups, commonly referred to as split ink cups, that allow you to print two or three colors. The limitation is that the colors must be side by side, unless your machine can pick up once and then stroke the print two or three times. In that instance, you can shuttle the part to print colors on top of one another. The other limitation is that split ink cups are difficult to manufacture, and thus are expensive.

 

indexer

             Indexers

The four types of indexers are pneumatic, electronic, stepper-motor driven, and manual. Pneumatic indexers are less expensive and more popular than the other automated shuttle systems. Pneumatic indexers can have multiple positions by means of either multiple cylinders or a single, more expensive cylinder equipped with magnetic brakes. Be very careful to avoid any fluctuation to air pressure when working with parts of a critical nature on pneumatic indexers.

Electronic indexers have programmable, servo-driven motors. These indexers are more expensive than their pneumatic counterparts and are somewhat hard to find. Stepper-motor-driven shuttles can be programmed to travel a desired number of steps between prints. Stepper-motor and electronic indexers will typically last longer than pneumatic indexers. Manual indexers are used for low-volume jobs where the registration of colors is not critical.

 

 

 rotary table     Rotary tables

Rotary tables for parts placement can also be electronic, stepper-motor driven, or pneumatic. Accuracy and price are determining factors. Electronic and stepper-motor-driven rotary tables are more expensive than pneumatic ones, but they can move weight more accurately. Rotary tables can be of just about any reasonable diameter, allowing anywhere from two to 12 or more fixtures to be attached.

Some manufacturers have modular rotary systems with up to four independently adjustable machine-mounting stations. Depending on the application, one, two, three, or all four machines can be used simultaneously, turned off individually, and even rotated 180º on their mounts to operate alone. This allows more than one job to run at the same time.

 

Hot-air dryers

Hot-air dryers are common on racetrack conveyors and rotary tables. Even though most pad-printing inks dry to the touch within a few minutes, most people prefer to have the additional drying equipment, especially if they are using two-component ink or printing multiple colors with a lot of coverage, or at high speeds.

 

racetrack conveyer

Racetrack conveyors

Racetrack conveyors are standard equipment on many multicolor machines. Racetracks are pneumatically driven in most cases and can have several nests or fixtures. If necessary, cams can be attached to allow the nests to rotate in between stations for printing multiple sides on a given part. These systems are rarely used outside of the pad-printing industry.

 

 

Walking beams

Walking beams are a mechanical means of moving parts from one print station to another. Walking beams are limited in that they usually require that the part be picked up, moved over, and located against a stop of some sort for each printing operation. In most multicolor operations, it is not recommended that the part be moved in this fashion.

 

over-under conveyorOver-under conveyors

Over-under conveyors are usually chain driven or precision-link mechanically driven. In most cases, parts simply fall off the nests into a container at the end of the line, or are transferred to separate conveyors for subsequent operations.

A few manufacturers use the bottom of under-over conveyors for secondary operations. One in particular has under-over conveyors that present the part at a 30º angle after printing, rather than upside-down. This allows for easier access for post-print operations such as assembly.

 

Air blasts

Automated closed-cup machines can have thinner-metering systems added to continuously add thinner to the ink cup. These systems simply drip a predetermined amount of solvent into the top of the ink cup at regular intervals. Unless the ink cup has some feature that allows the thinner to be mixed into the ink, the thinner just sits on top of the ink, having very little effect on viscosity.

 

pad shuttles

          Pad shuttles

Pad shuttles can be a less-expensive alternative to the purchase of a larger machine in some applications. Using a split pad, a pad shuttle can, in some cases, print an image that would otherwise exceed the cliche or ink cup’s maximum image area. For example, let’s say you have two images of the same color that must print with their respective centerlines being 45 mm apart. When etched separated by this dimension, the two images don’t fit within your machine’s maximum image area. If these two images fit when separated by, for example, 30 mm, then you could etch them that way, pick them up with two pads butted together, and then shuttle the two pads apart to achieve the desired 45-mm separation prior to image transfer.

Pad shuttles can also be used to print two images on two different sides of the same part when both images, etched side by side, are picked up at the same time by two separate pads. After image pick up, the pads move along the X-axis to position the first print. After the first print, the nest rotates while the pad shuttles into position for the second print. In order for this to work, your machine needs to be able to pick up once and print twice, and you must have both a pad shuttle and a rotating nesting fixture. You can also print two colors this way if you have a two-color ink well on a one-color machine.

 

Nesting fixtures

All too often nesting fixtures are an afterthought in tooling up for a job. In pad printing, it is necessary for the part to be properly supported, especially at critical stress points and areas where the forces of pad compression are greatest. The nests also need to be ergonomically correct and where several nests are necessary, within a few thousandths of an inch of being exactly the same. In some applications, the type of pad to be used must be taken into consideration when designing the nests.

In the interest of saving time and money, it is sometimes tempting to go to the tool maker down the street to have your nests built. That is fine, provided that your tool maker has experience dealing with pad printing. On several occasions, I have seen quality problems result from a lack of pad-printing-process knowledge in the design of nests, especially on automated systems.

Pad-printing-equipment manufacturers should know how to design and build nesting fixtures correctly. Let them build your nesting fixtures, at least until you become proficient enough to be able to educate the tool maker you use.

Of course, not all parts are critical enough in nature to warrant having someone build your nests. Some parts require little more than double-sided tape or a lump of modeling clay as a nest. A lot of people make their own nests for one-up printing jobs by using automotive body filler. You can find or build a container, mix the filler, pour it into the container, then place your part in at the angle you want. (Spray the part first with a light lubricant so you can get it out of the filler after it cures.) After 30 minutes or so, the filler is cured hard enough for uneven surfaces, tight corners, and rough edges to be sanded away for a reasonable, consistent fit.

Safety guards

Operator safety is everyone’s concern. Some pad printers don’t require any safety equipment, while others require complex enclosures or light curtains. Most automatic machines come with standard safety guards or shields that are effective and don’t interfere with the efficient operation of the printer.

The potential for productivity

If you can develop a way to hold a part steady and transport it, chances are good that the product is a suitable candidate for pad printing. Consider the types of jobs you currently accept, think about the types of projects you’d like to handle, and involve the equipment manufacturer in these processes. In the end, you’ll come to appreciate that pad printing is both a precise and flexible method of decorating.

About the author

John Kaverman is national sales manager for Innovative Marking Systems, Lowell, MA. He holds a degree in printing technology from Ferris State University and has more than 20 years of combined experience in the pad-printing and screen-printing industries. Kaverman welcomes comments and questions and can be reached by e-mail at john@padprinters.com.

Editor’s note: This article is an excerpt from John Kaverman’s Pad Printing Technical Guidebook. You can purchase the book by visiting the ST Online Bookstore at http://www.stmediagroup.com/st-bin/quikstore.cgi
or by calling 513-421-2050.