Screen Printing Best Practices
Screen printing stands out from other printing process as being one that requires a more hands on approach. While there is an automatic screen printing process as well as a manual one, there is still an air of craft about it that is truly unique.
There are a lot of variables, and in order to get the best results from this technique the following must be considered and factored into your own processes.
One element of the process that can’t be underestimated in importance is the quality of your equipment – but with the focus on how you are able to set it up. A low cost, low option press will enable you to create a print, but the quality of that print will be limited by the capabilities of that press.
This is because improper set-up is the reason behind most production problems, and ability to fine tune the press will allow to you correct problems quickly. Keeping a record of these settings for each task will then allow you to achieve consistent results over multiple runs.
Controls that allow you to alter the numerous variables of set-up should be high on your list of desirable features:
- Off Contact Adjustment combined with the Screen Angle are primary variables you will want to control, allowing you to determine the proper snap off point to produce a crisp print.
- Platen Levelling Adjustment will keep the angle of contact correct to give a consistent contact across the whole screen.
- Screen Clamps will keep everything in place to ensure a clean registration of ink onto the substrate. The option for Pneumatic Clamps is also advisable to speed up the process and reduce wear on the press.
- Micro-Registration Adjustment will let you make small tweaks without having to reset the screen, which will speed up the production process and improve accuracy.
Cleaning and Maintenance
If you’ve invested in a better quality press, you’re also going to want to ensure you keep it in optimal condition to realise the return on it.
The single most important thing you can do is to keep the press clean. Taking care not to unnecessarily soil the machine in the first place is a good start, but it will inevitably accumulate dirt and grime which should be cleaned often and as part of a regular maintenance schedule.
A good habit is to check the machine during each run to pick up on anything that may have come loose or even broken. This will improve the quality of your prints by catching loose screens, and also prevent excessive wear on parts that aren’t correctly in place.
Take care of your tools and they will take care of you.
Right Tool for the Right Job
Ink – With the number of variables governed by ink choice being so great, the choice of ink will have a large effect on the end result; viscosity, surface tension, size of pigment particles, solvent
evaporation rate, operating temperatures, and shear are all factors to consider.
Whether or not to use UV ink will be the main decision that has to be made. You don’t have to worry about drying times with UV ink – but on the other hand you must protect them from UV light sources before they are ready to be cured e.g. sunlight. Otherwise they could start to cure prematurely.
Screen/Stencil – The type of screen used will have an effect as more complex and detailed designs will benefit from higher mesh counts and finer threads. The standard 110 count screens will handle
most tasks, but can struggle to produce what a fine 400 count screen is capable of.
The quality of the screen will also have an impact on the quality of print produced. Higher tension screens need less pressure and thus less effort to deposit ink. This is of critical importance on a manual press where that difference impacts directly onto an operator, but is also relevant to an automatic press where the it allows for less off contact distance and a faster registration time.
Squeegee/Blade – Being responsible for bringing the ink into contact with the substrate, this is another element that will have a noticeable effect. Blade hardness (or durometer) is a key consideration which should be determined by the surface of the substrate. Softer blades are suitable for uneven surfaces but are generally less durable and degrade - harder ones should be used where possible.
For manual presses, anything that will affect the operator is also a consideration; flexibility, length, angle, speed, pressure, height etc. Whatever makes it easier to operate will maintain consistency of the print by limiting fatigue.
Process and Technique
When it comes to the act of printing itself, experienced operators will have honed their skills over a long period of time, and built their knowledge through trial and error across a variety of tasks.
There will no doubt be some debate over what that exact best process is and will be based on the individual and their own personal experiences - likely governed in some part by the peculiarities developed by the combination of equipment and tools they have used.
When establishing your own technique these are some of the things to consider:
- Pushing or Pulling in a manual press will affect the operator differently. Pushing is seen as taking less effort and will tire you less, giving more consistent results.
- Excess Ink in the screen is not recommended. It can clog up and the longer it stays exposed, it’ll will compromise the quality and increase contamination. Add small amounts often.
- The Right Angle and Pressure is a balance between ensuring proper registration and accuracy on the substrate without excess force increasing wear and damage on the equipment. The correct angle should be 45 degrees, but can be high as 80 degrees if using the ‘Pull’ method – typically tighter (lower) angles impart more ink.
- Cure Your Ink properly to eliminate smudging and ink transfer, and reduce waste. UV inks should be simple to set using the appropriate type of light, but for solvent and water based inks you should always adhere to the manufacturers guidelines on drying times and temperatures – don’t try to short cut it.
- Testing and Accuracy. Always carry out tests to make sure your set-up is correct and performing as expected. This will identify issues immediately rather than halfway through a print run. You will also endear yourself to your clients if do thorough checks on the finished production run to ensure the highest accuracy. Repeat business is good business.
By following these guidelines you can create an effective process that produces professional results to benefit on you and your customers. Or at least pick up a few points you may not have considered before to help improve your technique.