Understanding the Lifecycle of a Screen

Abstract

In order to create an image using the screen printing process a stencil is required for each individual colour being used within a particular design.

As a stencil is basically a “hole”, a mesh is required to hold together complex shapes.

The mesh is stretched and fixed under tension to a rectangular frame known as a screen

In order that the screen can be used it is subject to a series of physical processes.

Brand new screens are purchased from an appropriate supplier and when they arrive need to go through the following processes to prepare them for use.

They are first cleaned / degreased to remove any impurities.

They are then coated with a photo reactive emulsion then dried. At this point they are known as a coated screens.

Note: It is good working practice to hold sufficient stock of “coated screens” containing a variety of mesh counts in a dark room. The screens control list layout provides functionality to aid this.

Next, a mask of the desired image is applied (aka imaged) to the back of the screen, which is then exposed to Ultra Violet light which changes the chemical properties of the emulsion. At this point, the screen is said to be under construction.

The masked emulsion will remain unexposed, and the screen can then be developed.
Developing in this context is a simple process of washing out the unexposed emulsion.

At the end of this process, a Stencil has been created.

The number of colours in a particular image to be printed determines how many stencils are required and therefore the number of screens that need to be manufactured to print a particular image.

It is important to understand that in order to print an image onto a garment, sets of screens or screen-sets are used.

The screen-set can be made of one or multiple screens, depending on the number of colours contained with the required image.

Terminology

Please note, in this user guide the term "screen" is used in several contexts - not only the physical frame with mesh attached, but also the physical frame with a stencil attached.

It should be noted, that the physical frames with mesh are manufactured externally to TOT Shirts Limited.
Thus, when reference is made to making a screen - it should be read and understood as making the stencil that is then applied onto the mesh on the physical frame.

Screen Life cycle

Each screen in a screen-set has a definable life-cycle - from its creation, to usage, to post print washing, filing, reprinting, and recycling (reclaiming.

Note: as the mesh is under tension it can also be damaged (split) at any point during its life cycle, at which point it can also be repaired (restretched)

This life-cycle can be represented diagrammatically.

The screen-set's status icon denotes which stage of the life-cycle it is currently in

Generally speaking, unless splits occur in the mesh, the life cycle of a screen takes a linear route, with new frames requiring :-

Degreasing
Coating
Stencil manufacture
Masking off
Being filed ready for the print process.

Once a screen set has been used in a print process,. It is then washed and inspected for any damages or splits, and then an evaluation is made as to its future usage there are three possible options as to how it proceeds in its life-cycle. The post wash indicator on a screen-set typically denotes which of the following three usage paths that the screen-set will follow: -

It may be required for a print process on another job, that is scheduled to occur, in which case it will be sent to pre-check to assess whether any changes are needed and whether the screen-set is fit for purpose for the reprint.
If not required on another job, then :-
- If the screenset has been flagged as being a one off job and marked for instant recycling, it is reclaimed.
- If not marked as such, the screen-set is archived. That is physically filed as a set.

Screen-sets that are filed, can be retrieved should the member screens be required on future re-print jobs. If this is the case, the screen-set is sent from filing to pre-check, where - identically to the post wash reprint usage case - it is assessed to see whether any changes are needed and whether the screen-set is fit for purpose for the reprint.

Additionally, utilising real time tracking tools such as the Screens Control List, senior screen room staff can, should the inventory of available coated screens be running low, decide to flag for reclaim and commission the drawing down of screens sets from the file. These can then be decommissioned and sent for reclaim to ensure sufficient are available for current production requirements.

(Note: whilst it is possible to select individual member screens for reclaim, it is generally not considered an efficient working practice at TOT Shirts Limited.)