As
covered in Understanding Screen Printing
Part One - The Stencil, TOT
Shirts Ltd uses the screen print technique as one of the methods in the
production process of garment printing.
A “screen” consists of two elements – a frame with a mesh
stretched across it and glued into place.
The
mesh is placed across the frame under tension and glued into place. An
example of this being done can be seen in the follow video
https://www.youtube.com/watch?v=sh2VHMS4cOM.
Any new mesh or reclaimed mesh will require de greasing to allow the emulsion to adhere correctly
https://www.youtube.com/watch?v=YbP8HzXhohU
The mesh is then coated with a photo sensitive emulsion, dried and stored in a light safe area.
The following video covers de greasing and manual coating techniques.
https://www.youtube.com/watch?v=xQePWRQCVSA&t=2s
Coating Machine
Here’s an example of a automatic coating machine
https://www.youtube.com/watch?v=GIjjkgLWLkY&t=101s
To create a stencil on a screen is simply a case of exposing the emulsion to an ultraviolet light source whilst preventing the light getting to the parts required to make the
stencil. This can be done in one of two ways.
Using an opaque
to ultraviolet light mask
or
Controlling the light source itself.
Exposure using a mask.
An opaque mask of the desired image is applied to the back of the screen, and it is then exposed to UV light which changes the chemical properties of the emulsion.
The “masked off” area of prevents the UV light getting to the emulsion which will remain unexposed.
Exposure using a laser
Using modern technology, it is now possible to expose emulsion by using a direct controlled light source thus eliminating the need to create a mask.
For both exposure methods the separation and ripping of the source artwork to a form suitable to manufacture as stencils is done at an art department level. Separation and ripping results in an electronic TIFF
(Tagged Image File Format ) for each colour. These files are saved to a central server which can be accessed by the machine that will apply the mask and exposure.
As at January 2024, TOT employs both methods
Spyder Printer
This printer uses wax and will image a MASK onto the back of a coated screen as shown in the following link
https://www.youtube.com/watch?v=gf3oykymwl4&t=3s
The Cube
This printer uses a series of lasers that image the emulsion directly.
This is shown in the following promotional video
https://www.youtube.com/watch?v=dKIhgiEFUh8
Developing
The screen can then be developed. This is a simple case of washing out the unexposed area of emulsion. This creates a STENCIL
Masking Off
Once a stencil has been manufactured and dried it requires a final check over whilst masking off any unwanted stencil (registration marks etc) areas.
It is then filed in a “ready to print” location.
Post Print Run
Once a print run has been processed using a screen set, the screen set is then returned to the screen room for washing and either filing or reclaim.
The number of colours in an image will determine how many stencils are
required and therefore the number of screens that are required to print
a particular garment.
Stencils have a definable life cycle - from creation, to use, to wash, to file, to re-use, to recycle (reclaim).
See Stencils Life Cycle Flow Chart for more detail.
In addition to the frames being cycled as above, it is important to note that screen sets can also be employed on unrelated jobs that carry a common image.
The life cycle of a screen takes a linear route; the following bullet headings should help to understand this life cycle.
New
stretched & reclaimed frames require:
-
De greasing
Coating
Stencil manufacture
Match pos id to mesh counts
Exposure
Developing
Masking off
Filing ready for print
Printing
Washing
At this point there are 4 possible alternatives to the screens further use: -
Archiving (For possible reprinting)
If there no print jobs scheduled that require the same screen-set, and staff have recorded that the screens should be retained, the Post Wash indicator field in Strokeone will state “File”
Reclaiming (Which puts the screen back into the same status as if it were a “new screen” whereby the above processes are repeated)
Similar to the above, except where staff have recorded that the screens can be discarded after the job, In which case, the post wash indicator will state “Reclaim”
Additionally, it is possible to Reclaim screen-sets that have been filed.
Re-stretching (If a mesh becomes damaged beyond use it can be removed and replaced with a new mesh which in effect makes it a “new screen”)