1. Art: Art begins with your imagination. Either a drawing on paper or computer generated art. In any case the end result of the art will be computerized and separated by colors onto a clear film positive. For each color in your design we will need a film positive. For each film positive, we will need a screen. In short, the less colors in your design, the less expensive your printing cost will be.
There are basically two different types of computer generated art, Vector and Raster.
2. Making of screens: Screens are basically a wooden or metal frame with a polyester fabric stretched onto them.
The polyester fabric is a lot like the screen on your screen door, It has anywhere from 32 threads per inch, to 385 threads per inch (mesh count). The mesh count we will use is determined by the type of design we will be printing. The finer the detail in the design, The higher the screen mesh count will be.
We begin the process of making our screens by stretching the polyester fabric (mesh) onto the wooden frame, and securing it with a very strong glue. Then trim any excess fabric of the edges of the frame.
Next, we take a light sensitive emulsion (in a dark room) and apply a even coat to the screen mesh. We will let that dry for about 6 hours.
After the light sensitive emulsion has dried, We will take the film positive (as described in the ART section) and tape it to the back of the screen mesh.
Then, we will place the screen on a device that emits light, Called an exposure unit (shown below), and expose the screen with light for a short period of time.
The dark areas (the image) on the film positive will prevent light from passing through and exposing the screen, The light will pass through clear areas of the film positive (where there is no design) and harden the emulsion.
Exposure unit shown
Next, we take the screen off the exposure unit and wash it with water. The water will not wash out the hardened emulsion. The water will wash out the soft areas that the light did not expose.
We are left with a screen that has an image in it (as shown at top of page). The ink will pass through the open areas of the mesh.
Setting Up the Screens for Printing: After making and exposing our screens, we need to prep the printing press for printing.
We do this by setting each screen (color) into the press heads (a six color press has six printing heads). We will set them in order by color, light colors first in sequence to the darkest color, usually black last.
We need to align each print color to the other to ensure correct registration throughout the printing process.
We then add ink colors to the screens and then squeegees to the screen print heads. The squeegees will move across the screen to push the ink through and onto the T-shirt.
A manual screen printing press
Printing: After the screens are placed and aligned into the press we are ready to begin printing. The automatic printing press shown above can print about 800 shirts an hour. It is a pneumatic press running on 155 lbs of compressed air. A compressor with a 10 hp three phase motor and a 200 gallon tank is needed to power this press.
The press shown above is an 8 color screen printing press, it has 8 printing heads and 10 pallets. The pallets are what we will place the shirt on for printing.
The screens will stay stationary during the printing process, while the pallets will rotate one at a time in a counter clockwise motion. Rising up to the screens after each index for printing. Then dropping down to move to the next station.
Two people are needed for this operation, one for loading the shirt onto the pallet, and the other for taking the shirt off the pallet, inspecting the shirt for imperfections and then setting it on the drying belt.
Shown is the M&R electric dryer.
Drying of the Shirt: After the shirt is printed we place it on the dryers moving belt. The temperature inside the dryer is about 980 degrees. The shirt will only stay inside of its dying chamber for about 37 seconds. Enough to heat the shirt and ink to about 350 degrees.
There is usually one more person on the other end of the dryer for quality control and folding.
Screen printing ink consist of four major components: Pigment, (for the color), Oil (for the base). PVC's and Plasticizers. When heated to 330 degrees, the oil evaporates and the splasticizer turn the PVC into plastic.
Yes, that print on your shirt is a thin coat of plastic bonded to the fabric of your shirt.
Packaging the Shirts: After the shirts are printed and dried, The folder at the end of the drying belt will inspect the shirt for quality and accuracy of the order.
There are various ways to ship the product. The most common and cost effective way is through UPS. The rates depend on your location. Time of Delivery also depends on your location.
The diferent Shipping methods are; Ground, 3 Day Select, 2nd Day Air Saver, 2nd Day Air, Next Day Air Saver and Next Day Air.