UNIT 3 MAPEH 6 LESSON 1 SCREEN PRINTING- ARTS.pptx
- 2. 2 Introduction to screen printing INDEX Preparation For Screen Printing Required Items For Screen Printing
- 3. 3 Types of Screen Printing INDEX Advantages Disadvantages
- 4. 4 Screen printing is a printing technique whereby a mesh is used to transfer ink onto a substrate, except in areas made impermeable to the ink by a blocking stencil. A blade or squeegee is moved across the screen to fill the open mesh apertures with ink, and a reverse stroke then causes the screen to touch the substrate momentarily along a line of contact. This causes the ink to wet the substrate and be pulled out of the mesh apertures as the screen springs back after the blade has passed. One color is printed at a time, so several screens can be used to produce a multicolored image or design. Screen Printing DEFINITION
- 5. 5 REQUIRED ITEMS FOR SCREEN PRINTING It refers to the number of the threads per inch of fabric. The usual mesh of screen employed for cotton and silk printing is 80 threads per inch. Screen Screen Frames .There are two types of screen frames(metal & wood) Screen frames are usually 26˝×55˝ and 23×55˝ for printing 45˝ wide cloth.
- 6. 6 REQUIRED ITEMS FOR SCREEN PRINTING Silk- Multifilament Weave Nylon- Multifilament or monofilament Polyester- Multifilament or Monofilament Screen Fabric Types Squeegee squeegee is moved across the screen to fill the open mesh apertures with ink
- 7. 7 PREPARATION OF SCREEN Photochemical method is the most widely used for preparing the screen. This based on the principle that when a coating of a solution of ammonium dichromate-gelatin or ammonium dichromate- polyvinyl alcohol is dried and exposed to light, insolubilisation takes place. Other method for screen preparation is lacquer and laser screen.
- 8. 8 TYPES OF SCREEN PRINTING 2. Rotary Screen Printing Upcoming Deposits 1. Flat(bed) screen printing Fully Automatic Flat Screen Printing Semi Automatic Flat Screen Printing Hand Screen Printing
- 9. Hand Screen Printing is a technique that allows to print, with greater accuracy, large and bright images on any type of fabric. It is an ancient technique, that has envolved over time and is still one of the most common for textile printing. Hand Screen printing is made with just a frame, ink and a stencils. The stencil is the negative of the image you want to print and is in waterproofing material. After mounting the fabric on the frame and placing the stencil, the ink is spread. The operation have to be repeated several times if working with multiple colors. In this case, the fabric must dry completely between one color and the next. The technique of Hand Screen Printing, while being less prone to human error, requires a high level of competence: the craftsman who makes the press must be familiar with the pigments used and the fabric, to be sure of obtaining a good results. SLIDE 6
- 10. Semi Automatic Flat Screen Printing The manual process has been semi automated by mounting the screen in a carriage and driving the squeegee mechanically across the screen. Long tables, typically 20-60m long, are used and some provision is usually made for drying the printed fabric. Semi automated flat screen printing is still very popular where the scale of production is not large or where capital investment is limited. In both hand and semi-automatic flat screen printing the colors are printed one after another with time for drying, which means that the situation approaches ‘wet-on-dry’ printing. SLIDE 6
- 11. Rotary Screen Printing In basic operation, rotary screen and flat screen- printing machines are very similar. Both use the same type of in-feed device, glue through, rotating blanket, dryer and fixation equipment. The process involves initially feeding fabric onto the rubber blanket. As the fabric travels under the rotary screens, the screens turn the white fabric. During printing, the paste is pressed through the surface via openings in order to obtain the desired design. The cylindrical screens allow more screens to be arranged per unit length than is the case with flat screen printing. Speed range from 30 to 50 m/min. The standard internal circumference of cylindrical screens is 640 - 640.1 mm. However, other dimensions are also · possible. SLIDE 6
- 12. 12 Advantages The inks used are very durable, the colors are extremely vivid, particularly for outdoor uses, making this a unique reproduction technique. We can print on a very large variety of materials and objects, and that we can choose from a plethora of special inks. This is a very flexible printing technology, with no limitation on the thickness. Advantages of Screen Printing
- 13. 13 Disadvantages The major disadvantage in Screen Printing is the amount of time it takes to set up a job. So preparation times are particularly long, particularly in high quality applications. This means that, as a method, it is financially impractical for the production of a single item, particularly for color printing advertising applications. Disadvantages of Screen Printing