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§13 Screen Printing

§13 Screen Printing. Prof. Dr. Cao Congjun Xi’an university of technology. Features of screen printing. Flexional plate Thick ink layer,20 – 100um Roughness surface printable Curved surface printable Products have some sense of 3D,but low definition. Application.

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§13 Screen Printing

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  1. §13 Screen Printing Prof. Dr. Cao Congjun Xi’an university of technology

  2. Features of screen printing • Flexional plate • Thick ink layer,20 – 100um • Roughness surface printable • Curved surface printable • Products have some sense of 3D,but low definition

  3. Application • Paper printing:paper,cardboard,corrugated board • Plastic container and toy • Metal plate and metal container • Glass • Textile • Architectural material

  4. Primary content and objectives • Technics of screen printing To know the method of screen printing • Application of screen printing • Screen printing machine To know the construction and process of screen printing machines

  5. 13.1Technics of screen printing 丝网印刷工艺 • Concept • 丝印制版Platemaking • 印刷准备Preparation • 安装刮墨板 • 安装丝网印版 • 安装回墨板 • 调配油墨 • 印刷Printing • 上墨 • 印刷 • 干燥

  6. 13.1.1 Platemaking • Screen Frames • There are diverse types of frames for screen printing.Wood, steel, and, more often, aluminum is used. • Screen Fabric • The type of fabric to be used depends only on the requirements arising from the process. The fabric’s material must allow good connection to the stencil material and must not be affected by the ink solvent or cleaning agents. It must be sufficiently abrasion-resistant to withstand the stress created when the squeegee is brought into contact with the substrate.

  7. 聚酯 Types:polyester,silk,nylon,stainless steel • Stencil The carrier of the printed information, the stencil, is produced in a different way. • Photographic Stencil Methods Indirect process Direct process Direct/Indirect process

  8. Indirect Process---P303 Figure 13.14 • The indirect uses a dry emulsion on a plastic support sheet. The stencil film is exposed through a transparent, right-reading positive and is then treated with a developer solution. The areas that light reaches harden during exposure.The remaining areas are washed away with a warm-water spray to form the image or printing areas.The stencil is adhered to a clean screen while it is wet from the spray,and the support sheet is removed after the stencil dries.

  9. Direct Process---P304 Figure 13.15 • The direct process uses a wet emulsion that is coated directly on a clean screen.The emulsion is exposed through a transparent positive to harden the nonimage areas.The image areas are washed away with a warm-water spray.When the emulsion is dry,the stencil is ready to print.Direct emulsions have a limited shelf life(保存期限) when compared to indirect materials which are basically unlimited because they are stored in an inactive form.

  10. Direct/Indirect Process-P305 Figure 13.16 • The direct/indirect process combines the indirect and the direct photographic processes. An unsensitized film material is placed under the stencil side of the screen on a flat table.The stencil emulsion is stored in two parts,a liquid emulsion and a sensitizer.When the two are mixed and coated on the screen,they become light sensitive and coat through the screen to the film support.When the emulsion is dry,the backing sheet of the stencil is removed and normal direct exposure techniques are carried out.

  11. 13.1.2 印刷准备 1. Squeegee刮墨板的调整 作用:刮墨板加压滑动,使油墨从网孔透过,到达承印物 A. 选择刮墨板材质-Chemical Makeup 材质:天然橡胶、硅橡胶、聚胺酯橡胶 要求:a. 肖氏硬度在 60 ~ 80 b. 有良好的弹性 c. 良好的耐溶剂性和耐磨性

  12. B. 选择刮墨板的形状-Shape 直角形Square :平面承印物,e.g.纸、薄膜 Single bevel硬质材料 Square edge with rounded corner 圆角形:厚墨 小面积实地印刷 Double bevel,flat point 织物印刷 尖角形Double bevel: 曲面印刷 C. 调整刮墨板的角度和刮印速度:影响透墨量 角度小,速度慢:透墨量大,印品墨层厚 角度大,速度快:透墨量小,印品墨层薄 平面承印物:20 – 70度 曲面承印物:30 – 65度

  13. 2. 安装丝网版,调节网面和承印物的间隙(H) H > 0 离网印刷,可进行较精细的印刷 H = 0 全接触印刷 网距过小:不易剥网,产生渗透、粘版、网线变粗、脏版 网距过大:张力过大,产生丝网松弛、损坏、精度降低 一般H 3 – 5mm 3. 安装回墨板 送墨 避免网孔油墨干燥 作用:

  14. 4. Selecting the proper ink:must freely pass through screen fabric and create an image of acceptable density. • 颜色正确 • Correct color 丝网印刷机不像平印机和凸印机 有较长的油墨分配和转移行程。 B. 粘度适中:Suitable viscosity 粘度过大:油墨转移不畅、缺墨 粘度过小:印迹扩大 C. 干燥度适中:Suitable dry-speed 过慢:粘页、蹭脏、印速低 过快:结网、拉丝、皱皮

  15. 5. 检查干燥装置 如:干燥架晾干 回转移动式干燥机 喷气干燥机 红外线干燥机IR drying 紫外线干燥机UV drying hot air drying

  16. 13.1.3 印刷Printing • 给料Position a press sheet • Pour a puddle of ink • 匀墨Distributing the ink • 接触Contacting • 刮印、剥网Squeegee • passes over the screen • 收料、换纸Removing • the press sheet • 干燥Drying

  17. 13.2Screen Printing Machine • Flat-bed screen printing machine • Curved screen printing machine • Cylindrical screen printing machine Paper feeding unit + Inking unit + Printing unit + Delivery unit

  18. Fig. Screen printing technologies. a Flatbed; b Flat-to-round/“body printing”; c Rotary printing

  19. Characteristics of screen machine • Direct printing • Lower automatization • Simple structure and lower speed

  20. 13.2.1 Flat-bed screen printing machine 1. Flat-bed screen printing machine 升降式 滑台式

  21. Flat-bed screen printing machine Fig.13.42,13.43

  22. 2. Round screen printing machine Replace the impression flat frame with impression cylinder . substrate Impression cylinder

  23. Cylinder screen printing press (flat-round). a Printing system (model: Maestro, Sakurai); b The printing sequence

  24. 13.2.2 Curved screen printing machine The surface of substrate is flexural (curving). Screening cylindrical surfaces. 承印物 可在圆柱面、 圆锥面、球面、椭 圆面上印刷。 滚轴

  25. Samples of printed products Fig.13.45,13.46 Screen printing device for printing on curved objects/bodies (RokuPrint/Steinmann)

  26. 多色曲面丝网印刷机 Multicolor automatic screen printing machine for printing on bottles, glasses, etc.

  27. 13.2.3 圆丝网印刷机 可以连续印刷。 适用于卷曲的织物、薄膜、金属箔、纸张。 金属圆丝网版 供墨辊 承印物

  28. Fig. Screen printing system for multicolor textile printing. a Diagram of a rotary screen printing unit; b “Pegasus” 12-color textile printing press with “RotaMesh” seamless rotary screens (Stork) Fig.13.47

  29. 13.2.4 静电丝网印刷机 墨粉 接正极 承印物 接负极 转印之后 加热使墨粉固 化。 金属板

  30. Homework • P329 review questions 1,2,7,8,9,10,21.

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