Lesson Notes By Weeks and Term v3 - Senior Secondary 2
Flexography Printing
Download the Lessonotes Mobile Nigeria 2025 app for faster lesson access on Android and iPhone.
Flexography Printing
Download the Lessonotes Mobile Nigeria 2025 app for faster lesson access on Android and iPhone.
Subject: Printing Craft Practice
Class: Senior Secondary 2
Term: 1st Term
Week: 5
Theme: Machine Printing
This page supports the lesson note with a companion video and a short classroom-ready summary.
For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.
Define flexography. Distinguish flexographic printing from other machine printings. Name three products of flexographic printing.
Unit: Dries the ink after each colour application. * Rewind Stand: Collects the printed substrate. 2.5 Products of Flexographic Printing Flexography's versatility makes it suitable for printing a vast array of products, especially those requiring printing on flexible packaging materials.
Examples common in Nigeria include:
1. Flexible Packaging: Sachet water sachets, milk sachets, bread wrappers, snack food bags (e.g., Gala, Indomie packs), detergent pouches, pharmaceutical packaging.
2. Labels: Pressure-sensitive labels for beverages, cosmetics, household products, often found on plastic bottles and containers.
3. Corrugated Board: Printed outer packaging for appliances, beverages, and other goods, often seen in retail stores and markets.
4. Plastic Shopping Bags: Branded plastic bags used by supermarkets, boutiques, and street vendors.
5. Other Specialty Items:** Gift wrap, non-woven fabric bags, hygienic products. 2.1 Definition of Flexography Flexography, often shortened to "flexo," is a relief printing process that uses a flexible relief plate to print on a wide range of substrates. In flexography, the image areas on the printing plate are raised, while the non-image areas are recessed. Ink is applied to the raised image areas and then transferred directly onto the substrate. The process uses fast-drying liquid inks, primarily water-based or UV-curable, and can print on both absorbent and non-absorbent materials. It is particularly known for its ability to print on non-porous substrates, making it ideal for flexible packaging. 2.2 Principle of Operation The basic principle involves:
1. Ink Application: An anilox roller, which has a surface covered with tiny cells, picks up ink from an ink fountain.
2. Ink Metering: A doctor blade scrapes excess ink from the anilox roller, leaving a precise amount of ink in its cells.
3. Ink Transfer to Plate: The anilox roller then transfers this metered ink to the raised image areas of the flexible printing plate (mounted on a plate cylinder).
4. Image Transfer to Substrate: The plate cylinder, carrying the inked image, rotates and presses against the substrate, which is supported by an impression cylinder. The pressure causes the ink from the raised image areas to transfer onto the substrate.
5. Drying: The printed substrate then passes through a drying unit before subsequent colours are applied or it proceeds to finishing. 2.3 Distinguishing Flexographic Printing from Other Machine Printings To distinguish flexography, it is helpful to compare its key characteristics with other common machine printing processes: | Feature | Flexography | Offset Lithography | Gravure (Rotogravure) | Letterpress (Relief) | | :----------------- | :---------------------------------------------- | :---------------------------------------------- | :--------------------------------------------------- | :-------------------------------------------- | | Printing Plate | Flexible photopolymer or rubber; image is raised. | Flat metal (aluminum); image and non-image on same plane (oil/water repulsion). | Metal cylinder (steel/copper); image is recessed (engraved cells). | Rigid metal/wood; image is raised (like flexo, but rigid). | | Ink System | Low viscosity, fast-drying liquid inks (water-based, solvent-based, UV-curable). | High viscosity, paste-like oil-based inks. | Low viscosity, fast-drying solvent-based inks. | High viscosity, paste-like inks. | | Ink Transfer | Direct from plate to substrate. | Indirect (from plate to blanket to substrate). | Direct from recessed cells to substrate. | Direct from plate to substrate. | | Substrates | Wide range: plastics, films, foils, paper, corrugated board, non-wovens. Excellent on non-porous. | Paper, cardboard. Less effective on non-porous films without special treatments. | Films, foils, paper, laminates. Excellent on thin, flexible films. | Paper, cardstock, envelopes. | | Impression | Relief (raised image). | Planographic (flat image). | Intaglio (recessed image). | Relief (raised image). | | Typical Products (Nigerian context) | Sachet water bags, bread wrappers, pure milk sachets, plastic shopping bags, corrugated boxes, labels. | Newspapers, magazines, books, brochures, calendars, office stationery. | High-volume magazines, catalogues, flexible packaging for snacks (premium quality), wallpaper. | Business cards, invitations, specialty items (often with debossing/embossing). | | Key Advantage | Versatility on substrates, fast drying, high speed, cost-effective for long runs on flexible materials. | High quality for paper-based products, good for medium-to-long runs. | Excellent image quality (photorealistic), high speed, long runs, consistent colour. | Distinct tactile feel, fine detail for certain applications. | 2.4 Components of a Flexographic Press (Brief Overview)
Unwind Stand: Holds the roll of unprinted substrate.
Inking Unit: Comprises the ink fountain, anilox roller, and doctor blade.
Plate Cylinder: Holds the flexible printing plate.
Impression Cylinder: Provides pressure for ink transfer from plate to substrate.
Drying Unit: Dries the ink after each colour application.
Rewind Stand: Collects the printed substrate. 2.5 Products of Flexographic Printing Flexography's versatility makes it suitable for printing a vast array of products, especially those requiring printing on flexible packaging materials.
Examples common in Nigeria include:
1. Flexible Packaging: Sachet water sachets, milk sachets, bread wrappers, snack food bags (e.g., Gala, Indomie packs), detergent pouches, pharmaceutical packaging.
2. Labels: Pressure-sensitive labels for beverages, cosmetics, household products, often found on plastic bottles and containers.
3. Corrugated Board: Printed outer packaging for appliances, beverages, and 3.1 Teacher Activities Introduction (5 minutes): Initiate a discussion by showing various printed items (e.g., sachet water, bread wrapper, a book, a newspaper) and ask students to observe the differences in material and print quality. Introduce Flexography as a key printing method responsible for many of these items, especially flexible packaging.
Explanation of Key Concepts (20 minutes): Define flexography using simple, clear language, emphasizing the "flexible relief plate" and "direct printing" aspects. Use diagrams or illustrations (if available) of a flexographic unit to explain the principle of operation, pointing out the anilox roller, plate cylinder, and impression cylinder. Systematically present the comparison table (or discuss point by point) to distinguish flexography from offset and gravure, highlighting plate type, ink, and substrate characteristics. Provide concrete Nigerian examples for each printing method during the distinction phase.
Demonstration/Visual Aid (10 minutes): Display actual samples of flexographically printed products common in Nigeria (e.g., empty sachet water nylon, bread wrapper, plastic shopping bag). Ask students to physically examine them, focusing on the material and how the print appears. If possible, show a short video clip (if internet/projector available) of a flexographic press in operation, highlighting its speed and how different colours are applied.
Facilitation of Discussion (10 minutes): Lead a discussion on the advantages of flexography for certain types of products (e.g., low cost for flexible packaging, ability to print on diverse materials). Address student questions and clarify any misconceptions.
Activity Guidance (5 minutes): Instruct students to work in small groups to list products they see daily that they believe are printed using flexography.
Conclusion: Summarize the main points and transition to guided practice. 3.2 Student Activities Observation and Participation: Students actively observe the displayed printed items and participate in the initial discussion.
Note-Taking: Students take notes during the teacher's explanation of definitions, principles, and distinctions.
Visual Analysis: Students examine product samples, noting the type of material and print characteristics.
Group Discussion: Students engage in group discussions, identifying local examples of flexographically printed products.
Questioning: Students ask clarifying questions about the definitions, processes, and comparisons.
Drawing (Optional): Students could attempt to sketch a simplified diagram of a flexographic printing unit based on the teacher's explanation/visuals.
Question 1: Define flexography in your own words, highlighting two key characteristics of its printing plate.
Solution 1: Flexography is a direct relief printing process that uses a flexible printing plate with raised image areas to transfer low-viscosity, fast-drying inks directly onto a wide variety of substrates, especially flexible materials.
Commentary: This answer directly addresses performance objective
1. It emphasizes the plate's flexibility and the raised image, which are fundamental to flexography.
Question 2: Consider a local bakery that needs to print its logo and product information on plastic bread wrappers. Which printing method, flexography or offset lithography, would be more suitable for this task, and why? Give two reasons.
Solution 2: Flexography would be more suitable for printing on plastic bread wrappers.
Reasons: Substrate Compatibility: Flexography is specifically designed to print effectively on non-porous, flexible substrates like plastic films (nylon, polyethylene), which is what bread wrappers are made of. Offset lithography is primarily designed for paper-based substrates and would struggle to adhere ink properly to plastic without extensive pre-treatment or specialized inks.
Ink Type and Drying Speed: Flexography uses fast-drying liquid inks (often water-based or solvent-based) that adhere well to plastics and dry quickly, facilitating high-speed production. Offset uses oil-based paste inks that take longer to dry and might not bond effectively with plastic films.
Commentary: This question addresses performance objective 2 by requiring students to distinguish between two methods in a practical Nigerian context. The explanation directly contrasts the suitability based on common material usage.
Question 3: Name three different products commonly found in a typical Nigerian home or market that are produced using flexographic printing.
Solution 3: Three products commonly found in a Nigerian home or market produced using flexographic printing are: Sachet water sachets (pure water sachets): The plastic film used for sachet water is typically printed using flexography due to its flexibility and the need for high-speed, cost-effective production.
Bread wrappers: The plastic bags used to package loaves of bread (e.g., for Agege bread or branded loaves) are commonly printed via flexography.
Plastic shopping bags: The branded plastic bags distributed by supermarkets, boutiques, or local vendors often feature flexographic print. (Other valid answers include: instant noodle packaging, biscuit wrappers, detergent pouches, labels on plastic bottles, corrugated cartons.)
Commentary: This directly addresses performance objective 3, requiring students to identify real-world examples relevant to their local environment.
Packaging Industry in Nigeria: Flexography is the backbone of the flexible packaging industry, which is vital for consumer goods in Nigeria. Students can observe how local food products (snacks, bread, sachet water, pure milk) are packaged. This directly relates to the Nigerian economy, as many small and large businesses rely on flexographic printing for branding and protecting their products. Knowledge of flexography can lead to careers in packaging design, printing operations, and quality control.
Environmental Impact and Sustainability: The shift towards water-based inks in flexography (away from solvent-based) addresses environmental concerns regarding VOC emissions. Discussing this allows students to connect printing practices to broader environmental sustainability efforts relevant to Nigeria's industrial development and health standards.
Entrepreneurship and Local Manufacturing: Understanding flexography can inspire students to consider entrepreneurial ventures in printing or packaging services for local businesses. For example, setting up a small-scale flexographic printing unit to produce custom labels or plastic bags for local markets, small product manufacturers, or events, contributing to local employment and economic growth.