AQA GCSE Design and Technology 8552 1 Sources,

AQA GCSE Design and Technology 8552 1 Sources,

AQA GCSE Design and Technology 8552 1 Sources, origins and properties Unit 5B Timber based materials

Objectives Understand the main processes involved in producing workable forms of timber including: conversion, seasoning and the creation of manufactured timbers Be aware of sustainability and ethical factors in timber production and use Understand the advantages and disadvantages of manufactured board compared with natural wood Sources, origins and properties Unit 5B Timber based materials

Trees Wood has been used as a material and a fuel for thousands of years Wood is a durable material, which should last a lifetime if well cared for Our planet is home to over 23,000 different kinds of trees What wooden products or objects have you encountered this morning? Sources, origins and properties

Unit 5B Timber based materials Forestry management If managed properly, forestry is a sustainable cycle Well managed forests offer many benefits: Provide an environment for leisure activities Employment What other benefits do you think managed forests offer?

Sources, origins and properties Unit 5B Timber based materials Thinning forests Managed forests contain trees of different ages When trees are finally felled they are replaced with new seedlings Young trees are thinned at around five years old Why do you think it is usual to 'thin' trees every five years? What do you think the thinnings might be used for?

Sources, origins and properties Unit 5B Timber based materials Felling A tree is felled when it is cut down Traditionally this was done using a hand axe or long saw Modern felling is done using a chainsaw or agricultural logging machinery that can fell a tree, de-branch it and cut it into equal length logs in one action What are the advantages and disadvantages of using mechanised felling methods

over manual methods? Sources, origins and properties Unit 5B Timber based materials Product mileage How much mileage might wood take from tree to end user? What stages might there be on its journey? Sources, origins and properties Unit 5B Timber based materials

Timber conversion Felled trees are cut into manageable lengths to be converted into timber planks and boards Timber is supplied in two main finishes: rough sawn or planed all round (PAR) Rough sawn timber is often used for exterior tasks PAR is smoother and has been planed down on all sides Where might PAR timber be used? What happens to off-cuts? Sources, origins and properties Unit 5B Timber based materials

Green timber Newly felled unseasoned trees are known as 'green' Green timber is very wet, with more than 50% moisture content Green timber can be more difficult to work with for interior applications Timber for exterior applications should have a moisture content of less than 20% Timber for domestic furniture should have a moisture content of less than 10% Why is it necessary to remove the moisture from timber?

Sources, origins and properties Unit 5B Timber based materials Seasoning Seasoning timber reduces its moisture content The two methods of seasoning are air or kiln drying What do you think the environmental advantages of air drying timber are? Aside from being faster, might there be any other advantages to kiln drying? Sources, origins and properties Unit 5B Timber based materials Faults

Faults can occur as timber dries. These include: Bowing Splitting / cracking Springing Cupping Twisting Sources, origins and properties Unit 5B Timber based materials Reducing faults Faults can make the timber unusable and increase the amount of wastage Why is kiln dried timber less prone

to faults than air drying? Why do you think the end grain of timber planks is often covered with a special sealant? Sources, origins and properties Unit 5B Timber based materials Sustainability Trees are one of our most valuable resources and yet we have not always treated them as such For a long time the rate of use has exceeded trees' rate of growth Demand for more exotic timbers like teak and mahogany has created a huge illegal logging industry

Sources, origins and properties Unit 5B Timber based materials Consequences of illegal logging Illegal logging destroys vast areas of rainforest and causes desertification, deforestation and ultimately plays a role in global warming What do you consider to be the possible consequences of

desertification, deforestation and global warming? Sources, origins and properties Unit 5B Timber based materials Timber provenance Timber provenance is regulated by bodies such as: FSC (Forest Stewardship Council) PEFCTM (Programme for the Endorsement of Forest Certification) In the UK, sustainably managed forests must be FSC or PEFC accredited

How do you think the FSC and PEFC regulate the industry? Sources, origins and properties Unit 5B Timber based materials Kit house construction Complete Task 1 of Worksheet 1 Sources, origins and properties Unit 5B Timber based materials Manufactured boards Manufactured boards come in large sheets, often made from waste or recycled wood and adhesives

Manufactured boards are usually produced using lamination or compression techniques Manufactured boards are often covered with veneers of higher quality timber Why do you think we can class manufactured boards as 'composite materials'? Sources, origins and properties Unit 5B Timber based materials Laminated boards Lamination is the technique of layering materials using heat, pressure and adhesives Veneers (thin layers) are layered with the grain direction of each layer at 90 to each other

Why are an odd number of layers always used? How does lamination improve the material properties? Are there are any aesthetic advantages of laminated manufactured boards? Sources, origins and properties Unit 5B Timber based materials Compression Compression uses adhesives, heat and pressure to combine shreds, chips or pulp to produce a larger board Oriented strand board comprises compressed shreds of wood Chipboard and MDF are often covered with a melamine or Formica laminate

Where might we obtain the raw materials for making compressed manufactured boards? Why are compressed boards weaker than laminated boards? Sources, origins and properties Unit 5B Timber based materials Rotational veneer production Veneer can be made by rotating a tree trunk on a large industrial machine similar to a wood lathe This creates a long ribbon of veneer that can be cut to length Sources, origins and properties Unit 5B Timber based materials

Using manufactured board Advantages Disadvantages Available in large sheets with few faults or defects Adhesives used in manufacture can be hazardous when inhaled Aesthetic flaws like knots can be eliminated, boards require very little finishing

Adhesives used in manufacture can also blunt tools quickly Made of wood that might otherwise go to landfill Many traditional woodworking joints cannot be used and the edges are hard to finish Available in a vast range of surface finishes Boards are prone to absorbing moisture

Sources, origins and properties Unit 5B Timber based materials Worksheet 1 Complete Task 2 on the worksheet Sources, origins and properties Unit 5B Timber based materials Plenary Forestry is the managed growing of trees for the timber industry When trees reach maturity they are felled using a chainsaw or industrial cutting machines

What happens next in the production process? How do environmental and ethical factors play a part? Sources, origins and properties Unit 5B Timber based materials Copyright 2017 PG Online Limited The contents of this unit are protected by copyright. This unit and all the worksheets, PowerPoint presentations, teaching guides and other associated files distributed with it are supplied to you by PG Online Limited under licence and may be used and copied by you only in accordance with the terms of the licence. Except as expressly permitted by the licence, no part of the materials distributed with this unit may be used, reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic or otherwise, without the prior written permission of PG Online Limited.

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