TABLE OF CONTENTS 1. 2. 2.1 2.2 2.3 2.4 2.5 3. 4. 5. 6. Acknowledgements Introduction Tools Pugmi 11 Flywheel press Trimming stands Tile racks and pallets KiIn Factory siting and layout Operation of a tile production unit Budget and finance Bibliography and relevant institutions 3 4 5 5 5 8 9 10 17 19 29 30
Intermediate Technology Development Group, 1986
The authors would like to thank the partners and employees of the Sumagi Tile Group, Morukkuliya, Dankotuwa, Sri Lanka for their open doors and generous sharing of information. We particularly thank Mr. Shelton Peiris, Mr. Lionel Perera, and Mr. T.Sivanadian for their substantial contributions. This work was funded by the Building Materials Programme of the Intermediate Technology Development Group. We express appreciation to the donors for this opportunity to share a successful industry with other countries and individuals who may wish to develop their own ceramic roofing tile industries.
This manual describes how fired clay roofing tiles are produced in Sri Lanka. Shown are the simplest tools required for medium to large scale tile production. While more sophisticated machines exist, the quality and profit possible using the production methods outlined in this guide are adequate, if not superior. These techniques have been proven for over 60 years in Sri Lanka alone. Tile factories are built up in production units. Each unit has one pugmill, two or more tile presses, adequate clay and tile storage, and a kiln. Some large factories will include as many as six of these units on the same site, operating for the most part independently. These units use capital, land and labour to their utmost, and are easily managed by two site supervisors. The smooth running of production starts with the proper selection of tools and careful site layout. This manual covers the essential elements from the clay supply to the correct chimney height for the kiln. Of course many additional local factors must be considered when planning to start a factory: at no point will the contents of this manual replace careful consideration and sound judgement. Proper management is most often the critical element for success. The range of clay products which can be made on a flywheel press is very great. Dozens of roof tile designs, plus pots, floor and wall tiles, relief decoration, and other ceramic wares can be produced within the factory described here. Beyond this, some Sri Lankan factories employ potters to throw flower pots and produce other hand made items as a side line, having the clay processing and firing facilities already in operation. Decisions on tile design and product range must be made in consideration of the local needs. Minimally, a standard roof tile and a ridge tile are required for basic gable roofs. As with any other manufacturing undertaking, it is advisable to undertake a careful market survey and economic feasibility study before putting spade to earth. Before buying land or equipment, one must assess and acquire the capital which will be needed through the first two years of operation. Working step by step through this manual, noting the tools and facilities, should give a realistic local production figure for labour, fuel and materials. This manual does not attempt to address such general business issues, keeping to those subjects which are unique to ceramic tile production.
Given access to a complete metal/machine shop and a carpentry shop, the required tools can be made in almost any country. It is advisable, however, to have each of the machined tools made from an example, so if the factory is to be in an area without examples, it may be necessary to import the first of some of these tools. Second-hand equipment can often be found in Europe for only a few hundred pounds sterling, and is completely serviceable. 2.1 PUGMILL
The Pugmill takes coarse aged clay, of correct moisture content and clay blend, and extrudes finely blended, workable clay. The Process Before the clay enters the pugmill all sticks, roots and debris are removed. The clay blend should be such that any lkg lump going into the mill is quite close to the correct proportion of each clay type and the correct water content (around 22-27 per cent by weight). If the clay has hard pea-sized lumps, the pugmill will not prepare it adequately (see Raw Clay Handling, p 23). The feed clay must be well softened and broken down. Getting it into this state requires time and weathering. A simple pugmill extrudes well blended clay without major air pockets. While some minor bubbles may remain, these are eliminated in the pressing process. More expensive 'de-airing' pugmills are widely available as well, but are not required. They are more delicate in operation, much more expensive, and require more power. A pugmill with an output of 80kg/min. is adequate to keep two presses busy for an output of up to 7,000 tiles per day. This mill will require at least 15hp to drive it, which can be provided by electric, diesel, or petrol engines. In Sri Lanka retired diesel tractors are often used and can last for more than 10 years of continuous operation. The wheels are replaced by belt drives going to turn the pugmill's gears and auger. 2.2 THE FLYWHEEL PRESS
The flywheel press is an invention of the 19th century which is still useful and appropriate. Variations of the concept come in all sizes, from three person operations to electrically driven powered presses capable of pressures up to 60 tons per square inch! The principle of the flywheel press is straightforward; a massive wheel is horizontally attached on top of a coarsely threaded shaft, which is attached to the top half of a die set. First the wheel is turned, thus raising the wheel and top die. Then the bottom die is slipped under the press with more than enough clay to produce the desired tile. The wheel is spun quickly down onto the clay. The tremendous momentum of the flywheel is converted into downward thrust by the threaded shaft, and the clay is quickly pressed into all points of the mould, with excess clay being ejected through holes in the extremes of the mould, and from between the dies.
By John Selker, Laurie Childrers, Published by Practical Action on 01/01/07
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