Tham khảo tài liệu 'manual gearbox design part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Gear tooth failures 51 refinement made to the gears to reduce either the size or weight improve the smoothness in operation or efficiency or reduce the operating noise level will usually lead to an increase in the cost of manufacture. Even so any one of the improvements listed could lead to better durability and longer life for the gear train which would permit the gear size to be reduced with a consequent saving in the amount of material used and the resultant reduction in overall cost. It can therefore be seen that great care must be taken at the design stage in order that the best compromise is reached to provide the transmission most suitable for the installation in hand. From the preceding paragraphs it can be seen that the choice is not always simple when deciding between a precision gears made from good quality material and light in weight with first-class heat treatment or b lower class gears made from a cheaper quality material and heat treatment which would mean heavier gears larger bearings and casings and more frequent maintenance and inspection with the consequent losses in available running time The minimum requirement of any transmission system is that it will not break or wear out prematurely. Beyond this the conditions and demands on the gears during operation will determine a the class of gear b the surface finish c the type of material d the heat treatment e the gear shaft mounting f the type of bearings g the transmission casing design and material in any particular transmission design. The transmission unit consists of four main components or units 1 The gears and shafts. 2 The bearings. 3 The lubrication system. 4 The gearbox casings. Any one of these units can be the cause of ultimate failure in the transmission system. In the majority of failures it is usually damage to the gear tooth surfaces which cause the first complaints to be raised and the lubricant and lubrication system are always one of the first sources to be investigated. .
