Five-axis Lathe-milling Technology And Its Application In Crank Machining

Five-axis lathe-milling is an integrated machining technology developed in thepast 20 years, in which advanced controlling technology, precision measuringtechnology and CAD/CAM application technology are synthesised based onconventional structural design and precise manufacturing process. Five-axis lathemillingcenter, as a carrier of lathe-milling technology till today has become one ofthe top grade machine tools in the world, whose manufacturing technical knowhowhas been held and monopolized by the developed western countries all through.This type of machine has the most optimum for circular part with complex shape,multi- process and high precision, as all or most of part processing steps can becompleted once loaded and fixed on the machine, ensuring high precision andefficiency, lowering costs of logistics and labour, reducing new productdevelopment time period. Consequently five-axis lathe-milling center exists to beirreplaceable for improving precision of some crucial parts in power source,spacecraft, aviation, naval vessel and war industries and shortening new productdevelopment period,which turn out to be a necessity of national key industries suchas national defence industry and war industry. It once has to be imported fromadvanced countries, expending a large volume of foreign money. Aplication anddevelopment leve of five-axis lathe-milling technology represents a country'sindustrial technological level and comprehensive competitive power, so five-axislathe-milling technology is decided to be the National "Ten Fifth" Key Science andTechnology Research Project by the government.The thesis in this paper, i.e."five-axis lathe-milling technology and itsapplication in crank machining"is from the key project of the National "TenFifth" Key Science and Technology Research Program, i.e. SSCKZ80-5/2000 modelfive-axis lathe-milling Center. Five-axis lathe-milling technology applying in crankmachining is originated from a practical project , i.e. HTM80300 model lathemillingcenter development project, which submitted to our company by HenanDiesel Engine Group Co., Ltd.. The machine in this project is the first customizedlathe-milling center developed for ship-use diesel engine crankshaft machining inour country, meaning a skip from technical research to market launch.In this paper, on design, key parts structures such as Cf axis, B axis and electric spindle etc. are studied, crucial technical problems are solved such as Cf axistransimission, precision warranty and locked up at any angle position, B axistransmission, precision warranty and locked up at any angle position, as well asmechanical powered spindle with high torque and speed. On machining andmanufacturing processes, machining and precision warranties of lockup ring gearof B axis, assembling process of bevel gear of transmission system in the poweredspindle are studied. Realization of main design such as B axis precision and Max.speed of the powered spindle are ensured by both machining and manufacturingprocesses. On basis of analysing and comparing conventional crankshaft processand lathe-milling process, superiority and merits of lathe-milling process arepresented. Overall sheme and layout of 5-axis lathe-milling center for use in shipdiesel engine crankshaft processes are made. In the overall sheme, Z axis drive andon-line angular positioning of crankshaft are the innovative points, of which 2 servomotors drive pinion and rack of Z axis, replacing conventional drive with lead screwand nut. This is a new idea for the design of 5-axis lathe-milling center formachining extra-long parts, making it posible for 5-axis lathe-milling center toevolve from small to long and large type, so meeting the demand of some importantenterprises for big 5-axis lathe-milling center. And crankshaft on-line angularpositioning can solve the crucial angular positioning problem for crankshaft lathemillingprocess, making it posible for parts as crankshaft that need angularpositioning to be machined on lathe-milling center,which is superior and meetsrequirement for similar part machined once loaded and fixed on the machine,making five-axis lathe-milling study more realistic. About control and applicationtechnology, automatic measuring is adopted to study on-line angular positioning ofcrankshaft and the imagination in overall sheme is realized successfully. Study andpresentation are made on CAD/CAM application technology. On all accounts, in thepaper discussion on the technology and problem in its application for crankshaftmachining is made from various aspects associated with 5-axis lathe-millingtechnoloty, solution and result are submitted .Advancement of 5-axis lathe-milling technoloty is to improve product qualityand reduce product manufacturing period. So this technology has comprehensiveapplication prospects in war industry, aviation, spacecraft and naval vessal as well as civil industries. Especially it has superiority in ship diesel engine crankshaftmachining. So very early 5-axis lathe-milling process has been adopted to machinemedium and large sized diesel engine crankshaft of ship in foreign countries. Westart later but at a higher level. Crankshaft precision machined by HTM80300subtype 5-axis lathe-milling center studied in the thesis can completely equal to that byrough grinding. Finish grinding can be made directly from lathe-milling. The first 5-axis lathe-milling center used for crankshaft complete machining which researchedand developed independantly and successfully at home is a milestone in the study inarea of lathe-milling, which has arrived at advanced international level.