UNIVERSITY OF BENIN,BENIN CITY NIGERIA
7TH OF FEBUARY 2013
This is closely related to the centre lathe in some features but differs in the sense that they are machine tools in which the parts are machined automatically.The working process is fully automatic that is repeated to produce many parts without the direct involvement of the operator.Both the working and non-working are performed in a definite sequence by the control system adopted in the automatic which is set up to suit given project.In real sense,no lathe machine is totally automatic because,it requires the presence of the operator to load the machine for a batch of parts and also to initiate each lathe operation. Classification of Automatic Lathe Machine
There are various ways of classifying the automatic lathes;
(a)Depending upon the type of work machined,these include
(i)Magazine loaded Automatics. These machine are used for producing component from accurate separate blanks.They are also called ‘Automatic chucking machine’. (ii)Automatic bar Machine.Automatic bar machine are designed for machining components from bar or pipe stock.These machines are mainly used for the manufacture of quality fasteners(screws,nuts and studs),bushings,shafts,rings,rollers,handles and other parts,usually made of bar or pipe stock. (b)Depending upon the number of work spindles,these include
(i)Single Spindle Automatics.The general purpose single spindle automatic lathes are widely used for quantity or mass production by machining of high quality fasteners;bolts,srews,studs e.t.c.,bushings,pins ,shafts,rollers,handles and similar small metallic parts from long bars or tubes of regular section and also often from separate small blanks.They are preferably and essentially used for large volume of production i.e mass production,they are used always for producing jobs of rod,tubular or ring type and of relatively smaller size,they run fully automatically,including bar feeding and tool indexing,and continuously over a long duration repeating the same machining cycle.It is also provided with up to five radial tool slides which are moved by cams mounted on a camshaft. (ii)Multispindle Automatics.These automatic lathes are modified from single spindle automatic lathes.They have 2 to 8 spindle.Operation are carried out simultaneously in all the spindles.In contrast to the single spindle machine,where one turret face at a time working on one spindle,the multi-spindle has all turret faces working on all workpieces at the same time.Their production capacity is higher that of single-spindle machines but their machining accuracy is somewhat lower.The rate of production of a multi-spindle machine,however ,is less than that of the corresponding number of single-spindle machine.For example,the production capacity of a four spindle machine is not four times but only 2.5 to 3 times more than that of a single-spindle machine. (c)Depending on the cycle control system used.
(i)In the first category,automatics have a single camshaft:In which it rotates at a constant speed on the given set up and which controls both working and idle motions.The speed of the camshaft corresponds to slow working motion and since the idle motions should be completed shortest possible time,considerable time will be wasted for these motions for the machines of this category. (ii)Automatics of the second category:they have only one camshaft but it has two speeds of rotation:slow for working motions and fast for idle motion.However,the camshaft has a large moment of inertia(due to whole set of working and idle cams)and due to this,changeover mechanisms will experience impact loads when switching over from one speed to other. (iii)The third group of automatics have one camshaft for working motion which rotates at high speed auxillary camshaft for actuating the idle motions.This group finds locations for machining complex shaped work-piece where many...