Selecting an Iemca servo-driven bar magazine from 1st MTA to feed a new lathe, rather than accepting the default pneumatic barfeed offered by the machine supplier, has raised productivity and is saving material at Downton subcontractor, Mikina Precision Engineering. In addition, the servo magazine is much more versatile due to its superior controllability and it is less noisy.
Mikina now operates five Mazak lathes, two of which were supplied as standard fitted with a third-party, pneumatically-actuated, short barfeed. However, when the subcontractor ordered its fifth Mazak, a QuickTurn Nexus 200-II MSY turn-mill centre, the decision was taken to omit the pneumatic barfeed. Instead, a servo-motor controlled, short bar magazine, an Italian-built Iemca KID 80, was sourced from UK agent, 1st MTA.
The supplier retrofitted the unit in October 2011. As part of the service, the liners were redesigned to accept the existing bush system used on Mikina's other lathes with pneumatic barfeeds. It means that the bushes for different sizes of bar used throughout the factory are interchangeable with all of the lathes. In other words, the Mazak / Iemca combination has been integrated into Mikina's turn-milling section and is not a stand-alone cell.
James Wood, Mikina's Works Manager, who has used Iemca equipment in previous companies, said, "Whereas a pneumatic bar feed is fully controlled from the lathe's CNC system, working with a servo feed is slightly different in that some parameters, when setting up for a new material size, are entered using a dedicated operator panel.
"During a batch, the CNC runs the cutting cycle and controls bar change, as usual, but the ability to program some functions separately allows a greater degree of control over how the magazine interacts with the lathe.
"For example, unlike on a pneumatic feeder, you can set the exact workpiece length on the Iemca because the system knows the bar length and precisely how much material has been used.
"The remnant piece can be longer if heavy roughing is needed on the last-off component, or more usually you set the remnant to be smaller, so there is less material wastage."
He said that the more definite movements provided by a servo-motor also improve versatility when programming the position to which the pusher retracts after a component has been fed out. Inadequate control over how far the material is pushed forward and retracted can result in either wasted cycle time or rattling at the bar-end interface.
Speaking of noise, Mr Wood added that the Iemca magazine supplied by 1st MTA is practically inaudible in operation, whereas the air supply from the compressor to pneumatic barfeeds hisses all the time. "All-electric bar feeding results in a much quieter machine shop and it is also low maintenance," he said.
More responsive control extends to programming the speed of bar pushing (up to 500 mm/min) and of retraction (up to 1,000 m/min) as well as the thrust pressure, which can be varied on the KID 80 but not on pneumatic magazines.
This facility allows the force with which the bar is advanced to be lowered when, for instance, hexagonal bar is being fed, which sometimes does not line up correctly with the collet in the spindle and could otherwise impact it and cause damage. Additionally, slower advance is advisable if delicate materials like plastics are being machined. Servo pushing can also eliminate the need for a bar stop in the lathe turret, which in some cases cuts the feed out time per cycle.
Changing over the KID 80 between batches is easy. Physically adjusting it to accept a new bar diameter is quickly achieved by turning a knob on the back of the magazine, unlike with pneumatic models on which it is necessary to open the lid and adjust toggle clamps. Entering values into the Iemca's operator panel takes a matter of seconds. Overall, set-up is much quicker compared with using a pneumatic barfeed.
The unit can handle bar diameters from 5 to 80 mm and lengths from 90 mm to 1,615 mm, although Mikina has standardised on bar lengths of one metre at its Downton factory, near Salisbury.