Maufacturing Technology- Back to Basics-Machining 5- Machining Centres
Posted : September 9, 2004 at 5:15 pm [IST]
Machining centers
Machining centers in vertical and horizontal configurations are becoming the universal choice for prismatic components for every volume of production.
As a general rule, horizontal machines are the choice for boxy parts, while vertical machines are preferred for flat work pieces.
On vertical machining centres, the work-piece is secured to the machine bed and the cutting thrust is directly transferred to the machine bed. In a horizontal machining centre, the chip removal is easier and the machining for various faces in single setup is possible even with simple fixture. Horizontal machines are more versatile. However, these preferences are totally application-based. The philosophy behind the machining centers is to machine the part completely or as much as possible in the minimum number of setups. Even for complicated part design, two or three setups are good enough to complete all machining operations.
Universal machining centers with larger tool capacity and 4 - 5 or more axes of movements of worktable or machine spindle remain the preference for one-off or small batch production. High part cost resulting with the use of the universal machining centers for large batch production has been the reason for abandoning them for volume production.
Machining centers for large volume application are faster, lighter, simpler, and cheaper. Fixed table or twin pallet machining centers are preferred to be integrated with material handling system to form a high production line. Many new machining centers are able to hit 20,000 rpm spindle speeds with slide feed rates as high as 80 to 100 m/min. Feed rates up to 40 m/min. with rolling guides and 36 m/min with sliding guides are quite practical. The preference of aluminum over cast iron for automotive parts has made high speed machining centers a practical proposition to replace conventional transfer machines. Additionally, non-cutting time for the high speed machining centers in high production application are kept minimum, as many of these prismatic parts in automotive industry require a succession of drilling, boring, reaming, and tapping operations on five or six sides of the work piece. So tool-change time, pallet changing or indexing times, besides rapid traverse rates are critical. Chiron’s high speed machining center used for high production change tools in 0.55 second, index the pallet in 2.0 seconds, and have top rapid traverse rate of 60m/min.
- Indra
Category: Machining |
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