Latest Trends in Machining centres
Posted : September 16, 2004 at 6:32 pm [IST]
“Doing More with Less.” Is the mantra today in machining. Users are looking for more parts, with better quality, in less time and with less labor. New machine offerings feature faster rapid traverses, spindle speeds, and tool-changers than previous generations. Many have automatic part loading and pallet changers that help users minimize labor input and provide untended machining capability.
For example, a high-speed vertical machining center designed for moldmakers has a 12,000-rpm, inline direct-drive spindle and high-speed control with full look-ahead capability.
Manufacturers are trying to reduce the cost of ownership by designing low-cost–affordable, not cheap–machines, while maintaining quality by using economies of scale and common components. Value-added services, such as same-day service, 90% first-call completion rate, and spare parts price and inventory are also important.
Production of machined parts is shifting to contract manufacturers. Contract manufacturers are also being compelled to invest in new technology due to five major factors.
” A shortage of skilled craftsmen in the tooling and machining area. Shops are being forced to look for alternative resources, and automated and integrated technology is a solution to enhanced productivity.
” Global competition, which makes it imperative to balance quality human resources with automated technology. In reality, automation and technology will end up saving jobs, not taking them away.
” A move toward high-mix, low-volume part production means traditional setup times can no longer be tolerated. Automation is no longer a ‘perk’ of the large OEM operation; it is becoming a requirement for tier-level and smaller operations..
” Ongoing demands for shorter lead times, faster production, and reduced cycle times. Everyone wants everything today, and often untended machining with automation and cell integration is the only answer.
” A need to address shorter product life cycles by expanding machining data and knowledge bases. Industry cannot continue to redevelop processes and procedures for new parts. We simply cannot re-invent the wheel with every new widget..
Manufacturers have restructured much of its machine technology to be more cost-effective in terms of both initial capital investment and cost of operation. This emphasis on value technology will take the form of a HMC, which features a high-torque spindle that is the most powerful integral-drive spindle in the world. The proprietary 50-hp (37.3-kW), 50-taper spindle produces 744 lb-ft (1009 N*m) of torque from 0 to 392 rpm and still maintains fast accel/decel rates. Users also expect service, training, and ongoing process improvement efforts from machine suppliers.
Another potential solution to increasing demands for improved metalcutting productivity is a cellular system built around HMCs, such as carrier pallet pool (CPP) and linear pallet pool (LPP) systems.
A CPP is a preconfigured flexible system, and an LPP is a modular, expandable flexible system. With these systems, HMC utilization typically increases to 85%, and even better in some cases. This results from the elimination of setup time from the HMCs in the system
.
The latest machining centers of Mori feature the Driven at the Center of Gravity (DCG) technology. Use of dual ballscrews on selected machine axes is said to hold down costs while improving part accuracy, surface finish, and tool life by reducing cutting vibration. Vibration destroys tooling, so decreasing vibration increases tool life. In one of the cutting tests, a DCG machining center yielded a 3.7 X increase in tool life versus a conventional machine. Considering perishable tooling can represent up to 50% of the cost to machine a part, this reduces overall costs dramatically. Mori’s DCG machining center lineup includes a VMC with five ballscrews–one on the X axis and two each on the Y and Z axes
Controller software and pallet handling is as important as machine technology for metalcutting cells. On a system, a three-level stacker system that uses a new high-speed rail-guided vehicle to move 12 pallets.
The cell l controller software, a Windows-based system is claimed to increase machine and operator productivity by up to 90% by determining the most efficient production schedule and automating multiple tasks.
For large and/or complex components, combining five-axis capability and high-speed machining can lead to big increases in machining productivity. Shops are looking for ways to combine more operations on one machine. While turn/mill centers and multitasking machines are offering more capabilities and becoming more prevalent, the use of five-axis machining centers is also increasing. Five-axis machining centers that provide multisided machining in one setup are available in the market at more affordable prices, and many shops are getting into this technology.
The definition of high-speed machining is changing as spindle and axis speeds continue to increase. A few years ago, machining centers had top spindle speeds of 8000 rpm, feed rates of 400 ipm, and acceleration of 0.1 or 0.2 g. Today, many high-performance machining centers are available in the market with spindle speeds up to 20,000 rpm, feed rates of 1600 ipm, and acceleration of 0.5 g. A further step above this are machines with spindle speeds up to 60,000 rpm, feed rates of 3000 ipm, and acceleration of 1 g and higher.
Smart machining can improve reliability, optimize machining performance, and allow reliable unmanned operation. Examples of smart machining technology are real-time monitoring of spindle vibration in a high-speed machining process, automatic compensation for thermal drift in a machine, and communication of the operating status of a machine from the CNC to a PC or cell phone.
A case in point is the UCP 600 Vario from Mikron, a five-axis, high-speed machining center that embodies all the above trends. The machine is equipped with a 20,000-rpm spindle, rotary/tilt table for five-axis/five-side machining, laser tool measuring system, part probe, integrated table chuck for palletization, an integrated seven-position pallet changer, and vibration monitoring and thermal control modules.
I shall be discussing about other important machine tools in next entry.
- Indra
Category: Machining |
Leave a Comment