Doosan Infracore Machine Tools introduced a new vertical machining center at IMTS 2014 in September, one that combines a traveling column design with a tilting spindle head. The VCF series is capable of machining a wide range of parts — deploying up to five axes of operation simultaneously.
The VCF 850LSR is a large capacity VMC with a tilting B-axis head. This versatility made possible by the travelling column design allows for machining on multiple sides of a workpiece at once. The head can rotate 110 degrees on either side of vertical, enabling the VCF 850LSR to machine large and complex parts in a single setup, eliminating costly fixtures and downtime. With its included 500 mm (19.685 in.) rotary table, up to five sides of a part can be accessed, extending the machines capabilities.
The bed is a rigid, one-piece, fine-grain Meehanite (iron) casting with heavy ribbing to reduce vibration and deformation during heavy cutting. Extra wide spacing of the roller guideways support the saddle, regardless of the load distribution on the table. The table is fully supported by the saddle in all positions with no overhang.
Because of the traveling column design the table, and therefore the workpiece, remains locked during machining. This promotes a uniform load to the guideways, ball screws, and motors.
All axes are of a roller linear-motion guide type (rather than the more common ball bearing guide types), for higher stiffness, accuracy, and surface finish. They are both heavy-duty (X - 45 mm / 1.772 in., Y - 45 mm / 1.772 in., Z - 45 mm / 1.772 in.) and widely spaced (X - 655 mm (x2) / 25.787 in., Y - 720 mm / 28.346 in., Z - 560 mm / 22.047 in.). The roller guideways are three times more rigid, with two times more life than ball bearing guideways, and provide optimal weight and force distribution, according to the developer.
Each axis is driven by a high-precision double nut ball screw that is centered between the guideways and supported on both ends by angular contact thrust bearings. All ball screws are cooled by circulated, refrigerated oil at all critical components including the ball nut, support bearings and the motor housing. This system, coupled with a double pretension design, provides outstanding positioning repeatability with virtually no thermal growth. All axes have large diameter ball screws (X - 63 mm / 2.480 in., Y - 50 mm / 1.968 in., Z - 50 mm / 1.968 in.) that are directly connected to oversize A.C. servo drive motors without gears or belts in order to help eliminate backlash.
The X, Y, and Z axes use absolute-type linear glass scales for higher positioning accuracy that do not require referencing at start-up. The scales virtually eliminate the impact of slides and ball screw thermal expansion and backlash. This improves the ability to hold tight part tolerances with fewer offset changes.
The supplied Doosan D500 rotary table allows for machining on multiple faces of the workpiece without having to re-fixture. This allows for reduced number of setups and much higher precision of the finished component. With 4 + 1 axes of simultaneous motion, very complex shapes are able to be produced, and when coupled with the machine’s ability to rotate the spindle head (+110 deg / -110 deg), it is possible to machine 5 sides of a workpiece in a single setup.
The powerful, 12,000 rpm built-in drive spindle motor has 18.5 / 22 kW (25 / 29.5 hp) and 147.25 nm (108.60 ft-lbs) of torque. This design promotes thermal stability and keeps vibration at higher RPM to an absolute minimum. A refrigerated cooling-control system circulates cooling oil around the spindle in order to maintain a constant temperature, increasing accuracy regardless of the ambient temperature of the cutting conditions. The CAT 40 Big Plus spindle system is a true cartridge type unit supported by high precision, permanently lubricated ceramic ball bearings with a spindle acceleration / deceleration time of 0 - 12k (1.3 sec) / 12k - 0 (1.5 sec). An encoder is attached to the spindle to allow rigid tapping, further increasing productivity.
The headstock is mounted to a rigid swiveling base which is driven by a heavy duty and high precision worm gear. This design allows the spindle to present tooling to the workpiece at any angle between +110 deg to -110 deg from vertical, enabling machining on multiple sides of the workpiece at once. The B-axis is capable of 900 ft-lbs of torque during contour machining or can be locked down by means of a hydraulic piston with 1,475 ft-lbs of torque for heavy duty cutting. Oil cooling around the assembly maintains constant temperature, regardless of the cutting condition, to ensure accuracy.
Big Plus Spindle System
According to Doosan, the Big Plus spindle system (developed by Big Daishowa Ltd.) and tooling “surpasses all other spindle concepts due to simultaneous taper and flange contact between the machine spindle and tool holder as well as complete interchangeability with existing machines and tools.” Upon mounting the tool holder into the machine spindle, contact occurs prior to clamping. Due to the retention force, the taper of the tool holder expands the machine spindle in its elastic range. The tool is pulled further in until the tool flange touches the spindle face for maximum rigidity.
The 60-tool, chain-type, double-arm automatic tool changer is servo motor-driven and provides reliable exchange of tools with a tool-to-tool time of 1.5 seconds.
A dedicated, positive displacement pump delivers the coolant directly to the tool tip. The immediate advantage is more aggressive feeds, and speeds can be maintained throughout the cutting process. Also, there is no need to stop tp adjust coolant nozzles, which increases both cutting time and operator safety.
Protecting the spindle and the vital rotary union from contamination is a cyclone filter that does not require the use of bags, reducing maintenance costs and downtime. The 360-liter (95 gallon) tank stores an ample supply of coolant and is isolated from the machine bed to help prevent heat transfer.
The hand-held manual pulse generator lets each axis move in increments of x1, x10 or x100 — making fixture or part alignment fast and simple. The 10-foot cord gives full access to the machine and the magnetic back allows for one-handed operation with the MPG being conveniently held in place on the machine table or guarding.
The keyed switch enables the protection mode for both the program and offset data. Removing the key limits access to only authorized personnel. In the unprotected position the key cannot be removed and all data is available for edit.
The Fanuc 31-iB series control is equipped with a slot for a PCMCIA and USB port on the control next to the display. A PCMCIA memory card can be used to upload and download programs as well as drip feed directly from the card. Programs running from the card will take the same time to run as a program that is stored in the control memory. It is possible to search through and restart anywhere in a program as long as it contains line numbers. The USB Port does not allow you to drip feed; it is only for uploading and back up of programs & parameters.
The control is mounted on a pendant that can be positioned anywhere along the door opening via a rail, and can swivel up to 180 degrees. This allows the operator a clear view of the working area wherever the workpiece is positioned or machining is taking place.