Application Example for Machine Tools

The IVS-200 pick-up lathe with vertically-arranged spindle was specifically designed by Yamazaki Mazak for fully automated operation and to reduce non-productive time. A main characteristic of this system concept is that it allows for a quick exchange of workpieces, including supply and transport. This is the perfect job for the VarioFlow chain conveyor system from Rexroth.

The vertical pick-up lathes are ideally suited to process series parts in medium to large lots. Vertically arranged spindles with corresponding travel ranges in the direction of the X and Y axes let the workpieces be taken directly from the workpiece pallet or the conveyor system by a clamping chuck, making expensive loading and unloading equipment redundant. In addition to lower investment costs, the main features that set this system apart are a reduction in non-productive time and an increase in productivity.

The main focus during the development of the IVS-200, a brand-new vertical lathe with a self-loading system, was to optimize processing times, using a high-revolution, high-performance spindle. Additional objectives included lowering non-productive times by perfecting acceleration and delay times for both spindle and axis drives. A spindle rpm of up to 7.000 min-1 speed pick-up of 0 bis 5.000 min-1 in 1,8 seconds, and switching times of just 0.17 seconds are just a few of this machine's fantastic features. Quick motion speeds in the direction of the X-axis of 110 m/min with a pick-up time of 0.9 G all help raise the bar for workpiece handling.

The feeding method to send the workpieces into the loading section of the vertical lathe can be individually selected to fit the application. Anything is possible, from a gravity slide to a pallet transport system. Quickly feeding in workpieces has a decisive effect on non-productive time, which is why this is considered an essential process in the total system concept. Mazak therefore offers optional standardized solutions that are based on the modular VarioFlow chain conveyor system from Rexroth.

Adapted Solutions from a Modular System

Consisting of a plastic link chain guided in an aluminum profile, and with components such as curve wheels, drive modules, and stoppers, VarioFlow has just the right modules to implement fully adapted solutions, even with critical system layouts. Since it is coordinated with the modular aluminum profile system and compatible with Rexroth's other transfer systems, specific tasks can be accomplished without any special constructions using modular components. A chain with an almost completely closed surface is able to convey small parts right on the surface. Alternatively, the parts may be placed on workpiece pallets made of processed plastic plates, as done for standard workpiece conveying for the IVS-200 vertical lathe.

Working with Rexroth, the company was able to create a special system layout that has separate positions for loading and unloading material and was designed to exactly fit the machine's loading section. After a workpiece has been removed with the pick-up spindle, the empty workpiece pallet is conveyed out of the loading section, where it travels around a sharp curve and is then sent back to the loading station on a different belt. While all this is going on, a new pallet follows behind with another workpiece. Thus, an empty and full workpiece pallet is always ready to continue through the system so that there are no waiting times for pallet supply. Under ideal conditions, the VarioFlow conveyor system is able to reach workpiece exchange times of less than 5 seconds.

Standard Variants for Single and Double Machines

The vertical lathes can be set up individually, or connected as a pair or in a series, as needed. A combination of two or more lathes, depending on the number of units and the process sequence, is a common layout when workpieces have to be processed on the front and back. Mazak offers two standard versions to transport workpieces on pallets with a universal mounting flange. This mounting flange can even be adjusted to fit different parts with complex geometries.

The workpieces are fed into a machine over an L-shaped section with an integrated curve wheel drive. To connect two machines to process the front and back of a workpiece, the section from the loading station of the first machine is extended to the other side to set up a connection to a mirrored section where the back is processed. This system layout uses a connecting drive rather than a curve wheel drive. This type of drive has the advantage of higher tensile forces and automatically compensates for chain yield, which occurs after a long period of use. Both types are equipped with a drip tray system to return media.

In addition to the standard 90 mm chains and sturdy, media-resistant slide rails made of PVDF (polyvinylidenefluoride), chains with a reinforced stainless steel surface and steel slide rails are also available for use in tough environments. The necessary stoppers and limit switch brackets are also a part of the Rexroth modular transfer system. Furthermore, all of the components are compatible thanks to a proven 10 mm mounting groove. The same goes for the modular aluminum profile system, which makes it so much easier to integrate a reversing station. This station, which is made up mostly of components from Rexroth's pneumatics program, is simply docked onto the connecting section between the machines that process the workpiece on the front and back. Its task is to turn the workpieces by 180° for further processing.

Ready for Any Task

Many applications require more than just two connected machines. In these cases, VarioFlow's modularity is a decisive advantage when implementing individual conveyor sections and links. Dr. Wolfhart Kaestner, Manager of the Engineering department at Yamazaki Mazak Deutschland GmbH in Goeppingen, Germany, states, "Feeding workpieces into the automatically-operated vertical lathes often has to be changed to fit the particular operation. This is why it is so important for us to have access to an open system including standard modular solutions for individual and double machines that can solve almost any problem. VarioFlow's flexibility allows us to link machines in any sort of configuration, integrate other processes, or create connections in the production lines. We can even easily adjust the system at a later point, with workpiece storage systems or ID systems. This all means that, in the end, our customers get the highest level of flexibility."

VarioFlow conveyor systems work self-sufficiently with their own control technology based on Rexroth's CL151 controller. When equipped with additional I/O modules, it can take over all of the system's functions, including a handshake process with Mazak's dialog programming controller. From hardware to software, Bosch Rexroth AG provides a complete workpiece conveying solution for Mazak's vertical pick-up lathe.