Start with the understanding that maximizing the benefits of multi-tasking machines requires a computer-aided manufacturing (CAM) approach that takes full advantage of the machine tool's capabilities.
Keep in mind that operations will vary from basic turning operations to complex 5-axis simultaneous milling, says mill/turn manager Olivier Thenoz of CAM specialist DP Technology Corp., Camarillo, Calif. His advice: Be as serious about the CAM software as you are with the selection of the multi-tasking equipment.
In DP's ESPRIT software, the operation manager handles any kind of milling (up to 5-axis simultaneously) and turning operations (including pinch strategies) in the same time and with several heads/turrets. He says the CAM system must also offer support for all the optional components and the special devices of the machines. Examples: steady rests, tall stocks, part catchers, devices for the transfer of the part, special milling heads, boring devices and special tool holders.
"One of our customers cuts crankshafts with two opposite milling tools that cut simultaneously while both spindles are holding the part," he says (refer to the graphic). "The programming requires a powerful CAM system, but the time saved with this process is important."
Thenoz emphasizes his basic premise: "Multi-tasking machines are very complex and challenging to program manually." He says a good CAM system is the best way for mastering "the beast" and therefore the programmer can use the machine to its full potential. "We're very successful programming high-end multi-tasking machines."
The multi-tasking world is rapidly evolving, Thenoz points out. "From the first single spindle, single turret mill-turn machines, many things have changed." He says machine tool manufacturers are offering multi-head and multi-spindle configurations. There are many variations of B-axis kinematics: B-axis head, index turret mounted on a B-axis tilting spindle or a B-axis on a Swiss-type lathe.
As a producer of multi-axis machining software, DP Technologies fully utilizes and supports the capabilities of the latest machine tool technology. "In order to support the latest technologies, we're working in partnership with tooling companies," Thenoz notes.
|ESPRIT simulation of a multi-tasking machine cutting a crankshaft with two tools cutting simultaneously.|
CAM software for multi-tasking -- such as DP's ESPRIT software -- bears conceptual similarities with software for conventional machines, notes Thenoz. "For example, someone who knows how to program a drilling operation for a vertical milling machine in ESPRIT is able to program the same operation for high-end multi-tasking machines. Regardless of the machine, individual operating definition is very similar, he adds. "The difference is in much higher requirements for process management, simulation and NC code for multi-tasking machines."
He says the programmer needs to balance the operations on the various turrets and spindles in order to reduce dead time and maximize productivity. "Simulation has to closely match the complex kinematics of the machine in order to prevent any collision. Then the NC program has to accurately reflect the calculated tool path."
Thenoz describes simulation and post-processors as two critical features for multi-tasking. "Simulation has to be accurate with full collision detection and a good representation of the machine and the cutting environment -- tools, fixtures, holders. Previously, a lot of time was required to verify the NC program."
ESPRIT 2008 (announced last August) introduces a new continuous B-axis cycle that reduces the number of cutting tools required, the number of tool changes and results in a smooth, stepless surface, adds Thenoz. He says the new B-axis contouring cycle is designed specifically to achieve higher performance levels from multi-tasking machines by fully utilizing the rotational capabilities of the B-axis. While traditional lathe contouring cycles rotate the B-axis once at the start of the cut, the ESPRIT B-axis contouring cycle allows for dynamic, continuous rotation throughout the cut.
The tool follows inner and outer contours without stopping for tool changes, emphasizes Thenoz. That allows a single tool to reach areas that would otherwise be inaccessible due to the tool's geometry. Using the new B-axis finishing cycle to reduce both the number of cutting tools and the required tool changes ultimately results in a significant savings in time and money, says Thenoz. "If you're using one tool instead of three you could save as much as 20 seconds," says Thenoz. "If you multiply that by the number of parts you're producing, the results can be very interesting." That's in addition to the smooth, stepless surface.