It used to be that CNCs fed basic motion programs into a machining center with the end effect of the production of a (mostly) finished part. And that was basically it. The sophisticated palletized systems and PC-based controls that can perform machine diagnostics, tool management, integrated automation control and power monitoring, among other things, were sci-fi-type things that were only being performed in a secluded basement at MIT.
However, the evolution of both mechanical and electronic componentry has prompted more synergistic function that gives users greater flexibility, accuracy, speed, and productivity.
The quick and ongoing evolution of electronic componentry has done a lot to advance machining center flexibility. For one thing, microchips are smaller and capable of holding a lot of information.
Things like complicated motion control algorithms no longer need to be stored in big boxes that sit like sentries beside the machine. They are now stored within the confines of the ever more sophisticated CNC control. Also stored in the CNC are handy little features like look-ahead programming, which enables the software to actually take into account the next few moves a tool has to make. Automatically slowing down to take corners smoothly or hog out large chunks of material and speeding up when movement is less complicated. This reduces machine time by letting the machine run at the optimal feed rate possible instead of the lowest speed possible to accommodate the more complex moves. It also prolongs both cutting tool life and machine tool life since there's less jarring.
And not only are the controls able to hold more information, but they are also able to process more. Block processing speed is basically the speed at which a control can digest information and set the desired chain of events into motion (i.e., make the machine move). It used to be that block processing speed moved as fast as the early controls could read the paper tape programs, but today's speeds can hit 64K per second (although 32K per second is the speed most advertised). This lets users program and execute complex parts more quickly. Switching over to another part program is also faster, since operators don't have to wait as long for the CNC to process new part programs.
Going hand-in-hand with this is more sophisticated control and computer aided machining (CAM) software. Things like making on-the-fly adjustments to CAM programs to accommodate one-off or short-run productions can be done much more easily. Such accommodating CAM software does two things. First, it capitalizes on the operator's knowledge of the machine/cell running the part. "Good software tools let people combine automation with their own knowledge," says CNC Software's (Tolland, CT) Ben Mund. In other words, software programmers are setting up the systems to take advantage of what the operators know.
On the same token, CAM software can also accommodate the less experienced operator, using a sophisticated GUI to walk the user through machining and/or troubleshooting applications.
Mechanically speaking, perhaps the biggest technological enhancement comes in the form of modularity. A flexible manufacturing system no longer has to be a special machine built for a specific job. Instead, manufacturers are taking more of a "plug-and-play" approach. The Palletech manufacturing cell line from Mazak Corp. (Florence, KY) is engineered around this principle. The line consists of several horizontal and vertical machining centers that are all designed similarly. Users start with as simple or complex a system as they want. Machines can be easily integrated into and out of the Palletech cell they essentially create based upon their needs. The same can be said of the cell's pallet system, which can be as simple as a two-pallet changer, or as sophisticated as a computerized conveyor system capable of handling 100 pallets and 4 loading stations. As needs change, machines and conveyors can be added, subtracted, or moved.
To be "cellable," machine tool designers have to keep their creations fairly compact in order to fit them into a finite amount of space. With this in mind, Okuma America Corp. (Charlotte, NC) engineered its CTV line of vertical machining centers with a fixed table and moving X, Y, and Z axes. The first concern that comes to mind with a design like this is the rigidity and robustness of the moving axes. To incorporate these two characteristics into the machine, its bed and columns are all one piece, with the axes' components supported by the integral columns.
Also adding to the workspace are newer spindle designs. The 40-taper version uses an integral spindle, where the motor and spindle are combined. The 30-taper machine uses a directly coupled motor to save space without sacrificing efficiency.
When electronic innovations are mated with machine functions, some pretty interesting productivity enhancements take place. For example, at Mazak flexible manufacturing systems are equipped with an automatic toolchanger (ATC). No big deal, but each tool in the magazine is equipped with a read/write chip that tracks what machine the tool was put into, when the tool was put in the magazine, and when it came off. Tool crib managers use that information to better estimate how much wear there is on the tool and how much maintenance needs to be done (and what kind). Those of the ultra high-tech set can even opt for a robotic unit to take tools to and from a central tooling area to the machine's magazine.
At Mitsubishi Machine Tool USA, Inc. (Itasca, IL) mechanics and electronics come together on its M-H4B horizontal machine with what it calls a "learning" ATC. Tooling can be loaded into the magazine any which way, and the ATC will rearrange the tools as the machine goes through first-piece machining, putting them in the order that will be most efficient. The objective is to enhance productivity in the long run, especially for those machining a few different parts during the course of the day, since the machine will automatically adjust itself for each part.
The union of the machine control and automation control, also a result of greater computer power, lets users changeover part programs along with robotic and sequential automation programs all in one shot. This makes changeover a heck of a lot easier than having to write then upload CAM programs, and motion control programs for conveyors, robots, and pallet changers. Not to mention having to test out everything to make sure it's all actually programmed correctly. Some CAD/CAM software vendors have gotten so bold as to include the automatic generation of motion control programming as a program goes through the verification process.
Future synergies between mechanics and electronics may include things like a sort of machine tool global placement system (GPS) that reads a tool's location and feeds it back to the control to make adjustments, thus improving accuracy and reducing scrap. Integrated computer diagnostics and automated repair is another possibility that would not only let machines evaluate themselves, so to speak, but also initiate making repairs through some sort of robotic system.
If space and speed are key concerns, the FZ-08 Series of vertical machining centers from Chiron America (Charlotte, NC) may be the ticket.
As for space: the machine has a 1-m footprint. As for speed: the 5-hp spindle cranks up to 8,500 rpm in 0.4 seconds. Need something faster? There are optional 15,000- and 27,000-rpm spindles (which reach top end rotations in 0.6 and 2 seconds, respectively). The standard toolchanger, which handles 12 HSK 32 tools, can make a swap in 0.5 seconds and go chip-to-chip in just 1.5 seconds.
As for space: the machine has a 1-m footprint.
As for speed: the 5-hp spindle cranks up to 8,500 rpm in 0.4 seconds. Need something faster? There are optional 15,000- and 27,000-rpm spindles (which reach top end rotations in 0.6 and 2 seconds, respectively).
The standard toolchanger, which handles 12 HSK 32 tools, can make a swap in 0.5 seconds and go chip-to-chip in just 1.5 seconds.
There are two models: the FZ-08S, with a traveling column, and the FZ-08W, with an integral workpiece changer. The axis travels are 11.7 × 9.8 × 9.8 in., X, Y, Z.
A "fully loaded" version of this Palletech manufacturing cell from Mazak Corp. can include up to eight machining centers and loading stations and can handle 100 pallets. It can also be integrated into a factory-wide computer system.
|stand-alone or place in a cell|
The FA 800 horizontal machining center from Toyoda Machinery USA (Arlington Heights, IL) can be used as a stand-alone machine. But the unit, which features a capable 61-ft3 work envelope and a standard 6,000-rpm 40-hp integral direct-drive motorized spindle that handles 50-taper tools, is designed so that fitting it into a cell or system is comparatively simple. Importantly, the machine is precise, providing a full length standard positioning accuracy of ±0.00012 in. and a repeatability of ±0.00006 in.