All Machine Tools Are Not Created Equal

By Colleen DeJong

There are almost as many machine tools as there are potential and actual users combined. Each builder has its own niche (or niches) and adds its own "flair" to the machine, making it that much different from the competition. To try and name every builder and every machine here would be impossible, yet a valiant attempt will be made to break everything down and let you know what to expect from a range of machine tools, from verticals to horizontals to universals.

 

Trend: Controls

While every builder goes to great lengths to make its machines unique, there are a couple of things happening out there that can be labeled "trends." The first of which is the evolution of controls from tape reader to full-out PC. Most, if not all, machine tool makers feature controls that are dubbed "PC-based" or "PC-compatible." A recent survey of those involved in control technology see industrial PCs completely overtaking the control market in the next few years. In fact, many companies have already begun creating "open architecture" controls, meaning that the user can configure the controls to exactly their specifications. Others have gone one step further, putting all capabilities into software, so that nearly any hardware will do, because the control is actually the software. Either way, users had better be pretty computer savvy, and had better be prepared to become more so.

Another trend seeping into the realm of controls is Windows NT. Most hardware and software providers are banking on the fact that Bill Gates will take over the machine control market also, and are converting to a Windows NT environment. Short of this, they may offer Windows NT as an option, and let you decide.

Combining these two technology directions leads to an exciting possibility for the future: networkability. While many controls are plugged into user local area networks (LANs), few have yet to be reliably brought into the realm of the World Wide Web. Once the issues of reliability and security are cleared up, Tier 1 and Tier 2 suppliers will further tighten up the supply chain, transferring CAD/CAM data from the design department at one company directly to a machine at another.

 

Some Specifics

Out of all of the newer control technologies out right now, the slickest looking features are coming from combining mega-capable hardware with creative software solutions that help boost machine capabilities. For example, the BostoMatic BDC 3200X CNC from Boston Digital Corp. (Milford, MA) uses software algorithms, 32-bit VME bus architecture, and multiple microprocessors to enable the processing of 1,100 five-axis blocks per second. While achieving such high speeds is something else, the control gets slicker when you consider that no preprocessing is required, even on the most data-intensive part programs. Contour optimization software and user-programmable servo parameters round out the 3200X's features.

Creative Technology Corp.'s (Arlington Heights, IL) Creative Evolution is a PC-based control that Defiance Machine & Tool Co., Inc. (Maryland Heights, MO) counts on to give its small machining centers a few extra punches. A look-ahead feature scans for corners, and automatically adjusts speed and feedrate to prevent gouging and provide rounder corners. The system also provides automatic chamfering, canned milling and Z-axis cycles, mirror-image programming, and an on-screen text editor that includes global program modification.

 

Trends: Spindles

There's something fishy going on with spindles. Everyone is talking about self-balancing, high-speed spindles, but no one we've found will talk specifically about them. Several machine tool companies are "looking into" the development of these units, but mum's the word until they're ready to launch the product. Of course, there are some self-balancing spindles out there already, but they are incredibly expensive, and are really still in the R&D stage of things. It should be interesting to see what develops in the next few months.

 

Some Specifics

In the mean time, there are some tangible advances being made in regard to spindle technology. One that stands out is the tilting head configuration at Mandelli (Rockford, IL). While tilting head spindles add a fifth axis, they tend to be too delicate to stave off vibration and other accuracy inhibitors. Taking that into account, the company's engineers have developed a high-torque spindle that can handle heavy-duty cutting applications, but without sacrificing accuracy. Combining that with the standard Sinumerik 840D control from Siemens, this system can really cook through some mold and die applications.

 

Trends: Toolchangers

As with the rest of the machine, toolchangers have gotten more sophisticated. Some systems are capable of tool condition monitoring, reporting data back to the control; and many ATCs feature a load cell that monitors whether the tool is present, and transfers tool length data to the control as the tool is mounted to the spindle. Manufacturing cells and flexible systems now use one toolchanging system for several machines, saving space, time, and money. A robotic system patched into the machine's control moves tools from machine to machine as needed.

 

Some Specifics

In the mean time, there are some tangible advances being made in regard to spindle technology. One that stands out is the tilting head configuration at Mandelli (Rockford, IL). While tilting head spindles add a fifth axis, they tend to be too delicate to stave off vibration and other accuracy inhibitors. Taking that into account, the company's engineers have developed a high-torque spindle that can handle heavy-duty cutting applications, but without sacrificing accuracy. Combining that with the standard Sinumerik 840D control from Siemens, this system can really cook through some mold and die applications.

 

Trends: Toolchangers

As with the rest of the machine, toolchangers have gotten more sophisticated. Some systems are capable of tool condition monitoring, reporting data back to the control; and many ATCs feature a load cell that monitors whether the tool is present, and transfers tool length data to the control as the tool is mounted to the spindle. Manufacturing cells and flexible systems now use one toolchanging system for several machines, saving space, time, and money. A robotic system patched into the machine's control moves tools from machine to machine as needed.

 

Some Specifics

Changeover times range from 10 seconds in cells and systems, to 1.5 seconds in some of the smaller horizontal machines. Capacity ranges from 12 tools to hundreds. Shank type depends on the spindle. A system from Mikron Corp. (Monroe, CT) uses rotary magazines with 12 positions each. This lets users set up tool sets for specific jobs, and switching from job to job only means lifting out one magazine and replacing it with another. The system is expandable up to 40 positions.

 

Trends: Feed & Speed Rates

With most vertical machines, the magic number seems to be 787 ipm rapid feeds in the Z-axis and around 1,100 ipm in the X and Y axes when you're talking vertical machining. Horizontals are capable of faster speeds, hitting around 1,100 to 1,400 ipm.

 

Some Specifics

Going fast isn't just a function of the spindle and the cutting tool anymore. Machine tool builders are using software to get things moving faster. Makino (Mason, OH), for example, has a software function called "rapid traverse bypass." It determines where the spindle needs to be, allowing rounded corners on rapid paths to get it there. Enshu U.S.A. Corp. (Elk Grove Village, IL) uses a programming algorithm to provide fast, synchronized tapping with forward control. According to Enshu, the algorithm works even for extremely small diameters.

 

Trends: Work Changing

To speed up automated pallet changeover, most companies are incorporating shuttle control into the programming of the machining system's control. Here again, the configuration of the changer is going to be up to the user.

 

Some Specifics

One of the more unique (and quick) workpiece changeover systems comes from Chiron America, Inc. (Charlotte, NC). Its flexible transfer lines employ a rail-guided robot moving from station to station, and back to a load/unload station. Moving at 8,000 ipm, the robot zips from machine to machine, and changes parts in around 10 seconds. An optional part magazine allows unattended operation for long periods of time.

 

Trends: Construction

Ribbed, cast iron, Meehanite, even concrete. The base material and construction of machining centers are both common and different. Not to say that machine tool builders have lost their creativity in this regard. Quite the contrary. Builders are left with the dubious task of making machines that have as large a work envelope as possible while maintaining rigidity, while damping vibration, while not taking up too much room. You get the picture.

 

Some Specifics

Looking again at Mikron Corp., its machines feature a cast structure in a portal design. Two portal supports are fixed on the base, and the transverse beam accommodates the cross slide. The Z-axis runs on top of this. According to the company, the symmetry of the design naturally minimizes vibration.

Clearly, the machine tool industry is extremely competitive, and builders work very hard to stay one innovation ahead of its competition. If they all stay on the track they're on, users will be machining parts in France from their living rooms in Ohio before we know it.