Edited by Charles Bates, senior editor
Mechanically, most machine tools can run significantly faster than shops operate them. The reason is that, in most cases, original controllers are unable to process data fast enough to push machines to their design limits.
A 20-year-old vertical machining center, for example, may be able to move at speeds of 300 ipm to 400 ipm. But if its CNC is unable to process data fast enough or read in large amounts of data at high speeds, the machine will not accurately run anywhere near those top-end speeds.
This is why entrepreneur Carlo Miceli developed the MTI constant velocity controller (CVC). The system provides more processing power, smoother machine movement, and an ability to run CAM software directly on the machine’s controller terminal. But most importantly, it pushes actual machine times closer to programmed time.
“Programmed machine feeds are reached only under near-perfect conditions and then for only a few seconds at a time,” Miceli said. “There are a lot of reasons for this, but what is important is that the average machining speed is only 30 percent to 40 percent of what the programmer specifies. CVC systems typically attain average speeds of 80 percent to 90 percent of what is programmed, or two to three times faster.”
Miceli’s company Miceli Technologies Inc. builds several major advancements into its CVC controller. These include up to eight interpolated axes and a program execution speed of 50,000 blocks per second – versus the 2,000 to 3,000-blocks-per-second speeds of even the best CNC controllers.
The CVC controller packs 80 highaccuracy smart buffers for look-ahead algorithms as opposed to the CNC norm of a few dozen lines of code – in effect, just one buffer. There are 4 million maximum (servomotor) encoder counts per second, a measure of maximized closedloop feedback, and the system achieves 15-digit motion control accuracy and a minimum resolution below one micron.
Another significant advantage of the CVC controller is that it retrofits to older machine tools to save costs for shops such as Fidelity Machine & Mould Solutions in Calgary, Alberta.
The shop is a major source for injection molds, and about 50 percent of its work is general and CNC machining. And as with most other shops, sound creative business decisions spring from insufficient cash at Fidelity Machine & Mould Solutions.
Instead of buying new, the shop purchased a low-cost used 1997 Fadal VMC15 vertical machining center retrofitted with the CVC by Miceli Technologies. The system gives the shop unlimited processing and communicating capabilities, and it can enter any size program without having to worry about taxing the machine or not feeding it with data fast enough.
“Retrofitting a well-cared-for, used mid-sized VMC costs about $120,000. That’s about one-sixth of the $750,000 installed price of an equivalent new machine – a price way beyond our budget,” Jeff Litster, one of the co-owners of Fidelity Machine & Mould Solutions, said. “We got a lower-cost machine that will perform better than high-end new machine tools.”
While the hundreds-of-inches-a-minute speeds offered by CVC machining with look-ahead capabilities are beneficial, high accuracy is just as important, if not more so, to Fidelity Machine & Mould Solutions.
Most of the shop’s jobs are small. For example, the injection-mold core and cavity for an over-mold are about the size of a paperback novel, and this type of work is a mainstay at the shop, with three or four such jobs per week.
According to Litster, these small blocks – often measuring 6 in. by 8 in. by 3 in. – actually present more of a problem than most machining because there is so little working area inside the core and cavity. Small cutters, tight radii, and difficult geometries also add to the challenge. The shop uses ball-nosed cutters as small as 0.015 in. in diameter.
“This is machining with almost no clearance for the cutter, so extremely precise control of all cutter movement is essential,” pointed out Litster.
The shop also makes tooling for several other types of molds besides over-molds, and surface finishes are always critical. Any imperfection in the molding surface will be picked up in the finished product, so the smoothest possible machine motion is needed when making finishing passes.
The controller lets Fidelity Machine & Mould Solutions program cutter paths with tighter tolerances, which provides more control over the cutter and helps generate better surface finishes. When using other machines without the CVC controller, the shop has to open up the tolerances and slow them down so much to keep them from violating the surfaces.
In addition, CVC reduces cut times by as much as one-third, and some onehour programs now run within 40 minutes, with better surface finishes and longer cutter life.
With the ability to install CAM software on the same CPU and interface as the controller, the shop lessens the amount of travel time between work center and machines, but also eliminates any reason or excuse to run a program that is less than perfect. This not only boosts efficiency, it helps operators understand the cutting tool and program limitations better. Operators program closer to target parameters the first time.
The next big decision at Fidelity Machine & Mould Solutions is when to retrofit its two other existing vertical machining centers, one of which is a vertical ram-type machine.
“The success of the CVC on the Fadal convinced us,” Litster confirmed. “With the Meceli Technologies controller, we have something unique to the Calgary market. We definitely plan to use its capabilities in our marketing.”
Information for this article supplied by Miceli Technologies Inc. (www.miceli-technologies.com)