by Kip Hanson
CNC builders bring new technology to bear in the battle for increased productivity
For those too young to remember, mechanical cams were once used to control automated machine tools. Cams gradually gave way to electronics though, and by the mid-70s, toolmakers were learning how to program, giving up their shapers and bastard cut files in favor of Teletype machines.
These crude devices turned hand-typed instructions into a series of Morse code-like holes running down the length of a 1″ wide spool of paper, one frequently long enough to traverse the length of the shop and out the shipping door. Machine controllers with all the intelligence of a vintage Pac-Man game would then interpret these holes—or their absence—as the 1s and 0s needed to communicate with any digital device. Numerical Control (NC) was born.
Answer the question
The next generation of machine controls made its debut on the manufacturing floor around the time Canadian Prime Minister Pierre Trudeau was contemplating his retirement plan, and by the late 80s, paper tape had largely gone the way of the slide rule. NC had evolved into CNC, the primary differences being onboard program storage, a CRT display and canned cycles designed to make machine programming simpler.
Like all things electronic, CNCs grew faster and more capable as the decades passed, and today’s machine controls are super-smart multitaskers that resemble those old tape machines like a smart phone compares to a rotary dialer. Modern controls boast data processing times best measured in nanoseconds, on-board program storage sufficient to handle the largest of files, and the ability to manage more simultaneous axes than players on a football pitch.
Machine builders have capitalized on this advanced control capability by adding their own proprietary software to otherwise standard controls—DMG MORI has its CELOS system, Mazak offers Matrix and Mazatrol SmoothX technology which debuted at IMTS, and Okuma has THINC-OSP. All are intended to make part programming easier, increase integration to third party systems and extend machine capabilities.
That’s not to say that the control builders themselves are idle. Julian Renz, TNC Product Specialist at CNC and motion control manufacturer Illinois-based Heidenhain Corp., says his company’s controls are designed specifically for the shop floor. “We have a large set of programming functions where all a user has to do is enter a few parameters to generate pockets, slots, hole patterns and the like.”
Conversational programming technology such as this was developed as CNCs grew more powerful, and a number of control manufacturers now offer onboard programming systems comparable to some commercial CAD/CAM packages. This makes these controls ideal for small shops that haven’t yet made the leap to CAD/CAM, and for prototype and low-volume shops that need the ability to program on the fly.
Renz admits, however, that the majority of toolpaths generated today are done so in the programming office, especially with complex part profiles and 3-D surfaces as seen in mould making. “The code needed to machine surfaces such as these would correspond to thousands of program lines. You simply can’t do that at the machine.”
More power, Captain
To program a mould cavity for the next greatest generation of a part requires powerful processing capability.
As Renz explains, the ability to smoothly drive a cutter through a high-speed toolpath composed of millions of multi-axis movements calls for a control that can look at that toolpath hundreds or even thousands of blocks in advance, calculate the correct axial motion, and then accelerate and decelerate the machine’s servomotors accordingly, thus maintaining the correct tool position while still achieving the programmed feedrate.
An example comes from Mazak’s new Mazatrol SmoothX Technology, which offers high precision machining of complex contours at high speed feedrates. (see sidebar page 78).
Renz points to additional motion control features available on some Heidenhain controls. “The TNC 640 offers advanced calculation of feed rates, or Advanced Dynamic Prediction, that smoothes out any inhomogeneous point distribution from CAM systems. The Contour Tolerance Cycle allows the operator to define acceleration/deceleration parameters according to the current job requirements, and the Tool Center Point Management (TCPM) function makes sure that the tool does not lift off the workpiece during compensating movements of linear axes during five axis machining.”
Granted, this is high-end stuff. Unless you’re machining freeform surfaces such as those used in orthopaedics and aerospace components, a machine control with this much power makes as much sense as using a semi-trailer truck to deliver a box of parts to the plater. It’s overkill. Many shops are more interested in controls that facilitate improved productivity through an open software platform, paving the way to advanced forms of systems integration. Multinational electronics and industrial conglomerate Siemens is one of these.
Ryan Legg, product manager for Sinumerik CNC systems at Siemens’ Chicago office, explains that the “manufacturing IT concept” has recently begun to emerge as a driving factor in control buying decisions. “Companies are becoming increasingly interested in analysis of their production,” Legg says. “What’s their throughput, for example, and how much downtime do they have? More importantly, what can be done to improve these things? This trend is still in its infancy, but we’re definitely seeing increased interest in the ability to understand what’s happening on the shop floor.”
Opening the lines of communication
To support this initiative, Siemens offers its Sinumerik Integrate software suite, a manufacturing IT system that integrates with the company’s Sinumerik CNCs. According to Legg, Sinumerik Integrate enables shop floor analysis by utilizing the control’s open architecture to gather statistics on machine performance and production information, giving shops the tools needed to manage scheduling, personnel, material movements, and overall equipment effectiveness (OEE).
“We’re seeing shops make great improvements on the shop floor with these tools.”
Of course, functionality such as this requires that disparate equipment and software can communicate easily. Siemens has accomplished this through the help of Cincinnati-based Techsolve, which recently developed an interface for Siemens controls using the MTConnect protocol. This allows customers, who have adapted MTConnect to easily deploy Siemens Sinumerik CNCs into their factory.
“There’s been a large uptick in robotics lately,” Legg says. “One of the things we’ve worked on with robot manufacturers is making the interface very transparent. The integration of the robot controller to the Siemens Sinumerik has reached the point where you can actually operate both pieces of equipment from the same interface—historically, they’ve been two very different interfaces in terms of operation. This makes it easier for those customers unfamiliar with robots, and garners greater operator acceptance when a shop is trying to make the move towards automated parts handling. It’s a big step forward.” SMT
Kip Hanson is a contributing editor. [email protected]