CNC Programming

The machine tool world is working with a 50-year-old programming paradigm (based in G code) that needs an update to take advantage of interoperability capabilities to allow easier data exchange with other software, rather than re-entering or recreating information. Plus, there's no standard means to quickly optimize tool usage via design parameters that decide which machine(s) can run the job m...

By Mark T. Hoske June 1, 2006


Computer numerical control

Feature preservation


Standard translation

Sidebars: Digital data: more places, faster Take the next step in CNC technologies

The machine tool world is working with a 50-year-old programming paradigm (based in G code) that needs an update to take advantage of interoperability capabilities to allow easier data exchange with other software, rather than re-entering or recreating information. Plus, there’s no standard means to quickly optimize tool usage via design parameters that decide which machine(s) can run the job most efficiently.

These are among laments of major end-users involved in the STEP-NC standardization effort. Perhaps not surprisingly, CNC manufacturers and software providers are listening to customers, and trying to provide some of those functions—even if they don’t use the emerging standard, or don’t use it yet.

Not embracing the standard defeats the purpose, some suggest. Such manufacturer foot-dragging prevents the machine tool world from becoming as interoperable and efficient as it should be.

Standards efforts continue in the OMAC (open, modular architecture controls) Machine Tool Working Group. STEP-NC is a subgroup working to understand and assess ISO 10303 in the context of the OMAC users group, now part of ISA. (Another subgroup, HMI-API, is defining a common HMI API for all CNC devices.) End-users and industry vendors have been demonstrating ways to apply the standard to show benefits of digital data transfer/preservation through various CNC design and machining processes.

More demonstrations

At a June 26-30 meeting for ISO TC184/Sc4 Wg3-T24 STEP-Manufacturing in Toulouse, France, users and vendors are expected to demonstrate a live STEP-NC machining of parts designed by Airbus and Boeing. Vendors involved in the meeting include Siemens, Fanuc, Fidia, Okuma, Step Tools, and LSC Co. (In May, another STEP-NC demonstration was given in Busan, South Korea.)

About 10 years ago, ISO STEP released a data exchange protocol for CAD called AP-203, OMAC explains; then, moving 3-D data between design systems was difficult and sometimes impossible; AP-203 enabled better information exchange. Similarly, this OMAC group is working on a protocol for exchanging data between CAM and CNC systems called AP-238 or STEP-NC.

‘With STEP-NC, CAM and CNC systems can exchange 3-D geometry, 3-D feature, 3-D tolerance, and 3-D process information, and, as a consequence, CNC machining jobs are going be easier to program, and CNC systems are going to be more intelligent and safer to use,’ says OMAC, in a statement describing the effort.

Data exchange protocols being developed by the STEP-Manufacturing team include:

AP-219 CMM Inspection data;

AP-223 Casting data;

AP-224 Manufacturing feature data;

AP-229 Forging data;

AP-238 CNC data;

AP-240 Process Planning data;

ISO 13399 Cutting Tool Catalog data; and

ISO 14649 CNC Operations.

Why it will help

David Odendahl, Boeing facilities equipment engineer, and Sid Venkatesh, chairman of the OMAC Machine Tool Working Group (and also with Boeing), explain that today CNC machines receive data defining axis movements required to manufacture a part. This is called machine control data (MCD), a very low level of instruction. Traditionally, CNC machines don’t have access to higher-level information about execution-related tasks or the part, they say. Because of lack of information portability, much higher-level intelligence is trapped in CAD and CAM systems.

STEP-NC (using an AP-238 file) aims to streamline data flow from computer-aided manufacturing (CAM) software to computer numerical controls programming, preserving and simplifying information. It eases selection of the machine that will most efficiently run a job, say those involved.

Also, unique data must be generated for each machine control combination on which the part is to be run. And the machine receives no information to help it adapt to real-time changes in machining dynamics and tool alignment. Prior standards are weak, with data format inconsistencies, Odendahl and Venkatesh say.

A better scenario, suggests Boeing and others involved, would be if the CNC received cutter movement data, instead of axis movement data. Sophisticated CNCs can convert cutter movement data to axis movement data. High-level information about the part features, materials, cutters, and dimensional tolerances also can be sent to the CNC. If a data standard, such as AP-238 (STEP-NC) is used, then cutter motion data are ‘machine neutral’ and can be used without vendor-specific translations for machines with other geometries. AP-238 includes part features, fixtures, tools, toolpaths, and geometry, with emphasis on transfer of process information, making implementation easier. The committee expects to phase-in part information as adoption and technology allow.

Instruction portability

Among multiple committee demonstrations has been machining and portability of instructions for a five-axis aerospace part using an AP-238 translation. Catia CL file size was 2,077 KB; AP-238 Part 21 file size: 2,305 KB; NC file size: 560-1,304 KB; total processing time: 20 seconds, with a 1 GHz Intel Pentium processor.

Among multiple CNC suppliers involved is GE Fanuc. Bill Griffith, GE Infrastructure, says GE Fanuc fully supports the efforts of STEP-NC, has attended most industry meetings, and has demonstrated STEP-NC running on GE Fanuc Open System product at trade shows and industry events. GE Fanuc works with a third-party software integrator for customers specifying STEP-NC using the GE Fanuc Open System CNC products.

Other industry providers not directly involved, such as MDSI, are watching the efforts; ‘STEP-NC is a consideration in our future software/hardware development plans,’ says Michael Tarr, MDSI director of global sales.

Greater investments

Greater efficiencies could lengthen the stride for productivity gains, since the industry is expected to spend more in 2006 than in 2005.

Worldwide NC software and related services market grew by 6.5% in 2005 to reach a level of $1.25 billion, according to CIMdata estimates, based on end-user payments; in 2006, these payments will further increase by 7.2% to $1.34 billion.

Growth rates are the highest since 1999 when the market grew by 8%, CIMdata says, talking about ‘Version 15 of the CIMdata NC Software and Related Services Market Assessment Report.’ There was no growth from 2000 through 2004 when the NC software market was in a recession, the firm says. Since then, the firm says:

Market has shown steady growth as global economies improved;

There has been worldwide growth in manufacturing output;

Greater emphasis is being placed on efficient operation of machine tools as manufacturing firms must enhance their competitive position; and

Overall PLM (product lifecycle management) market (CAM is a component), has shown strong growth.

CAM software purchases are directly related to all of these factors, CIMdata says.

‘Although software to control machine tools to cut parts is a relatively mature market, it has been active and exciting in the past couple of years,’ says Alan Christman, CIMdata chairman and primary author of the report.

‘Some software vendors have had revenue growth of as much as 40% per year, acquisitions are driving market consolidation, new manufacturing areas such as China are emerging, corporations are placing greater emphasis on streamlining manufacturing operations, and the underlying CAM software technology continues to evolve,’ Christman says.

Related reading For more on STEP-NC from Control Engineering , please see:

Standards demo: 6 software packages operate 3 CMM;

OMAC standards yield operational savings; and

Standard enables data flow between CNC, CAD/CAM. Also, type STEP-NC or CNC in the search box atop

Digital data: more places, faster

Making metal-forming processes more efficient by carrying information from design through manufacturing is part of a larger trend of ‘improving performance through digital manufacturing,’ said Dick Slansky, senior analyst, ARC Advisory Group, at an ARC meeting earlier this year.

The consulting firm, and its collaborative manufacturing model, expect that as digital manufacturing merges with automation and controls, it will produce a more integrated tool set for design, manufacturing processes

robotics, and production lines. Slansky says results include validation via simulation before commissioning, integrated product design and production processes, and process optimization modeling using virtual designs for higher efficiency production lines, workcells, and machines.

There’s a need to harness manufacturing information to improve corporate performance, said Greg Gorbach, another ARC Advisory Group VP. He talked about data velocity, the speed at which users become aware or react when manufacturing data changes. There’s a need to increase the speed with greater data velocity (intelligence) and automation (business processes), Gorbach suggests.

Slansky adds, ‘Digital manufacturing is process-centric, not just data-centric. It merges the virtual world with the real world; real operations with intellectual property; simulation and automation.’ It means validating control design, generating code, and transferring it to real operations with reduced cost and development.

Among companies moving to digital manufacturing are Boeing, Daimler-Chrysler, Ford, General Motors, Lockheed-Martin, Nissan, and Toyota.

Take the next step in CNC technologies

Next-generation CNC technologies add efficiencies. They’re seen as more ‘open’ or more readily able to transfer information and integrate with other tools, even if not from the same vendor. Tools incorporating STEP-NC technologies may offer additional benefits, according to those involved.

Fidia C20 numerical control takes full advantage of the potential offered by combining the performance of Intel Pentium 4 and Motorola RISC Power PC processors. The control is designed to manage the most sophisticated high-speed 5-axis applications with RTCP. It uses the Microsoft Windows XP Professional operating system in multitasking mode and is a powerful tool in the cost-effective use of the machine tool. It has 17-in. TFT video and imports CAD mathematics directly in IGES, DXF, and DWG formats thanks to the HI-MILL 3D CAM and Isograph 21/2D CAD/CAM. This improves and simplifies tool-path management, company says.

NFR Partners Inc. released the first version of editNC in 1993. Since then, five major revisions, several OEM versions, and dozens of minor revisions have been produced. EditNC, a CNC program editor designed to complement CAD/CAM systems, also provides powerful capabilities for manual G-code programming. Release 8.5.0 is said to offer improved user interfaces, an enhanced analysis function, better performance, and other additions. From its first release, NFR editNC has been designed to work in conjunction with CAD/CAM systems and the enormous files they can generate. Files well over 60 MB can be edited. Superior performance is maintained by using highly efficient techniques throughout. For example, many functions use completely different processing techniques depending on the size of the file.

Open CNC, at Fanuc and GE Fanuc, refers to an optimized combination of CNC and PC hardware and software via a serial high-speed interface, which allows transfer of large volumes of data. Series 30i/31i/32i CNC have two open versions: 300i/310i/320i are open, high-performance CNCs under Microsoft Windows 2000/XP. Series 300is/310is/320is use industry-compatible Windows CE .Net, which does not require a hard disk. Both support the fast protocol FOCAS2 (Fanuc Open CNC API Specification Version 2) for exchanging data between CNC and PC. An open CNC enables use of individual applications on machines that have to be adapted by machine tool manufacturers to special customer requirements, the company says.

Okuma ADMAC Parts with 3-D Virtual Monitor Function offers advanced program verification and crash detection through empirical confirmation of the manufacturing process as it will occur on the machine. It can qualify tool lengths and holder types, check and confirm synchronization codes during simultaneous processes, and catch any errors before they create scrap. Okuma creates every 3-D model, allowing the user to see the part before it’s made. Many Okuma machines have cutting demos to view at

Siemens Sinumerik 840Di sl is said to be a fully PC-integrated numerical control system for up to 20 axes, interworking with the Sinamics S120 drive system. The control has open hardware and software functions and is suited for users requiring distributed automation systems with regard to PLC I/Os and drives and/or prefer a fully PC-integrated control system. It is used for applications performed on machine tools, special-purpose machines, robot systems as well as retrofit machines. It has HMI and PLC openness, flexible communication via USB and Ethernet interfaces and via isochronous Profibus flexible solutions through open hardware and software functions using standard applications on a rugged industrial PC.

Step Tools Inc. says its ST-Machine product simplifies proveout, helps load balancing, reduces costs for quality control, and improves accuracy of NC machining, while deploying STEP-NC AP-238 machine-independent tool paths for manufacturing processes. STEP-NC goes to/from CAM with DLLs for adding AP-238 support to GibbsCAM, MasterCAM, and existing APT-CL based processes. It also goes on the CNC with loader, monitor, and interpreter components for Fanuc and Siemens controls. It has data checkers and simulators for verification and examination.

Many more…. Please search on CNC software for other suppliers and products in the Control Engineering online buyer’s guide at

Author Bio: Mark Hoske has been Control Engineering editor/content manager since 1994 and in a leadership role since 1999, covering all major areas: control systems, networking and information systems, control equipment and energy, and system integration, everything that comprises or facilitates the control loop. He has been writing about technology since 1987, writing professionally since 1982, and has a Bachelor of Science in Journalism degree from UW-Madison.