CNC Programming
Importing machining directions from CAD programs and exporting commands to CNC hardware is one way to save time and effort in next-generation tools.
Mark T. Hoske -- Control Engineering, 6/1/2006
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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:
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AP-219 CMM Inspection data;
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AP-223 Casting data;
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AP-224 Manufacturing feature data;
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AP-229 Forging data;
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AP-238 CNC data;
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AP-240 Process Planning data;
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ISO 13399 Cutting Tool Catalog data; and
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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.
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| 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:
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Market has shown steady growth as global economies improved;
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There has been worldwide growth in manufacturing output;
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Greater emphasis is being placed on efficient operation of machine tools as manufacturing firms must enhance their competitive position; and
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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:
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Standard enables data flow between CNC, CAD/CAM. Also, type STEP-NC or CNC in the search box atop www.controleng.com.
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