Paris, France- "Will the program run collision free?" "How do the machine components interact?" "How long will the part take to machine?" "Is the tool set-up correct?"
Checking an NC tool path can give valuable information about cutting a part based on cutter location data. But it does not assure that the tape image sent to the machine is correct. Because of this limitation, answers to the above questions have historically required a trial run on the actual machine-often with expensive consequences.
New simulation software, developed by SILMA Inc., gives NC programmers the tools they need to verify post-processed machine code data before running the real equipment. With Soft Machines(R), errors in the post processor show up as errors in the simulation. Users not only realize productivity gains by reducing prove-out time, but eliminate the risk of costly collisions that can take sophisticated machine tools out of production.
"When you have a machine that costs $1,000,000, and you are building components from exotic materials like titanium," says Dominique Humblot of SILMA France, Vilizy-Villacoublay, France,"you can't afford to break a part or the machine. Realtime 3-D images which look, operate, and program like the actual hardware, make the need for dry runs obsolete."
CAD compatible. To create a model of the NC machine, parts, and fixtures, and to drive the machine programming, the simulation software relies on three-dimensional CAD models supplied by the manufacturer. With the CAD information, virtually any NC machine can be simulated to provide an exact representation of the user's machine tool. This includes full machine kinematics, tool changers, optional material handling equipment, and a machine controller emulator. Tool assemblies are loaded graphically from existing databases and stored in tooling libraries. They can also be generated from libraries of individual tools, adapters, and tool holders.
Direct interfaces between Soft Machines and a variety of CAD/CAM vendors ensure compatibility with the customer's existing CAD/CAM data. Such interfaces include Computervision CADDS, IBM/Catia, Manufacturing & Consulting Services (MCS) ANVIL, EDS Unigraphics, and Parametric Technology Corporation's Pro/Engineer.
Once a simulated NC machine tool is created, it can read and execute the same tape image as the physical machine. Machine-code data requires no modification before it is loaded. Programmers may view the simulated machine-tool motion from any orientation or distance to validate machine speed, tool changer routines, feed rates, interactions between machine components, and potential collisions-all before the program is sent to the real machine.
Soft Machines also reports errors in detail, so that the programmer can make corrections before the actual machining process begins. If an adjustment needs to be made, the simulation routine can be stopped, corrected, and then restarted from that point. There is no need to repeat the entire program.
Advanced applications. The new software will help Boeing verify high-speed Boko, Cincinnati Milacron, Ingersoll, and Mazak machining centers at its Portland, OR, plant. The site machines wing flaps, engine mounts, aisle stands, steering columns, and landing-gear beams for all of Boeing's airplanes. Equipment complexity varies from four to eight axes of motion, and, in some cases, includes tool changers and rotating part tables.
Paul Cannon, supervisor in charge of NC programming for Boeing's Portland facility, confirms the need to verify post-processed, machine-code data. "Until Soft Machines," he reports, "the only way we could be sure that the tape image generated from our NC programming package was collision free was through trial runs with the actual equipment. Now, we can use the software to prevent machine collisions and production delays."
Chrysler Corp., another Soft Machines user, employs the software to keep its Ingersoll Adjustable Rail Milling Machine (ARMM) on a 24-hour schedule, five days per week. A $4 million, five-axis machine with multiple heads, the ARMM cuts large dies for hoods, roofs, decks, and prototype parts. The cost to prove out these dies averages about $200 per hour. A single collision on the machine requiring replacement of a head can cost upwards of $250,000 to repair.
By executing post-processed, machine-code data, the software frees the real hardware for its cutting operations, as well as eliminating the risk of programming errors. Soft Machines is available on graphic workstations from Hewlett Packard, IBM, Silicon Graphics, and Sun Microsystems.
Slx axes 'plus'
Of the many NC machines modeled by Soft Machines, the 'octahedral-hexapod' may be the most unusual. Designed and built by the Ingersoll Milling Machine Co., Rockford, IL, the machine's self-supporting, space-frame structure features 12 beams joined at six places. Its inherent rigidity and stiffness eliminates the need for a special foundation.
The actuator-attached at, and suspended from the structure's top-employs six telescoping arms that join at the spindle. Loads exerted by the actuator transmit as tension or compression only, negating bending forces. As a result, cutting accuracy is said to be as much as five times greater than that possible with conventional six-axis machines. Ingersoll claims that even faster cutting speeds are possible.
Further advantages include: scalability of design, portability, and ease of assembly.