Machine Design

Midrange CAM assists advanced machining

SolidCAM embeds in SolidWorks to create an integrated CAD/CAM system.

Mill-turn machining of a mechanical part done in SolidCAM.

Simultaneous five-axis machining of an aerospace component done in SolidCAM.

Together, they provide an associative design and NC package aimed at the midrange solid-modeling market. In addition to knowledgebased machining where templates direct operations such as pocketing, thread milling, and corner finishing, the NC software supports advanced features such as three to five-axis milling, turning, grooving, and mill-turning, and toolpath simulation and machine-tool control.

In three-to-five-axis milling, users select faces on the Solid-Works model to identify areas to be machined. In SolidCAM they define check surfaces to avoid (an APT-like function providing a containment area for work to be done or not done). This feature permits a variety of machining capabilities, including parallel plane, constant Z, zigzag, boundary collapse, and 3D stepover.

As in 2.5D operations, the software uses automated rest machining in three-axis operations, accomplished on block stock or 3D-cast models. Rest machining is useful in cutting complex parts because it removes the material left when tools are too large to reach into corners or valleys. The NC software determines the rest material from an in-process model generated with each cutting pass, updating the amount of stock remaining. With this model, which also includes 2D part areas, the software takes the difference between the stock and target model to optimize subsequent toolpaths.

SolidCAM has a variety of options for control of toolpath stepover, important for obtaining smooth surface finishes. Options include 2D and 3D stepover, control by the maximum scallop height to be left on the surface, and by an angle stepover for radial machining. Users can morph stepovers between two distances or between two surfaces.

In addition, the NC software supports high-speed machining. It handles both roughing and finishing operations. To support high-speed milling the software rounds all corners, adds loops to the toolpath for smooth transitions, and makes rounded connections between adjacent toolpaths, among other functions. Another function lets users sequentially machine multiple parts in high speed.

To meet industry demand for simultaneous five-axis machining, the NC software has licensed a program from ModuleWorks that handles this process. Five-axis machining capabilities include trimming, morphing between curves or surfaces, cutting at a constant lead, lag, or tilt, and swarf cutting by tilting the tool 90 degrees. As in 3-axis milling, the 5-axis module lets users establish check faces or surfaces to be avoided, and provides rest machining and associativity.

Additionally, the NC software tackles turning, grooving, and mill turning. As in milling, all turning operations accommodate rest machining, and changes made to SolidWorks models update toolpaths. When this happens, the software also tells users the jobs that are affected.

Users can select either long or short G-code and set feedrates to obtain constant surface speeds, or apply a custom feedrate to any segment of the boundary. Other turning features include an option to change feeds and speeds in the middle of a toolpath, tool control that backs-off the tool at the end of a profile to avoid a dwell mark, and cycle-time estimating, which includes tool changes.

For grooving, SolidCAM supports a large number of tool shapes and includes ISCAR's Turn-Groove tool library.

Mill turning requires a separate module. Mill turning involves lathes equipped with milling attachments that let users mill and turn on the same tool. The three modes of operation in mill turning are: mill turn with XZC, with XYZC, or with XYZCB.

Lastly, the NC program provides simulation and machine-tool control. It comes with basic toolpath and 2D simulation. In addition, the developer has licensed MachineWorks for 3D toolpath simulation and verification. Simulation in MachineWorks occurs before posting and before the postprocessor generates G-codes. Some users have expressed concern because they can't view the code after posting. During verification, users can rotate parts and the entire machine tool, including fixtures and the part, is simulated in five-axis operations. (The entire machine tool is not simulated in two and three-axis operations.)

The developer has written a language-based postprocessor generator, with the language being similar to Basic. The company provides specific posts from a large postprocessor library. In addition, resellers of the software often generate additional postprocessors or customize them, typically charging for this service. When the G-code is created in the post, it requires no further editing before being sent directly to a machine.

Instead of generating CL-files as typical of most CAM systems, SolidCAM uses its internal code, called parameter or P code. The company believes P code is more efficient than CL-files because sub-routines are built into P code. Thus, SolidCAM output is efficient — if the same operation is performed several times, the commands are only recorded once in the output, minimizing program length.

SolidCAM comes from SolidCAM Ltd., Or-Yehunda 60305, Israel,>

Alan Christman is a software analyst with CIMdata Inc., Ann Arbor, Mich.,

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