Although today’s high-end automotive CAD and CAM systems have multiple capabilities, their main function is to help take a car concept from the drawing board to the production line.
In terms of manufacturing capabilities, these systems must at least support numerical control (NC) tool path generation for two to five-axis milling/turning, wire/die erosion (EDM) and sheet-metal fabrication capability.
Performance is determined by a system’s ability to graphically examine and visually verify machine tool paths, machine kinematics and any robotic movements. If a manufacturer wants to produce rapid prototypes, the CAD/CAM system must use STL, which is a file format native to the stereolithograhy CAD software.
Dassault Systemes, Structural Dynamics Research Corporation and Unigraphics Solutions are big-name developers which claim to be among the few to address these principles at the required level. But there are many smaller developers who have made significant inroads.
These include 4D Engineering (Mastercam); Open Mind (hyperMILL); Delcam (PowerMILL, FeatureCAM); Planet Systems (Pathtrace EdgeCAM); and SolidCAM.
Their CAM packages appeal to automotive subcontractors who cannot justify investing in the same CAD/CAM system as the OEM they supply. In fact, many of these ‘smaller developers’ have become experts in specific areas as a result of the competition and are widely recognised for their own merits.
For example, Gibbs and Associates, creator of GibbsCAM, developed a CAM-based knowledge library. The great advantage of this for GibbsCAM users is that the machine shops programming knowledge can be standardised by programmers drawing upon a single library together. Referencing standardised processes ensures the operators machine the same features in the same way, and in particular, that they use the same tooling choices.
The machine shop as a whole can therefore make machining cycles more consistent and predictable, and so reduce the number of different tools it has to order and track. It can also help with tool rationalisation, which means a carefully selected set of tools can be used to do all the required jobs. The library itself is based on a file structure that the user organises by creating directories.
Delcam, which is primarily associated with mould and die toolmaking, has recently branched out to cover more general machining, most notably automotive, offering specific toolpath strategies for cylinder port machining.
The company’s FeatureCAM 2008 system offers a variety of methods for controlling the tool axis in five-axis simultaneous machining applications. The user can set a specific lead and/or lean angle. This can be done either to access areas unable to be reached with three-axis machining or to give better cutting conditions.
Alternatively, the tool angle can be set in an orientation either to or from a point, or to or from a line. Many three-axis toolpaths generated in FeatureCAM can be converted to a five-axis toolpath by using automatic collision avoidance to change the tool axis when collisions might occur.
The software automatically tilts the cutter away from the obstacle by the specified tolerance and then returns the cutting angle to the value set for the overall toolpath once the obstacle has been cleared.
Five-axis drilling is also supported. This new functionality, coupled with FeatureCAM’s advanced feature-recognition, makes it possible to create drilling programs in seconds for multiple hole types and sizes. Delcam has also broadened the range of post-processors included with the software for Mori Seiki. New posts have been added for the NT series of integrated mill-turn centres and the NZ series of multi-axis machines — all developed in association with Mori Seiki.
Another program that features several enhancements to increase manufacturing ability is CGTech’s Vericut 6.2. This allows engineers to develop, analyse, inspect and document the CNC programming and machining process.
A new ‘NC Program Preview’ offers the option to process a Vericut program without actually simulating material being removed. This quick check is claimed to be very fast and use much less memory. In preview mode, Vericut displays a tool trace of the program over the design model, checking for collisions, gouges, minimum excess and instances where axis limits are exceeded.
Several new utilities have been added to the ‘Review’ window, including a calculator, user-configurable text colouring, syntax checking and block renumbering options.
To complement the milling tool set-up wizard introduced in Vericut 6.0, the company has added a turret set-up wizard, which enables users to load tools or change their positions in a turret. Users can also easily create a swept model of a turret.
The tool manager has also been enhanced to enable users to describe the shape, position, and orientation of a waterjet cutter or a tap in a tap tool assembly. Tapped holes are visually differentiated from other drilled, bored or reamed holes. Vericut checks for correct feed rate and direction when using a tap, and also detects if the tap hole is pre-drilled the correct size.
So while the automotive sector favours a handful of CAD/CAM solutions, many smaller software developers are successful in this area because they appeal to subcontractors working with OEMs.
While the automotive sector favours a handful of CAD/CAM solutions, many smaller developers are successful because they appeal to subcontractors working with OEMs. Martin Oakham reports.