Advances in hybrid solid and surface modelling
Inventor from Autodesk
Release 6 of Autodesk’s Inventor delivers significant advances in hybrid solid and surface modelling based on their proprietary ShapeManager kernel, first introduced in release 5.3.
Whilst in many respects the kernel debate such as ACIS v.
Parasolid is somewhat passé, Autodesk’s decision to diverge from ACIS potentially trades off their benefits of control and flexibility against robustness of a less widely debugged product and necessary development effort.
In the real world, translation of data between modellers remains a significant issue and development of yet another proprietary format will cause issues; as history has shown even products at their peak such as Pro/E have not achieved total data dominance.
In many applications, forms more complex than prismatic geometries are required.
Current design centric modellers aim to include surface modelling capabilities to generate complex forms without compromising the speed and ease of use offered by parametric solid modelling.
Autodesk calls their implementation of such hybrid modelling Unified Shape Technology, which allows models to be converted from solid to surface and back at any time whilst maintain their parametric history.
One modelling strategy can then be to create simple approximate shapes as solids then to sculpt them towards the desired complex shapes using the surface tools.
Although the extrude, loft, revolve, sweep, knit, replace face, thicken and offset surface tools add powerful new modelling capabilities, the current absence of trim and extend options can limit their application.
The dual Thicken / Offset tool creates offsets from part faces or surfaces to create new parallel surfaces or add or remove material from a part.
Thickening a surface into a solid can create a disjoint volume.
Although this and many other operations can inadvertently create non-manifold solids, there appears to be no obvious way in which this is flagged, with even mass properties reported for the composite, disjoint whole.
Although the Thicken / Offset tool identifies the correct feature type automatically in the history browser, Delete Face is indicated even if the command has in fact removed a solid as a Lump.
Alongside the extended surface modelling capabilities are improved tools for creating and manipulating splines.
Points can be manipulated dynamically and be defined as a bowtie with handlebars to adjust tangency, radius of curvature and curve influence.
The handle can also be dimensioned or constrained to other model entities.
In addition to creating and manipulating surfaces within the normal parametric modelling environment, a construction environment exists to prepare imported data for inclusion in the model.
Tools are available to analyse edge quality and highlight problem areas, add fillets and to knit multiple surfaces into a single quilt.
These non-parametric surfaces can then be promoted into the main modelling environment.
Somehow despite many elements of the interface succeeding in aiding ease of use, other elements such as construction geometry not existing in the construction environment, or surfaces being able to be created in both the surface construction environment and the modelling environment seem to complicate terminology unnecessarily.
Similarly work features are described as abstract construction geometry and include work planes, work axes and work points.
3D curves can be generated from the intersections of freeform surfaces, work planes, or faces.
These can be useful for pipe routing and complex lofts which can now include multiple sections and guide curves.
The Emboss tool enables planar text to be engraved or embossed from a surface with options to specify resultant surface colour and to wrap around a surface keeping draw perpendicular to the surface.
Tolerances can be applied to dimensions in model features.
The part can also be rebuilt to max, min or nominal in order to evaluate extremes of design tolerances.
All dimensions can be accessed and values, max and min conditions viewed and set in the Parameters dialog.
Component precision and tolerance range schema can be pre-defined in the document settings.
In addition to editing parts in-context within an assembly in order to create features that relate to other parts, some elements need to exist in the assembly itself rather than the discrete parts.
Examples that affect multiple parts can include specific manufacturing processes such as post-machining, match drilling and weldments.
The scope of components that the assembly features affect can be specified.
A dedicated weldment environment exists to define the weldment assembly, weld bead specification, weld edge preparation and post-weld machining.
Drawings can include views of the assembly at each state of manufacture.
A Find Other Half option is available on assembly constraints in order to identify mated components which can be tricky in complex assemblies.
A standard parts library can be called in the browser pane of an assembly allowing part selection and a placement history and favourites list to be generated.
18 international standards of screws and bolts, nuts, washers, adjusting rings, bearings, circlips, O rings, parallel keys, pins, rivets, roller bearings, shaft seals and Woodruff keys are available.
A create view dialog allows view properties such as label, tangent edges and view style to be set while a shaded view is moved dynamically in the drawing sheet for placement.
For projected views the preview updates based on the cursor location including isometric when not in line of an orthographic projection.
Sketches can be used to create break-out views to reveal internal details.
Centrelines and centremarks can be added automatically with a dialog allowing the projection and feature types to be defined.
Minimum and maximum threshold values outside which they should not appear can also be set independently for fillets and circular edges.
Draft sketch views can also be defined for manual creation of 2D views using sketcher tools.
Part list functionality has been enhanced to allow nested entries to be expanded selectively, individual fields to be updated and tables to be split.
In addition to the manual balloon placement command, Balloon All automates the addition of balloons for all parts in the selected view.
True to AutoCad form, there is considerable control over dimensioning styles.
Parameters now include tolerances with the option to specify a different font than the dimension.
New styles can be created and applied simultaneously to multiple selected dimensions of different styles.
As may be expected with the increasing functionality in Inventor, Autodesk are aiding the migration from Mechanical Desktop with an improved translator.
Widely used Surfcut features are translated as fully editable Split features and ribs arrive with editable sketches.
BYLAYER colour properties are retained so that components are more readily identifiable after translation.
Similarly AutoCad layers translate into independent part or drawing sketches with dimensions appropriately assigned, line scales preserved and the ability to map line types.
Inventor 6 is a significant release, aimed principally at Autodesk’s three top goals of providing all the necessary functionality for machine design and drawing generation, industry specific tools for cable and pipe routing and welding and enhancing the shape creation capabilities.
As a credible player in the competitive design centric market, it is an obvious upgrade for existing Inventor users.
For new entrants into 3D modelling, it may be issues of legacy data, partner compatibility and belief in developer strategy that differentiate rather than core modelling capability.