Making surface modelling approachable
SurfaceWorks from AeroHydro, Inc
Despite the addition of a range of surfacing tools in mid-range, design-centric modellers such as Solid Edge, SolidWorks and Inventor 4, there can still be times when parts of a product need more extensive freeform design capabilities.
From a 25 year background of developing a surface modelling technology, MultiSurf for designing ships and boats, AeroHydro Inc.
now offer mainstream Windows native surface modelling packages.
Principally launched as an add-in for SolidWorks, it is also available as a stand-alone package offering the same modelling functionality under the name SurfaceWorks Solo.
A SolidWorks Integration Module is also available to allow stand-alone users to upgrade from Solo to a fully integrated SolidWorks solution if requirements change.
Aimed primarily at mechanical engineering and industrial design applications, extensive tutorials are available to explain the intricacies of surface modelling, such as tangency control, given their significant differences to solid modelling.
The SurfaceWorks modeller can be launched independently or from within SolidWorks in which case sketch entities can be pre-selected for transfer.
Bi-directional associativity ensures that any edits in either modeller can be automatically reflected in the other so that for instance changing the size envelope of the mechanical elements of a design in SolidWorks can drive the surfaces based on it.
The required surfaces can be selected for returning to SolidWorks, subsequently appearing in the feature manager as imported surfaces that can be used in any appropriate SolidWorks commands such as cut with surface or thicken into a solid.
Right clicking any such surfaces in the Feature Manager allows them to be reopened directly in SurfaceWorks.
Despite the wide range of surface specific tools buttons, the SurfaceWorks interface will be familiar to SolidWorks users with a feature manager down the left of the graphics area.
Entities can be viewed from parent surfaces down through driving curves to points or from the child entity back up.
A second pane indicates entities in the current selection set while a third displays entities available for selection according to set selection filters or suitability for the current command.
In SurfaceWorks relationships are captured as part of each entities definition during creation.
This means that there is a wide range of creation tools, one for each entity type such as a Bead which as a point on a curve must by definition be coincident with its parent curve.
Points are used to define curves of which there are eighteen types and these are subsequently used to create up to fifteen main surface variants.
In addition to arcs, lines and helices, curves include B-splines which creates a continuous imitation of the polyline that passes through all the control points but only itself passes through and maintains tangency to the polyline at the first and last control points.
In a C-spline the curve passes through all the control points.
B-spline and C-spline snakes are similar but are constrained to lie on a surface.
Other generated curves include intersection snakes, projected or relative curves and mirrored curves.
Projected curves can be assigned draft for moulding and casting applications.
Equivalent surface types include B-spline and C-spline lofted surfaces determined by whether the surface passes through all of the control curves, mirrored, offset, swept and revolution surfaces.
A blend surface allows two surfaces to be smoothly blended with G1 or G2 tangency.
G0 describes curves that join at an arbitrary angle and therefore have no tangency.
When curves have the same direction at the junction but dissimilar curvature such as a line tangent to an arc, G1 continuity exists.
The smoothest and most aesthetically pleasing tangency is G2 where in addition to the same direction the curves also have the same curvature at the junction.
This is commonly described as set back in applications such as casings to avoid harsh highlights where flat surfaces must transition into edge radii.
Although the required design principles must be understood in order to efficiently construct geometry capturing the design intent, surface curvature tools are available to analyse the end result.
The capture of intelligence during entity creation facilitates editing flexibility.
This combination of geometric entities and the relationships between them AeroHydro describe as Relational Geometry.
Additional relations between entities can include distances, angular positions, symmetry and fixed geometry.
Editing can include dragging points on curves or adjusting values of surface control points either by graphical sliders or numerically in a u, v control values table.
By careful construction technique such as using a common edge to define attached surfaces, models can be created with what are described as durable joins so that even during substantial edits the model behaves predictably and robustly.
In addition to the integration with SolidWorks, surface, curve and point data can be shared with other modellers through IGES import and export.
SurfaceWorks Flattener is available as a separately licensable add-on utility with one license being able to serve five SurfaceWorks users on a single LAN.
Based on established MSPLEX technology, Flattener enables surfaces to be unwrapped or unfolded, whilst taking into account the distribution of in-plane strain required to produce the specified 3D shape.
By exporting an expanded outline of the surface as a 2D DXF file, patterns can be NC cut which through the application of a suitable compounding process such as die pressing, can be evolved into curved surfaces precisely fitting the designed form.
Although solid modelling is very efficient for the majority of modelling, principally prismatic forms, there are inevitably times when alternative methods of construction are appropriate.
Despite not being a SolidWorks Gold Partner offering full single window integration, SurfaceWorks does an excellent job of making surface modelling approachable.
Whether used as a surfacing toolset for SolidWorks or in the standalone Solo format, the relational approach anticipates the inevitable editing required in the design phase by making underlying geometry easily accessible and by reacting predictably.
Although the design-centric modellers are progressively adding surfacing functionality, it is unlikely they will achieve the same level of control and flexibility in the immediate future.
In the meantime the trade-off will remain between native tool ease of use and ultimate functionality.
At present SurfaceWorks is excellent where multiple interrelated freeform surfaces are required and where control over location, tangency, and smoothness is necessary between adjoining surfaces.