By Andy Fulcher Technical Manager Solid Solutions Management Ltd
Lets face it - we all want to be car designers From our earliest days, many of us have drawn all manner
of cars and imagined all sorts of fantastical vehicles – mainly ugly ones in my
Designing car bodies
in practice is an expensive and time-consuming process involving designers (we used to call them “stylists”), clay modellers, feasibility
engineers, ‘Body-in-White’ (BIW) engineers and manufacturing engineers. The
objective is to create an attractive shape that fulfils the aesthetic and
functional requirements of the car company – but creating that shape is not
easy. Subtleties of how light interacts with the shape are crucial and so significant
expertise and much time and money are invested in the process.
Since the early 90’s
we have had CAD systems to help us
and now the ‘master’ shapes are no
longer locked into the physical tooling models (‘master models’) but are stored in CAD systems in the form of numerical surfaces. From this data, the
engineering of dependent parts (body, chassis and trim) can be progressed. Ultimately,
all forms of tooling (press tools, injection moulding tools, RIM tools etc.)
can be manufactured from the CAD data. Capturing the crucial surface shape has
evolved from spline based systems requiring a lot of care and time to more
powerful systems available today.
Traditional methods ‘engineer’ the surfaces by laying out
curves and then sweeping and lofting.
Blends and fills can then be added. SOLIDWORKS can do this pretty well, but it
can be time consuming and results in very long feature trees.
But there is an
alternative – using the SOLIDWORKS Power Surfacing partner product. This is a tool that allows creation and
manipulation of surfaces with 'push and pull' techniques. It is intuitive, easy to use and very fast – much faster for free-form work than with the
conventional ‘multiple sketch and
technology is called 'SubD'modelling
meaning 'Sub Division Modelling'.
The method is based on a mathematical approach where a polygon is sub divided
recursively to progressively form a smooth surface. The more sub divisions that
are made, the smoother the surface. Typically, 3 – 6 sub divisions are
sufficient to obtain very smooth shapes. There are several methods of doing
this, but the ‘Catmull-Clark’ method is commonly used.
What's the benefit of this?
The answer is that the method creates surfaces that are automatically matched
across all boundaries in tangency (‘C1’ continuity) AND curvature (‘C2’ continuity). Car bodies require C2 continuity
(except for deliberate creases and styling lines) so tools that inherently
create C2 continuous surfaces are hugely beneficial.
To demonstrate how
Power Surfacing can be used to build automotive surfaces, I have recorded a Webcast series entitled 'Power surfacing for Automotive Applications' covering...
1. Introduction including an illustration of how to design a bonnet shape.
2. Free Form Design – showing how to create a complete exterior car body surface in 30minutes!
3. Working from Renders and Images– showing how I built an E-Type Jaguar.
4. Using Scan Data – showing how you can create a sports car body from scan or digitised data.
Below is an animation
of an E Type Jaguar that I built from images in a couple of hours.