2D or not 2D?

CAD vendors claim that the case for three-dimensional design is cut and dried. But many engineers still prefer to stick with 2D. Brian Davis finds out why.

A survey by research outfit Business Advantage of more than 250 UK companies using CAD/CAM reveals that nearly 40% have a combination of 2D and 3D systems.

Just over half use only 2D drafting tools, while just 7% have moved exclusively to 3D. The lowest levels of 3D usage were in the electrical/electronic engineering and construction engineering sectors. Half the mechanical engineering firms used 3D solutions to some extent.

And vendors will be disappointed to learn that about three-quarters of those not currently using 3D CAD software have no plans to move to it. Ignorance isn’t the main reason for refusal to upgrade. Two-thirds of the companies are aware of the opportunities offered by 3D systems, but a significant number still maintain that 2D is the ‘more appropriate’ tool.

Richard Shepherd, a research analyst at Leeds University, has studied some 700 mechanical CAD users over the past five years. He believes the slow take-up is ‘due to the fear of change by many designers’.

Main criticisms

Three key criticisms keep cropping up in both studies. Many users feel 3D is too expensive, takes too long to learn to become productive, and is difficult to use. Some firms claim it can take a couple of years before the software can be used effectively, although vendors are eager to suggest that expertise can be gained in a matter of days, weeks or months. However, most of the firms that have moved to 3D said they had gained big productivity benefits, with clear bottom-line benefits.

Autodesk has the biggest CAD user base among smaller manufacturing firms. In June it introduced AutoCAD Mechanical Design 6 for 2D work, and Mechanical Desktop 6 and Inventor 4 for 3D. Product marketing manager Neil Dunsmuir says: ‘Most companies use 2D because they’ve always worked that way. Many engineering firms still favour 2D systems for the detailing of parts for assembly, while 3D is generally used for conceptual design. It’s a question of being aware of the benefits of working in 3D.’

Dunsmuir says the benefits of using 3D packages are significant productivity gains and reduced cost of prototyping. ‘Designers working solely in 2D often have to produce a prototype to find it doesn’t work. But with AutoCAD Inventor you can simulate operation to determine, for example, clashes in moving parts.’

West Midlands-based industrial design house Nova Designs has progressed in recent years from 2D CAD packages, such as Microstation, to AutoCAD, Mechanical Desktop and Inventor. Designer Nick Parry says: ‘Our productivity has increased by 25% and now we can get it right first time. But we still use 2D for some communication of design with the shop floor.’

Even a leading vendor such as UGS (formerly Unigraphics) recognises that 2D drafting still plays a key role in communicating information to manufacturing, whether in-house or to a third-party supplier. One of the advantages of using a 3D modelling system is the ‘associativity’ it provides between the 3D model and the 2D drawings, and between different views of the same part, so if a change is made to the model, all views update automatically.

By contrast, in a 2D drafting system, each drawing has to be produced as a separate file that has no knowledge of any other drawing files. UGS spokesman Neil McLeod recognises there is still a lot of demand for 2D drawings. ‘But the case for 3D is unquestionable, except for inherent 2D jobs such as schematic diagrams of electronic circuits.’

Company campaign

West Yorkshire-based Bibby Transmissions designs and manufactures flexible couplings and torque limiters. A year ago it launched a campaign to encourage its design engineers, who were using an AutoCAD 14 2D drafting system, to begin switching to UGS Solid Edge 3D modelling. Engineering manager Ron Cooper says: ‘We had been using a 2D system for many years to produce drawings for our shop floor and wanted to see what benefits 3D solid modelling could offer.’

‘After only a few months,’ Cooper says, ‘we recognised the limitations of our 2D drafting system – conceptual design is difficult in 2D because of the lack of associativity. With Solid Edge all the necessary detail and arrangement drawings are produced semi-automatically from the solid 3D model. This saves a lot of time, and design concepts can be generated more easily and visualised in 3D.’

Some are less enthusiastic. Bibby design engineer John Bowman appears to be not entirely convinced of the need for 3D: ‘It’s basically considered to be ‘Ron’s toy’,’ he says.

Richard Serna of CoCreate reseller Definitive Applications says: ‘Many companies are still wary of breaking into 3D, despite the benefits for visualisation of complex components.’ He maintains that manufacturers of complex machines, such as printing, food and packaging equipment, prefer to work in 2D because assemblies consist of simple components like extrusions, bars and plates, which can easily be visualised using 2D.

Food coating and preparation machinery manufacturer Arcall, based in Dorset, recently bought a copy of 3D package Solid Designer. ‘But we made a conscious decision to stay in 2D for most of our design work,’ says technical director Richard Wollard. The company has six seats of ME10 to handle most of its design work, but the 3D system is used for visualisation, rendering and imaging for marketing purposes.

Geoff Sutcliffe, UK marketing manager at SDRC, says: ‘There are many industries that now design in 3D and recognise the value of eliminating 2D drawings. However, a lot of the industrial machinery manufacturers also rely on 2D production drawings and even in aerospace production there is a reliance on certification from 2D drawings.’

‘You can’t force people to change to different working practices without providing a transition path,’ says Sutcliffe. Using ‘I-deas’ engineers can continue to work in standalone 2D or 3D and produce the same standard of 2D drawings for production on the shop floor.

I-deas version 8 can produce 2D views from the 3D solid model, fully annotated as if they were drawings, for manufacture, inspection, assembly or other purposes. ‘This is the first application to provide all the information usually given in a 2D drawing, generated directly on the solid model,’ says Sutcliffe.

But he admits: ‘In the current economic environment there are still circumstances where it may be faster and cheaper to produce simple parts in 2D.’ Ultimately, he believes it’s a question of determining the role of design information within a company’s business processes. ‘If a large number of departments, from the shop floor to marketing, are involved in the design process, then a 3D representation is more easily understood by more disciplines than 2D.’

Easing the transition

PTC also realises the importance of offering an easy transition from 2D drawings to a 3D-modelling environment. It plans to launch a new product, Pegasus, in February 2002 to address this migration. Based on the 2D drawing engine Medusa, formerly from Computervision, it will offer seamless integration with PTC’s Pro/Engineer, to run on Unix, Windows NT and Windows 2000. ‘We also believe it will appeal to AutoCAD users,’ says technical marketing director David Blair.

Blair, an ardent advocate of 3D, also recognises there are several compelling reasons why companies keep 2D systems. For example, many firms maintain a large legacy in 2D drawings. There is a preference for factory layout and service provision drawings in 2D. The drafting tools are used for rapid creation of bid and proposal drawings using cut and paste from existing 2D data. People also like to create miscellaneous charts, tables, diagrams or layouts in 2D.

Small departments or branch offices often annotate drawings based on customer requests. And 2D tools can complement 3D, for example, to show electrical and service plans installed in a building.

In the current engineering climate, the answer still seems to be mixing and matching between 2D and 3D systems rather than outright elimination of the old drafting tools.