Solid performance

Written by: Tom Shelley | Published:

Tom Shelley reports on some of the advantages of moving to 3D CAD

While there is still no sign of a massive switch from 2D to 3D CAD, the trend is still in that direction.
Once a model has been created in 3D, it can be re-used for finite element analysis, clash detection, preparing NC machining programmes, and for the production of photo realistic images for sales and marketing purposes. It normally takes longer to produce a 3D model than a 2D drawing, but once the model is in 3D the potential savings are enormous.
Simon Booker, SolidWorks marketing manager for Europe, says that 51% of machine designers now use 3D rather than 2D. The company says that 90% of its growth in the UK is from former 2D users, mostly AutoCAD.
Phil Squance, engineering and development director of Caged, which makes roll cages for sports cars has taken on board a single seat of SolidWorks Premium and used it as a key component of a £600,000 investment that has secured a contract to supply all space frames for sports car manufacturer Caterham. His company re-uses its models for finite element analyses, clash detection and to prepare NC cutting and welding programs. The system was supplied by Cadtek Systems.
Historically, the Caterham space frame was made of cut steel tubes, which were then hand-brazed together. The process was expensive, inaccurate and time consuming. There was also a major issue with quality. Sometimes the roll cages would not fit the cars. Under new ownership, Caterham approached Caged to ask if it could apply modern technology to improve accuracy and stiffness and reduce cost. The space frame must be made in left- and right-handed versions and accommodate five different engines.

Caged designed the K series engine version of the new space frame in 3D, then used Cosmos to benchmark torsional stiffness and optimise tube positions. This resulted in a 14% improvement in torsional stiffness against a target of 10%. An added benefit was that insertion of the engine model file highlighted a clash between the alternator and the space frame - that would previously have been discovered only by building it. Moving tubes in the software model solved the problem and also gave an additional 0.5% stiffness improvement.
The space frame is entirely modelled using the sheet metal functionality in SolidWorks, including the folding of beams and the making of complex end cuts and bush and rivet holes. The model is turned into a DXF file and transferred to the company's CAM software, where it is used to program a laser cutter to an accuracy of 0.1mm, instead of the 1/8 inch tolerance of the previous hand-manufacturing technique. Chassis box section rails are cut in 30 minutes instead of five hours.
SolidWorks was also used to design the jig fixtures on which the tube sub assemblies and final assemblies are robot welded together. Everything goes together right first time with no re-drilling of holes or other adjustments.

Locked in
Era Products, which makes locks, uses 3D modelling as a basis of 3D images to sell its products. The 150 year-old company, based in Willenhall, makes 3 million locks a year - one third of them in China.
Graham Loakes, director of design engineering, said, "3D CAD is essential. Our product designer, Steven Wilkes, takes his designs to the US on his laptop so he can raise customer expectations. We recently saved £1000 by rendering a door and a lock in two hours. Previously, we would have had to do a photoshoot and hire models."
The company also uses SolidWorks, though has previously used HP's ME10 and SDRC's Ideas. New designs to be made in China, such as the company's new HPD multi-point lock for the US and a door lock illuminator for Europe, can be used to generate tooling in China straight from the CAD model. The company also uses PDMWorks, which Graham Loakes said provides "excellent security, access and drawing control - especially for Chinese operations".
The current concept-to-product process takes about 12 months, as opposed to 24 months previously. The door lock illuminator was also rendered in 3D for the benefit of the marketing board at DIY chain Wickes - which accepted the product. 3D models are also used to produce STL files for stereolithography and SLS models where required.
Cosmos is also used for finite element modelling. The locks must resist forces applied by burglars breaking and entering and have to survive 'soft and hard body impact tests' - which involve blows being struck by a large, swinging pendulum. Each test costs around £600, because the door has to be replaced, but more importantly, better designs which pass tests on the first or second design iteration save much time, as compared with the previous technology, where there might be as many as ten design iterations.
Cosmos is used to check the strengths of lock components, such as spindles and followers, and the company intends to use it to reduce the amount of brass and zinc alloy in its lock components, now that the cost of zinc has tripled in three months.
Era Products has five seats of SolidWorks - one with advanced Cosmos - supplied by Solid Solutions.

SolidWorks 2007

SolidWorks 2007 includes a number of labour-saving enhancements. Blocks for sketching include: belts and chains; traction relations, such as racks and pinions; and relation paths, for cams and followers. Surfacing includes an improved freeform feature and Sheet Metal facility includes curved edge flanges and lofted bend lines. Assemblies are facilitated by a Multiple Mate capability. The Swift (Solid Works Intelligent Feature Technology) now includes FeatureXpert which, if the user fillets, then wants to impose a draft angle, will realise when invoked, that the draft needs to be done first and automatically put it right. SketchXpert offers possible solutions to designs that are over-constrained, while MateXpert sorts out mating problems in a similar manner. A new search tool will find all references to a word, and PhotoWorks offers improved rendering. Cosmos may now be integrated with Animator and FEA results can be included in eDrawings files including indications of regions likely to exceed yield stress. Adaptive meshing automatically refines meshes in high stress areas without the rest of the mesh having to be refined.


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