TechArchive

Original article date: April 1999

In only 3 years from the first stereolithography product from 3D Systems the company has now launched its first office-sized machine no larger than an office photocopier.

Developed by 3D Systems in Valencia California the Actua 2100 is a 3D concept modeller no larger than a standard office photocopier. It allows designers to produce three-dimensional models direct from their CAD systems but in their own offices. The machine is now being introduced in the UK via Bix one of three companies promoting its technology in the UK. Prices are reportedly in the order of (UK pounds)40 0

The Actua 2100 which also operates noiselessly and can therefore sit comfortably alongside other office equipment takes advantage of new 3D printing techniques under development at MIT in the USA. In a dry process the model is built up in successive layers using black white or grey Thermojet material a specially developed thermopolymer to produce an accurate 3D model in a few hours. The material is delivered point by point data being converted and individual nozzles triggered via piezoelectric signals analogous to an inkjet printer. Models are produced by means of a raster-based 96 printing process which uses a cutting algorithm to build up the model in a process similar to inkjet or phase-change printing. As a typical example it would take about five hours to produce a model of cup and saucer.

A key element in the development of the machine was the compatibility of material and printing head. The material to be developed needed to have a low melting point and a low viscosity. At the same time it has to withstand high temperatures without burning up in the process. The material that was used was paraffin. Although the newly developed nozzle heads withstood the temperatures the material failed to solidify quickly enough. Eventually the Thermojet material was developed which can be heated to 120degC and solidifies immediately on contact with the existing surface.

Designed to complement other stereolithographic processes the Actua 2100 is finding early uses with manufacturers of domestic appliances and household goods. German chair manufacturer Scharf is using the machine to carry out studies of the ergonomics of armrests for office chairs.

The Allegro software supplied with the Actua 2100 displays a simple control panel on the CAD workstation allowing the designer to select the models to be built and the scale factor. The software checks the data and alerts the designer to any errors before building the requested models. Allegro can run on any commercial UNIX platform or under Windows NT. The software can be installed within the network on several PCs allowing access to the Actua 2100 from several terminals. The software also allows several copies or different designs to be edited from different terminals at the same time working with the same carrier plate.

Allegro positions the model in the build space and generates a support grid geometry. This is necessary to be able to remove the model more easily from the support plate after the work cycle has been completed. Undercuts and overhangs can be represented. The design space itself is 250 x 200 x 200mm. After completion the entire platform is removed together with the component The support grid geometry is removed using a glass brush.

Once the build request is submitted it is queued for modelling enabling the designer to work on other tasks while the model is being completed. So the day when designers can fax real models to one another as our own correspondent Griff forecast last year draws ever nearer!

• Bix Computer Applications
• Andrew Miller
• 0115 840 4060

April 1999