Computer-Aided Industrial Design
for Ceramics and Glass Industries
Author: Charles Woodward
Company: DeskArtes Oy
Contact address:
Särkiniementie 5 C 13, FIN-00210,
Helsinki, Finland
Tel. +358-207-414-510, Fax
+358-9-644 330
e-mail DA@deskartes.fi
www.deskartes.com
Abstract
This article discusses aspects of 3D CAD implementation for ceramic and glass industries. The emphasis is put on modeling interaction and visualization for decision-making in early production stages. Different software tools are described and demonstrated with practical design cases.
1. Introduction
Way back in 1985 a research project was launched between Helsinki University of Technology and Oy Arabia Ab, the leading Scandinavian manufacturer of ceramic tableware, in order to apply computerized design techniques for Arabia's production. It was taken as a specific goal to produce a 3D CAD system to be used directly by the designers, instead of having to involve computer engineers in the creative design process.
The 3D CAD system called DeskArtes IDS (Industrial Design System) was developed in co-operation with the design artists and tested during 1986-90 in several design exercises and authentic design projects. The software was commercialized by DeskArtes Oy in 1991, and it is nowadays used by most leading ceramic tableware companies in the Northern Europe (e.g., Wedgwood, Royal Worchester, Royal Daulton, Denby, Rosenthal, Hutschenreuter, Tools&Technologies), as well as glass tableware manufacturers around the world.
The outline of this article is as follows. Section 2 evaluates some problems related to manual production methods in ceramics and the requirements for a 3D CAD system to be useful in the application. While even a superficial explanation of all the involved software tools would not be possible, sections 3 and 4 give an overview of the modeling and visualization techniques available. The concluding section sums up the main issues and experiences. The main emphasis is given to ceramic applications, but most of the discussion applies to glass design as well.
2. CAD and ceramics - why and how?
Besides good design and quality, the ability to present novelties faster than before has become an important competitive factor in the ceramic industry. However, both product development and manufacturing are complex and time consuming processes involving a lot of skilled manual labour. Getting the right form into clay requires constant negotiations with the designer and the model maker, and predicting the material deformations in the high temperatures of the manufacturing process is another problem, usually taking several experiments before the desired form comes out of the kiln. The manufacturing of a fired prototype for a single non-rotational object takes therefore several weeks.
A complete dish set consists of several pieces, where not only the properties of individual parts need careful consideration, but also their shapes and sizes related to each other. Most of the prototype models actually never appear in the market, but are discarded in early product development stages, either by the designer, the production managers, or the marketing people.
The bulk of the product development is not only in the difficult manufacturing processes but also in the decision-making at the various levels of the production. With all the production iterations involved, it typically takes two to four years to carry out a set of dinnerware grom the design idea into complete products in the market (Fig. 1).
Figure 1. Manual Product Development Process (courtesy of Hackman/Arabia).
Several weeks and usually even months of savings in the production times can be gained by employing 3D CAD technologies in the early product development phases. Modern 3D CAD software enables the designers to visualize their design ideas faster than before, thus easing the communication between different production levels already before the first prototypes are made.
Taking 3D CAD to the production already in the early design stages can also improve the quality of the products. With manual working methods it would not be reasonable to ask the model maker a quantity of minor but time-consuming changes to the model, and something less perfect may have to be accepted due to the time-schedules. The CAD system allows the designer to go through all the variations he wants even before the first prototype has to be made. Thus the dimensioning and computation of physical properties such as volumes can also be associated to the initial form-giving process.
For the most flexible production environment, the 3D CAD software should encourage the designers to define their ideas directly with the computer. For this to happen, the modeling methods must bear good intuitive correspondence to accustomed manual drafting methods, not demanding unnecessary numerical or mathematical manipulation. In order to rely on the computer models for decision making, the visualization methods must provide an ultimate level of realism to correctly render objects with different materials and textures.
3. Modeling techniques
Following from the original request of ceramic tableware artists, the DeskArtes IDS system does not operate with 3D coordinate manipulation at all. Instead, all 3D models are conveniently defined by drawing simple 2D curves, out of which complex free-form shapes are produced at the push of a button.
Fig. 2 gives an example of model construction from 2D curves. Resembling the manual drafting convention, the perfume bottle is defined from different views with B-spline curves, some of which denote profile shapes and the others define the surface cross-section shapes. Only a minimal set of section curves has to be defined, while the intermediate shapes are filled in automatically. For surface construction, the system automaticaly transforms the cross-sections between the profiles, and the corresponding surface is computed to match all the given curves.
Figure 2. Surface creation from profiles and cross-section curves.
This way 3D CAD is made easy, most of the modeling interaction being concentrated in creative form giving process with free-form curves. A wealth of curve editing tools has been developed together with design artists to support curve design at the most easy-to-use level.
While the profile/cross-section method provides immediate correspondence with the designer's intuition of geometric description, it has also turned out general enough to cover the majority of modeling applications typically met in ceramics and glass tableward design. For some of the more demanding models, the DeskArtes IDS software also provides various higher-level tools to combine separately defined surfaces into one piece.
In the example case, the strip around the bottle was defined by projecting a curve onto the bottle surface, thickening the curve to a solid strip, and finally cutting the strip away from the bottle. Additionally, the join between the surfaces was smoothed out with a blend between the parts: alternatives for this are constant and variable radius blends, and ultimately free-form blends to create any imaginable join shape between the given base surfaces.
4. Visualization
To serve for the visualization requirements at different levels of product design, methods with alterning complexity are required. For the sketching phase of the design, OpenGL shading allows inspection of the geometric models from different views and close-ups in real time
However, once the designer is happy with his design, the need for a higher level of realism in visualization arises for final production and manufacturing judgement. The ray tracing method accounts for global illumination in the scene, which is vital to visualize complete dish sets with several pieces.
In fact, for rendering glass material, ray tracing is the only available method to produce realistic material behavior. Figure 3 shows an example of chrystal glass rendered with completely designed and DeskArtes IDS, demonstrating also the software’s capability to produce fine cuts in the basic geometric shape.
Figure 3. Glass model rendered by ray tracing.
In ceramic industry, the products are usually marketed with different patterns, sometimes exclusively for specific customers. Using DeskArtes IDS, texture mapping is finally used for the image synthesis. The software provides various methods of texturing, from so-called uniform mapping to adaptive mapping, color image or bump maping, up to high-end methods such as projective textures and surface flattening.
Figure 4 gives a ray traced textured example from Wedgwood’s production, out of which over 90% is nowadays produced starting from DeskArtes computer models. Instead of having to manufacture all the alternative variations, products can now be marketed based on computer image catalogues, and actual production begun only at the customer order.
Figure 4. Texturing applied on ceramic tableware.
5. Conclusions
From the company's point of view the most important benefit of 3D CAD is faster product development that allows novelties to be presented in a shorter cycle, in turn leading to a greater richness of assortment. To fully exploit the method, the CAD workstation should be considered as a working tool for the original designers. The profile/cross-section techniques enable the designers to visualize their ideas with an immediate link from 2D sketches to 3D CAD models. High-quality ray traced color images of the computer models can then be immediately used to ease the communication between different departments and people involved in the product development, up to marketing and customer cases. The total time savings of well over 50% are today a reality when comparing CAD/CAM to traditional design and manufacturing methods.