Advantages of the material extrusion process include use of readily available ABS plastic, which can produce models with good structural properties, close to a final production model. In low volume cases, this can be a more economical method than using injection moulding. However, the process requires many factors to control in order to achieve a high quality finish. The nozzle which deposits material will always have a radius, as it is not possible to make a perfectly square nozzle and this will affect the final quality of the printed object (Chua et al., 2010).Accuracy and speed are low when compared to other processes and the quality of the final model is limited to material nozzle thickness (Krar et al., 2003).
When using the process for components where a high tolerance must be achieved, gravity and surface tension must be accounted for (Gibson et al., 2010). Typical layer thickness varies from 0.178 mm – 0.356 mm (Chua et al., 2010).
One method of post processing to improve the visual appearance of models is through improving material transmissivity. Methods have been explored by Ahn et all, include increasing temperature and the use of resin. Experiments using cyamo acrylate resin, often used to improve the strength of parts, resulted in a 5% increase in transmissivity after 30 seconds and sanding (Ahn, 2004). As with most heat related post processing processes, shrink- age is likely to occur and must be taken into account if a high tolerance is required.
Machine Example:
Machine
Area
Layer Thickness
Built Volume
Insstek MX3
1000 x 800 x 650 mm
Al, Cobalt, Copper and Nickel alloys
520l
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