A study of recoating in stereolithography

Recoating in a stereolithography apparatus (SLA) involves dipping the part being built into a vat containing liquid resin and sweeping a blade over the top of the part. There are two problems with the recoating operation in existing SLA systems. Firstly, the process is slow because the blade sweep speed is usually restricted to minimize disturbances to the resin surface and also because, after each sweep, the machine has to wait idly for any disturbances to subside and the resin surface to become level before scanning by the laser can be performed. In a part made up of hundreds or thousands of layers, these measures considerably lengthen the build time. The second problem is the dif culty of ensuring that the thickness of the generated layers is even and accurate in parts that incorporate upward-facing concave areas. For such parts, recoated layers may be either thinner or thicker than speci ed. In the worst case, the part may become delaminated or the blade may strike the cured resin during recoating, resulting in build failure. This paper reports on an experimental study of the recoating operation. The paper discusses the setting of parameters controlling the operation and proposes guidelines for producing good quality SLA parts while reducing build times.