An approach to minimize build errors in direct metal laser sintering

Abstract

This paper discusses the effect of geometric shape on the accuracy of direct metal laser sintering (DMLS) prototypes. The percentage shrinkages due to different shapes are investigated and their empirical relationship is determined. A new speed-compensation (SC) method is proposed to reduce uneven shrinkage affected by the two-dimensional geometric shape at each layer. From case studies conducted, the optimized SC method is found to be efficient in improving the accuracy of prototypes fabricated. Note to Practitioners-This paper aims to address the problem of dimensional errors of parts built by the direct metal laser sintering (DMLS) process. Existing compensation approaches are normally based on a general relationship between the nominal dimensions and the errors after sintering. However, the effect arising from different geometric shapes is not considered. A new approach is proposed using different scan speed settings to compensate for the effect of geometric shapes to improve the dimensional accuracy of the entire part. During processing, the laser sinters along the trajectory are guided by the hatch vectors or dexel. An appropriate experimental method is used to establish the relationship for different scan speeds with the dexel length to the final accuracy. When building the part, the laser scan speed is adjusted dynamically according to the dexel length which varies with the geometric shape of the part. The case study demonstrates that the proposed method can generate correct speed settings to effectively increase the dimensional accuracy of the final part. Although this method has been developed based on the DMLS process, it is also applicable to other laser sintering processes. In future research, other process parameters, such as laser power, will be considered independently, or together with the scan speed, for possible further improvement on the dimensional accuracy.