PurposeIn stereolithography (SL), the total exposure absorbed by photopolymer is variable and is a function of height. This phenomenon causes heterogeneous properties and develops residual stresses during process. Consequently, a pronounced deformation occurs especially when small and more intricate objects are fabricated. The purpose of this paper is to predict this deformation when miniature and complicated parts are fabricated.Design/methodology/approachIn this paper classical lamination theory is employed to model mechanical properties of layers, layers shrinkage and residual stress growth during SL process. Distortion is predicted based on the developed model.FindingsResults show that final distortion is proportional to part thickness and it increases exponentially as parts thickness or layers thickness decrease.Practical implicationsTo verify the results, several test pieces were built with SLA 5000 machine and SOMOS 11120 resins. Their distortions were measured with video measuring machine (VMM‐3020D machine). The estimation agrees very well with the experimental results (less than 10 per cent error).Originality/valueThe paper considers the heterogeneous properties of SL parts during fabrication process; an item which was ignored in previous researches. This theoretical and experimental study provides useful information about estimation of deformation of SL parts after building. This information helps the SL machine user to select the best parameters when fabricating miniature and intricate features, especially for biomechanics parts.
Drilling composite materials is one of the secondary processes of manufacturing industrial structures. However, drilling composite materials presents a number of problems such as degradation of mechanical behavior. In this study, effects of spindle speed, feed rate, and drill point geometry on residual tensile strength are studied. Acoustic emission technique with a wavelet-based signal processing method is developed to monitor the residual tensile strength of drilled laminates. Cumulative count, amplitude, and energy are used as time-domain parameters to characterize the process. According to wavelet analysis, frequency distribution and energy percentage of each damage mechanism (matrix cracking, fiber breakage, and fiber slipping) during tensile test are determined.
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