Dimensional Evaluation of Miniaturized Parts Manufactured by 3D Printing
Abstract
The development of the manufacturing process to fabricate miniaturized components goes through aspects such as modifications of machines and tools, process optimizations, improvements in precision and accuracy, and fabrication of adapted geometries. Hot-embossing, laser abrasion, and microinjection molding are applicable methods of fabrication to a diversity of geometries and polymeric materials. Rapid prototyping and fabrication assist in the development of new products in a short amount of time with a reduction in costs, allowing the manufacturing of objects with tenths of millimeters and with an accuracy in the order of micrometers. 3D Printing process with photocurable resin is a recent method of rapid prototyping that is growing in the market. Intending to analyze how precise and accurate is the process of 3D printing of miniaturized models and analyze their dimensional tolerance, it was conducted a dimensional analysis of parts fabricated in a printer EDEN 250 by Objet. Qualitative results showed that EDEN 250 prints satisfactory small parts mainly with round formats. Parts with sharp edges show limitations regarding precision and accuracy. FullCure ® 720 is a resin with average quality since it absorbed moisture and is heat sensitive. Studied samples were classified according to the technical standard NBR 6158 as IT11 parts (max tolerance of ± 60 μm).
Keywords
Download Options
Introduction
A change in part of the manufacturing industry of plastic components has been noticed, evidencing a tendency for miniaturization of devices and systems [1]. Market consolidation of miniaturized parts is demonstrated by the global growth between the years 2004 and 2009, from 12 billion to 25 billion dollars. It is known that the principal difficulty in the miniaturization of devices and parts is the existed limitation regarding precision and accuracy of fabrication processes. The development and adaptation of the manufacturing processes of miniaturized components go through aspects such as modifications in machines and tools, process optimization, improvements in precision and accuracy, and fabrication of adapted geometries [2][3]. The methods of miniaturization and micro-fabrication of polymeric components are an alternative with low cost for the technology of micro electromechanical system (MEMS) [4][5]. Hot-embossing, laser abrasion, and micro-molding by injection are applicable fabricated methods for a diversity of geometries and polymeric materials.
Prototyping and rapid-fabrication techniques as stereolithography (SL), selective laser sintering (SLS), and tridimensional printing (3DP) assist the development of new products in a short period with a reduction in costs [6][7]. These techniques allow the creation of objects in the range of hundreds to tenths of millimeters with an accuracy in the order of micrometers. EDEN 250 is a printer from Objet that allow the creation of models with layers of 0,016 mm and walls of 0,6 mm [8]. Intending to analyze how precise and accurate is the printing process of miniaturized models which are the dimensional tolerance according to ISO 286-2-1998, it was conducted an analysis of the dimensions of parts fabricated with the printer EDEN 250 from Objet based on the methodology developed for parts fabricated by SL in the Laboratory CIMJECT of the Department of Mechanical Engineering on the Federal University of Santa Catarina (UFSC) [9].
Conclusion
With qualitative results, it is possible to notice that EDEN 250 prints satisfactorily small parts, mainly with round formats. Parts with sharp corners do not perform as well as the round format, presenting poor precision and accuracy in the edges.
Even in bigger parts, with 100 mm, for example, the edges resolution is not satisfactory. The resin FullCure® 720 is a good resin for work, however it has high moisture absorption, and it is sensitive to heat.
Classifying the samples according with the technical standard NBR 6158, it is possible to classify the parts in the category IT11 (maximum tolerance of ± 0,06 mm). According with the experiments, the four specimens with circular and squares holes, had variation in the dimensions below the tolerance allowed, what demonstrate a great reliability in the printing process.
In the experiments with pins, most of the specimens presented variations below the maximum allowed. Specimens 1 and 4 of the square pins exceeded in 0.002 mm the tolerance allowed. Showing that the reliability of the printing process of square pins are 50%.
Analyzing the diagonals of the squares, all samples presented results above the maximum tolerance allowed, reaching 9.8% below the nominal size. Expected results due to the roundness of the sharp edges.