Ultrasonic cleaning of 3D printed objects and Cleaning Challenge Devices

Abstract

a b s t r a c tWe report our experiences in the evaluation of ultrasonic cleaning processes of objects made with additive manufacturing techniques, specifically three-dimensional (3D) printers. These objects need to be cleaned of support material added during the printing process. The support material can be removed by dissolution in liquids with or without ultrasonic cavitation.Distinctive stages in the cleaning processes were found for two different liquids (water and NaOH solutions). The combination of ultrasound and high concentration of NaOH has the best results for support material dissolution in the particular conditions studied.The sonication of cleaning processes in ultrasonic baths is typically a slow process. Here we show the advantages of using an ultrasonic horn to clean the surface of small parts and holes more effectively.We introduce a Cleaning Challenge Device design to be used for the universal evaluation of cleaning performance of different equipment or processes, and specifically for ultrasonic baths. The results and conclusions can be of use for different cleaning situations besides 3D printed parts, such as when deciding which protocol has a better performance or comparing different equipment.

Assessment of trapped powder removal and inspection strategies for powder bed fusion techniques

“…Several stage 1 techniques have been previously investigated including: grit-blasting [4][5][6][7], dry-ice blasting [8] and structurally induced removal [9]. A number of stage 2 techniques have also been investigated such as corrosive baths [7,10], electrochemical and plasma polishing [11,12], ultrasonic baths [10] and 'vacuum boiling' [13]. Grit-blasting has become the industry standard and subsequently the most researched.…”

“…Ultrasonic cleaning is widely used as a stage 2 technique [3] and is effective at removing trapped material from polyjet acrylic test pieces [10]. However, sonicating may damage small features due to the explosive collapse of cavitation bubbles.…”

“…Inspection of trapped powder in prior investigations was fairly simple due to the simple test piece geometries. Successful techniques demonstrated for inspecting test geometries have included 'ruler-drop' [4-7, 10]-where a ruled object is used to measure the depth of the cavity and this depth relative to the designed depth is used as a measure of remaining powder, microscopy [7,10] and shadowgraphs [5,17]. However, some AM parts have complex internal geometries and may require nonline-of-sight inspection techniques.…”

“…XCT of AM components is occasionally required for structural integrity checks, with powder inspection being an additional result, but in the general case, the technique is time-consuming and expensive and adds significant costs to each part [18]. An effective solution to this was given by Verhaagen et al [10] who detailed a 'powder challenge device'. This idea stems from the medical industry, where batch inspection of many instruments with complex internal geometries is substituted by a single object with an internal geometry of greater complexity.…”

A novel ultrasonic cavitation enhancer

“…The dye removal occurred in a very specific 'honeycomb' pattern, corresponding to the locations of the pits in the opposite wall of the CIB. A Cleaning Challenge Device (CCD) [8] was printed in two-fold using a DLP 3D printer (S30L, RapidShape). The CCD represents a challenging 3D printed model from which support material needs to be removed.…”