Shape Deposition Manufacturing Process Research Articles

Application of rapid tooling to manufacture customized nasal mask cushion for continuous positive airway pressure (CPAP) devices

PurposeA continuous positive airway pressure (CPAP) device is one of the main treatments for obstructive sleep apnea (OSA) patients. Most patients treated by this method complain about the comfortableness of the mask, but the commercial mask cushions are only available in fixed sizes. Therefore, the purpose of this paper is to apply the rapid tooling (RT) technique to manufacture customized nasal mask cushions, to increase the performance and with price competitiveness.Design/methodology/approachThe patient's face was first duplicated twice by Hygrogum and plaster. The face model, on which the cushion CAD design was based, was digitized by the reverse‐engineering technology. The RT of the cushion was then designed and manufactured by two rapid prototyping techniques – Objet's PolyJet and shape deposition manufacturing (SDM). Finally, silicone was cast into the RT to obtain customized cushions. The customized cushion was compared with two other commercial cushions through fit testing and cost estimation.FindingsThe proposed approach can successfully manufacture customized cushions within a day. The SDM process has advantages in this application over Objet's system. The fit testing showed that the fit factor of the customized cushion was better and less loading was required, which should lead to great improvement in the patient's comfort. Moreover, the price‐to‐performance ratio of the customized cushion can be lower than the commercial ones if more than three cushions were made by a single rapid tool.Originality/valueThis paper has proposed a new application of RT on customized nasal mask cushions for CPAP devices. The customized cushion has lower price‐to‐performance ratio and the cost remains competitive.

Part decomposing algorithm based on STL solid model used in shape deposition manufacturing process

Shape deposition manufacturing is an innovative rapid prototyping technology combining CNC machining and deposition processes and in which if a surface of the part is visible from the build direction it can be directly shaped into desired geometry on part material; if the part features are undercut or face away from the build direction, these part features will be sculptured into the support material in order to form a negative cavity at first, then the part material is deposited into this negative cavity in order to replicate these features into part material. This process is cyclically repeated until all segments have been built. Finally, the sacrificial material is removed, and the finished part is left. This innovative technology has the benefits of commercial rapid prototyping technology; meanwhile, it inherits the accuracy and high surface quality of traditional machining process. For this process to be realized, it is essential to decompose the CAD solid model into a series of manufacturable segments which have no undercut surfaces at the data pretreatment step. In this paper, a solid decomposing strategy is proposed with a detailed discussion on the classification of the segments based on the value of triangle face normal vector, and then an algorithm for auto-decomposing a CAD solid model in STL data format is developed.

Fabrication of meso-scale underwater vehicle components by rapid prototyping process

Underwater vehicles have been developed in many ocean exploration and rescue applications. In smaller scale of underwater vehicles, critical components are not usually commercially available. The cost of non-standard parts is relatively high in the development stage if special molding or precision machining is involved. In this research, major components, propellers and the hull structure, for a meso-scale underwater vehicle were needed in the prototyping stage. Rapid prototyping process was targeted for this purpose. Due to the 3D profile and resolution requirements, shape deposition manufacturing (SDM) process was selected to fabricate these polymer components. Without special fixtures or molds, propellers with smooth surfaces were successfully manufactured by the SDM process. Besides, two types of assembly strategies of the hull structure were investigated. Type I involves dividing the hull vertically and screwing the two halves together, while Type II separates the hull horizontally and seals by glue after assembly. The parts of the hull for these two approaches were both achievable by the SDM process and Type II was favored in terms of time consumption. In conclusion, this research has provided a solution to fabricate 3D complex components of the meso-scale underwater vehicles prototypes and can be extended to other similar-scale vehicles.

Manufacture of three-dimensional valveless micropump

Abstract Up to the present, the manufacture of the micropump generally used MEMS processes to obtain micro scale channels. However, the geometry of the channels is usually 2.5D and the cost is relatively high due to the characteristics of the most micro fabrication techniques. In this research, we focused on manufacture of three-dimensional valveless micropumps in inexpensive approach. The design of the micropump consists of three horizontal inlet channels and one vertical outlet channel. The 3D geometry of the channels with minimum width of 80 μm gives great challenges in fabrication and is difficult to be achieved by traditional micro fabrication techniques. Shape deposition manufacturing (SDM) process, a layered manufacturing technique involving repeated material deposition and removal, was used to manufacture the chamber and channels of the micropump. CAD/CAM software was applied to slice the 3D model and plan the manufacturing sequences. The piezoelectric buzzer was attached to the fabricated valveless micropump chamber to test the performance. Three different channel width designs were manufactured successfully and tested at various piezo-triggered frequencies. This research provides a solution to manufacture the three-dimensional micropump geometry inexpensively. SDM process was proved to be a suitable approach to generate pre-assembled valveless micropump structure with micro channels, and is applicable to other similar applications.

Part strength improvement in polymer shape deposition manufacturing

Shape deposition manufacturing (SDM) is a layered manufacturing process which iteratively combines material addition and removal to create artifacts in a variety of materials. Castable thermoset resins have been used to build a variety of parts via polymer SDM. The strength of these parts is determined by the bulk material properties of the part materials and by their interlayer adhesion. Early polyurethane materials had high bulk strength but poor interlayer adhesion, resulting in weak multilayer parts. Interlayer strength improvements were achieved through additional processing steps or the use of different polyurethane and epoxy part materials. These improvements allowed the fabrication of aerodynamic flap mechanisms used in wind‐tunnel testing. These parts are examples of the intricate, functional mechanisms to which the polymer SDM process is ideally suited.