Subtractive Rapid Prototyping Research Articles

Additive and subtractive rapid prototyping techniques: a comparative analysis of FDM & CNC processes

Additive and subtractive rapid prototyping techniques: a comparative analysis of FDM & CNC processes

Optimization of Material Removal Rate and Dimensional Errors in Subtractive Rapid Prototyping of Polycarbonate Material

None of the research found in the literature investigates and optimizes the subtractive rapid prototyping process parameters in order to fabricate polycarbonate material. This research is conducted to optimize the subtractive rapid prototyping process parameters of polycarbonate material in order to achieve the maximum material rate removal without exceeding the dimensional error value of 1 mm, similar to the result of additive manufacturing. The response surface methodology is implemented in this research to optimized three process parameters, which are feed rate, step-over, and depth of cut. Two responses investigated in this research are material rate removal and dimensional error. The response optimizer is used to optimize the responses. The result shows that optimum material removal rate and dimensional error that can be achieved is 2.494 mm3/s and 0.97 mm respectively. A confirmation test experiment has been conducted to verify the optimization result.

Optimisation of subtractive rapid prototyping process parameters using response surface methodology

Subtractive rapid prototyping machine is the most suitable tool to manufacture a polymer based prosthetic part because it is able to achieve a low surface roughness value for a complex and customised part. Many investigations have been conducted to explain the relation among the surface roughness value, the material rate removal, and the subtractive rapid prototyping process parameters. It is important to find the optimum process parameters in order to achieve the most efficient and productive process. However, none of the research found in the literature optimises the subtractive rapid prototyping process parameters in fabricating polycarbonate part. Therefore, this research aims to find the optimum process parameters to achieve the lowest arithmetic average of surface roughness value of the polycarbonate part in maximum material removal rate. In this research, the response surface methodology is implemented to optimised feed rate, step-over, and depth of cut of the subtractive rapid prototyping process. This research finds the feed rate, step-over, and depth of cut values that can be used to achieve the best result in manufacturing of polycarbonate material.

Application of FDM technology to reduce aerodynamic drag

Purpose The purpose of this paper is to analyze the aerodynamic improvements obtained in a wing section with a NACA 0018 airfoil manufactured using the fused deposition modeling (FDM) technique with regard to a smooth surface made by milling. The creation of micro-riblets on the surface of the airfoil, due to the deposition of the material layer by layer, improves the general aerodynamic performance of the parts, provided that the riblets are parallel to the flow line. The incidence of the thickness of the thread deposited in each layer – to be the variable on which the geometry of the riblets is based – was studied. Design/methodology/approach The wing section was designed using 3D software. Three different models were designed by rapid prototyping, using additive and subtractive manufacturing. Two of the profiles were manufactured using FDM varying the thickness of the layer to be able to compare the aerodynamic improvements. The third model was manufactured using a subtractive rapid prototyping machine generating a smooth surface profile. These three models were tested inside the wind tunnel to be able to quantify the aerodynamic efficiency according to the geometry and the riblets size. Findings The manufacture of an aerodynamic profile using FDM provides, in addition to the lightness and the ability to design parts with complex geometries, an improvement in the aerodynamic efficiency of 10 per cent compared with profiles with a smooth surface. Practical implications With the aerodynamic advantage gained through the use of FDM positions, the additive manufacturing serves as an excellent alternative for the manufacture of lightweight aerodynamic parts, with low structural loading and with low Reynolds number (∼5·105). This technological advantage would be applied to the UAV (unmanned aerial vehicle) industry. Originality/value The study carried out in this article demonstrates that the use of FDM as a manufacture process of end-used parts that are subject to movement generates an additional advantage that had not been considered. The additive manufacturing allows us to directly manufacture riblets by creating the necessary surface so as to reduce the aerodynamic drag.

The Influence of Depth of Cut, Feed Rate, and Step-over on Dimensional Accuracy in Subtractive Rapid Prototyping of Polycarbonate Material

Subtractive rapid prototyping is fast and automatic three dimensions physical modelling that uses computer aided design model as the input. The dimensional accuracy of the result of the subtractive rapid prototyping is influenced by its process parameters. The aim of this research is to study and then develop a model that shows the influence of depth of cut, feed rate, and step-over on the vertical length error, horizontal length error, and depth error in subtractive rapid prototyping of polycarbonate material. This research implements response surface methodology to develop the model and then followed by the residual tests to evaluate the developed model. The result shows that the increase of the feed rate and the step-over will increase the horizontal dimension error. The most influenced factor on the horizontal dimension error is the step-over. Meanwhile, the vertical dimension error will be affected mostly by the step-over. Last, the depth error is influenced by the feed rate, the step-over, and the depth of cut. The depth of cut is the most critical factor that increases the depth error. The developed models give an insight on how several process parameters of rapid prototyping will influence the dimensional accuracy of a polycarbonate material. Based on the model, efficient resources utilization can be achieved.

A Method to Represent Heterogeneous Materials for Rapid Prototyping: The Matryoshka Approach.

The purpose of this paper is to present a new method for representing heterogeneous materials using nested STL shells, based, in particular, on the density distributions of human bones. Nested STL shells, called Matryoshka models, are described, based on their namesake Russian nesting dolls. In this approach, polygonal models, such as STL shells, are "stacked" inside one another to represent different material regions. The Matryoshka model addresses the challenge of representing different densities and different types of bone when reverse engineering from medical images. The Matryoshka model is generated via an iterative process of thresholding the Hounsfield Unit (HU) data using computed tomography (CT), thereby delineating regions of progressively increasing bone density. These nested shells can represent regions starting with the medullary (bone marrow) canal, up through and including the outer surface of the bone. The Matryoshka approach introduced can be used to generate accurate models of heterogeneous materials in an automated fashion, avoiding the challenge of hand-creating an assembly model for input to multi-material additive or subtractive manufacturing. This paper presents a new method for describing heterogeneous materials: in this case, the density distribution in a human bone. The authors show how the Matryoshka model can be used to plan harvesting locations for creating custom rapid allograft bone implants from donor bone. An implementation of a proposed harvesting method is demonstrated, followed by a case study using subtractive rapid prototyping to harvest a bone implant from a human tibia surrogate.

Biopolymer‐Based Gel Casting of Ferroelectric Ceramics

Ferroelectric ceramics have a wide range of industrial applications. While components can be formed through simple ‘press and sinter’ approaches, there is an increasing need for more flexible processing methods. Suspension based forming promotes greater homogeneity, through elimination of processing defects, and allows the formation of more complex shaped components. In the present work, the application of aqueous gel casting technologies is reviewed, and in particular the use of natural biopolymers as gelation aids for such approaches. Recent studies of the application of such technology to complex shape forming of BaTiO3 ferroelectric ceramics are examined. Emphasis is placed upon a simple subtractive rapid prototyping method, utilizing aqueous gel casting in combination with green machining.

Accuracy and precision of polyurethane dental arch models fabricated using a three-dimensional subtractive rapid prototyping method with an intraoral scanning technique

ObjectiveThis study aimed to evaluate the accuracy and precision of polyurethane (PUT) dental arch models fabricated using a three-dimensional (3D) subtractive rapid prototyping (RP) method with an intraoral scanning technique by comparing linear measurements obtained from PUT models and conventional plaster models.MethodsTen plaster models were duplicated using a selected standard master model and conventional impression, and 10 PUT models were duplicated using the 3D subtractive RP technique with an oral scanner. Six linear measurements were evaluated in terms of x, y, and z-axes using a non-contact white light scanner. Accuracy was assessed using mean differences between two measurements, and precision was examined using four quantitative methods and the Bland-Altman graphical method. Repeatability was evaluated in terms of intra-examiner variability, and reproducibility was assessed in terms of inter-examiner and inter-method variability.ResultsThe mean difference between plaster models and PUT models ranged from 0.07 mm to 0.33 mm. Relative measurement errors ranged from 2.2% to 7.6% and intraclass correlation coefficients ranged from 0.93 to 0.96, when comparing plaster models and PUT models. The Bland-Altman plot showed good agreement.ConclusionsThe accuracy and precision of PUT dental models for evaluating the performance of oral scanner and subtractive RP technology was acceptable. Because of the recent improvements in block material and computerized numeric control milling machines, the subtractive RP method may be a good choice for dental arch models.

Technique Achievement of Glass Objects Using Kiln Casting Method

In the context of the competitive actual environment, the production need to adapt to the preferences of the consumers, this represents the essential goal for all manufacturers. The production flexibility can be achieved by designing and marketing of new products or/and modify existing products in short time and at low cost. The technique presented in these article addresses of manufacturers and designers who made glass products unique or small series, adapted to consumer demands. In recent decades, digital fabrication methods are developed in various fields (aeronautics, shipbuilding, automotive, construction, architecture, industrial design and so on) and gained great popularity due to relevant advantages over the traditional production methods. Sculptural surfaces (also called free form surfaces) of the product with aestethetic requirements and/or functional role can be achieved through various technologies RP & M (Rapid Prototyping and Manufacturing). The Rapid Prototyping technologies can be grouped unto two major categories. First one refers to additive processes RP. From this point of view there are over 40 different types such as: stereo lithography (SL), Laminated Object Manufacturing (LOM), Selective Laser Sintering (SLS), 3D Printing (3DP), Solid Ground Curring (GSC) and Fused Deposition Modelling (FDM). The second one consists of subtractive Rapid Prototyping. Subtractive Rapid Prototyping (SRP) is one of the methods used for processing digital models into physical objects used for RP and for Rapid Tooling (RT). It is difficult to say what method is the best RP/RT; every one of them has advantages and disadvantages. The choice of the appropriate method depends on many factors, such as: product geometry, material type, dimensional accuracy, surface roughness on finished product, and so on. The starting point of this work consists in three photographs that are digitally processed to achieve the expansion of 2D in 3D structure. The expanded model is imported into computer-aided manufacturing (CAM) software. The parameters required to processing on Computer Numerical Control (CNC) machine are set, in order to obtain the shape of the casting mold. The schedule of heat treatment for glass is adapted according to the characterics of glass, mold material and the type of kiln. Rheological behaviour of glass has a key parameter in processing glass. The steps of kiln casting process (temperature ramps, heat treatment time) are choose at some values of viscosity (also called viscosity points ) related with glass type and size of object. The presented method can be successfully used in the manufacturing process offering to companies the possibility of increasing the capacity of new product development.

Computing Axes of Rotation for Setup Planning Using Visibility of Polyhedral Computer-Aided Design Models

This paper presents a method for determining feasible axes of rotation for setup planning, based on the visibility of a polyhedral model. The intent of this work was to develop a feature-free approach to setup planning, with the specific focus on multi-axis machine setups. Visibility mapping can provide a quantitative evaluation of a surface, a feature or an entire part model; however, the next step is to use this information for process planning. In this paper, we present an approach of using a visibility map to evaluate axes of rotation that could be used in an indexer-type setup on a machine tool. Instead of using expensive and complicated multi-axis machining, it may be feasible to machine using multiple three-axis toolpaths if a single axis of rotation can be used to rotate the part through the minimum set of orientations. An algorithm is presented that is capable of processing visibility information from a polyhedral model; hence, the method is generic and does not require feature detection. As such, the work is applicable to a variety of applications; in particular for subtractive rapid prototyping where complex geometry may not contain recognizable features.

Advanced process planning for subtractive rapid prototyping

PurposeSubtractive rapid prototyping (SRP) uses layer‐based removal from a plurality of orientations in order to create geometry in a highly automated manner. However, unlike additive means, the method can be inefficient due to redundant cutting operations on previously machined regions. The purpose of this paper is to present process planning methods for SRP, specifically dealing with stock material management in multiple setup operations.Design/methodology/approachAnalysis of remaining stock material was performed by considering slices of respective stereolithography (STL) models. Further, an initial approximation was made of accessibility to enable iterative visibility analysis. The combination of these approaches led to efficient and fast algorithms. After analysis, the slices could be converted back to useful STL models through polyhedral reconstruction.FindingsThis method of approximation yields results similar to exact geometry. Using remaining stock data from this approach leads to a significant reduction in tool path length and processing time in SRP.Originality/valueThis paper presents novel methods of geometric representation and inaccessible volume calculation for four‐axis layer‐based machining and shows a successful implementation in an SRP system.

Rapid fabrication of custom patient biopsy guides

Image‐guided surgery is currently performed using frame‐based as well as frameless approaches. In order to reduce the invasive nature of stereotactic guidance and the cost in both equipment and time required within the operating room, we investigated the use of rapid prototyping (RP) technology. In our approach, we fabricated custom patient‐specific face masks and guides that can be applied to the patient during stereotactic surgery. While the use of RP machines has previously been shown to be satisfactory from an accuracy standpoint, one of our design criteria – completing the entire build and introduction into the sterile field in less than two hours – was unobtainable. (1) Our primary problems were the fabrication time and the nonresistance of the built material to high‐temperature sterilization. In the current study, we have investigated the use of subtractive rapid prototyping (SRP) machines to perform the same quality of surgical guidance, while improving the fabrication time and allowing for choosing materials suitable for sterilization. Because SRP technology does not offer the same flexibility as RP in terms of prototype shape and complexity, our software program was adapted to provide new guide designs suitable for SRP fabrication. The biopsy guide was subdivided for a more efficient build with the parts being uniquely assembled to form the final guide. The accuracy of the assembly was then assessed using a modified Brown‐Roberts‐Wells phantom base by which the position of a biopsy needle introduced into the guide can be measured and compared with the actual planned target. These tests showed that: 1) SRP machines provide an average technical accuracy of 0.77 mm with a standard deviation of the mean of 0.07 mm, and 2) SRP allows for fabrication and sterilization within three‐and‐a‐half hours after diagnostic image acquisition. We are confident that technology is capable of reducing this time to less than one hour. Further tests are being conducted to determine the registration accuracy of the face mask on the patient's head under IRB‐approved trials. The accuracy of this new guidance technology will be verified by judging it against current frame‐based or frameless systems.PACS number: 87.57.Gg

Automated fixture design for a rapid machining process

PurposeThe purpose of this paper is to present a methodology for the automated design of a fixturing system for a rapid machining process.Design/methodology/approachThe method proposed is the use of sacrificial fixturing, similar to the support structures in existing rapid prototyping (RP) processes. During the machining process, sacrificial supports emerge incrementally and, at the end of the process, are the only entities connecting the part to the remaining stock material.FindingsThe support design methods have been shown to be extremely flexible in securing a variety of complex parts with relatively tight part tolerances using a rapid machining process.Research limitations/implicationsThe automated design of support structures is currently relegated to use in a CNC rapid prototyping process that uses a fourth axis for rotary setups.Practical implicationsThe methods used here make rapid machining feasible, as it solves the daunting problem of automated fixturing.Originality/valueThe paper proposes an innovative solution for an automatic fixturing system in subtractive RP.

Complete arch implant rehabilitation using subtractive rapid prototyping and porcelain fused to zirconia prosthesis: A clinical report

The applications of various technological advances in implant dentistry and in all aspects of the diagnostic, treatment planning, surgical, and restorative phases are gaining popularity. Additive rapid prototyping and computer-aided design/computer-aided manufacturing (CAD/CAM) technology are used to generate stereolithographic surgical guides and prefabricated interim prostheses to facilitate implant surgery and immediate loading, respectively. Subtractive rapid prototyping is used for fabrication of zirconia frameworks for definitive implant prostheses. This clinical report describes the comprehensive application of these technological advances in implant rehabilitation to optimize surgical and prosthodontic outcomes as well as patient comfort.

SU-FF-J-22: Rapid Fabrication of Custom Router Guides for Craniotomy

Purpose: Image guidance allows surgeons to perform accurate and minimally invasive surgical procedures. Advancements in the field of rapid prototyping have provided the opportunity to design patient specific guidance systems. At the University of Florida, this technology has been applied to the fabrication of patient specific routers that allows guiding a surgical drill during craniotomy. Methods and Materials: First, the CT scan of a patient's head is used to model the patient's face. A custom fitted facemask is built from this model and physically fabricated using our subtractive rapid prototyping (SRP) machine. Second, the same CT scan is used to model the patient's skull and to draw a craniotomy contour on the surface of the skull. The model and the contour are then processed to build a router guide that can provide guidance not only for following the craniotomy contour, but also for monitoring the depth of the drill bit as it is moved around the route. The router guide is fabricated with our SRP and attached to the facemask. During surgery, the facemask provides a unique positioning for the router on the skull. A head CT scan was used to fabricate 3 different router guides. A plaster phantom representing a hybrid head (face on the front and skull on the back) was fabricated from the CT scan and used to experiment the router guides. Results: The 3 facemasks provided a unique fit on the phantom and the cut along the route was regular, leaving only a thin layer of bone (from 0.1 to 0.3 mm) that could be easily broken and detached from the skull. Each device was designed and fabricated in less than 4 hours. Conclusion: This experiment demonstrates that a SRP machine can be used for fast and accurate fabrication of custom guides for surgical tools.