Freeform Products Research Articles

Automated deviation-aware landmark selection for freeform product accuracy qualification in 3D printing

Landmarks are essential in non-rigid shape registration for identifying the correspondence between designs and actual products. In 3D printing, manual selection of landmarks becomes labor-intensive, due to complex product geometries and their non-uniform shape deviations. Automatic selection, however, has to pinpoint landmarks indicative of geometric regions prone to deviations for accuracy qualification. Existing automatic landmarking methods often generate clustered and redundant landmarks for prominent features with high curvatures, compromising the balance between global and local registration errors. To address these issues, we propose an automatic landmark selection method through deviation-aware segmentation and landmarking. As opposed to segmentation for semantic feature identification, deviation-aware segmentation partitions a freeform product for high-curvature region identification. Prone to deviation, these regions are generated through curvature-sensitive remeshing to extract vertices of high curvature and automatic clustering of vertices based on vertex density. Within each segment or high-curvature region, a curvature-weighted function is tailored for the Gaussian process landmarking to sequentially select landmarks with the highest local curvatures. Furthermore, we propose a new evaluation criterion to assess the effectiveness of selected landmarks through registration. The proposed approach is tested through automatic landmarking of printed dental models.

Task allocation and coordinated motion planning for autonomous multi-robot optical inspection systems

Autonomous multi-robot optical inspection systems are increasingly applied for obtaining inline measurements in process monitoring and quality control. Numerous methods for path planning and robotic coordination have been developed for static and dynamic environments and applied to different fields. However, these approaches may not work for the autonomous multi-robot optical inspection system due to fast computation requirements of inline optimization, unique characteristics on robotic end-effector orientations, and complex large-scale free-form product surfaces. This paper proposes a novel task allocation methodology for coordinated motion planning of multi-robot inspection. Specifically, (1) a local robust inspection task allocation is proposed to achieve efficient and well-balanced measurement assignment among robots; (2) collision-free path planning and coordinated motion planning are developed via dynamic searching in robotic coordinate space and perturbation of probe poses or local paths in the conflicting robots. A case study shows that the proposed approach can mitigate the risk of collisions between robots and environments, resolve conflicts among robots, and reduce the inspection cycle time significantly and consistently.

An integrated curvature surface inspection and prediction system for 5-axis synchronization machining

There is an urgent demand for free-form products in industry at the present time because of their superior appearance and the wide variety of functions they perform. Five-axis high-speed CNC machining technology has developed to satisfy this demand, but further improvement in surface quality metric inspection technology is the big challenge it now faces. In this study, the effects of jerk on the performance of five-axis synchronous high-speed CNC ball nose end mills on a freeform turbine mold were investigated. The relationships of characteristics of the images of 14 jerk-cluster finished workpieces with different jerk setting values were established, allowing surface texture features to be analyzed and surface roughness predicted. In addition, machine learning methods were integrated with the surface feature analysis to construct a virtual machining module that acts as a performance prediction system, merging the virtual machine tool functions, surface texture processor, and AI roughness prediction processor. Using the geometric information of the workpiece, cutting parameters and machine tool parameters as inputs, product performance metrics combining surface roughness and machining time can be predicted as outputs of the system. The integrated system provides users with a way to evaluate manufacturing performance before performing actual operations and to reduce test time for cutting parameter development. The model is suitable for complex surface finishes as well as for the production of small batches with high parametric variance. In addition, the partial set of image processing and roughness prediction modules can be used alone as an effective intelligent surface quality inspection system.

A hybrid transfer learning framework for in-plane freeform shape accuracy control in additive manufacturing

Shape accuracy control is one of the quality issues of greatest concern in Additive Manufacturing (AM). An efficient approach to improving the shape accuracy of a fabricated product is to compensate the fabrication errors of AM systems by modifying the input shape defined by a digital design model. In contrast with mass production, AM processes typically fabricate customized products with extremely low volume and huge shape varieties, which makes shape accuracy control in AM a challenging problem. In this article, we propose a hybrid transfer learning framework to predict and compensate the in-plane shape deviations of new and untried freeform products based on a small number of previously fabricated products. Within this framework, the shape deviation is decomposed into a shape-independent error and a shape-specific error. A parameter-based transfer learning approach is used to facilitate a sharing of parameters for modeling the shape-independent error, whereas a feature-based transfer learning approach is taken to promote the learning of a common representation of local shape features for modeling the shape-specific error. Experimental studies of a fused filament fabrication process demonstrate the effectiveness of our proposed framework in predicting the shape deviation and improving the shape accuracy of new products with freeform shapes.

Design of powder nozzle for high resource efficiency in directed energy deposition based on computational fluid dynamics simulation

Directed energy deposition (DED), an additive manufacturing process, is a suitable approach for freeform production with metallic materials. By generating a melt pool with a high-power laser beam, injected material powder is contentiously laminated on a baseplate by melting and solidifying. Although all supplied powder should be molten and solidified in order to reduce the material waste, powder distribution is difficult to converge owing to turbulence around the melt pool. Furthermore, an inappropriate powder supply easily leads to sputter generation, which also increases the material waste. In this study, the gas flow under a powder nozzle was analyzed by a computational fluid dynamics (CFD) simulation in order to achieve a high convergence in the powder supply. By measuring the powder distribution with a laser light sheet system and conducting deposition tests, the powder distribution and supply efficiency were experimentally evaluated. According to a gas-solid multiphase-flow simulation, the convergence distance of the powder flow should be shorter than the laser beam focus distance to improve the powder convergence with a lower gas-flow rate. Moreover, the powder nozzles were redesigned by taking the simulation results into consideration, and deposition tests were conducted to evaluate the powder supply efficiency, porosity rate, and penetration rate. The experimental result of the designed nozzle shows a clear improvement in the powder supply efficiency from 50.2 to 66.0%.

Prescriptive Modeling and Compensation of In-Plane Shape Deformation for 3-D Printed Freeform Products

Although 3-D printing or additive manufacturing (AM) holds great promise as a direct manufacturing technology, the geometric accuracy of AM built products remains a critical issue, especially for freeform products with complex geometric shapes. Efforts have long been attempted to improve the accuracy of AM built freeform products. But there is a lack of generic and prescriptive methodology transparent to specific designs and AM processes. This paper fills the gap by establishing the methodology to predict and compensate the in-plane ( $x-y$ plane) geometric deformation of AM built freeform products based on a limited number of simple trial shapes. Built upon our previous predictive model and optimal compensation study for the cylinder and polyhedron shapes, this paper makes a breakthrough by directly controlling arbitrary freeform shape deformation from computer-aided design. Experimental investigation using stereolithography process successfully validates the proposed prescriptive modeling and compensation methodology. This paper provides the prospect of proactively improving printing accuracy of arbitrary products built by a variety of AM processes.

An Initial Study of Aerosol Jet® Printed Interconnections on Extrusion-Based 3D-Printed Substrates

The combination of different additive manufacturing techniques to produce freeform products with multifunctional properties is gaining increasing popularity. In the research presented, Aerosol Jet® Printing (AJP) is combined with extrusion-based 3D printing. AJP starts with an ink to create micro-tracks. These tracks commonly have widths ranging from a few micrometers up to several millimeters and track heights ranging from a few tenths of a micrometer up to several micrometers, unlike extrusion-based 3D printers with which the extruded material usually has a resolution of tenths of millimeters. AJP can therefore be a complementary technique for extrusion-based 3D printing; in this manner, fine high resolution features can be added onto relatively rapidly produced extrusion-based 3D printed parts. Furthermore, AJP can be used to produce electrically conductive tracks to create interconnections, inductors, capacitors, strain gauges, etc. In this paper, the creation of AJP-manufactured interconnects on extrusion-based 3D printed substrates is investigated. The relevant AJP process parameters to take into account are the flow rates of the aerosol, the flow rate of the sheath gas, the temperature settings of the ink and substrate, and the platform speed and nozzle-to-substrate distance. To obtain reliable results, the AJP process parameters are optimized for printing single-layered and multilayered silver ink tracks on extrusion-based 3D-printed surfaces. Important quality output parameters include the dimensions and the electrical properties of the printed interconnects.

Material properties and selection for selective laser sintering process

Nowadays, to produce better quality products with less cost, shorter lead times, more customer delights have become the key requirements to remain competitive in the global market. To fulfil these requirements, additive manufacturing (AM) provides a technological tool for making solid free form products. Selective laser sintering (SLS) is one of the AM techniques using wide range of materials developed by various groups of technology for producing high strength parts with good aesthetic quality satisfying the customer needs. To make this technology viable, more investigation is required to improve the properties of fabricated parts, its accuracy and development of new materials for various applications. Currently, limited materials are available with very high cost that impedes growing number of applications of AM. Knowledge of SLS material properties and fabrication parameter relationship leads to appropriate selection of material for various applications without compromising the value and quality of the SLS fabricated part and customer satisfaction.

901 力覚デバイスによるデザイン教育の可能性(OS5-1 技術教育・工学教育I,OS5 技術教育・工学教育)

This paper describes potentiality of design education by using force sensors device. The device is like a 3D-mouse (PHANTOM) which gives a feeling of object recognition. Generally, designing like an idea-sketch is the first process for manufacturing and it is very important to use the digital data for modeling. FreeForm modeling with the PHANTOM is introduced as a tool for design education. The SensAble Technologies PHANTOM product line of haptic devices makes it possible for users to touch and manipulate virtual objects. In this paper, potentiality of design education using the FreeForm product is discussed and it is indicated that the FreeForm system is effective for 3D clay digital-modeling.

Tool Path Planning and NC Generation of Tilted Plane Machining Features for Five-Axis Machining

Designs of free-form surface products are becoming increasingly complex. In traditional three-axis machine tool machining, errors that are caused by repetitive positioning and the costs of fixture jig design and manufacturing are critical. Since multi-axis machining provides two more rotational degrees of freedom than a three-axis machine tool, the former can solve these problems, and has therefore become the trend of precision cutting. As multi-axis machined parts often have holes and grooves on the tilted plane, this work proposes a method for machining tilted working plane features and for NC generation on a five-axis machine. The developed module can provide common geometric features, allowing the user to alter the machining feature and sequence on the tilted plane quickly using the parent-child relationship in a tree diagram, and plan the tool path. The postprocessor module developed in this paper can transform the tool path into an NC program required for machining. Finally, solid cutting simulation software is utilized to confirm the feasibility and correctness of the tool path and NC data of the tilted plane machining feature.

Single-Point Incremental Micro-Forming of Thin Shell Products Utilizing High Formability

This paper describes single-point incremental micro-forming of miniature shell products 50 µm to 1000 µm in size. First, the conditions of the micro-forming of a pyramid with a 1 mm square base were optimized to cause large elongation of a blank up to 128%, resulting in a tall pyramid with an elevation angle of 64°. Next, the influence of the tool rotational speed on the forming limit in forming a pyramid with a 50 µm square base was investigated. It was found that the optimum rotational speed decrease with the size of a pyramid. Finally, letters and numbers 100 µm to 500 µm in size were formed as free form products. The effect of grain size on the miniature shell products was discussed based on the results and it was concluded that the effect must be taken into consideration in micro-forming processes of miniature products smaller than 100 µm in size as far as the grain size is not very small as compared with the size of a product.

Integrated Manufacturing Technology for Design, Machining and Measurement of Freeform Optics

Ultra-precision machining technology plays an important role in the manufacture of advanced freeform optics. An integrated manufacturing platform is developed to cover freeform optics design,CAD continuous data transform,freeform model re-construction,simulation and cutting optimization of multi-axis machining,compensation of machining errors,and the measurement and characterization of freeform surfaces. The adoption of the platform technology shortens the time to develop complex NC programs for different multi-axis machine tools to manufacture different types of freeform optics. This system helps to avoid expensive repeated cutting tests,as well as to improve the surface quality of freeform products. The stability and effectiveness of the proposed integrated platform are verified through a series of tests.

Volume Parameterization for Design Automation of Customized Free-Form Products

This paper addresses the problem of volume parameterization that serves as the geometric kernel for design automation of customized free-form products. The purpose of volume parameterization is to establish a mapping between the spaces that are near to two reference free-form models, so that the shape of a product presented in free-form surfaces can be transferred from the space around one reference model to another reference model. The mapping is expected to keep the spatial relationship between the product model and reference models as much as possible. We separate the mapping into rigid body transformation and elastic warping. The rigid body transformation is determined by anchor points defined on the reference models using a least-squares fitting approach. The elastic warping function is more difficult to obtain, especially when the meshes of the reference objects are inconsistent. A three-stage approach is conducted. First, a coarse-level warping function is computed based on the anchor points. In the second phase, the topology consistency is maintained through a surface fitting process. Finally, the mapping of volume parameterization is established on the surface fitting result. Compared to previous methods, the approach presented here is more efficient. Also, benefitting from the separation of rigid body transformation and elastic warping, the transient shape of a transferred product does not give unexpected distortion. At the end of this paper, various industry applications of our approach in design automation are demonstrated. Note to Practitioners-The motivation of this research is to develop a geometric solution for the design automation of customized free-form objects, which can greatly improve the efficiency of design processes in various industries involving customized products (e.g., garment design, toy design, jewel design, shoe design, and glasses design, etc.). The products in the above industries are usually composed of a very complex geometry shape (represented by free-form surfaces), and is not driven by a parameter table but a reference object with free-form shapes (e.g., mannequin, toy, wrist, foot, and head models). After carefully designing a product around one particular reference model, it is desirable to have an automated tool for "grading" this product to other shape-changed reference objects while retaining the original spatial relationship between the product and reference models. This is called the design automation of a customized free-form object. Current commercial 3-D/2-D computer-aided design (CAD) systems, developed for the design automation of models with regular shape, cannot support the design automation in this manner. The approach in this paper develops efficient techniques for constraining and reconstructing a product represented by free-form surfaces around reference objects with different shapes, so that this design automation problem can be fundamentally solved. Although the approach has not been integrated into commercial CAD systems, the results based on our preliminary implementation are encouraging-the spatial relationship between reference models and the customized products is well preserved

From virtuality to reality: Individualized freeform model design and rapid manufacturing

AbstractIndividuation, customer involvement, and rapid prototyping are crucial factors for developing a new product. A novel method addresses these issues by allowing both professional designers and general customers to freely express their design ideas for creating freeform product models and quickly developing physical prototypes. A virtual design environment is created to achieve natural human–computer interaction and multidesigners' collaboration via the Internet. Ray‐casting and other techniques are adopted to achieve real‐time calculation, stereo display, and haptic feedback. A design and manufacturing experiment is conducted to test feasibility and provide a preliminary understanding of how to improve this method. © 2005 Wiley Periodicals, Inc. Hum Factors Man 15: 445–459, 2005.

Parting line formation by slicing a 3D CAD model

An effective computer-aided parting line/surface formation algorithm can increase the overall efficiency in the mould design and manufacturing processes. The presence of free-form surfaces in a product model imposes a burden on mould makers to determine the parting line and parting surfaces. Previously proposed algorithms, although available, are few, and mainly deal with product with planar or simple curved surfaces. A new algorithm, which adopts an uneven slicing on the product model, is proposed. The algorithm provides a quick and effective way to locate the parting line and parting surface of a free-form product model.

Sketch input for conceptual surface design

Contemporary CAD systems do not encourage a designer to change the geometry of free-form surfaces. The lack of flexibility to modify preliminary design objects is, in general, the major obstacle for effective computer support during conceptual modelling. We have studied this problem for the process of fast creation of three-dimensional (3D) free-form product shapes. Any tool in this process must at least offer the speed, flexibility and intuitiveness common for traditional working procedures based on sketching on paper. A feasible way to significantly enhance conceptual shape design is fast and easy entering of paper sketches into 3D model space. Utilizing this principle we have developed a new algorithm for the input and modification of hand-sketched profile curves. The algorithm has been incorporated in a prototype surface modeller in which the profiles, and thus the surfaces in 3D, can be directly modified by sketching. The resulting system has been tested by industrial design professionals. Their opinions were encouraging and led to a number of recommendations for the tool. We describe the algorithm, its implementation and its application in geometrical design. We also present examples and results obtained with the sketching system.