Sculptured Surfaces Research Articles

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.

A topological-free method for three-axis tool path planning for generalized radiused end milled cutting of a triangular mesh surface

A tool path generation method for a sculptured surface defined by a triangular mesh is presented. Existing tool methods require extensive computer processing power mainly because surface topology for triangular meshes is not provided. The three-axis tool path planning method presented in this paper for generalized radius end mills avoids this problem (and does not need topological information) by offsetting each triangular facet individually. Offsetting a single triangle results in many more triangles, many of which are redundant, increasing the time required for data handling in subsequent steps. To avoid the large number of triangles, the proposed method creates a bounding space to which the offset surface is limited. Applying the boundary space limits the size of the offset surface resulting in a reduction in the number of triangular surfaces generated. The offset surface generation may still result in unwanted intersecting triangles. The tool path planning strategy addresses this issue by applying hidden-surface removal algorithms. Simulation and machining tests are used to validate the tool paths generated using this method.

A new approach to generating arc length parameterized NURBS tool paths for efficient three-axis machining of smooth, accurate sculptured surfaces

With the development of a new function of computer numerical control controllers, nonuniform rational B-spline (NURBS) interpolation, NURBS tool path generation for sculptured surface machining is under extensive research. The common procedures of the current NURBS tool path planning methods are as follows: first, to find a group of cutter contact points on a sculptured surface; second, to calculate their corresponding cutter locations (CLs); then, to fit a NURBS tool path to the CLs within a prescribed tolerance; and finally, to inspect the tool path for possible gouge by the tool and delete the invalid path segments, if any. However, the NURBS tool path has the following problems: (a) although it passes through the discrete CLs of the theoretical CL path, the deviation along the two paths could be larger than the tolerance; (b) its parameter is not the arc length of the path; and (c) it is difficult to detect gouge along the NURBS path and to remove the invalid segments from it. Consequently, NURBS tool paths generated with the current methods of commercial computer-aided design/computer-aided manufacturing (CAD/CAM) software cannot be used to make smooth and accurate surfaces. To address these problems, this work proposes a new approach to generating arc length parameterized NURBS tool paths with high accuracy in terms of the theoretical CL paths and without gouge and interference. Two practical examples in this work clearly demonstrate the feasibility of this approach and the advantages of the generated NURBS tool paths. Therefore, this approach can be implemented into the CAD/CAM software to promote NURBS machining in industry.

Application of Siemens 840Di System in the Reconstruction of KISC Roll Collar Grinder

This work studies the reconstruction of high-speed roll grinder for sculptured surfaces with high feed rates. Experiments and predictions were focused on representative surfaces of dies and molds, whose geometric complexity and complexity distribution were modified parametrically. CNC programs for machining these surfaces were executed in a HERKULES HSF2CNC machining center with a SIEMENS 840D controller, with different levels of programmed feed rate. Discrepancies between programmed and actual feed rates were evaluated. A mechanistic approach for roll grinder in high-speed milling of sculptured surfaces is proposed. The mechanistic model construction is based on: (a) the frequency distribution of linear interpolation path lengths in the CNC program and (b) a characterization of the machine tool for brisk and smooth movements. Two case studies were used to demonstrate the effectiveness of the proposed approach. The reconstruction model is capable of the manufacturing.

Improved Rotary Contact Method for 5-Axis Sculptured Surfaces Machining

The 5-axis tool positioning strategy named rotary contact method (RCM) for sculptured surfaces machining has been developed in our previous paper (Fan et al., 2012, “Rotary Contact Method for 5-Axis Tool Positioning,” Trans. ASME J. Manuf. Sci. Eng., 134(2), p. 021004). The RCM finds the optimal tool positions by rotating the tool backward based on the offset surface, and can generate big machined strip width. However, the RCM can only guarantee a contact point because of the design surface's geometric asymmetry in most cases, which leads to the poor surface quality. To resolve this problem, the improved rotary contact method (IRCM) is developed in this paper. The parametric equation of the circular curve of the toroidal cutter defined by the backward and the sideward tilt angle of the tool is strictly deduced. According to the nested optimization of the two tool's angles, there are two contact points found between the tool's cutting surface and the design surface around the feed direction without gouging. Tool positions investigation, machining simulation and cutting experiment are all performed based on a test surface. The results verify the correctness and effectiveness of the IRCM and show that the IRCM can apparently improve the surface quality compared to the RCM.

Multi-cutter selection and cutter location (CL) path generation for five-axis end-milling (finish cut) of sculptured surfaces

This paper presents an optimization method for planning five-axis end milling (finish cut) of sculptured surfaces with multi-cutters. Compared to single-cutter machining, the application of multi-cutters can produce much shorter cutter location (CL) paths and, hence, reduce the machining time. The work presented in this paper focuses on the selection of an optimal multi-cutter set that is utilized to finish different regions of a design surface, followed by the generation of CL paths for each region/cutter combination. The planning starts by identifying all the feasible cutters that form all the possible multi-cutter sets by evaluating their accessibility. The candidate multi-cutter sets are then extracted by maintaining every cutter's cutting region sufficiently large. Based on a proposed method for machining time estimation without generating the tool path, the optimal multi-cutter set with the best cutting efficiency is selected. The iso-planar CL paths are then generated for the cutters in the optimal set for machining their allocated surface regions. Examples are given to show the validity and robustness of the developed methods.

Application of NURBS Technique in Measurement for Aeroengine Blade

A method for tortuous sculptured surface reconstruction of the aeroengine blade was presented. The non-uniform relational B-spline (NURBS) technique method was adopted to reconstruct the surface within a specified accuracy. And it could satisfy our desired requirement in the continuity of the surface, tangent and curvature. The basic theory of NURBS was introduced. And the 3D graphics standard and the graphics library of OpenGL were used to show the result of the tortuous sculptured surface reconstruction on the platform VC++6.0.

Integrated Dexels Geometric Model and Predictive Force Model for Feedrate Optimization in 03 Axis Milling Machine

Machining of sculptured surfaces engender abrupt variations in cutting forces, excessive tool deflections and undesirable vibrations and therefore poor surface finish. To reduce these problems and to have a stable machining it is more indispensable to select the appropriate cutting conditions. The aim of this paper is to propose an approach for determining the optimum feedrates along tool path during finishing of sculptured surfaces with ball end tools on 03-axis CNC milling machines using a predictive mechanistic model of cutting forces. Its steps are :1) approximation of the workpiece geometric model by dexels, 2) localization of the contact zones between tools and workpiece using machining simulation, 3) prediction of the cutting forces, 4) optimization of the feedrates and 5) updating of the machining program « G-Code ».

Line-based sunken relief generation from a 3D mesh

Sunken relief is an art form made by cutting the relief sculpture itself into a flat surface with a shallow overall depth. This paper focuses on the problem of direct generation of line-based sunken relief from a 3D mesh. We show how to extract, post-process and organize the messy feature lines in regular forms, applicable for lines engraving on the sculpture surfaces. We further describe how to construct a smooth height field from the input object, and derive a continuous pitting corrosion method to generate the cutting paths. The whole framework is conducted in object-space, making it flexible for stroke stylization and depth control of the engraving lines. We demonstrate the results with several impressive renderings and photographs used to illustrate the paper itself.

Digital Machining Simulation for Francis Hydro Turbine's Blade

In order to high-quality manufacture the hydro turbine blade efficiently, a series of innovative digital techniques have been developed. It includes 3-D modeling based on machining requirement, multi-axis tool path planning and generating, tool axis orientation for multi-axial NC machining of blades, machining simulation environment establishment, computer simulation for machining of a large blade to verify the gouges and collisions between machine tool, blade and fixtures. The techniques of multi-axis digital machining simulation for large-size blades can be directly applied into digital simulation processing of other sculptured surface parts, and it will completely change the traditional design and manufacturing process of turbine.

Prediction of tool deflection and tool path compensation in ball-end milling

This article presents a tool deflection calculation and compensation methodology based on a recent model developed for the prediction of cutting forces in free-form milling. From global and local geometry of the tool, initial surface and tool path, this approach allows predicting cutting forces and now surface form and roughness directly from CAM data. This model was developed and validated for a rigid case and some improvements are necessary in order to propose an efficient optimization tool for industrial and complex milling operations. In particular, the tool paths can be improved by targeting a reduction of cutting forces linked to cutting stability, tool's life and part's quality. In the same way, the tool deflection, predicted thanks to the cutting forces, can be limited and by the way the generated form defects. The cutting forces prediction can be performed analytically or numerically and the coupling with Computer Assisted Manufacturing data is necessary to optimize industrial milling operations but it is not sufficient to consider tool path and part quality. The idea is to make benefit from the fine geometrical description developed for tool-workpiece engagement calculation to deduce resultant cut surface, cutting forces and tool deflection directly from CAM data. For this reason, this work is based on the development of an analytical model and a comparison is made with a finite element model for the calculation of the tool deflection in 3 axes milling. The suggested model is confronted to another models already published in literature to show its specificity. This approach is enriched by a deflection compensation procedure efficient for sculptured surface milling and allowing limiting resultant errors on machined surfaces. Good results were observed, even for complex ball-end milling operations, and the combination of different calculation procedures opens the way to a more complete virtual milling approach.

계단형상 체적의 엔드밀 가공시 절삭력 변화 특성에 관한 연구

Article history: This study analyzed thevariation in the cutting force when the cutting area of a terrace volume is machined, which is generally left after the rough cutting of a sculptured surface. The numerically simulated results for the cutting forces are compared with cutting force measurements by considering the theoretical prediction of the cutting area formation and specific cutting volume. The variation in the cutting force is measured using a dynamometer installed on a machining center for 19 different kinds of test pieces, which are selected according to the variation in the terrace volume factor, tool diameter factor, and cutting depth factor. As a result, it is verified that the cutting forces evaluated by the numerical analysis coincide with the measured cutting forces, and it is proposed as a practical cutting force prediction model.

Smooth trajectory generation for five-axis machine tools

This paper presents a smooth spline interpolation technique for five-axis machining of sculptured surfaces. The tool tip and orientation locations generated by the CAM system are first fitted to quintic splines independently to achieve geometric jerk continuity while decoupling the relative changes in position and orientation of the cutter along the curved path. The non-linear relationship between spline parameters and displacements along the path is approximated with ninth order and seventh order feed correction splines for position and orientation, respectively. The high order feed correction splines allow minimum deviation from the reference axis commands while preserving continuous jerk on three translational and two rotary drives. The proposed method has been experimentally demonstrated to show improvements in reducing the excitation of inertial vibrations while improving tracking accuracy in five-axis machining of curved paths found in dies, molds and aerospace parts.

Prediction of cutting force in ball-end milling of sculptured surface using improved Z-map

This paper presents an approach for prediction of cutting forces in three-axis ball-end milling of a sculptured surface along an arbitrary tool path. The idea of differentiation is adopted to deal with the problems of varying feed direction, varying cutter engagement, and the consequent varying cutting forces in sculptured surface machining. Based on the differential idea, the whole process of sculptured surface milling is discretized at intervals of feed per tooth, and each segmented process is considered as a small steady-state cutting. For the discrete cuttings, mathematical models of feed turning angle and feed inclination angle are proposed according to the position of start/end points. By using an improved Z-map method, the detailed algorithms of determining the cutter–workpiece interface and the instantaneous in-cut edge segment for sculptured surface machining are suggested. A new integrative chip thickness model which involves the effects of feed turning angle, feed inclination angle, and cutter engagement is also presented. In validation experiment, two practical examples of a sculptured surface three-axis ball-end milling with arbitrary tool path are operated. Comparisons of the predicted cutting forces with the measurements show the effectiveness of the proposed approach.

The extreme efficiency of the new model in milling of complicated surfaces

The colleagues of the author of this paper applied the concept of “contact” in differential geometry into the machining of the sculptured surface (Chun et al., Math Theor Appl, 23(3):105–108, 2003) and presented the second-order contact principle of the machining of complicated surfaces, using the circumference circle of the flat-end mill to sweep the curved surface instead of ball-end mill. But only mathematical deductions were presented in the paper. This paper proves that it is a highly effective method. Compared with other references, the theory of this paper is more restricted, and the method of this paper is suitable to the primary analytic geometry and the simulation surface of the numerical geometry as well. With definite procedure of calculation, the equations in this paper are easily solved.

Using rotary contact method for 5-axis convex sculptured surfaces machining

The 5-axis tool positioning strategy named rotary contact method (RCM) for sculptured surfaces machining has been developed in our previous paper (Wengang Fan et al., J Manuf Sci E-T ASME 134(2):021004.1-021004.6, 2012). The RCM finds the optimal tool positions by rotating the tool backward based on the offset surface instead of the design surface, and can generate big machined strip width without gouging. However, the RCM only deals with concave sculptured surfaces machining well at present, and the special property of convex sculptured surfaces machining has not been fully exploited. To resolve this problem, the general convex sculptured surfaces machining using the RCM is implemented in this paper. Firstly, the tool position error distribution for different tool feed directions is deeply investigated. It is concluded that the best tool feed direction is collinear with the maximum direction of curvature, which is completely opposite to the case for concave sculptured surfaces machining. Then the relationship between the key parameters in the RCM and the tool position error distribution as well as the tool path generation is totally discussed. Finally, machining simulation and cutting experiment of a convex sculptured surface example are performed. The results show that the RCM can apparently raise the efficiency of manufacturing process by contrast with the algorithm in the software UG for convex sculptured surfaces machining.

Form error compensation in ball-end milling of sculptured surface with z-level contouring tool path

Form error compensation in ball-end milling of sculptured surface with z-level contouring tool path

Evaluation of Dynamic Behavior of Machine Tools for Sculptured Surface Manufacturing

The production sector of molds and dies is under a continuous pressure for process optimization due the high lead time required for the production of complex tools. In recent years, to improve this sector, numerous studies have been aimed at optimization of the CAD/CAM/CNC chain. However, despite recent technological innovations such as development of cutting tools, machine tools, and process simulation systems, the machining step still represents a major bottleneck in this process. The current generation of Numerical Control (NC) programs that represents the tool path do not consider the dynamic characteristics of the machine tool in the decision-making process to choose the most appropriate cutting strategies, resulting in NC programs that do not reach levels of excellence. The main objective of this paper is to present the development of a reference index based on the dynamic characteristics of the Machine Tool to support the NC programming with a commercial CAM system. This index considers the Machine Response Time (MRT) of NC controller, the acceleration and deceleration on the axes of the machine tool and the tool path segment (size and inclination). The index makes possible an experimental evaluation of relationships between the programmed feed rate for the tool path and dynamic performance due to movements of the machine axes, thus becoming an important decision-making factor in choosing the best machining strategy and consequently a better plan of the production process in die and mold industries.

环形刀铣削复杂曲面路径规划<br>Tool Path Planning for High Speed Milling of Sculpture Surface with Toroidal Cutter

根据路径的拓扑结构和参数，从算法简单程度、计算量、效率及加工精度等方面，分析了国内外现有的数控加工刀具路径规划的方法及优缺点，结合环形刀及被加工曲面的局部几何特征，提出了一种新的刀具路径规划方法。并通过仿真实验证明，此方法在加工复杂曲面时，能够充分发挥五轴数控加工的优势，大大减小相邻路径间的依赖性，有效地避免误差叠加和放大的缺点。 Based on the topology and parameters of tool path planning, this paper presents a new method to plan tool path in high-speed machining. It considers both the conditions of maximum cutting efficiency and average machine width. So, the dependence between two adjacent tool paths is greatly reduced. And the magnified errors can be avoided effectively, which play more advantages in five-axis CNC machining.

She Ornaments Her Limbs

She Ornaments Her Limbs Translated by Andrew Schelling (bio) aṅgeṣv ābharaṇaṃ karoti bahuśaḥ patre'pi saṃcāriṇi prāptaṃ tvāṃ pariśaṅkate vitanute śayyāṃ ciraṃ dhyāyatiity ākalpavikalpatalparacanāsaṃkalpalīlāśata- vyāsaktāpi vinā tvayā varatanur naiṣā niśāṃ neṣyati aṅgeṣu. on her limbs ābharaṇaṃ. adornment karoti. she makes bahuśaḥ. repeatedly patra. a leaf api. when even saṃcāriṇi. quivers, moves about prāptaṃ. have arrived tvāṃ. you pariśaṅkate. she imagines, fancies vitanute. she spreads out śayyāṃ. bed ciraṃ. for a long time dhyāyati. she studies, meditates iti-ākalpa-vikalpa-talpa-racanāsaṃkalpa-līlā-śata-vyāsaktā. (bv. cmpd.) engaged in fantasies of one hundred varieties of love on the prepared bed iti. thus ākalpa. ornament vikalpa. variety, art, fantasy talpa. bed, couch racanā. making saṃkalpa. idea, conception, notion līlā. play śata. one hundred vyāsaktā. engaged in api. but vinā. without tvayā. you varatanuḥ. the thin girl na-eṣā [and] neṣyati. will she not (perish) niśāṃ. tonight neṣyati. will perish [End Page 114] She ornaments her limbsif a single leaf stirsin the forest.She thinks it’s you, folds backthe bedclothes and staresin rapture for hours.Her heart conceives a hundredamorous games on the well-prepared bed.But without you thiswisp of a girlwill fadeto nothing tonight. Internal rhyme and repetition of sound underlie each of Gīta-Govinda’s verses. Jayadeva particularly used anuprāsa (alliteration) and assonance, creating a trance-like quality in many of his stanzas. Barbara Miller writes of the poem: “alliterative combinations of consonants and vowels reinforce the meters and the sensuous imagery of the songs.” This verse, written in classical kāvya style, shows the way the poet works: ākalpa-vikalpa-talpa in line three. The ending, naiṣā niśāṃ neṣyati, reproduces Radha’s restlessness, impatience, and anguish, carrying the reader back to the opening image of her bahuśaḥ (repeatedly) adorning her limbs at the hint of a quavering leaf. The repeated sounds, repeated ornamentation, repetition of her thoughts—all fit the erotic tension. Elsewhere in the poem, Krishna too has been taken up by furious desire, as he stumbles in and out of the dark kuñja (thicket), where he first made love to Radha. Miller writes, “the redundancies are incessant, complex, and multileveled. They create a sensuous surface of verbal ornamentation that suggests comparison with the sculptured surfaces of the medieval Hindu temples of Bhubaneswar and Khajuraho.” Rhythm and repetitive sounds of this sort are used in mantra, liturgy, prayer—all those forms of language which, like poetry, are not meant to describe something, but to propel the speaker or listener into a particular state of mind. Or to provoke supernatural acts. I’m certain that Jayadeva chose the repeated sounds carefully, based on India’s archaic science of speech-magic. [End Page 115] Andrew Schelling Andrew Schelling, born in 1953 at St. Elizabeth’s Hospital, Washington, D.C., has written, edited, or translated twenty books. Early opposition to American involvement in Vietnam, plus an encounter with India’s texts, set him on a lifelong engagement with Asian literature. He studied Sanskrit at the University of California at Berkeley, and began to translate from its classical poetry tradition around 1978. His first book, Dropping the Bow: Poems of Ancient India, received the Academy of American Poets translation award in 1992, the first time the Academy had honored work done from an Asian language. Schelling’s own poetry and essays emerge from the Southern Rocky Mountain bioregion in which he lives. Recent books of poetry wrangle with the Arapaho language as a way of reading landscape and the natural cycles; they include From the Arapaho Songbook and A Possible Bag. He has edited The Oxford Anthology of Bhakti Literature and Love and the Turning Seasons: India’s Poetry of Spiritual and Erotic Longing (forthcoming from Counterpoint Press). Living on the Front Range of Colorado, he is active on land-use issues and teaches at Naropa University. He also teaches regularly at Deer Park Institute, in India’s Himalayan...