Modeling and Analysis of Fixel Designs for Micromanufacturing Active Fixturing

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Troy B. Rippere ◽  
Koustubh J. Rao ◽  
Gloria J. Wiens
Keyword(s):  
Manufacturing Systems ◽  
Compliant Mechanisms ◽  
Variable Stiffness ◽  
Theoretical Models ◽  
Milling Process ◽  
Contact Forces ◽  
Modeling And Analysis ◽  
Design Alternatives ◽  
Expected Performance ◽  
Stiffness Characteristics

This paper presents an investigation of fixel design alternatives for active (dynamic) fixturing to be incorporated into mesoscale manufacturing systems. Using simple compliant mechanisms and components, fixels exhibiting mechanically adjustable stiffness characteristics are achievable. Via manual or automated stiffness adjustments, these fixels provide functionality for enabling greater control of the dynamic response of the workpiece subject to vibrations and/or variations in contact forces at the tool-workpiece-fixture interface. To quantify the fixel functionality, this paper presents theoretical models of the stiffness characteristics expressed as a function of the mechanical variable(s), thus forming a basis for exploring the adjustability in stiffness achievable for each fixel design. Also presented are results of the dynamic behavior of the active fixturing implemented in a milling process based on a “regenerative force, dynamic deflection model” augmented with the active fixturing variable stiffness model and inclusion of tool runout. These simulation results indicate the expected performance of the active fixturing upon its implementation in actual fixturing for the creation of micron features on micro- and macroparts.

Active Fixturing for Mesoscale Manufacturing Systems: Fixel Design Alternatives

2008 ◽  
Author(s):  
Gloria J. Wiens ◽  
Koustubh J. Rao ◽  
Troy B. Rippere
Keyword(s):  
Manufacturing Systems ◽  
Material Handling ◽  
Dynamic Range ◽  
Compliant Mechanisms ◽  
Slenderness Ratio ◽  
Theoretical Models ◽  
Contact Forces ◽  
Advantages And Disadvantages ◽  
Design Alternatives ◽  
Stiffness Characteristics

This paper presents an investigation of fixel design alternatives for active (dynamic) fixturing to be incorporated into mesoscale manufacturing systems. Using simple compliant mechanisms and components (e.g., monolithic four-bar mechanisms and/or cantilever beams), fixels exhibiting mechanically adjustable stiffness characteristics are achievable. Manually or automating the stiffness adjustments, these fixels provide a functionality for enabling greater control of the dynamic response of the workpiece due to vibrations and variation in contact forces at the tool-workpiece-fixture interface. To quantify the fixel functionality and its dynamic range, this paper presents the theoretical models of the stiffness characteristics expressed as a function of each fixel design’s mechanical variables. Upon establishing a common stiffness range for the different fixel designs, a metric is formed based on the sensitivity of stiffness expressed as a function of slenderness ratio and an operation range, bounded by a maximum possible stiffness value shared by all fixture models. Using this metric, results are generated to delineate the advantages and disadvantages of each design and their potential impact on fixturing and material handling in the creation of micron features on micro and macro parts.

Hybrid modeling and analysis of multidirectional variable stiffness of the linear rolling guideway under combined loads

2020 ◽  
Vol 234 (13) ◽  
pp. 2716-2727
Author(s):  
Lei Yang ◽  
Lei Wang ◽  
Wanhua Zhao
Keyword(s):  
Machine Tool ◽  
High Speed ◽  
Complex Loading ◽  
Variable Stiffness ◽  
Time Varying ◽  
Modeling And Analysis ◽  
Combined Loads ◽  
Machine Tool Structure ◽  
High Feed ◽  
Stiffness Characteristics

In the working process of high-speed multiaxis machine tools, inertial loads due to high feed acceleration and time-varying gravity loads due to changing configuration of multiaxis structure result in time-varying complex loads applied to linear rolling guideway. Existing models cannot efficiently represent the effect of complex loads on multidirectional stiffness variation of linear rolling guideway. In this paper, a hybrid model of multidirectional stiffness of linear rolling guideway and the solving algorithm are proposed. The complex loading conditions of linear rolling guideway in high-speed multiaxis machine tool structure are considered. And contact flexibilities between rolling balls and grooves are modeled with the effect of elastic deformations of runner block and rail. The proposed model can calculate the multidirectional stiffness with high accuracy. Meanwhile the differences between the stiffness characteristics in different directions are represented correctly. The variations of multidirectional stiffness of linear rolling guideway under time-varying combined loads are analyzed. This study provides an effective way to comprehensively evaluate the stiffness characteristics of linear rolling guideway which can contribute to the dynamic analysis and active design of high-speed machine tool structure.

Fixture Clamping Force Analysis during Milling Process

2013 ◽  
Vol 278-280 ◽  
pp. 385-388 ◽  
Author(s):  
Shao Gang Liu ◽  
Qiu Jin
Keyword(s):  
Analytical Method ◽  
Linear Equations ◽  
Milling Process ◽  
Contact Forces ◽  
Clamping Force ◽  
Contact Deformation ◽  
Force Analysis ◽  
Equilibrium Equations ◽  
Tangential Contact ◽  
Fixture Element

This paper presents a analytical method to calculate the minimum clamping force to prevent slippage between the workpiece and spherical-tipped fixture elements during milling process. After the contact deformation between the workpiece and spherical-tipped fixture element is determined, the relationships between the workpiece displacement and the contact deformations are obtained. Based on the static equilibrium equations, these equations are combined and linear equations are obtained to calculate the tangential contact forces between the workpiece and spherical-tipped fixture element. According to the maximum tangential contact force, the minimum clamping force to prevent slippage between the workpiece and spherical-tipped fixture elements is calculated. At last, this method is illustrated with a simulation example.

A Coupled Bio-Chemo-Hydro-Mechanical Model for Bio-cementation in Porous Media

2021 ◽  
Author(s):  
Ronak Mehrabi ◽  
Kamelia Atefi-Monfared
Keyword(s):  
Reactive Transport ◽  
Theoretical Models ◽  
Porous Matrix ◽  
Spatiotemporal Variability ◽  
Attachment Rate ◽  
Unknown Parameters ◽  
Stress Strain ◽  
Precipitated Calcium Carbonate ◽  
Cement Distribution ◽  
Stiffness Characteristics

A key challenge involving microbial induced carbonate precipitation (MICP) is lack of rigorous yet practical theoretical models to predict the intricate biological-chemical-hydraulic-mechanical (BCHM) processes and the resulting bio-cement production. This paper presents a novel BCHM model based on multiphase, multispecies reactive transport approach in the framework of poroelasticity, aimed at achieving reasonable prediction of the produced bio-cement, and the enhanced geomechanical characteristics. The proposed model incorporates four key components: (i) coupling of hydro-mechanical stress/strain alterations with bio-chemical processes; (ii) stress/strain changes induced due to precipitation and growth of bio-cement within the porous matrix; (iii) spatiotemporal variability in hydraulic and stiffness characteristics of the treated medium; (iv) and velocity dependency of the attachment rate of bacteria. The fully-coupled BCHM model predicts key unknown parameters during treatment including: concentration of bacteria and chemical solutions, precipitated calcium carbonate, hydraulic properties of the solid skeleton, and in-situ pore pressures and strains. The model was able to reasonably predict bio-cementation from two different laboratory column experiments. The Kozeny–Carman permeability equation is found to underestimate permeability reductions due to bio-cementation, while the Verma–Pruess relation could be more accurate. A sensitivity analysis revealed bio-cement distribution to be particularly sensitive to the attachment rate of bacteria.

Modeling and analysis of soft robotic fingers using the fin ray effect

2020 ◽  
Vol 39 (14) ◽  
pp. 1686-1705
Author(s):  
Xiaowei Shan ◽  
Lionel Birglen
Keyword(s):  
Contact Forces ◽  
Accurate Estimation ◽  
Modeling And Analysis ◽  
Physical Experiments ◽  
Fin Ray ◽  
And Performance ◽  
Difficult Challenge ◽  
Kinetostatic Model ◽  
Individual Contact ◽  
The Impact

Soft grasping of random objects in unstructured environments has been a research topic of predilection both in academia and in industry because of its complexity but great practical relevance. However, accurate modeling of soft hands and fingers has proven a difficult challenge to tackle. Focusing on this issue, this article presents a detailed mathematical modeling and performance analysis of parallel grippers equipped with soft fingers taking advantage of the fin ray effect (FRE). The FRE, based on biomimetic principles, is most commonly found in the design of grasping soft fingers, but despite their popularity, finding a convenient model to assess the grasp capabilities of these fingers is challenging. This article aims at solving this issue by providing an analytic tool to better understand and ultimately design this type of soft fingers. First, a kinetostatic model of a general multi-crossbeam finger is established. This model will allow for a fast yet accurate estimation of the contact forces generated when the fingers grasp an arbitrarily shaped object. The obtained mathematical model will be subsequently validated by numerically to ensure the estimations of the overall grasp strength and individual contact forces are indeed accurate. Physical experiments conducted with 3D-printed fingers of the most common architecture of FRE fingers will also be presented and shown to support the proposed model. Finally, the impact of the relative stiffness between different areas of the fingers will be evaluated to provide insight into further refinement and optimization of these fingers.

scholarly journals Spring Effects on Workspace and Stiffness of a Symmetrical Cable-Driven Hybrid Joint

Symmetry ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 101 ◽  
Author(s):  
Shan Zhang ◽  
Zheng Sun ◽  
Jili Lu ◽  
Lei Li ◽  
Chunlei Yu ◽  
...  
Keyword(s):  
Variable Stiffness ◽  
Robotic Manipulator ◽  
Spring Model ◽  
Cable Tension ◽  
Stiffness Analysis ◽  
Hybrid Joint ◽  
Compression Spring ◽  
Spring Force ◽  
Basic Parameters ◽  
Stiffness Characteristics

This paper aims to investigate how to determine the basic parameters of the helical compression spring which supports a symmetrical cable-driven hybrid joint (CDHJ) towards the elbow joint of wheelchair-mounted robotic manipulator. The joint design of wheelchair-mounted robotic manipulator needs to consider lightweight but robust, workspace requirements, and variable stiffness elements, so we propose a CDHJ which becomes a variable stiffness joint due the spring under bending and compression provides nonlinear stiffness characteristics. Intuitively, different springs will make the workspace and stiffness of CDHJ different, so we focus on studying the spring effects on workspace and stiffness of CDHJ for its preliminary design. The key to workspace and stiffness analysis of CDHJ is the cable tension, the key to calculate the cable tension is the lateral bending and compression spring model. The spring model is based on Castigliano’s theorem to obtain the relationship between spring force and displacement. The simulation results verify the correctness of the proposed spring model, and show that the spring, with properly chosen parameters, can increase the workspace of CDHJ whose stiffness also can be adjusted to meet the specified design requirements. Then, the modelling method can be extended to other cable-driven mechanism with a flexible compression spring.

scholarly journals Multistable Morphing Mechanisms of Nonlinear Springs

2019 ◽  
Vol 11 (5) ◽  
Author(s):  
Chrysoula Aza ◽  
Alberto Pirrera ◽  
Mark Schenk
Keyword(s):  
Design Space ◽  
Large Deformations ◽  
Compliant Mechanisms ◽  
Helical Structures ◽  
Nonlinear Springs ◽  
Structural Assembly ◽  
Stiffness Characteristics ◽  
Nonlinear Components ◽  
Type Of Behavior ◽  
Initial Geometry

Compliant mechanisms find use in numerous applications in both microscale and macroscale devices. Most of the current compliant mechanisms base their behavior on beam flexures. Their range of motion is thus limited by the stresses developed upon deflection. Conversely, the proposed mechanism relies on elastically nonlinear components to achieve large deformations. These nonlinear elements are composite morphing double-helical structures that are able to extend and coil like springs, yet, with nonlinear stiffness characteristics. A mechanism consisting of such structures, assembled in a simple truss configuration, is explored. A variety of behaviors is unveiled that could be exploited to expand the design space of current compliant mechanisms. The type of behavior is found to depend on the initial geometry of the structural assembly, the lay-up, and other characteristics specific of the composite components.

Pseudo-rigid-body dynamic modeling and analysis of compliant mechanisms

2017 ◽  
Vol 232 (9) ◽  
pp. 1665-1678 ◽  
Author(s):  
Yue-Qing Yu ◽  
Qian Li ◽  
Qi-Ping Xu
Keyword(s):  
Rigid Body ◽  
Dynamic Model ◽  
Dynamic Modeling ◽  
Dynamic Models ◽  
Compliant Mechanisms ◽  
Lagrange Equation ◽  
Dynamic Responses ◽  
Modeling And Analysis ◽  
Rigid Body Dynamic ◽  
Body Dynamic

An intensive study on the dynamic modeling and analysis of compliant mechanisms is presented in this paper based on the pseudo-rigid-body model. The pseudo-rigid-body dynamic model with single degree-of-freedom is proposed at first and the dynamic equation of the 1R pseudo-rigid-body dynamic model for a flexural beam is presented briefly. The pseudo-rigid-body dynamic models with multi-degrees-of-freedom are then derived in detail. The dynamic equations of the 2R pseudo-rigid-body dynamic model and 3R pseudo-rigid-body dynamic model for the flexural beams are obtained using Lagrange equation. Numerical investigations on the natural frequencies and dynamic responses of the three pseudo-rigid-body dynamic models are made. The effectiveness and superiority of the pseudo-rigid-body dynamic model has been shown by comparing with the finite element analysis method. An example of a compliant parallel-guiding mechanism is presented to investigate the dynamic behavior of the mechanism using the 2R pseudo-rigid-body dynamic model.

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