A contribution for increasing workpiece location accuracy in a 3-2-1 fixture system

Filho, Joel Martins Crichigno; Medeiros, Ricardo de; Cardoso, Renan Pereira

doi:10.1177/0954405417728313

Cited by 5 publications

(3 citation statements)

References 7 publications

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“…Filho et al 16 proposed a novel approach to increase the position and orientation accuracy of the workpiece in the fixture with a 3-2-1 locating system by reducing the tangential stiffness of the locators. Parvaz and Nategh 17 used reaction force values to predict jamming occurrence conditions in the fixture design application.…”

Section: Introductionmentioning

confidence: 99%

Analysis of reaction forces in fixture locating points: An Analytical, numerical, and experimental study

Parvaz,

Hosseini

2023

Proceedings of the Institution of Mechanical Engineers, Part B:

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Reaction forces are important parameters in fixture design. They are generated by the clamping forces and machining loads at the fixture locating points. These forces are used as input values in the determination of clamping forces, fixture stiffness, and workpiece deformation. In this paper, an analytical model based on the minimum norm principle was developed to calculate these forces. Numerical simulations and experimental tests were performed on a 3D polyhedral workpiece to validate the model. The simulations were conducted using Abaqus® software and the experimental tests used a fixture and a 3D polyhedral workpiece. The theoretical, numerical, and experimental results showed good agreement for the normal component of reaction forces. The maximum errors of 3.9% and 15% were observed between the theoretical predictions compared to the numerical and experimental results, respectively. The model was also used to study the effects of two influential parameters, the coefficient of friction and clamping force, on the reaction forces. The good agreement between the theoretical, numerical, and experimental results demonstrated the efficiency of the proposed model in the rapid calculation of reaction forces for fixturing 3D polyhedral workpieces.

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Section: Introductionmentioning

confidence: 99%

Analysis of reaction forces in fixture locating points: An Analytical, numerical, and experimental study

Parvaz,

Hosseini

2023

Proceedings of the Institution of Mechanical Engineers, Part B:

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“…They calculated the displacement of the workpiece relative to the fixture elements. Filho et al 30 investigated the effect of friction and stiffness of the contact between the workpiece and the fixture components, and by comparing the use of two types of rigid and flexible locators (with different structural stiffness in the tangential direction), showed that the displacement of the workpiece and its orientation are a function of clamping force but by reducing the tangential stiffness of the locator, the position and orientation accuracy of the workpiece can be improved.…”

Section: Introductionmentioning

confidence: 99%

Evaluation, calibration, and modal analysis for determination of contact stiffness between workpiece and components of milling fixture

Sohrabifard

Nategh

Ghazavi

2022

Proceedings of the Institution of Mechanical Engineers, Part B:

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The stability of workpiece inside fixture influences the dynamics of machining. Although, the workpiece is uniquely and deterministically positioned and grasped by the fixture, it undergoes small displacements due to the contact compliance resulting from the frictional slip under the external loads and vibrations. The frictional slip of workpiece, along or around the main axes relative to the fixture components is a major cause of instability and the main element influencing the contact stiffness between the workpiece and the fixture. In the present study, a procedure has been developed to evaluate the contact stiffness by employing mathematical and experimental tools. The grasp matrices defined in analytical model were obtained by a combination of calibration and measurement of forces, displacements, and friction coefficient. The contact stiffness was also determined by modal analysis of the assembly of workpiece and fixture and the results were compared. It was evidenced that the dry friction existing in the contact areas between the workpiece and fixture elements could lead to the stick-slip instability, detrimental to the dynamics of machining. The main contribution and novelty of the present study can be outlined, as follows. The contact stiffness between workpiece and fixture was modeled and measured. The frictional slip was modeled and measured in addition to the physical compliances. Dry friction between workpiece and fixture was detected as a source of stick-slip. Procedures were developed to calibrate and measure all forces and displacements. Modal analysis was done as a complementary tool to verify the results.

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“…The traditional six-point locating principle is to set three, two, and one positioning points on the primary datum, secondary datum, and tertiary datum respectively to limit the six degrees of freedom of the workpiece. 6 Although this locating principle can satisfy the positioning requirements of the workpiece, it is only applicable to rigid parts and is not valid for flexible thin-walled parts. 7,8 The main problem for flexible thin-walled parts manufacturing is the deformation in the normal direction caused by the machining load and the workpiece weight.…”

Section: Introductionmentioning

confidence: 99%

Fixture layout optimization for car dashboard based on N-X locating principle

Liu

Sun

2022

Proceedings of the Institution of Mechanical Engineers, Part B:

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A fixture is a crucial component in the car dashboard manufacturing system and is used to position and restrain the car dashboard under external forces. However, the conventional fixture is only suitable for a specific type of car dashboard, which has poor adaptability. To this end, a new flexible fixture based on the N- X locating principle is proposed in this paper to adapt to different types of car dashboards. In the presented fixture, N clamping elements clamp the dashboard edge, while X movable supporting elements support the area close to the tool along the machining path. Furthermore, the fixture layout is optimized by combining a genetic algorithm (GA) and finite element analysis (FEA). In the optimization program, a multi-objective optimization function is established to suppress the deformation of the car dashboard. FEA is applied to calculate the machining deformation. The optimal locations of the fixture elements are determined by GA. A case is implemented to validate the proposed method and the results show that the maximum deformation and average deformation are reduced by 53.8% and 40%, respectively, compared with the empirical method.

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A contribution for increasing workpiece location accuracy in a 3-2-1 fixture system

Cited by 5 publications

References 7 publications

Analysis of reaction forces in fixture locating points: An Analytical, numerical, and experimental study

Analysis of reaction forces in fixture locating points: An Analytical, numerical, and experimental study

Evaluation, calibration, and modal analysis for determination of contact stiffness between workpiece and components of milling fixture

Fixture layout optimization for car dashboard based on N-X locating principle

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