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Numerical and Experimental Studies on 3D Printed Compliant Mechanisms in Gripper Applications

Niedziałek Piotr Wiesław, Figurski Aleksy, Kowalik Michał

Advances in Science and Technology. Research Journal

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2023

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Vol. 17, no 6

228--244

EN

The article describes two versions of a gripper's fingers that utilize compliant revolute kinematic pairs in their operation. The goal in designing the gripper was to create a universal structure that allows for easy adjustment of torsional stiffness and maximum rotation angle as needed. Two compliant revolute joints were proposed and applied in the creation of two versions of the gripper’s fingers. In both joints, one geometric parameter was selected for variation. Finite element analysis was conducted to calculate the statics within the parameter range. Based on the calculations, stiffness charts were created as a function of parameter values. Subsequently, using 3D printing technology in resin, two gripper fingers were produced. Experimental tests were conducted on these fingers to assess their torsional stiffness. The computational and experimental results were compared. The designed fingers are best suited for pneumatic grippers. When using them, complex force control can be eliminated because the gripping force increases gradually in accordance with the compliance of the gripper, rather than abruptly. The fingers also exhibit different stiffness characteristics depending on the direction of the grip - outward or inward.

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Compliant joints with remote centre of compliance for the improvement of the motion accuracy of a gantry stage

Pöhlmann Patrick, Peukert Christoph, Merx Marcel, Müller Jens, Ihlenfeldt Steffen

Journal of Machine Engineering

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2022

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Vol. 22, No. 2

68--79

EN

Gantry stages, which consist of two parallel acting servo drives, are commonly used in machine tools. One drawback of this concept is the crosstalk between both drives, when a stiff mechanical coupling is present. This can lead to a limited bandwidth of the position control or to high reaction forces. One way to overcome these issues is the usage of joints to create an additional degree of freedom, which allows the drives to move independently. The design of these joints as compliant elements offers advantages compared to common rolling bearings, such as low friction and the absence of backlash. Another benefit is the variability in the design of the compliant joints allowing for adjustments to the position of each joint’s centre of compliance. Thus, the position of the resulting pivot, and the transfer matrix between the motion of the drives and the motion at the gantry stage’s tool centre point, change as well. This paper addresses the placement of the joint’s centre of compliance in order to improve motion accuracy. For this purpose, joints with modular arranged compliant links have been designed. The characteristics of the joints and their effect on the behaviour of the gantry stage are compared using analytical investigations as well as experimental results.

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Compliant joints for the improvement of the dynamic behaviour of a gantry stage with direct drives

Pöhlmann Patrick, Peukert Christoph, Merx Marcel, Müller Jens, Ihlenfeldt Steffen

Journal of Machine Engineering

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2020

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Vol. 20, No. 3

17--29

EN

Gantry stages, which consist of two parallel acting servo drives, are commonly used in machine tools. One drawback of this concept is the crosstalk between both drives due to the structural coupling that can cause stability issues and therefore limits the bandwidth of the position control. This paper deals with the development of compliant joints to solve the coupling between the drives. When compared to solutions containing bearings, the advantages of such flexible elements are low friction and the absence of backlash. To adjust the properties of the joints, packages of spring-steel-sheets are used as compliant links. One design aspect of the flexible joints is a low stiffness relating to the rotation around one specific axis, but a high stiffness relating to the other degrees of freedom. With this method, the dynamic behaviour of the gantry stage is modified and the bandwidth of the controllers can be increased. Additionally, by releasing the mechanical coupling of the drives, the reaction forces the actuators have to provide can be reduced. Both systems with flexible and with rigid connecting elements, are analysed by measured frequency response functions.