Thoughts on Design for Intelligent Manufacturing

1.Introduction Given the emergence of intelligent manufacturing capabilities,we may wonder whether design for manufacturing(DFM)practices should be reconceptualized to take advantage of these capabilities.And,if so,what should design for intelligent manufacturing(DFIM)be?The integration of cloud computing,data analytics,artificial intelligence(AI),and the Internet of Things(IoT)with advanced manufacturing technologies has enabled the emergence of what has been called new-generation intelligent manufacturing[1].Such new-generation intelligent manufacturing capabilities will enable transformational new products and services with unprecedented levels of quality,responsiveness,and efficiency.

Projection micro stereolithography based 3D printing and its applications

Projection micro stereolithography(PμSL)is a high-resolution(up to 0.6μm)3D printing technology based on area projection triggered photopolymerization,and capable of fabricating complex 3D architectures covering multiple scales and with multiple materials.This paper reviews the recent development of the PμSL based 3D printing technologies,together with the related applications.It introduces the working principle,the commercialized products,and the recent multiscale,multimaterial printing capability of PμSL as well as some functional photopolymers that are suitable to PμSL.This review paper also summarizes a few typical applications of PμSL including mechanical metamaterials,optical components,4D printing,bioinspired materials and biomedical applications,and offers perspectives on the directions of the further development of PμSL based 3D printing technology.

A regularization scheme for explicit level-set XFEM topology optimization

Regularization of the level-set(LS)field is a critical part of LS-based topology optimization(TO)approaches.Traditionally this is achieved by advancing the LS field through the solution of a Hamilton-Jacobi equation combined with a reinitialization scheme.This approach,however,may limit the maximum step size and introduces discontinuities in the design process.Alternatively,energy functionals and intermediate LS value penalizations have been proposed.This paper introduces a novel LS regularization approach based on a signed distance field(SDF)which is applicable to explicit LSbased TO.The SDF is obtained using the heat method(HM)and is reconstructed for every design in the optimization process.The governing equations of the HM,as well as the ones describing the physical response of the system of interest,are discretized by the extended finite element method(XFEM).Numerical examples for pro?blems modeled by linear elasticity,nonlinear hyperelasticity and the incompressible Navier-Stokes equations in two and three dimensions are presented to show the applicability of the proposed scheme to a broad range of design optimization problems.

Modified commercial UV curable elastomers for passive 4D printing

Conventional 4D printing technologies are realized by combining 3D printing with soft active materials such as shape memory polymers(SMPs)and hydrogels.However,the intrinsic material property limitations make the SMP or hydrogel-based 4D printing unsuitable to fabricate the actuators that need to exhibit fast-response,reversible actuations.Instead,pneumatic actuations have been widely adopted by the soft robotics community to achieve fast-response,reversible actuations,and many efforts have been made to apply the pneumatic actuation to 3D printed structures to realize passive 4D printing with fast-response,reversible actuation.However,the 3D printing of soft actuators/robots heavily relies on the commercially available UV curable elastomers the break strains of which are not sufficient for certain applications which require larger elastic deformation.In this paper,we present two simple approaches to tune the mechanical properties such as stretchability,stiffness,and durability of the commercially available UV curable elastomers by adding:(i)mono-acrylate based linear chain builder;(ii)urethane diacrylate-based crosslinker.Material property characterizations have been performed to investigate the effects of adding the two additives on the stretchability,stiffness,mechanical repeatability as well as viscosity.Demonstrations of fully printed robotic finger,grippers,and highly deformable 3D lattice structure are also presented.

Hydrogel-elastomer-based stretchable strain sensor fabricated by a simple projection lithography method

Stretchable strain sensor detects a wide range of strain variation and is therefore a key component in various applications.Unlike traditional ones made of elastomers doped with conductive components or fabricated with liquid conductors,ionically conductive hydrogel-based strain sensors remain conductive under large deformations and are biocompatible.However,dehydration is a challenging issue for the latter.Researchers have developed hydrogel-elastomer-based strain sensors where an elastomer matrix encapsulates a hydrogel circuit to prevent its dehydration.However,the reported multistep approaches are generally time-consuming.Our group recently reported a multimaterial 3D printing approach that enables fast fabrication of such sensors,yet requires a self-built digital-light-processing-based multimaterial 3D printer.Here,we report a simple projection lithography method to fabricate hydrogel-elastomer-based stretchable strain sensors within 5 minutes.This method only requires a UV projector/lamp with photomasks;the chemicals are commercially available;the protocols for preparing the polymer precursors are friendly to users without chemistry background.Moreover,the manufacturing flexibility allows users to readily pattern the sensor circuit and attach the sensor to a 3D printed soft pneumatic actuator to enable strain sensing on the latter.The proposed approach paves a simple and versatile way to fabricate hydrogel-elastomer-based stretchable strain sensors and flexible electronic devices.