Quantifying part irregularities and subsequent morphology manipulation in stereolithography plastic injection moulding

Abstract

The direct use of moulds produced by stereolithography (SL) provides a rapid tooling technique which allows low volume production by plastic injection moulding. The greatest advantage of the process is that it provides parts that are the same as those that would be produced by metal tooling in a fraction of the time and cost. However, work by the authors demonstrates that the parts possess different characteristics to those produced by metal tooling. This knowledge defies the greatest advantages of the SL injection moulding tooling process – the moulded parts do not replicate parts that would be produced by metal tooling. This work specifically demonstrates that a different rate of part shrinkage is experienced and subsequently investigates the mechanisms in SL tooling that induce these different part properties. The work culminates in different approaches to modifying the moulding process which allow the production of parts whose key morphological characteristics are closer to those that have been produced from metal moulds.     

Effect of processing parameters,antistiction coatings,and polymer type when injection molding microfeatures

Thermoplastic polyurethane (TPU) and silicon tooling with microscale features on its surface was employed to investigate the impact of three factors on the quality of injection molded microscale features: (1) optimized process parameters, (2) use of a more flexible thermoplastic material, and (3) used as an antistiction coating. The molded parts and tooling surface were characterized by atomic force, confocal, and scanning electron microscopy. Although both improved filling of the tooling trenches, higher mold temperatures significantly enhanced replication, but faster injection velocities contributed moderately to replication quality. With medium aspect ratio (2.3:1) trenches, the antistiction coating doubled depth ratios, enhanced the edge definition and flatness of the features, and significantly reduced tearing of the features during ejection. The flexibility of the TPU permitted easier part ejection and left less polymer residue on the tooling surface in comparison to polycarbonate and other thermoplastic polymers. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Failure mechanisms in stereolithography injection molding tooling

Stereolithography tooling is a form of rapid tooling that has been used to injection mold limited runs of prototype parts. However, the process is not well understood and tooling life for fine mold features is difficult to predict. Injection molding processing conditions and feature geometry affect the number of parts that can be made before a mold fails. To study the effects of feature geometry, general purpose polystyrene parts were injection molded in molds made of DSM Somos 7110 stereolithography resin. The ACES build style was used, and no polishing was performed on the mold. The experimental results were compared with theoretical models developed for the two failure mechanisms for raised features in a stereolithography mold—failures during injection due to the flow pressure of the injected polymer; and failures during ejection, whereby the part pulled out a feature of the mold. Injection failures occurred in taller mold features due to the force of flow and the feature's geometry. Ejection failures occurred in the shorter features when the stress from the ejection force (distributed over the bond area) exceeded the yield strength of the mold material. Models were developed to predict the number of parts that a mold could make before mold features break off and were validated through experimental results.     

Infiltration as post-processing of laser sintered metal parts

Laser sintering of metal parts is an additive production method applied in the field of rapid prototyping and rapid tooling. Direct metal laser sintering (DMLS) is a variant of the laser sintering processes. Metal powder is locally molten in this process and parts are built from layers. A fast laser sintering process, which is economically favourable, results in porous metal parts. For a technical application as e.g. the production of injection moulds for plastic parts, the surface has to be dense at a defined quality. A post-processing via infiltration is a possible solution for creating such surfaces. This paper describes the results of a study of the infiltration process: A model for describing the infiltration behaviour has been developed and validated through experiments.     

400KL高铁车头客舱3D造型及其工装设计

本文主要阐述4OO公里高铁车头客舱各零件、部件3D造型设计方法,零件、部件成形工装（模具、夹具、型架）设计原理并简要介绍工装制造工艺。     

基于UG平台的塑料异型材挤出模标准件库的建立

针对塑料异型材挤出模中存在大量标准件这一特点,以UG软件为开发平台,利用VC++6 0面向对象的编程技术,在UG/OpenAPI开发平台上,创建参数化图库、设计用户界面、实现参数化尺寸驱动,总结了系统的主要功能和特点,建立了三维塑料异型材挤出模的标准件库。     

Spark plasma sintering of structure-tailored ultrahigh-temperature components: First step to complex net shaping

The net-shaping capability in spark plasma sintering (SPS) of ultrahigh-temperature ceramics has been explored in this study. The annular or ring-like shape is considered here as the first step to a more complex geometry compared to a solid cylinder or disk. ZrC powders have been SPS processed in specially designed graphite tooling to achieve the annular shape geometry. Experimental runs have been carried out to determine the optimal processing parameters for producing highly dense ZrC specimens in this geometry. Finite-element modeling framework has been constructed to determine the internal stress evolution, as well as densification, during the SPS of the annular-shaped ZrC. The formulated processing schemes for ZrC have been adapted to process SiC/ZrB₂ composite powder with the purpose of making tooling components for SPS applications. The applicability of the obtained composite SPS tooling has been evaluated at high temperature and high pressure associated with SPS regimes.     

耐高温皱纹纸压敏胶带的研制

采用100份的天然橡胶为主要弹性体、加入20份丙烯酸酯橡胶（ACM）、3-5份ZnO,0.8-1份硬酯酸制得混炼胶，在适量甲苯溶解上述混炼胶并加入60-80份的萜烯树脂、6-9份的2402酚醛树脂、8-12份改性剂及适量防老剂制得耐温压敏胶。将该胶涂布在耐温的皱纹纸上制得皱纹纸胶带，其粘性佳、耐高温、保持力强、无残胶、可用于电容器等电子元件的“编带“及机动车辆“烤漆保护“等生产环节。     

螺旋折流板的加工方法

螺旋折流板换热器已成为目前换热器研究领域的热点，螺旋折流板的加工制造更是其中的主要工作。分析了螺旋折流板换热器的结构，介绍了螺旋折流板的加工方法，设计了螺旋折流板加工所用的三种工装，即平台划线工装、钻孔工装和立车工装。     

Simulation and experimental validation of mould tooling forces in RTM and CRTM for nonplanar components

To date, simulation of the forces exerted on mould tools during RTM and Compression RTM (CRTM) has focused on planar cases. While a flat plate case has some limited validity in practical applications, the majority of applications are for nonplanar geometry components. Such components present a more challenging case to simulate, as the nonplanar geometry introduces an additional out‐of‐plane shear component to the local tooling stresses as well as effects due to the geometry itself (such as race‐tracking in corners). This article presents the first thorough study of mould tooling forces for a nonplanar geometry. A number of RTM and CRTM experiments were undertaken using a truncated‐pyramid mould with an acrylic top platen to allow flow front visualization to be undertaken. Repeatability studies showed variations in fill time and peak tooling forces observed during RTM and CRTM cases which could not be accounted for by variation in the sample mass or fluid viscosity alone. This demonstrated that the processes were influenced by the spatial variability in the areal mass of the preforms. The experimental results were also compared to numerical simulations of the processes. Good agreement between experiment and simulation was observed for both RTM and CRTM cases in terms of flow front evolution. Peak forces were also well predicted, within the variability observed in the experimental results; this was partly due to the out‐of‐plane shear component of the tooling force being well predicted, in combination with the normal component. In addition to the velocity‐controlled mould closure cases, force‐controlled mould closure was also investigated for CRTM. Good agreement with simulation was also achieved for this complex situation. The range of processes and conditions investigated here show that the simulation package is providing good agreement to experiment for both flow evolution and tooling forces and stresses. POLYM. COMPOS., 36:591–603, 2015. © 2014 Society of Plastics Engineers     

基于Pro／MOLDESIGN及NC的不规则破孔壳体件塑料模成型零件快速设计与制造

应用Pro／MOLDESIGN和NC模块实现了不规则破孔壳体件塑料模具成型．零件的快速设计与制造，从而缩短模具开发周期，降低开发成本。开模仿真结果验证了模具设计的合理性。     

T cells enhance gold nanoparticle delivery to tumors <Emphasis Type="Italic">in vivo</Emphasis>

Gold nanoparticle-mediated photothermal therapy (PTT) has shown great potential for the treatment of cancer in mouse studies and is now being evaluated in clinical trials. For this therapy, gold nanoparticles (AuNPs) are injected intravenously and are allowed to accumulate within the tumor via the enhanced permeability and retention (EPR) effect. The tumor is then irradiated with a near infrared laser, whose energy is absorbed by the AuNPs and translated into heat. While reliance on the EPR effect for tumor targeting has proven adequate for vascularized tumors in small animal models, the efficiency and specificity of tumor delivery in vivo, particularly in tumors with poor blood supply, has proven challenging. In this study, we examine whether human T cells can be used as cellular delivery vehicles for AuNP transport into tumors. We first demonstrate that T cells can be efficiently loaded with 45 nm gold colloid nanoparticles without affecting viability or function (e.g. migration and cytokine production). Using a human tumor xenograft mouse model, we next demonstrate that AuNP-loaded T cells retain their capacity to migrate to tumor sites in vivo. In addition, the efficiency of AuNP delivery to tumors in vivo is increased by more than four-fold compared to injection of free PEGylated AuNPs and the use of the T cell delivery system also dramatically alters the overall nanoparticle biodistribution. Thus, the use of T cell chaperones for AuNP delivery could enhance the efficacy of nanoparticle-based therapies and imaging applications by increasing AuNP tumor accumulation.     

Low cost tool builds ISS parts

A LOW cost composite tooling system developed by Boeing and RenShape Solutions is being used to make parts for the International Space Station.This is a short news story only. Visit www.reinforcedplastics.com for the latest plastics industry news.     

Properties of rapid prototype injection mold tooling materials

Epoxy acrylate‐based sterolithography resins have been used successfully as tools for injection molding. Molds made out of these resins fail at distinct times: during the first injection of plastic; during the first part first ejection; during either injection or ejection, but after a certain number of parts have been produced, which can be compared to a fatigue process. This paper presents corelations between measured properties of stereolithography molds and injection molding processing conditions so as to understand and predict mold failure. The study focuses on two stereolithography resins (SL 7510 and SL 7510) and one epoxy‐based composite material used for the high speed machining of prototype molds (Renboard). Rapid tooling materials are studied in fatigue, tensile, and fracture at injection molding operating temperatures and at room temperature. Finally, a method to address failure of molds is proposed using the theory of fracture.     

Design of intelligent chitosan/heparin hollow microcapsules for drug delivery

In this study, a novel strategy has been developed for the assembly of polyelectrolyte multilayer (PEM) on CaCO₃ templates in acidic pH solutions, where consecutive polyelectrolyte layers (heparin/poly(allylamine hydrochloride) or heparin/chitosan) were deposited on PEM hollow microcapsules established previously on CaCO₃ templates. The PEM build‐up, hollow capsule characterization and successful encapsulation of fluorescein 5(6)‐isothiocyanate (FITC)‐Dextran by coprecipitation with CaCO₃ are demonstrated. Improvement by the removal of CaCO₃ core was achieved while the depositions. In the course of the release profile, high retardation for encapsulated FITC‐Dextran was observed. The combined shell capsules system is a significant trait that has potential use in tailoring functional layer‐by‐layer capsules as intelligent drug delivery vehicles where the preliminary in vitro tests showed the responsiveness on the enzymes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44425.     

Polymer crystallization induced by sorption of CO2 gas

Previous work has shown that sorption of CO₂ at relatively high pressures by glassy polymers reduces their glass transition temperatures and may convert the glass into a rubber under certain conditions. It is shown here that this plasticization by a gas can induce crystallization just as sorption of vapors or liquids is known to do. This point is extensively explored for miscible blends of poly(vinylidene fluoride) and poly(methyl methacrylate) and to a lesser extent for poly(ethylene terephthalate). In some cases, this secondary crystallization process results in small crystals whose melting endotherms are just above the glass transition and are very similar to peaks resulting from heat capacity overshoots, or enthalpic relaxation, caused by sub-T_g annealing; however, by appropriate techniques peaks arising from these two separate mechanisms can be distinguished. For oriented materials, evidence is shown which demonstrates that the additional crystals formed on CO₂ sorption have the same preferential orientation as the original material.     

Modification of poly(vinyl chloride). XXXIII. Novel poly(vinyl chloride) foam crosslinked with 6-dibutylamino-1,3,5-triazine-2,4-dithiol

The formulation for producing the PVC foam crosslinked with a novel crosslinking agent such as 6-dibutylamino-1,3,5-triazine-2,4-dithiol (DB) was studied to determine the processing conditions. DB was almost consumed by radical combination with a coexistent blowing agent such as azobisformamide to give a high-density foam with excessively low crosslinking density. Blowing agents such as p-toluenesulfonylhydrazide (TSH) and 4,4′-oxybis(benzenesulfonylhydrazide) (OBSH) gave a crosslinked foam of low density, while a combination of the two crosslinking agents had moderate crosslinking reaction rate. The formulation recommended in the present study consists of PVC Zeon 101EP or Zeon 121 for paste, 100 parts; DOP, 100 parts; DB, 3–5 parts; OBSH or TSH, 10 parts; MgO, 1–3 parts; and RP101 (mixture of Ba, Ca, and Zn stearate), 2 parts, which gave colorless and insoluble foam of apparent density 0.14 under hot pressing at 180°C. The molded foam could be released without extraction of heat from a hot mold for fusion and expansion.     

New developments help composites compete

The use of fibre reinforced plastics, including carbon fibre composites, continues strong in automotive applications. Reducing mass is growing in importance due to increased demand for more fuel-efficient and cleaner cars and trucks. Manufacturers have introduced niche vehicles with innovative styling that would not be economically feasible without the design flexibility and reduced tooling costs possible with composites. New materials and technologies have been developed to improve the surface quality and performance of moulded automotive components while lowering production costs. Richard Stewart reports.     

Retraction: A Photoclick Thiol-Ene Collagen-Based Hydrogel Platform for Skeletal Muscle Tissue Engineering

Macromol. Mater. Eng. 2023 , 308, 2300029 DOI: 10.1002/mame.202300029 The above article, published online on April 18, 2023, in Wiley Online Library ( https://onlinelibrary.wiley.com/ ), has been retracted by agreement between the journal Editor-in-Chief, David Huesmann, the authors, and Wiley-VCH GmbH. The retraction has been agreed on following concerns raised by third parties regarding Figures 8 and 9. Further investigation conducted by the journal concluded that elements of the figures in question were duplicated, affecting the interpretation of the associated data and related results. This issue was acknowledged by the authors, who were unable to access and provide the original data. Thus, this article was retracted based on the consequent uncertainty on parts of its conclusions. R.H. was not available to comment on the missing original data and approve the retraction.     

内藏式分型线汽车外饰件模具的基本结构

本文介绍了汽车外饰零件如保险杠、防擦条等外观零件中内藏式分型线注塑模具的基本结构和模具动作要点。通过浅显易懂的插图和描述向同行业介绍了这一可以令相关模具制造厂商提升设计水平的技术。