Automated Deposition System Research Articles

CFRP layer-by-layer curing using research-based automated deposition system

Composite laminates of carbon fibres and a toughened snap-cure epoxy matrix were manufactured using a proof-of-concept layer-by-layer curing technique and compared to equivalent hot-press cured laminates. The layer-by-layer approach used a roller and a heated metal tool to deposit and cure a pre-preg layer to a degree-of-cure below gelation (αGel= 0.41) before applying the next layer, removing the need for a further curing step after deposition. The layer-by-layer process was found to produce laminates with evenly distributed micro-porosity (∼2.9 %), whereas press molded laminates at equivalent pressures featured higher porosity (∼4.7 %), that was concentrated in the inter-ply regions that were laminated together. Further work is needed to optimize the process variables for laminate quality, manage roller contamination, and study non-flat geometries.

A strategy to analyse composite designs to improve automated production speeds

When a composite laminate is tailored to suit its design intent, it is possible to improve the individual ply shapes to reduce component mass. If the laminate is going to be manufactured using an automated deposition system such as an automated fibre placement machine, then the design of the laminate will also influence the material deposition speed. This article identifies methodologies for indicating the likely impact on automated manufacture at the design optimisation stage by evaluating the ratio of ply perimeter to ply surface area when the laminate is defined as a simplified array of cells which are filled or unfilled to create a two-dimensional representation of the ply shape. A set of recommendations are made for using the methodology for improving deposition speed.

Bead modelling and implementation of adaptive MAT path in wire and arc additive manufacturing

Wire and arc additive manufacturing (WAAM) is a promising alternative to traditional subtractive methods for fabricating large aerospace metal components that feature high buy-to-fly ratios. This study focuses on the development of an automated manufacturing system in order to free the operator from intervening in the analysis of the CAD model, planning the deposition path, and then manually setting the welding process parameters. Firstly, the relationship between single bead geometry and welding process parameters is established through an artificial neural network (ANN) model. Then, the adaptive medial axis transformation (MAT) algorithm for void-free deposition with high geometrical accuracy is introduced. The adaptive MAT path is implemented by using the single bead ANN model together with a previously developed multi-bead overlapping model. Finally, the adaptive MAT path planning strategy and the established bead models are tested through experimental deposition of two metal components. The results show that the developed bead model and adaptive MAT-based path are capable of producing depositions with high quality (void-free) and geometrical accuracy through automated selection of process variables for the WAAM process. This study developed an automated wire arc additive manufacturing system.An artificial neural network (ANN) bead model is established.An innovative path planning strategy is introduced.Practical implementation of an automated deposition system is reported.Experiments are conducted through automated selection of process variables.

Note: Influence of rinsing and drying routines on growth of multilayer thin films using automated deposition system

A versatile, high speed robot for layer-by-layer deposition of multifunctional thin films, which integrates concepts from previous dipping systems, has been designed with dramatic improvements in software, positioning, rinsing, drying, and waste removal. This system exploits the electrostatic interaction of oppositely charged species to deposit nanolayers (1-10 nm thick) from water onto the surface of a substrate. Dip times and number of deposited layers are adjustable through a graphical user interface. In between dips the system spray rinses and dries the substrate by positioning it in the two-tiered rinse-dry station. This feature significantly reduces processing time and provides the flexibility to choose from four different procedures for rinsing and drying. Assemblies of natural montmorillonite clay and polyethylenimine are deposited onto 175 microm poly(ethylene terephthalate) film to demonstrate the utility of this automated deposition system. By altering the type of rinse-dry procedure, these clay-based assemblies are shown to exhibit variations in film thickness and oxygen transmission rate. This type of system reproducibly deposits films containing 20 or more layers and may also be useful for other types of coatings that make use of dipping.

Ultra-high quality surface passivation of crystalline silicon wafers in large area parallel plate reactor at 40 MHz

We use a new in-house, large area and automated deposition system: the usable deposition area is 410 × 520 mm with RF-frequency of 40 MHz. We deposit intrinsic a-Si:H layer on flat p-type or n-type c-Si wafers after performing an HF dip. The overall recombination of these double-side passivated c-Si wafers is measured with an effective lifetime measurement set-up. We pay particular attention to the uniformity of the passivation obtained on the whole deposition area. We point out a major role of hydrogen dilution on quality of c-Si passivation. Excellent uniformity is obtained on the whole area with implied open-circuit voltages ( V oc) in a ± 1.5% range. We achieve excellent passivation with overall lifetimes approaching 7 ms (at Δ n ≈ 4.5·10 14 cm − 3 ) resulting in implied V oc of 708 mV on p-type c-Si; and lifetimes superior to 4.7 ms resulting in implied V oc of 726 mV on n-type c-Si ( S eff less than 2 cm/s for both). These results open the way to very high efficiency heterojunction solar cell fabrication in large area reactors.

X-ray photoelectron spectroscopy of low surface concentration mass-selected Ag clusters

We have developed an experimental setup for the study of small mass-selected clusters delivered by soft landing to a model oxide support. An automated deposition system to achieve accurately quantified homogeneous surfaces is described which also overcomes beam instability. Finally we present some recent photoelectron spectroscopic data from the analysis of mass-selected Agn+ clusters deposited on a Xe covered Al2O3 surface. Large core-level binding energy shifts are observed as a function of deposited cluster size and diffusion/agglomeration within the noble gas layer.

High-rate automated deposition system for the manufacture of complex multilayer coatings

A previously described automated thin-film deposition system based on rf-magnetron sputtering could deposit quite complex optical multilayer systems with good precision and with no one in attendance [Sullivan and Dobrowolski, Appl. Opt. 32, 2351-2360 (1993)]. However, the deposition rate was slow, and the uniform area on the substrate was limited. We describe an ac-magnetron sputtering process in which the same deposition accuracy has been combined with significantly better film uniformity and a fivefold or sevenfold increase in the deposition rate. This makes the equipment of commercial interest. Experimental results are presented for several difficult coating problems.

Manufacture of complex optical multilayer filters using an automated deposition system

It is now possible to design complex thin film multilayer coatings that can achieve almost any desired spectral performance. Moreover, these coatings can consist of tens or hundreds of layers each of which may have a different thickness. It is a challenge to accurately manufacture such complex coatings. An automated deposition system (ADS) has been developed which is able to fabricate complex optical coatings on a routine basis. This deposition system uses a wideband optical monitor to accurately determine the deposited layer thickness and to re-optimize the remaining layer thicknesses, if required. One advantage of this process is that no operators are required during the manufacture of a filter. For this technique to work, however, an energetic deposition process such as sputtering is necessary in order to achieve thin films with a bulk-like refractive index with little or no porosity or inhomogeneity. As well, the optical constants of the thin film materials must be accurately known. A number of thin film filters have been manufactured using this ADS. These include all-dielectric coatings as well as metal/dielectric filters. In this paper, the ADS and the real-time process control algorithms will be described in more detail and several examples of manufactured complex thin film filters will be described for different applications.

Optimization of the Growth of CdTe Thin Films Formed by Electrochemical Atomic Layer Epitaxy in an Automated Deposition System

This paper describes the deposition of CdTe thin films by electrochemical atomic layer epitaxy (ALE). ALE involves the formation of compounds an atomic layer at a time, using surface‐limited reactions. That is, atomic layers of the elements making up a compound are deposited in a cycle, where each cycle produces a monolayer of the compound. In electrochemical ALE, the surface‐limited reactions that produce the atomic layers are referred to as underpotential deposition (UPD). This article describes the dependence of the deposit structure, morphology and composition on a number of the steps in the deposition cycle. Separate optimized solutions and potentials are used to deposit each of the elements. Specifically, a variety of deposition and stripping potentials have been examined, resulting in a broad range of deposit compositions and morphologies. The dependence of the deposits on the potential used to form Cd atomic layers is a good example. If the potential was too positive, no CdTe deposits were formed, as no Cd was deposited, so there was nothing for Te UPD to form on. If the potentials were too far negative, bulk Cd began to deposit, and Cd‐rich three‐dimensional growth predominated. There was a 0.2 V plateau for the Cd deposition potential where stoichiometric films were deposited; however, the highest quality films were formed within a 0.1 V wide plateau, between −0.55 and −0.65 V. The optimal Te deposition potentials appear to be between −0.7 and −0.8 V. At more positive potentials, the Cd atomic‐layers stripped, while at more negative potentials Te dendrites were formed and the surface roughened badly. Potentials of −1.2 V and below should be used for the Te stripping step, in order to remove all excess Te, above an atomic layer. If more positive potentials were used, some excess Te remained and three‐dimensional growth resulted. Te stripping should be performed for at least 20 s to completely remove the excess Te. Neither substrate orientation, nor annealing to 300°C had much effect on the quality of the deposited films.