Medium Batch Sizes Research Articles

Experimental investigation of design parameters on geometrical accuracy of selective laser sintered parts

Selective Laser Sintering (SLS) is becoming a popular choice for the fabrication of polymer parts of medium batch sizes. Understanding the effect of various factors influencing the geometrical accuracy of parts fabricated with selective laser sintering is key to ensuring consistent quality. This study attempts to evaluate the effects of different design parameters on a part-to-part variation in the geometrical accuracy of fabricated parts within the same build. A three-level Box-Behnken response surface methodology was adopted with the part orientation, part thickness, build position, and feature size as factors to investigate the impact on geometrical accuracy. A specimen comprising various through holes of different thicknesses was fabricated using SLS. The part-to-part variation in dimensional accuracy and circularity was inspected with a video measuring system to evaluate the effect of factors. The part orientation, part thickness, and build position impart a stronger influence on dimensional accuracy while the circularity was highly affected by the part orientation of the specimen. Further, the geometrical accuracy of the fabricated features was optimized separately with different sets of factors and validated experimentally.

Preparation of Nanosized Pharmaceutical Formulations by Dual Centrifugation.

Dual centrifugation (DC) is an innovative in-vial homogenization and in-vial nanomilling technique that has been in use for the preparation of liposomes for more than one decade. Since then, DC has continuously been developed for preparing various liposomes and other lipid nanoparticles including emulsions and solid lipid nanoparticles (SLNs) as well as polymersomes and nanocrystals. Improvements in equipment technology have been achieved over the past decade, so that DC is now on its way to becoming the quasi-standard for the simple, fast, and aseptic production of lipid nanoparticles and nanocrystals in small and medium batch sizes, including the possibility of simple and fast formulation screening or bedside preparations of therapeutic nanoparticles. More than 68 publications in which DC was used to produce nanoparticles have appeared since then, justifying an initial review of the use of DC for pharmaceutical nanotechnology.

A model to account for magnetic permeability changes resulting from edge damage caused by laser cutting in a high performance cobalt-iron alloy

Laser cutting is the mainstay of electrical machine stator core manufacture for prototyping and for high value, small and medium batch sizes. However, it can introduce localized damage into electrical steels, with reduction in magnetic permeability and increase in core loss in regions adjacent to the edge. These phenomena have been studied in Silicon-iron alloys, but there is little published data on Cobalt-iron. This paper presents experimental measurements on magnetic edge damage effect in Cobalt-iron alloys due to laser cutting. The paper then uses magnetic measurements for an increasing number of cuts in test samples to develop a model that represents the deterioration of magnetic permeability with distance from the cut edge, including cumulative damage effects from multiple cuts. The model is suitable for incorporation into finite-element models, either as a continuous function of position or to generate individual magnetization curves for discrete layers in finite-element mesh. The paper concludes by using the model to generate a series of magnetization curves which include the damage effect and in turn uses these to predict the net magnetic behavior of a series of rectangular strips. Good agreement is obtained between these predictions and measurements of samples from the same batch of Cobalt-iron.

PRODUCTION OF INDIVIDUALISED MULTI-MATERIAL COMPONENTS USING A ROBOT-BASED PROCESS CHAIN

The production of individual work pieces in small to medium batch sizes requires an adaptation of the manufacturing strategy. Particularly, the manufacturing of multi-material components out of metal and plastic is characterized by high production costs as well as high production times. To resolve this challenge, a new, modular process chain for the production of these structures in a single manufacturing cell was developed. In this cell, a robot manufactures multi-material components with multiple end-effectors in several successive process steps. In the first step, interlocking structures are manufactured on a metal part by a surface structuring tool. Afterwards, an extruder is used to add a thermoplastic onto the structured metal part. Due to mechanical interlocking effects, the applied thermoplastic shows improved adhesion behavior. A study was conducted to analyze the achievable joint strength of the additive material application onto the structured metal samples. Investigations to determine the achievable manufacturing quality of a robot guided milling process for multi-material parts have been carried out. A recently developed suction hood is used to capture the metal and plastic chips. In this paper, the results regarding the efficiency of the individual end-effectors, including the extraction hood, are presented and it is demonstrated how they interact within the robot-based process chain.

Process Performance of High Energy Wire EDM

Wire EDM is increasingly used for the production of components in small and medium batch sizes. Due to the higher wear capacity and electrical conductivity of electrodes with larger diameters and its electrical properties, higher discharge energies can be realized. Thus, cutting rates can be increased and larger working gaps occur. However, a higher energy input in the material also has a significant impact on the surface integrity. Therefore, in this paper the process performance and surface integrity of a steel material machined by using a brass and coated wire with a standard wire diameter and a 0.4 mm diameter are compared.

Impact of Cyber-physically enhanced manufacturing on the product requirement documentation in high-tech applications

Conventional machining of high-tech parts and components is often associated with complex processes, long lead times and small to medium batch sizes. Obviously, there is great interest to shorten process development periods and increase process reliability. The transformation of conventional machines into cyber-physical production systems (CPPS) promises significant improvements here. In fact, CPPS allows real-time data acquisition and processing, enabling to target integrated process improvement and quality assurance. In the present work, a methodical procedure for structured data aggregation is introduced for a Cyber-physical enhanced machining process while being explained from a high-tech application point of view. This includes data generation, extraction, transfer and storage, data-consolidation, linkage, visualization and interpretation. Finally, the paper illustrates these aspects in terms of the effects on the “digital product requirements” in order to achieve the presented “analytics-ready” data model using the example of a high-tech application.

Dimensional and Geometrical Quality Enhancement in Additively Manufactured Parts: Systematic Framework and A Case Study.

In order to compete with traditional manufacturing processes, Additive Manufacturing (AM) should be capable of producing medium to large batches at industrial-degree quality and competitive cost-per-unit. This paper proposes a systematic framework approach to the problem of fulfilling dimensional and geometric requirements for medium batch sizes of AM parts, which has been structured as a three-step optimization methodology. Firstly, specific work characteristics are analyzed so that information is arranged according to an Operation Space (factors that could have an influence upon quality) and a Verification Space (formed by quality indicators and requirements). Standard process configuration leads to characterization of the standard achievable quality. Secondly, controllable factors are analyzed to determine their relative influence upon quality indicators and the optimal process configuration. Thirdly, optimization of part dimensional and/or geometric definition at the design level is performed in order to improve part quality and meet quality requirements. To evaluate the usefulness of the proposed framework under quasi-industrial condition, a case study is presented here which is focused on the dimensional and geometric optimization of surgical-steel tibia resection guides manufactured by Laser-Power Bed Fusion (L-PBF). The results show that the proposed approach allows for part quality improvement to a degree that matches the initial requirements.

Replicability of Ultrasonic Molding for Processing Thin-Wall Polystyrene Plates with a Microchannel.

Ultrasonic molding is a new technology for processing small and micro polymeric components with reasonable cost and energy savings when small and medium batch sizes are required. However, when microcomponents are manufactured, the replicability of different micro features has to be guaranteed. The aim is to investigate the capability of ultrasonic molding technology for processing thin-wall plates of polystyrene with a microchannel, analyzing the filling behavior, the optical transparency, and the dimensional accuracy of the thin plate. The replicability of the manufactured microchannel is studied according to dimension and shape. The results reveal that plunger velocity influences transparency and filling cavity, whereas the vibration amplitude has less effect in both cases. The thickness deviation achieved on the final part is below 7% and the replication of the microchannel is better in depth than width, obtaining an average deviation of 4% and 11%, respectively. This replication also depends on the orientation of the microchannels and the distance from the injection gate. The replicability and repeatability for processing thin-wall plates with microchannel in polystyrene polymer are proved in this paper.

The performance of tool shape on efficiency and quality of forming in incremental sheet-forming process

Incremental sheet-forming process is an economical alternative of conventional sheet metal forming process to manufacture parts in small or medium batch size as well as to produce sheet metal prototypes. In the present investigation, to study the effect of tool shape on efficiency and quality of the formed component, two different kinds of tools of same diameter with hemispherical end and spherical end are employed. Forming time is considered as a measure of process efficiency and profile accuracy as a quality of forming. The Taguchi experimental design is applied for experimentation. ANOVA is performed to know the level of significance of the process parameters. It is found that incremental depth step is the most significant process parameter affecting forming efficiency followed by forming speed (feed). Forming speed, wall angle and incremental depth step are the most significant parameters that affect the forming quality.

Design of Deformable Tools for Sheet Metal Forming

Traditionally, industrial sheet metal forming technologies use rigid metallic tools to plastically deform the blanks. In order to reduce the tooling costs, rubber or flexible tools can be used together with one rigid (metallic) die or punch, in order to enforce a predictable and repeatable geometry of the stamped parts. If the complete tooling setup is built with deformable tools, the final part quality and geometry are hardly predictable and only a prototypal production is generally possible. The aim of this paper is to present the development of an automatic tool design procedure, based on the explicit FEM simulation of a stamping process, coupled to a geometrical tool compensation algorithm. The FEM simulation model has been first validated by comparing the experiments done at different levels of the process parameters. After the experimental validation of the FEM model, a compensation algorithm has been implemented for reducing the error between the simulated component and the designed one. The tooling setup is made of machined thermoset polyurethane (PUR) punch, die, and blank holder, for the deep drawing of an aluminum part. With respect to conventional steel dies, the plastic tools used in the test case are significantly more economic. The proposed procedure is iterative. It allows, already after the first iteration, to reduce the geometrical deviation between the actual stamped part and the designed geometry. This methodology represents one step toward the transformation of the investigated process from a prototyping technique into an industrial process for small and medium batch sizes.

Thermally Sprayed Coatings as Effective Tool Surfaces in Sheet Metal Forming Applications

Two approaches to produce wear-resistant effective surfaces for deep drawing tools by thermal arc wire spraying of hard materials are presented. Arc wire spraying is a very economic coating technique due to a high deposition rate. The coated surface is very rough compared to that of conventional sheet metal forming tools. In the first approach, the coated surface is smoothed in a subsequent CNC-based incremental roller burnishing process. In this process, the surface asperities on the surface are flattened, and the roughness is significantly reduced. In the second approach, the hard material coatings are not sprayed directly on the tool but on a negative mould. Afterward, the rough “as-sprayed” side of the coating is backfilled with a polymer. The bonded hard metal shell is removed from the negative mould and acts as the surface of the hybrid sheet metal forming tool. Sheet metal forming experiments using tools based on these two approaches demonstrate that they are suitable to form high-strength steels. Owing to a conventional body of steel or cast iron, the first approach is suitable for large batch sizes. The application of the second approach lies within the range of small up to medium batch size productions.

Knowledge‐based benchmarking of production performance

PurposeRecently, benchmarking has become a common approach to optimize production processes by comparing certain aspects of a company with its competitors. However, one of the biggest challenges is not only to define suitable benchmarking topics and partners, to gather and statistically evaluate characteristic data, but to derive concrete measures to interpret the results, i.e. to overcome the revealed weaknesses. The purpose of this paper is to present an already implemented and successfully used functional benchmarking methodology for production performance of small and medium batch size processes, that is currently extended by using a knowledge base for reasoning strategies to semi‐automatically support the interpretation of the extracted statistical data.Design/methodology/approachA comprehensive approach is presented to develop a new model for the evaluation of a small to medium‐sized enterprise's production performance using an existing European database called BETT Benchmark.FindingsThe knowledge‐based concept enables sophisticated interpretation strategies to be used on an already existing base of real company data. The decisive point of the approach presented is to map production variables on room for improvement by taking varying parameters into account.Originality/valueThe proposed tool is a valuable tool that takes advantage of a statistically firmed analysis of a substantial database and combines it with the comprehensive expertise of experienced specialists in the field of performance assessment.

The Prototrak system

Automation first made an impact in the automotive and other mass production markets. This was followed by developments such as computer numerical control that introduced automation to small and medium batch sizes. Until recently, the one‐off and very small batch sizes encountered in toolrooms and prototype production remained the domain of manual machine tools. Describes the Prototrak system which was developed to address this market.