Influence of Elastomer Layers in the Quality of Aluminum Parts on Finishing Operations

In finishing processes, the quality of aluminum parts is mostly influenced by static and dynamic phenomena. Different solutions have been studied toward a stable milling process attainment. However, the improvements obtained with the tuning of process parameters are limited by the system stiffness and external dampers devices interfere with the machining process. To deal with this challenge, this work analyzes the suitability of elastomer layers as passive damping elements directly located under the part to be machined. Thus, exploiting the sealing properties of nitrile butadiene rubber (NBR), a suitable flexible vacuum fixture is developed, enabling a proper implementation in the manufacturing process. Two different compounds are characterized under axial compression and under finishing operations. The compression tests present the effect of the feed rate and the strain accumulative effect in the fixture compressive behavior. Despite the higher strain variability of the softer rubber, different milling process parameters, such as the tool feed rate, can lead to a similar compressive behavior of the fixture regardless the elastomer hardness. On the other hand, the characterization of these flexible fixtures is completed over AA2024 floor milling of rigid parts and compared with the use of a rigid part clamping. These results show that, as the cutting speed and the feed rate increases, due to the strain evolution of the rubber, the part quality obtained tend to equalize between the flexible and the rigid clamping of the workpiece. Due to the versatility of the NBR for clamping different part geometries without new fixture redesigns, this leads to a competitive advantage of these flexible solutions against the classic rigid vacuum fixtures. Finally, a model to predict the grooving forces with a bull-nose end mill regardless of the stiffness of the part support is proposed and validated for the working range.This research was funded by Basque Government (Eusko Jaurlaritza) under the ELKARTEK Program, SMAR3NAK project, grant number KK-2019/00051

Study of abrasive techniques for lunar and planetary solid rock geological sampling

Abrasive techniques for lunar and planetary geological samplin

Automatic polishing process of plastic injection molds on a 5-axis milling center

The plastic injection mold manufacturing process includes polishing operations when surface roughness is critical or mirror effect is required to produce transparent parts. This polishing operation is mainly carried out manually by skilled workers of subcontractor companies. In this paper, we propose an automatic polishing technique on a 5-axis milling center in order to use the same means of production from machining to polishing and reduce the costs. We develop special algorithms to compute 5-axis cutter locations on free-form cavities in order to imitate the skills of the workers. These are based on both filling curves and trochoidal curves. The polishing force is ensured by the compliance of the passive tool itself and set-up by calibration between displacement and force based on a force sensor. The compliance of the tool helps to avoid kinematical error effects on the part during 5-axis tool movements. The effectiveness of the method in terms of the surface roughness quality and the simplicity of implementation is shown through experiments on a 5-axis machining center with a rotary and tilt table

エンドミル加工における加工誤差予測のための複合モデリング

機械加工は、製造業における部品製造プロセスにとして重要な加工方法です。生産性と製品品質は、常に製造技術の重要な課題として考えられてきました。現代の製造業は、部品や製品の加工精度と効率を向上させることを求められています。機械加工プロセスには、複雑な加工現象が含まれ、多くの場合ではプロセスの制約が発生し、製品の品質が低下します。加工誤差は、複雑な加工現象の代表的なもののひとつであり、切削条件、工作物形状、材料特性、切削抵抗、工作物変形などの変化に影響されます。したがって、これらの要件を解決するには、加工誤差を予測するための信頼できる方法が不可欠です。新たな製造業のトレンドとして、小ロット生産が注目されています。消費者の行動の変化により、個人化された高品質の製品が求められる傾向が高まり、消費者と直結した製造サービスが提案されています。また、大量生産のための製品試作や金型製作も、エンドミル加工によって実現される小ロット生産といえます。エンドミル加工は、多種多様な材料を使用した部品や製品を直接加工するための有効な方法です。この加工方法は、費用と時間のかかる金型の準備を必要としません。この研究では、柔軟弾性体のエンドミル加工における加工誤差モデリングを扱います。これは、柔軟弾性体が独特の弾性変形特性と亀裂の発生形態を有し、加工誤差の制御が難しいためです。柔軟弾性体エンドミル加工における加工誤差の従来の制御方法は、柔軟弾性体部品の機械加工サービスを提供する企業のノウハウに依存し、体系的な研究は十分なされていません。したがって、本論文は、提案する加工誤差モデル化手法の対象として柔軟弾性体のエンドミル加工を対象とすることにしました。加工精度を確保し、加工プロセスを制御するために、本論文では、加工誤差モデリングのための体系的なフレームワークをもとにした加工誤差モデルの構築手法を提案します。提案するフレームワークでは、モデル変数の候補は予備実験に基づいて評価されます。候補となるモデル変数は、切削条件と、工作物の変形や切削抵抗などの物理的状態変数です。提案されたモデルは、従来のデータ中心のアプローチ、経験的な知識を基にしたアプローチ、および主成分分析（PCA）を基にした統計的アプローチによって構築されます。モデルの係数を計算し、線形回帰モデルを形成するために、相関係数と重回帰法が採用されています。従来の切削条件ベースモデル、経験的モデル、統計ベースモデルの3つの異なるモデルが構築されます。統計モデルの構築では、有効変数を決定するために提案された体系的な手順が利用されます。その後、評価実験としてより大きな実験事例を用いてモデルの妥当性を評価します。実験結果は、提案手法により構築されたモデルを用いて計算された加工誤差と測定された加工誤差の比較に用います。比較の結果として、提案手法を基にした統計ベースモデルは実験結果と最も良好な一致を示しました。以上の結論として、提案された加工誤差モデリング手法の妥当性を確認することができました。Machining is a method that important to the manufacturing process in the industry. Productivity and product quality are always concerned with significant issues in manufacturing technologies. Modern manufacturing aims to improve the machining accuracy and efficiency of parts and products. However, machining variables involve the complex machining phenomenon that usually generates process limitations and reduces product quality. Machining error is one of responsiveness in complex machining phenomenon. It has directly influenced by varying cutting conditions, workpiece shape, material characteristics, cutting force, and workpiece deformation. Therefore, a reliable method for predicting machining errors is essential to solving these requirements. Small-lot production has attracted attention in the new tendency of manufacturing. Due to the changing consumer behavior, the personalized, high-quality, and technology trends require the service of direct-to-consumer manufacturing. Product prototype and mould making for mass production are regarded as small-lot production that suitably serves by milling process. On the other hand, end-milling is also a capable method for direct operating on parts or products with a large variety of materials. This method does not require expensive and time-consuming preparation. This research deals with a machining error modelling for the end-milling of elastomer material because it\u27s uniquely elastic deformation, crack generation, and difficult to control machining error. Conventional control method of machining error in elastomer end-milling has been studied with a limitation because most machining services of the elastomeric parts are based on enterprise-dependent dexterities or know-how. Therefore, this material has been selected to be a case study in this research. In order to secure machining accuracy and control the phenomenon, this dissertation proposes the machining error models through a systematic framework for machining error modelling. In the framework, the candidates of model variables are evaluated based on the preliminary experiments. Candidate variables are the cutting conditions and physical state variables such as workpiece deformation and cutting force. The proposed models are constructed by conventional data-centric approach, mechanistic knowledge-based approach, and principal component analysis (PCA) based statistical approaches. The correlation coefficient and multiple regression method are employed to compute the model\u27s coefficient and form the linear regression model. Three different models: the conventional cutting condition model, mechanistic model, and statistical model are constructed. At the statistical model construction, a proposed systematic procedure to determine the effective variable is utilized. Afterward, the models are investigated by using larger experimental cases as the evaluation experiment. From the experimental results, it become possible to make a comparison between calculated and measured machining errors. In addition, the statistical model provides relatively good agreement. Therefore, it could be confirmed the proposed machining error modelling method can generate the appropriate process model.室蘭工業大学 (Muroran Institute of Technology)博士（工学

Vibrations characterization in milling of low stiffness parts with a rubber-based vacuum fixture

Fixtures are a critical element in machining operations as they are the interface between the part and the machine. These components are responsible for the precise part location on the machine table and for the proper dynamic stability maintenance during the manufacturing operations. Although these two features are deeply related, they are usually studied separately. On the one hand, diverse adaptable solutions have been developed for the clamping of different variable geometries. Parallelly, the stability of the part has been long studied to reduce the forced vibration and the chatter effects, especially on thin parts machining operations typically performed in the aeronautic field, such as the skin panels milling. The present work proposes a commitment between both features by the presentation of an innovative vacuum fixture based on the use of a vulcanized rubber layer. This solution presents high flexibility as it can be adapted to different geometries while providing a proper damping capacity due to the viscoelastic and elastoplastic behaviour of these compounds. Moreover, the sealing properties of these elastomers provide the perfect combination to transform a rubber layer into a flexible vacuum table. Therefore, in order to validate the suitability of this fixture, a test bench is manufactured and tested under uniaxial compression loads and under real finish milling conditions over AA2024 part samples. Finally, a roughness model is proposed and analysed in order to characterize the part vibration sources.Financial support from the Basque Government under theELKARTEK Program (SMAR3NAK project, grant numberKK-2019/00051) is gratefully acknowledged by the authors

Vibrations Characterization in Milling of low Stiffness Parts with a Rubber-Based Vacuum Fixture

Fixtures are a critical element in machining operations as they are the interface between the part and the machine. These components are responsible for the precise part location on the machine table and for the proper dynamic stability maintenance during the manufacturing operations. Although these two features are deeply related, they are usually studied separately. On the one hand, diverse adaptable solutions have been developed for the clamping of different variable geometries. Parallelly, the stability of the part has been long studied to reduce the forced vibration and the chatter effects, especially on thin parts machining operations typically performed in the aeronautic field, such as the skin panels milling. The present work proposes a commitment between both features by the presentation of an innovative vacuum fixture based on the use of a vulcanized rubber layer. This solution presents high flexibility as it can be adapted to different geometries while providing a proper damping capacity due to the viscoelastic and elastoplastic behaviour of these compounds. Moreover, the sealing properties of these elastomers provide the perfect combination to transform a rubber layer into a flexible vacuum table. Therefore, in order to validate the suitability of this fixture, a test bench is manufactured and tested under uniaxial compression loads and under real finish milling conditions over AA2024 part samples. Finally, a roughness model is proposed and analysed in order to characterize the part vibration sources.Financial support from the Basque Government under the ELKARTEK Program (SMAR3NAK project, grant number KK-2019/00051) is gratefully acknowledged by the authors

A centrifugo-magnetically actuated gas micropump

This paper describes a novel gas micropump on a centrifugal microfluidic platform. The pump is integrated on a passive and microstructured polymer disk which is sealed with an elastomer lid featuring paramagnetic inlays. The rotational motion of this hybrid disk over a stationary magnet induces a designated sequence of volume displacements of the elastic lid, leading to a net transport of gas. The pumping pressure scales linearly with the frequency, with a maximum observable pressure of 4.1 kPa. The first application of this rotary device is the production of gas-liquid flows by pumping ambient air into a continuous centrifugal flow of liquid. The injected gas volume segments the liquid stream into a series of liquid compartments. Apart from such multi-phase flows, the new pumping technique supplements a generic air-to-liquid sampling method to centrifugal microfluidic platforms

Experimental investigation of machining error in elastomer endmilling

This paper deals with fundamental investigation for machining error in elastomer endmilling. In the conventional metal machining, cutting force during endmilling is one of the most important factors to machining error. Because of low-rigidity of elastomers, influence of cutting force may be more important. Therefore, relationship between the cutting force and machining error is investigated. From the experimental results, it becomes clear that cutting forces affect to the machining error only in the down cut machining.特集 : Special Section for the Papers Presented at the Symposium on Mechanical Engineering, Industrial Engineering, and Robotics held at Noboribetsu, Hokkaido, Japan on 11 - 12 January 201

CUTTING FORCE AND SURFACE ROUGHNESS IN CRYOGENIC MACHINING OF ELASTOMER

ABSTRACT Most products based on elastomers are produced by some kind of molding and curing process. This paper deals with a new method of elastomer machining. A series of cutting experiments under different rake angle, cutting speed, feed and constant depth of cut has been conducted on cutting force and surface roughness under ambient and cryogenic condition. From experimental data it can be clearly seen that increase of cutting force become more significant with higher cutting speeds for cryogenic cutting. Cryogenic machining showed remarkable reduction in surface roughness compared ambient machining especially at high rake angle