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Article
Publication date: 27 September 2011

Arne Burisch and Annika Raatz

Economic, flexible and efficient micro production needs new miniaturized automation equipment (desktop factories). Micro assembly processes make demands on precision of…

Abstract

Purpose

Economic, flexible and efficient micro production needs new miniaturized automation equipment (desktop factories). Micro assembly processes make demands on precision of miniaturized robots used in desktop factories and the driving concepts, as well as miniaturized machine elements. The purpose of this paper is to investigate miniaturized drives using micro harmonic drive gears, which are promising driving concepts.

Design/methodology/approach

The analysis of the miniaturized precision robot Parvus (using micro harmonic drive gears) shows a good repeatability but also room for improvement concerning the path accuracy. Thereby the transmission error of the micro gears is identified as main disturbing influence concerning the robot's precision characteristics. Owing to the size reduction of the micro harmonic drive gear and the slightly different working principle compared to larger harmonic drive gears, the transmission error are more pronounced. Therefore, it is necessary to discuss approaches to compensate for this effect.

Findings

A very promising approach is the use of a simplified model of the kinematic error within the robot control to compensate for this disturbing effect. Measurement data of the transmission error is mathematically transformed into the frequency domain and filtered to the most important frequency modes of the function. These modes are used to build up a simplified mathematic model of the gear transmission error. A final test using this model as compensation function demonstrates that it is possible to reduce the transmission error of the micro gears by more than 50 percent.

Originality/value

The paper presents the first investigation into compensation of the transmission error of micro harmonic drive gears.

Details

Assembly Automation, vol. 31 no. 4
Type: Research Article
ISSN: 0144-5154

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Article
Publication date: 9 April 2018

Ruilong Du, Yinglong Chen and Hua Zhou

The purpose of this paper is to propose a simulation model for studying the lubricating gap between the ring gear and the case in internal gear pumps.

Abstract

Purpose

The purpose of this paper is to propose a simulation model for studying the lubricating gap between the ring gear and the case in internal gear pumps.

Design/methodology/approach

The pressure distribution of the wedge-shaped oil film between the ring gear and the case is obtained based on the theory of film lubrication using the Reynolds equation implemented with MATLAB. After that, the balance of the ring gear is achieved by the radial micro motion of the ring gear. The power loss due to the leakage and the shear stress is then calculated for optimized design of the radial clearance.

Findings

The hydrodynamic effect and the squeezing effect of the wedge-shaped oil film play a role in the hydrodynamic balance of the ring gear, and they become more intense when the operating speed gets lower and the pressure gets higher. The optimal radial clearance should stay between 20 and 25 µm for the minimum power loss.

Originality/value

The present research provides the first simulation model that treats the oil film between the ring gear and the case as wedge-shaped oil film and explains why the ring gear stays balanced. Furthermore, the simulation model can be regarded as a tool for optimized design of the radial clearance.

Details

Industrial Lubrication and Tribology, vol. 70 no. 3
Type: Research Article
ISSN: 0036-8792

Keywords

Content available
Article
Publication date: 1 December 1998

Abstract

Details

Industrial Lubrication and Tribology, vol. 50 no. 6
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 9 March 2015

Menderes Kalkat

The purpose of this paper was to perform an experimental investigation to analyze vibration and noise of unloaded gearbox with different oil quality. All motor-driven…

Abstract

Purpose

The purpose of this paper was to perform an experimental investigation to analyze vibration and noise of unloaded gearbox with different oil quality. All motor-driven machinery used in the modern world can develop faults. The maintenance plans include analyzing the external relevant information of critical components, in order to evaluate its internal state. From the beginning of the twentieth century, different technologies have been used to process signals of dynamical systems.

Design/methodology/approach

A proposed neural network (NN) is also employed to predict vibration parameters of the experimental test rig. Moreover, four types of oils are used for gearbox to predict reliable oil. Vibration signals extracted from rotating parts of machineries carry lot many information within them about the condition of the operating machine. Further processing of these raw vibration signatures measured at a convenient location of the machine unravels the condition of the component or the assembly under study. The experimental stand for testing an unloaded gearbox is composed by actuated direct current (DC) driving system.

Findings

This paper deals with the effectiveness of wavelet-based features for fault diagnosis of a gearbox using two types of artificial neural networks (ANNs) and stress analyzed with computer-based software ANNs. The results improved that the proposed NN has superior performance to adapt experimental results.

Practical implications

This paper is one such attempt to apply machine learning methods like ANN. This work deals with extraction of wavelet features from the vibration data of a gearbox system and classification of gear faults using ANNs.

Originality/value

These kind of NN-based approaches are novel approaches to predict real-time vibration and acceleration parameters of unloaded gearbox with five types of oils. Also, the investigation contains new information about studied process, containing elements of novelty.

Details

Industrial Lubrication and Tribology, vol. 67 no. 2
Type: Research Article
ISSN: 0036-8792

Keywords

Content available
Article
Publication date: 1 February 1999

Abstract

Details

Industrial Lubrication and Tribology, vol. 51 no. 1
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 20 June 2017

Reza Gheisari, Paulo Bártolo, Nicholas Goddard and Marco Andre das Neves Domingos

The use of microstereolithography (μSL) parts as micro-injection molding (μIM) tools greatly reduces the time and cost to product and offers unique solutions for complex…

Abstract

Purpose

The use of microstereolithography (μSL) parts as micro-injection molding (μIM) tools greatly reduces the time and cost to product and offers unique solutions for complex design issues. However, they present challenges to designers because of their strength, thermal characteristics and shorter lifetimes as compared to other mold materials. The purpose of this study is to use SL to build rapid injection mold tools directly combining micro features for short-run production.

Design/methodology/approach

In total, three tool inserts were produced. Two different μSL mold inserts were produced and evaluated in terms of different build approaches of micro features. One of the inserts includes micro features built horizontally, while the other one collaborates features built vertically, both having same geometrical dimensions. To evaluate the replication capability of prototype tools, two different thicknesses were set for micro features, that is, 30 and 120 μm. The mold inserts were assembled on a metallic mold frame and tested with polypropylene (PP).

Findings

It was observed that using inappropriate resin to fabricate the mold inserts can lead to inaccurate geometrical dimensions of the tool. Therefore, the material with high glass transition temperature (Tg) and low thermal conductivity is preferred. Also, the results of this research work showed that the processed material and technology play an important role both on part quality and tool life. After investigating the tool failure mechanisms during the injection, it was observed that tool failure occurred mainly because of excessive flexural stresses and ejection forces during the cavity filling and part ejection phases, respectively.

Originality/value

The paper describes the capability of μSL mold inserts for the production of small batches of micro-cantilevers which are used in MEMS relays.

Details

Rapid Prototyping Journal, vol. 23 no. 4
Type: Research Article
ISSN: 1355-2546

Keywords

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Article
Publication date: 10 July 2017

Christian Engelhardt, Jochen Witzig, Thomas Tobie and Karsten Stahl

Water can alter the performance of modern gear lubricants by influencing the flank load carrying capacity of gears significantly. The purpose of this paper is to…

Abstract

Purpose

Water can alter the performance of modern gear lubricants by influencing the flank load carrying capacity of gears significantly. The purpose of this paper is to investigate the influence of water contaminations in different kinds of base oils on the micro-pitting and wear performance of case carburized gears.

Design/methodology/approach

Concerning micro-pitting and wear, tests, based mostly on the following standardized tests, are performed on a Forschungsstelle fuer zahnraeder und getriebebau (FZG)-back-to-back gear test rig: micro-pitting short test Graufleckenkurztest (GFKT) according to DGMK 575 (screening test), micro-pitting test Graufleckentest (GT) according to FVA 54/7 (load stage test and endurance test) and Slow-speed wear test according to DGMK 377. To investigate the effect of water on the gear load carrying capacity dependent on different types of base oils, two polyglycol oils (PG1 and PG2), a polyalphaolefin oil, a mineral oil and an ester oil E are used. Each of these oils are common wind turbine gear oils with a viscosity ISO VG-220. Additionally, a manual transmission fluid with a viscosity of society of automotive engineers (SAE) 75W-85 is tested.

Findings

Considering the micro-pitting and wear performance, a significant decrease caused by water contaminations could not be detected. Regarding pitting damages, a generally negative influence was observed. This influence was differently distinctive for different base oil types. Especially non-polar lubricants seem to be affected negatively. The documented damages of the tooth flanks confirm this observation. While typical pitting damages appeared in test runs with polar lubricants, the disruption in test runs with non-polar lubricants was more extensive. Based on the experimental investigations, a general model of the damaging mechanisms of water contaminations in lubricants was derived. It is split into three partitions: interaction lubricant–water (effect of water on the molecular structure of base oils and additives), chemical-material-technological (especially corrosive reactions) and tribological influence (effect of water droplets in the contact zone). It has to be considered that the additive package of lubricants affects the influence of water contaminations on the flank load carrying capacity distinctively. An influence of water on the micro-pitting and wear performance in other than the given lubricants cannot be excluded.

Originality/value

While former research work was focused more on the effects of water in mineral oils, investigations concerning different types of base oils as well as different types of damages were carried out within this research project.

Details

Industrial Lubrication and Tribology, vol. 69 no. 4
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 27 February 2007

Arne Burisch, Jan Wrege, Annika Raatz, Jürgen Hesselbach and Reinhard Degen

Until now, the size range of most machines for precision assembly was much larger than the size of the pieces to be handled or the necessary workspace. Flexibly scalable…

Abstract

Purpose

Until now, the size range of most machines for precision assembly was much larger than the size of the pieces to be handled or the necessary workspace. Flexibly scalable miniaturised production machines can help to develop much more flexible micro production systems. The paper aims to describe the development of a micro‐parallel‐SCARA robot adapted in size to MEMS products.

Design/methodology/approach

The robot consists of a miniaturised parallel structure, which provides a high level of accuracy in a workspace of 60 × 45 × 20 mm3. It has a base area of 130 × 170 mm2 and offers four degrees of freedom.

Findings

Based on simulations, the degree of miniaturisation in terms of a smaller structure and a high level of accuracy is determined. The results show that a miniaturised hybrid robot with a plane parallel structure driven by miniaturised zero‐backlash gears and electric motors can reach a theoretical repeatability better than 1 μm.

Research limitations/implications

The first prototype provides good prospects that the concept will be used in a visionary desktop‐factory. As regards the accuracy parameters of the robot, there will be further efforts to optimise the robot's structure and drive mechanism.

Practical implications

The repeatability of this first prototype is better than 14 μm. A better stiffness of optimised microgears and joints of the structure will guarantee a much better repeatability.

Originality/value

The paper illustrates that the Parvus is one of the smallest industrial robots for micro assembly equipped with a full range of functionalities like conventional industrial robots.

Details

Assembly Automation, vol. 27 no. 1
Type: Research Article
ISSN: 0144-5154

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Article
Publication date: 1 December 2005

R.I. Amaro, R.C. Martins, J.O. Seabra, S. Yang, D.G. Teer and N.M. Renevier

Provide tribological information about the applicability of multi‐layer carbon‐chromium composite coatings to gears. Discuss the protection provided against scuffing…

Abstract

Purpose

Provide tribological information about the applicability of multi‐layer carbon‐chromium composite coatings to gears. Discuss the protection provided against scuffing failures, wear and the influence on gear power losses.

Design/methodology/approach

Several screening tests, such as Rockwell indentations, ball cratering, pin‐on‐disc and reciprocating wear tests, were performed in order to evaluate the adhesion to the substrate and the tribological performance of the carbon/chromium composite coating. Afterwards, twin‐disc tests were performed at high contact pressure and high slide‐to‐roll ratios to confirm the good adhesive and tribological properties of the coating under operating conditions similar to those found in gears. Gear tests were performed in the FZG machine in order to evaluate the anti‐scuffing performance of the carbon/chromium coating using additive free gear oils. Finally, the carbon/chromium composite coating was also applied to the gearing in a gearbox and its influence on the gearbox efficiency was analysed.

Findings

The C/Cr has got very good adhesion to the steel substrate, provides low friction coefficients between contacting solids in relative movement, gives excellent protection against scuffing and wear reduction in gears, and promotes a slight improvement of the gears efficiency.

Research limitations/implications

The protection of this carbon/chromium coating against gear micro‐pitting should be investigated.

Practical implications

This study confirms the applicability of this coating to industrial gear applications, especially in two particular applications: severe applications involving high contact pressures and high sliding, frequent start‐ups and inefficient lubrication; and acting as tribo‐reactive material and substituting non‐biodegradable and toxic additives in environmental lubricants.

Originality/value

This work validates and quantifies the influence of this C/Cr multi‐layer composite coating in gear applications in terms of adhesion to the substrate, anti‐scuffing performance and efficiency.

Details

Industrial Lubrication and Tribology, vol. 57 no. 6
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 2 October 2007

Won‐Shik Chu, Sung‐Geun Kim, Woo‐Kyun Jung, Hyung‐Jung Kim and Sung‐Hoon Ahn

The purpose of this research, is to develop a nano composite deposition system (NCDS) to fabricate three dimensional functional nano composite parts.

Abstract

Purpose

The purpose of this research, is to develop a nano composite deposition system (NCDS) to fabricate three dimensional functional nano composite parts.

Design/methodology/approach

The NCDS is a hybrid system in which material removal process by mechanical micro machining and/or the deposition process is combined.

Findings

Hybrid RP technology showed higher precision than those made by casting or deposition process. Tensile strength of the hydroxyapatite‐acrylic composite was about four times higher than that of resin‐only specimen while MWCNT composite did not show much improvement.

Originality/value

The paper illustrates new approaches for rapid prototyping techniques with various materials and high precision.

Details

Rapid Prototyping Journal, vol. 13 no. 5
Type: Research Article
ISSN: 1355-2546

Keywords

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