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On Manufacturing Technology as an Enabler of Flexibility: Affordable Reconfigurable Tooling and Force-Controlled Robotics
Linköping University, Department of Management and Engineering, Manufacturing Engineering. Linköping University, The Institute of Technology.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In order to survive in today’s global market many manufacturing companies seek flexibility to reduce product lead times and meet changing market demands. Manufacturing equipment forms the base of the production system and manufacturing technology with the capability to adapt to any changes in prerequisites is thus a key enabler of flexibility. Industrial robots and fixtures are common in all types of manufacturing. Robots are versatile re-programmable units capable of performing many tasks, such as welding, part transfer, etc. Industrial robots have traditionally been unable to handle disturbances and lack of constraints of input. This has led to manual operations often being preferred to automation when some level of flexibility is needed. One way to enhance manufacturing equipment’s capability to handle unknown events is to integrate different kinds of sensors to gain more knowledge of the manufacturing environment. Force sensors, for example, can be used to close the feedback loop and, together with an adequate control system, enable the robot to react to force stimuli. This is useful in manufacturing applications like assembly and deburring, which have previously been difficult to automate.

Fixtures are devices that hold and position parts during a manufacturing process. Traditionally many fixtures have been dedicated, i.e. designed for a specific part and purpose. This means that fixtures have not been able to handle different products in the same unit, thus hindering flexibility. Sensors, like measurement systems, can be used together with fixtures to de-couple the structure of the fixture from the accuracy, which is the traditional approach to fixturing. This reasoning forms the base of the Affordable Reconfigurable Tooling (ART) concept, developed at Linköping University. The ART concept aims at increasing flexibility in manufacturing, while ensuring affordability and efficiency.

This thesis explores how common manufacturing equipment, like industrial robots and fixtures, combined with sensor input, can enhance flexibility in manufacturing. The research shows that force-controlled robots, reacting to force stimuli, produce consistent results in assembly of compliant structures and in complex deburring. Force control also makes the system more robust, as it is able to handle variance in the assembled and deburred parts which adds to system flexibility. It also lessens the need for accuracy in other equipment used, such as grippers and fixtures, and makes programming easier and safer. Force control would, however, benefit if parameter tuning was simplified in order to fit an industrial environment and if presented user information is tailored for the intended user.

Using measurement sensors to build fixtures, new ART devices aimed at increased flexibility in fixtures have been developed. These devices reduce the resources needed for fixture build and reconfiguring between products and also open up for making fixtures more active in manufacturing and similar to robots, while still being affordable. ART also reduces resources needed for design, as shown by the developed design aid programs. ART also supports concurrent design, as fixture specifications may be finalized before the product specifications are fully set.

The overall results indicate that the explored sensors in combination with today’s emerging technologies can give additional benefits for applications like assembly and deburring and for fixtures. Furthermore, it is shown that it is possible to increase flexibility on different levels in a manufacturing system by using sensors in combination with industrial robots and fixtures.

Abstract [en]

För att överleva och växa på dagens globala arena försöker många tillverkande företag vara flexibla, och korta sin produktutveckling och sina ledtider för att på så sätt snabbare kunna möta marknadens krav. Den utrustning som används i produktionen lägger grunden för hur enkelt systemet kan anpassa sig till förändringar vilket gör att den teknik som används för tillverkningen är en viktig byggsten för att möjliggöra flexibilitetet.

Industrirobotar och fixturer är vanliga typer av utrustning som används för tillverkning. Industrirobotar är mångsidiga, omprogrammeringsbara enheter och kan till exempel användas för svetsning, förflyttning av gods etc. De har traditionellt sett haft svårt att hantera avvikelser vilket har gjort att höga krav ställts på inkommande material och omgivande utrustning. Detta har i sin tur lett till att om ett visst mått av flexibilitet krävts, så har manuell arbetskraft föredragits framför robotar. Ett sätt att öka förmågan att hantera relativt ”okända” miljöer är att integrera sensorer med produktionsutrustning, för att på så sätt få information om tillverkningens förutsättningar. Kraftsensorer tillsammans med kontrolllogik, gör det möjligt för en robot att reagera på kraft. Detta är användbart om roboten skall användas för avgradning och slipning, eller för montering, tillverkningstyper som annars har varit svåra att automatisera.

Fixturer är enheter som håller en produkt i önskat läge under tillverkningsprocessen. En fixtur har traditionellt konstruerats för att passa en produkt och en process. De har således inte kunnat användas t.ex. för olika produkt-typer eller när produkter förändrats på något sätt, vilket har påverkat systemets flexibilitet negativt. Sensorer, som t.ex. olika mätsystem kan användas för att frikoppla en fixturs struktur från dess interna noggrannhetskedja, något som annars är ett vanligt sätt att uppnå önskad noggrannhet i fixturen. Det tidigare utvecklade ART konceptet (Affordable Reconfigurable Tooling ungefär Kostnadseffektiva Rekonfigurerbara Verktyg) bygger på denna princip. ART fokuserar på att öka flexibiliteten för fixturer samtidigt som de fortfarande är resurseffektiva.

Denna avhandling behandlar hur vanligt förekommande produktionsutrustning, såsom robotar och fixturer, kan kombineras med sensorer för att uppnå ökad flexibilitet i tillverkning. Den genomförda forskningen visar att kraftstyrda robotar möjliggör ett bra och jämt resultat vid montering av icke formstabila strukturer/komponenter och vid komplicerad slipning/gradning av gjutgods. Kraftstyrningen gör att systemet klarar av att hantera variation hos de bearbetade/monterade detaljerna. Den minskar också behovet av noggrannhet hos omgivande utrustning, såsom fixturer och gripdon, och både förenklar och ökar säkerheten vid programmering jämfört med traditionella metoder. För att passa de industriella förutsättningarna skulle dock parameterinställning och användarvänlighet behöva utvecklas ytterligare.

Genom att använda mätsystem tillsammans med fixturer har nya fixturenheter till ART utvecklats. Dessa enheter minskar resursåtgången vid sammanbyggnad och omkonstruktion av fixturer. De öppnar även för att aktiva fixturer som är mer lika robotar, men som fortfarande är kostnadseffektiva. ART påverkar också design av fixturer positivt, eftersom stödjande mjukvaruverktyg för design kan tas fram.

Det övergripande resultatet tyder på att de använda sensorerna tillsammans med nydanande teknik ger mervärde i applikationer som montering och slipning. Vidare så visar forskningen att det är möjligt att öka flexibiliteten på flera nivåer i tillverkningssystemet med sensorer i kombination med industrirobotik och fixturer.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2013. , 118 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1501
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-88177ISBN: 978-91-7519-691-6 (print)OAI: oai:DiVA.org:liu-88177DiVA: diva2:601924
Public defence
2013-02-22, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (Swedish)
Opponent
Supervisors
Available from: 2013-01-30 Created: 2013-01-30 Last updated: 2013-01-30Bibliographically approved
List of papers
1. Fixture design using Configurators
Open this publication in new window or tab >>Fixture design using Configurators
2008 (English)In: Proceedings of the 2008 Swedish Production Symposium / [ed] Lindberg, B.; Stahre, J., 2008Conference paper, Published paper (Refereed)
Abstract [en]

Design and manufacture of fixtures are among one of the major cost drivers in product industrialization. Modular or reconfigurable fixture solutions that may be adapted to encompass a large variety of parts or products have been researched and employed in applications ranging from machining to assembly. These solutions have not only the potential to reduce fixture manufacturing cost, but they also render it possible for different solutions to facilitate and speed up actual design work. The process of designing fixtures today is complicated, time consuming and require long experience by the tool designer. In this paper we present the Configurator approach - add on programs to the CAD-software which aids the designer in the design process. The Configurators are semi-automated and interactive, designed to use in compliance with the ART-concept, a reconfigurable fixture concept for assembly applications. The Configurator approach has been tested on industrial cases and parts of the results are presented in this paper.

Keyword
Fixture design, Reconfigurable fixtures, Configurators
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-63187 (URN)
Conference
Swedish Production Symposium 2008, November 19-20, Stockholm, Sweden
Projects
Flexa
Available from: 2010-12-13 Created: 2010-12-13 Last updated: 2013-01-30Bibliographically approved
2. Development of a new flexible fixturing device for Affordable Reconfigurable Tooling
Open this publication in new window or tab >>Development of a new flexible fixturing device for Affordable Reconfigurable Tooling
2010 (English)In: 3rd CIRP Conference on Assembly Technologies and Systems: Responsive, customer demand driven, adaptive assembly / [ed] Terje K. Lien, Trondheim: Tapir Akademisk Forlag, 2010, 103-108 p.Conference paper, Published paper (Refereed)
Abstract [en]

To use thin wedges of metal to adjust fixtures, i.e shimming, has been a common approach to achieve desired position and tolerance. To build a fixture using shims is time-consuming and results in a fixture that is difficult to modify. The newly developed ART (Affordable Reconfigurable Tooling) concept addresses the need for flexible fixturing by means of reconfigurable supports that are set to desired position by guidance from an outer measuring system. The ART concept can be realized by means of several different reconfigurable devices, among these is the newly developed “Mini Flexapod”. This small 6 degree of freedom reconfigurable device was designed to eliminate shimming and therefore has a small working envelope of approximately 4x4x4 mm. The Mini Flexapod is a result of working with several manufacturing cases  described in this paper.

Place, publisher, year, edition, pages
Trondheim: Tapir Akademisk Forlag, 2010
National Category
Production Engineering, Human Work Science and Ergonomics
Identifiers
urn:nbn:se:liu:diva-63186 (URN)9788251926164 (ISBN)
Conference
3rd CIRP Conference on Assembly Technologies and Systems (CATS2010), June 21-22, Trondheim, Norway
Projects
Fixture, Fixturing, RMS, FMS, Tooling; Assembly technology
Available from: 2010-12-13 Created: 2010-12-13 Last updated: 2016-05-26Bibliographically approved
3. Development of an automated reconfigurable device for affordable fixturing
Open this publication in new window or tab >>Development of an automated reconfigurable device for affordable fixturing
2011 (English)In: Proceedings of the 21st International Conference on Production Research (ICPR2011), 31st July - 4th August, Stuttgart, Germany / [ed] D. Spath, R Ilg and T. Krause, 2011Conference paper, Published paper (Other academic)
Abstract [en]

Fixtures are used in manufacturing to hold and position products or workpieces. Linköping University has over a period of several years developed an approach to flexible fixturing that relies on an outer measuring system to ensure accuracy rather than the more common approaches of high internal accuracy or a built-in chain of tolerances. The Linköping system fuses modularity, a rebuildable framework, with reconfigurability, through the means of adjustable devices. To address the need for speed in reconfiguration an automated approach has been developed as a proof-ofconcept. The system consists of electrical motors attached to the legs of the Flexapod 6, a PC, controller cards and an external measuring system. The measuring system feeds information to the PC that is utilized to calculate desired leg length using a Visual Basic program that communicates with CATIA V5. This program then sets signals to the motor controller cards which run the actuators. Due to the motors used the accuracy achieved are in the range of +/-0.15 mm but this may be enhanced with other types of motors developed for higher strengthrather than speed. The system can be further developed by having the actuators as the actual legs of the Flexapod, making it a cheaper Hexapod robot. The paper presents the automated Flexapod 6 in the current system along with possible further development.

Keyword
Tooling, Hexapod, Reconfigurable, Manufacturing, RMS
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-88172 (URN)3-8396-0293-9 (ISBN)978-3-8396-0293-5 (ISBN)
Conference
21st International Conference on Production Research (ICPR2011), Innovation in Product and Production, 31st July - 4th August, Stuttgart, Germany
Note

Published in CD-ROM.

Available from: 2013-01-30 Created: 2013-01-30 Last updated: 2013-01-30Bibliographically approved
4. Aspects of reconfigurable and flexible fixtures
Open this publication in new window or tab >>Aspects of reconfigurable and flexible fixtures
2010 (English)In: Production Engineering, ISSN 0944-6524, Vol. 4, no 4, 333-339 p.Article in journal (Refereed) Published
Abstract [en]

The design and manufacture of fixtures and other dedicated tooling for positioning of workpieces are among the major cost drivers in product industrialization. This has spurred research and commercial interest towards other fixturing solutions like reconfigurable fixtures, with the ability to be changed, or  reconfigured , to suit different parts and products. When reconfiguring, the product interface not only has to be moved but moved to a desired position and orientation. Several different approaches have been used to move and position these devices, all with their own advantages and disadvantages. This article presents different methods used to position and reconfigure flexible fixture devices using a parallel kinematic device as a case. Discussing the different ways to reconfigure a flexible device, the article aims to arrange the techniques according to their key features.

Place, publisher, year, edition, pages
Heidelberg: Springer Berlin, 2010
National Category
Production Engineering, Human Work Science and Ergonomics
Identifiers
urn:nbn:se:liu:diva-63174 (URN)10.1007/s11740-010-0256-z (DOI)
Projects
KooFixProFlexaFlexa
Available from: 2010-12-13 Created: 2010-12-13 Last updated: 2013-01-30
5. Force Controlled Assembly of a Compliant Rib
Open this publication in new window or tab >>Force Controlled Assembly of a Compliant Rib
2011 (English)In: Proceedings of SEA AeroTech Congress and Exhibition 2011, 18th-21st October, Toulouse, France, 2011Conference paper, Published paper (Refereed)
Abstract [en]

Automation in aerospace industry is often in the form of dedicated solutions and focused on processes like drilling, riveting etc. The common industrial robot has due to limitations in positional accuracy and stiffness often been unsuitable for aerospace manufacturing. One major cost driver in aircraft manufacturing is manual assembly and the bespoke tooling needed. Assembly tasks frequently involve setting relations between parts rather than a global need for accuracy. This makes assembly a suitable process for the use of force control. With force control a robot equipped with needed software and hardware, searches for desired force rather than for a position. To test the usefulness of force control for aircraft assembly an experimental case aligning a compliant rib to multiple surfaces was designed and executed. The system used consisted of a standard ABB robot and an open controller and the assembly sequence was made up of several steps in order to achieve final position. The result shows that the process is robust and repetitive and has the potential to reduce the need for bespoke jigs and fixtures.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-88173 (URN)10.4271/2011-01-2734 (DOI)
Conference
SEA AeroTech Congress and Exhibition 2011, 18th-21st October, Toulouse, France
Available from: 2013-01-30 Created: 2013-01-30 Last updated: 2014-10-14Bibliographically approved
6. On force control for assembly and deburring of castings
Open this publication in new window or tab >>On force control for assembly and deburring of castings
Show others...
2013 (English)In: Production Engineering, ISSN 0944-6524, Vol. 7, no 4, 351-360 p.Article in journal (Refereed) Published
Abstract [en]

Traditional industrial robots have problems interacting with an uncalibrated, ill-dened environment where part geometry and position may vary. Active force control technology has therefore been suggested as a solution to add the extra sensory dimension needed to handle manufacturing tasks like assembly and deburring. The technology is proposed to give increased exibility compared to other solutions and force control systems are available commercially. Active force control installations however, are is still uncommon in industry. This paper presents two cases of force control applications; assembly of a compliant carbon ber structure and deburring/cleaning of iron castings. Based on these two cases, some issues are raised on how the technology can be further developed to t the industrial setting, and the proposed benets are re-examined and refined. The two cases show that programming, parameter setting and ease of use are critical components in lowering the industrial threshold, together with increased possibilities of application-specic compensation and filtering. Force control does however, show great potential in increasing the boundaries for variance in product and equipment like grippers and xtures as well as decreasing the need for calibration of for example virtual models used for programming compared to traditional automated solutions.

Place, publisher, year, edition, pages
Springer, 2013
Keyword
Industrial robotics Machining Debur- ring Force Control Assembly
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-88174 (URN)10.1007/s11740-013-0459-1 (DOI)
Available from: 2013-01-30 Created: 2013-01-30 Last updated: 2014-02-24Bibliographically approved
7. On emerging manufacturing technology as enablers of Lean
Open this publication in new window or tab >>On emerging manufacturing technology as enablers of Lean
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Purpose - This paper discusses the impact of emerging automation technologies on the reduction of waste/muda in Lean manufacturing. Two industrial cases are used to highlight the increasing complexity of investment decisions and technology management.

Design/methodology/approach - The 7 wastes are mapped along with their drivers in an automated manufacturing cell. Using two industrial cases; non-contact robotized scanning of car structures and force control de-burring, as illustrative examples their impact on drivers and waste reduction is established.

Findings - Emerging technology has a high potential for reducing waste, not only on a cell level but also up-, and downstream the actual manufacturing process, for example on programming efforts. However, this increases the complexity of how technology impacts waste, and to what extent and scope.

Research limitations/implications - New models for planning of manufacturing cells have to be researched that consider the possible impact of technology solutions to a wide aspect of the manufacturing organization.

Practical implications - The identified drivers of waste in automation along with the presented waste reducers can be used by industry practitioners as a tool to evaluate and design manufacturing cells.

Originality/value - This paper links new automation technologies with the waste concept and discusses the issues of increasing complexity in manufacturing, which is valuable for researchers and practitioners in technology management. It also lists drivers and summarizes possible technical solutions for waste reduction.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-88176 (URN)
Available from: 2013-01-30 Created: 2013-01-30 Last updated: 2016-09-26Bibliographically approved

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