Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: The conceptual design of a fixtureless reconfigurable automated spot welding
system for manufacturing subassemblies for residential circuit breakers was
investigated. This research was aimed at developing a possible low cost automation
alternative to a South African industrial manufacturer, which is presently heavily
dependent on personnel for manual assembly of their core products.
System reconfiguration allows for the assembly of a range of subassemblies with
geometric component variation on a given system configuration, as well as the
potential for the system to be reconfigured to assemble other ranges of circuit
breaker subassemblies.
The subassembly selected as focus consists of six different components, which vary
geometrically from one product variant to another. A fixtureless approach was
selected, to minimise reconfiguration down time and the need for reconfigurable
fixtures since reconfigurable fixtures have not found significant acceptance in
industry. This varies from a fixture-based approach, which was considered in related
research.
The conceptual assembly system presented here consists of the following modules:
a flexible vision based part feeder, twin 6 DOF robotic manipulators each with a
multipurpose gripper, and a stationary spot welding station. Critical conceptual
design elements were further investigated to refine their selection and confirm
feasibility with respect to the target industry application. This process ended with a
preliminary cost estimate which served as a basis for comparison between the
fixtureless, fixture-based and present manual assembly process. The fixtureless
concept was overall more expensive than the fixture-based concept, primarily
because of the limits to production throughput. The fixtureless concept was
however cheaper than the present manual assembly approach but had a far longer
payback period than desired by the industry. The complexity and possible
uncertainties of the concept combined with the long payback period indicated that
the fixtureless concept is not suitable for the target application. / AFRIKAANSE OPSOMMING: Die konsepsionele ontwerp van 'n setmaatlose herkonfigureerbare outomatiese
puntsweisstelsel vir die vervaardiging van subsamestellings van huishoudelike
stroombrekers is ondersoek. Hierdie navorsing is gemik op die ontwikkeling van 'n
moontlike lae koste outomatiese alternatief vir 'n Suid Afrikaanse industriële
vervaardiger, wat tans sterk afhanklik is van werkers wat die montering van hul kern
produkte met die handsamestelling doen. Stelsel herkonfigurasie laat die
samestelling van 'n reeks subsamestellings, met geometriese komponentvariasies,
op 'n gegewe stelsel toe, asook die potensiaal om die stelsel te herkonfigureer om
ander reekse van stroombreker-subsamestellings te monteer. Die subsamestelling
wat as fokus gekies is, bestaan uit ses verskillende komponente met geometriese
verskille van tussen produkvariante. 'n Setmaatlose benadering is gekies ten einde
aftyd vir herkonfigurasie en die noodsaaklikheid van herkonfigureerbare setmate te
minimeer, omdat laasgenoemde nie noemenswaardig deur die industrie aanvaar
word nie. Hierdie benadering verskil van 'n setmaat-gebaseerde benadering wat in
verwante navorsing ondersoek is.
Die konsepsionele monteringstelsel wat hier aangebied word, bestaan uit die
volgende modules: 'n plooibare, visiegebaseerde voerapparaat; dubbele sesvryheidsgraad
robotiese manipuleerders, elk met 'n veeldoelige gryper; en 'n
statiese puntsweisstasie. Kritiese elemente van die konseptuele ontwerp is verder
ondersoek om hul keuses te verfyn en uitvoerbaarheid in die teiken industriële
toepassing te bevestig. Hierdie proses is afgesluit deur 'n voorlopige kosteraming
wat gedien het as 'n basis vir die vergelyking van setmaatlose, setmaat-gebaseerde
en die huidige handsamestellingstelsels. Die setmaatlose konsep was oorhoofs
duurder as die setmaat-gebaseerde konsep, hoofsaaklik as gevolg van beperkings op
die produksie-deurset. Die setmaatlose konsep was egter goedkoper as die huidige
handmonteringsproses, maar het 'n veel langer terugbetalingstydperk as wat deur
die industrie verlang word. Die kompleksiteit en moontlike onsekerhede van die
konsep, gepaard met die lang terugbetalingstydperk, dui daarop dat die setmaatlose
konsep nie vir die teiken toepassing geskik is nie.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/1941 |
| Date | 12 1900 |
| Creators | Dymond, F. S. D. |
| Contributors | Basson, A. H., Kim, Y., University of Stellenbosch. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Stellenbosch |
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