| Summary: | Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010. === ENGLISH ABSTRACT: This project investigates the use of Rapid Prototyping (RP), with specific focus
on Three Dimensional Printing (3DP), in the manufacture of complex shaped advanced
composite parts, using variants of the Resin Transfer Moulding (RTM)
method of composite manufacture. This study developed design guidelines, cost
models and a process chain by studying data obtained by making example parts,
from literature and consultation with industry. Advanced composite materials offer
some of the best low weight and high specific strength properties for the solution
of design problems. A major disadvantage of these processes, however, is the
low production rates possible and the need of costly moulds. The 3DP technologies
combined with the RTM composite process was found to enable a lowering
of costs and increase in productivity if smaller batch sizes are considered. The
most meaningful area of application for RP techniques seems to be for smaller
and more complex components. The geometrical freedom allowed by RP technologies
allowed the manufacture of parts which are challenging to manufacture
by conventional technology such as CNC machining. Example part case studies
were completed for a simple part utilising the one sided mould Resin Infusion
RTM variant as well as for a complex part utilising the closed mould Vacuum Assisted
Resin Transfer Moulding (VARTM) process variant. During these two case
studies it was clear that proper part infusion with resin is critical for the manufacture
of good quality composite parts free of voids and dry spots. It is possible to
improve the resin infusion by correct placement of resin inlet and outlet ports as
well as resin channels incorporated in the mould. Correct placement of these features
for the case studies was obtained through simulations done with RTM-Worx
software. Results also indicated that another useful application of RP technology
to RTM is the manufacture of disposable cores for parts with thick cross sections.
Resin channels were included on the surface of these cores to improve the mould
filling with resin and consequently part quality. An early cost estimation model,
based on the work of Veldsman (1995), was developed for the combined RP and
RTM manufacturing process. This model may help designers to eliminate expensive
design features and enables a quick cost comparison with competing processes.
Drawbacks of applying RP techniques to RTM include the limited lifetime
of moulds produced with 3DP and the size and accuracy limitations of the RP
t echnology. === AFRIKAANSE OPSOMMING: Hierdie projek handel oor die toepassing van die drie-dimensionele druk metode
van Snel-Prototipering (Rapid Prototyping) op die vervaardiging van komplekse
gevorderde saamgestelde materiaal komponente met die Hars-Inspuit Giet
(Resin Transfer Moulding) metode. Die projek behels die opstel van ontwerpsriglyne,
koste-modelle en ’n proses-ketting deur data te bestudeer wat bekom
is deur middel van die vervaardiging van eksperimentele parte, literatuurstudie
asook raadpleging met individue in die industrie. Gevorderde
saamgestelde materiale verskaf van die beste sterk, dog ligte oplossings vir sekere
ontwerpsprobleme. ’n Ernstige nadeel van hierdie materiale is egter die stadige
produksietempo moontlik en die vereiste van duur gietstukke. Die Snel-
Prototipering metodes, gekombineerd met ’n saamgestelde materiaal vervaardigingsproses,
maak laer kostes met beter produktiwiteit moontlik indien ontwerpers
die part grootte- en akkuraatheidsbeperkings in ag neem. Die mees betekenisvolle
area van toepassing blyk kleiner en meer komplekse komponente te
wees. Die vryheid in geometrie wat moontlik gemaak word deur die Snel-
Prototipering tegnologie laat die vervaardiging toe van parte wat uitdagend is om
te vervaardig met konvensionele tegnologie soos CNC masjinering. ’n Gevallestudie
is voltooi vir ’n eenvoudige part vervaardig met die enkelkant gietstuk
vakuum-infusie weergawe van die Hars-Inspuit Giet metode asook vir ’n komplekse
part wat vervaardig is met die geslote gietstuk Vakuum Hars-Inspuit Giet
weergawe van die basiese metode. Dit het tydens die twee gevallestudies duidelik
geword dat deeglike hars infusie van kritieke belang is vir die vervaardiging van
goeie kwaliteit parte sonder enige droë kolle of lugruimtes. Dit is moontlik om die
hars infusie te verbeter deur hars inlate en uitlate asook hars kanale in die korrekte
posisies te plaas. Die korrekte posisies vir hierdie komponente is verkry deur
middel van ’n reeks simulasies met die RTM-Worx sagteware. Resultate dui ook
daarop dat Snel-Prototipering tegnologie handig te pas kom by die vervaardiging
van verbruikbare kerne vir saamgestelde materiaal parte met groter diktes. Hars
kanale kan maklik op die kerne se oppervlak geskep word om die hars verspreiding
en gevolglik part kwaliteit te verbeter. ’n Vroeë kostevoorspellings model,
gebaseer op werk voltooi deur Veldsman (1995), is saamgestel vir die gekombineerde
Snel-Prototipering en Hars-Inspuit Giet proses. Hierdie model kan gebruik
word om duur ontwerpsbesonderhede op parte te elimineer en om ’n vinnige
koste vergelyking met ander vervaardigingsprosesse te toon. Nadele van die toepassing
van Snel-Prototipering tegnieke op Hars-Inspuit Giet sluit die beperkte
gietstuk-leeftyd en beperkte akkuraatheid in.
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