manufacturing steps - mcgill
TRANSCRIPT
Manufacturing of composite violin top plates and design of composite tailpieces By : Maxime Beaulieu
Supervised by : Prof. Larry Lessard and PhD student Steven Phillips
Department of Mechanical Engineering, McGill University, Montreal Quebec
BackgroundMaking a violin top plate out of composite material has the following advantages:
•Resistance to heat and humidity
•Fewer manufacturing steps
•Better material consistency
•Possible to make resonating plate lighter
•Excellent mechanical properties
This project was first initiated last summer and the first prototypes had issues with
delamination in areas where the wood core was present.
Another violin part that could benefit from composite materials is the tailpiece. The tailpiece
is a part used to hold the strings of the violin and it needs to be strong to withstand the high
tension loading.
Objectives•Produce violin top plates using different combinations of carbon fiber/epoxy ply sequences to
find the best sounding.
•Solve local delamination problem caused by the unique loading condition of a violin.
•Design a mold to manufacture violin tailpieces out of composites.
Manufacturing Steps
Conclusions•Carbon fiber/epoxy can produce parts much lighter than spruce wood
with sufficient stiffness.
•Composites allow freedom in the design of the top plates, such as the
graduation of the thickness in different areas.
•The delamination problems were addressed by modifying the layup
design.
•The flexibility of composite materials shows potential in designing
violin tailpieces.
Results•Some composite defects from processing include: surface finish, core alignment, warping and
unformed regions. Lack of pressure in certain regions or resin quality could be the cause.
•In general, the plates are lighter then a typical 2.5mm thick spruce plate which weighs 84g but some
plates were made heavy on purpose for comparison.
•The delamination problems were addressed by changing the shape of the center core and removing
the balsa from the edges. Some plates were made without using any core at all.
•By varying the shape of the pre-preg layers and balsa core, different graduations of thickness in the
top plates were achieved.
Acknowledgements : Peter Purich – Luthier, Funding - NSERC
Further research•Test the violin top plates using the Chladni pattern method and Tap Tone method.
•A qualitative analysis of the acoustics when the plates are attached to the violin
body.
•Design a way to add a composite bass bar to the top plates.
1 2 3 4 5 6 7 8 9
Mass(g) 48 65.2 127.6 65.1 65.5 62.3 67.6 70.7 68.4
Delamination
Fig. Delamination problem from previous prototypes
Fig. Violin Parts diagram
1. Balsa core cutting 2. Pre-preg cutting 3. Layup of the material 4. Vacuum bagging 5. Curing in the oven 6. Finished part
1. Traditional Tailpiece
3. 3D CAD Model of the tailpiece 4. 3D CAD mold of the tailpieces
A total of 9 different top plates have been produced
Fig. Core shape change
Tailpiece Mold Design
Innovative features of the mold:
•The tailpiece was redesigned to be thinner than traditional tailpieces
•Each cavity is a different variation of the tailpiece.
•One sided mold to make it cheaper to manufacture and easier to use.
•The tailpieces are made using the vacuum bag method.
•The lay out of the mold allows the possibility to produce each tailpiece
individually to reduce the use of unnecessary material.
•The mold is made out of aluminum making it reusable, produces good
surface finish and can be used in the oven.
Surface finish Corner formation Core alignment
2. Modified tailpiece design