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How to create a large presentation model

Real-size (1.8 m) model of a fork lug: eye-catcher for trade show

Redaelli Tecna S.p.A. in Milano (Italy) is one of the world market leaders in specialty wire ropes, used for many purposes. Like for instance the wire ropes used in the enormous cable-stayed bridge over the river Adige, near Zambana Vecchia, Trentino, Italy (2008). The bridge is shown on the pictures below, you can see it on your right side when following the Autostrada del Brennero from Austria to Italy.

Important part when working with these ropes is the Fork Lug at the end of each rope, used to securely connect the rope to the construction. This page concerns the creation of a scale 1 to 1 presentation model of such fork lug by DeskProto user PROTOway, for a trade show.

Bridge over river
Top part of the bridge
The actual product, used for a cable-stayed bridge

Redaelli's wire ropes and lugs are used for many more applications, one of which is building large sports stadiums. This is why Redaelli exhibited on the Expo Estádio 2010 in Rio de Janeiro (Brazil): a trade show for the design, construction, furnishing and management of stadiums and sports venues. At the stand Redaelli wanted to show a model of a fork lug, serving as eye-catcher.

Big problem was the very short lead time for this trade show: the model needed to be ready for shipment within three days ! This is why Redaelli contacted model maker PROTOway in Porcia (also in Italy), known for their product quality and on-time delivery.

CAD screenshot
DeskProto screenshot
The fork lug geometry in 3D CAD, and toolpaths in DeskProto.

The large model was created in foam, by CNC machining. For this project DeskProto proved to be a big help as the toolpaths could be generated very quickly. Alessandro Mineo of PROTOway states:
"Really, DeskProto helped so much. It was like a video game, in few minutes we produced paths for the whole work."

Roughing in green foam
Roughing in green foam
On the CNC milling machine.

The model has been machined in a very light type of foam: only 35 kg/m3. A low weight was needed for shipment by air, and this also made it possible to machine very fast. PROTOway uses a custom made router of 1750 x 900 x 250 mm, with an ELTE spindle.
The two pictures above show some of the round slices that were needed for the foot of the lug.

Combining blocks of foam
Making a smooth surface using filler.
Assembly of the foam model and creating a smooth surface.

A number of slices and other parts have been machined separately. These needed to be assembled using glue, and after that the complete model needed to be plastered and sanded. PROTOway sprayed a special shock resistant plastic coating on the model to make it more durable, as the light foam is extremely fragile. The result is a composite model: a tough skin with a soft core inside.

Finished model, in the workshop
Finished model, in the workshop
Model being packed into a a wooden crate
Just before shipment to the trade show in Rio.

Finally the model of course has been sprayed in the correct color. PROTOway also made a wooden pedestal for the model, with a wax finish, however only the lug model has been used at the expo.
The total weight for the resulting model only was about 10 kg: not much for a 1800 mm high model !

Model on the trade show
The complete stand, with the model
The resulting model on the Redaelli expo-stand.

The resulting model on the Redaelli stand (at the Expo Estádio 2010 in Rio), where it served it's purpose and indeed attracted extra visitors to the stand.