Nestled in the heart of Stratford-upon-Avon is a delightful alternative to the usual ‘Shakespeare Trail’ in the form of the MAD (Mechanical Art & Design) Museum. This unusual museum was created by a local business entrepreneur, Richard Simmons, to house an “exhibition of all things mechanical, weird and wonderful!” The unique collection of kinetic art and automata contains pieces that are each a fusion of science, engineering and art. They come from all parts of the globe, made from a huge variety of materials and often comprising dozens of moving parts; they are also in need of almost constant maintenance!
Mike Abbotts, MAD Museum’s Technical Manager, soon realised that CNC was the ideal technology to help them in their almost-daily challenge:
A lot of the exhibits are one-offs with precise custom made parts, for example gears, that cannot be bought off the shelf. To make them by hand is simply too time consuming and not accurate enough. By using CNC we can replicate parts that are virtually identical to the originals and make new versions as and when required.The situation became urgent a few months ago when an incredibly intricate wooden clock, on loan from its creator, Lukas Kuka, suffered a catastrophic failure of one of the wooden chain links supporting the clock’s weight:
While on display, one of the wooden chain links holding the clock’s heavy lead weight broke. The weight, along with the chain links and a gear, fell to the floor smashing its wooden case. With Lukas’ permission, we started repairing the clock and this was one of the reasons we decided to purchase a CNC machine.
Mike settled on a Shapeoko 2 from Inventables, which was the right mix of price and capability for their needs, and he also bought VCarve Pro after seeing the positive feedback about the software online:
It was from the Shapeoko community forums and wiki pages, which discussed the various software options available and the compatibility with the Shapeoko, that we heard about Vectric’s software.
VCarve Pro is very easy to use and quick to pick up, even having never used this kind of software before. Being able to save tool info saves a lot of time and the ability to simulate the cutting process makes it easy to visualise how it will cut - you can picture how it would cut and adjust the settings to make it more efficient.
The process of recreating parts without dimensioned drawings first required the conversion of bitmap images of the broken pieces into vector geometry.
As we didn’t have the original drawings to hand, we scanned the broken parts and created vector drawings. These were used in VCarve Pro to create and calculate the required toolpaths.
Once he had the vector drawings, Mike also took the opportunity to strengthen the weight case by thickening the sides and adding a back-face to create a stronger complete box.
We tried to match the original material which was a high quality 3mm and 188 mm Birch plywood. For cutting the chain links, box base and sides a 3mm 2 fluted endmill was used. For the gear and box face we used a 1mm fishtail bit to match the engraving on the box face, as well as cutting the gear teeth.
Simon Partridge, Mike’s colleague and MAD Museum’s Technical Engineer, finished the parts with a combination of wax to highlight the engraving, and a lacquered finish.
This was the first project using the Shapeoko2 CNC, so cutting the parts was slower than it could have been, but it has all been part of the learning process of using the machine and software.
Overall it was 5 hours to complete the engraved face, sides and base of the weight box, as well as the gear and chain links. The finished pieces were as close to the originals as we could have hoped for. We also feel a great sense of achievement to have been able to repair it and have back on display for visitors to enjoy.
The video below shows the clock in action before the accident and I’m sure you will all agree that getting such and amazing device back up and running was definitely worth the effort!
For further information about the MAD Museum please visit www.themadmuseum.co.uk
Additional Links - www.inventables.com & http://www.shapeoko.com/wiki/index.php/ShapeOko_2
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