Freeman Makes “Night at the Museum” Tablet with Delcam’s ArtCAM and PowerMILL
“The Night at the Museum: Battle of the Smithsonian” is a major box-office success – the 6th highest grossing movie of 2009 and the 180th ever after only 27 days in release. The most important prop in the movie is the Tablet of Ahkmenrah which, when its dials are set to the proper combination, brings the exhibits in the museum to life. Andy Freeman, an independent prop designer and builder based in London, England used Delcam’s ArtCAM to convert the studio designer’s conception into a mathematically precise, functional and manufacturable design using ArtCAM’s powerful engraving and mould-making toolset. Freeman used both ArtCAM and PowerMill to generate the computer numerical control (CNC) programs used to machine the tablet and used ArtCAM’s reverse and mirroring tools to design the mould used to build a lightweight version of the tablet that is carried by Dexter the Capuchin Monkey in the movie.
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“The Night at the Museum: Battle of the Smithsonian” is a sequel to the original Night at the Museum movie which was filmed at the Museum of Natural History and released in 2006. In the original movie, night guard Larry Daley (Ben Stiller) teamed up with characters from the exhibits in the museum to defeat other guards that were plotting to steal the tablet. In the new movie Larry, now a successful entrepreneur, returns to the Museum of Natural History to visit his friends from the exhibits only to learn that they are being shipped off into storage at the Smithsonian Institution. He learns that his friends are in grave danger from characters in other exhibits led by the pharaoh Kahmunrah (Hank Azaria) and including Ivan the Terrible (Christopher Guest), Napoleon (Alain Chabat), and Al Capone (Jon Bernthal). These characters are plotting to use the tablet to take over the world. Larry recruits other exhibit characters such as Amelia Earhart (Amy Adams), Teddy Roosevelt (Robin Williams) and General Custer (Bill Hader) to help him to help him defeat the threat.
Freeman is an experienced set and prop designer that has proven he can build high-quality props and deliver them on time for movies such as I, Robot, X-Men II, X-Men III, The Core, Paycheck, Blade Trinity, Chronicles of Riddick and others. The project started when Freeman was given the plaster tablets that had caused problems in the original “Night at the Museum” because they were heavy and fragile. He took a laser scan and photographs of one of the tablets. He imported the point cloud data and photographic images into ArtCAM. He used ArtCAM’s silhouette function to create a vector boundary around the model that he later used as the toolpath when cutting the tablet out from the surrounding material. Freeman exported the design as an STL file and imported it into Freeform software from Sensible Technologies where he added weathering and aging effects. He then sent the modified design to ArtCAM as another STL file.
A studio artist provided calligraphy that he had created in Adobe Illustrator as a DWG file. Freeman imported the file into ArtCAM and separated it into layer. Freeman used the bitmap-to-vector function in ArtCAM to convert the calligraphy into geometric entities that could be machined into the surface of the tablet. Freeman converted the calligraphy back and forth several times from bitmap-to-vector and vice versa in order to take advantage of editing tools available for each type of geometry. Freeman layered the calligraphy over the surface of the dials that spin on metal shafts.
Freeman used the machining module of ArtCAM to generate the majority of the two CNC program used to produce the tablet. The first CNC program machined the dials in place on the tablet but did not cut the calligraphy. Leaving the dials in place made it possible to precisely position the calligraphy, while the dials were still attached to the tablet for improved accuracy. The second CNC program cuts two holes in each dial – one accommodates the shaft that the dial spins on and the other is for another shaft used to lock the dials in place. The second program finally cuts around the dials to free them from the tablet and allow them to spin.
The spinning dials play a significant role in the movie when Kahmunrah captures the tablet along with Larry and Amelia. He plans to use the tablet to open the gates of the underworld but discovers the combination has been changed. He orders Larry to decipher the tablet’s riddle combination before sunrise. Larry and Amelia consult a group of Albert Einstein bobbleheads who solve the riddle. Larry delays giving the combination to Kahmunrah but the evil Pharaoh learns it anyway and uses it to open up the gates to the underworld, commencing the climactic battle.
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The second program also cuts the calligraphy. Before creating this part of the program, Freeman greatly increased the resolution of the model to 5 million pixels using the relief edit toolbar. Then he created another CNC program to machine only the calligraphy using vector boundaries. Freeman used the ArtCAM v-bit engraving tool to express the calligraphy as a v-bit groove. The angle of the v-bit was specified to match the shape of a v-bit cutter that Freeman later used to cut out the calligraphy. He used a v-bit cutter with a stepover of only 0.003 inch. Freeman utilized the high speed machining capabilities of ArtCAM’s postprocessor to prevent overshoot.
Freeman also exported the design into PowerMILL to take advantage of several unique capabilities offered by its machining module. He used the profile area roughing machining strategy in PowerMILL to cut out several areas that required large volume material removal. This strategy saved machining time by automatically detecting which areas on the part could not be finished by each successive cutter. The larger cutters were used to remove as much stock as they could to save machining time. The program automatically rapid traversed each cutter over the areas that did not require machining to save additional time.
Freeman used a MotionMaster CNC router to cut the tablet from ruby red Renshape 5000 urethane. The tablet was later treated with gold leaf to provide an aging effect. Freeman used the reverse mould and mirroring features of ArtCAM to design the mould used to make a lighter version of the tablet for the monkey to carry. He used the mirroring tool when he reversed the mould so the type would read from left to right after moulding. Freeman also produced other props for “Night at the Museum: Battle of the Smithsonian” such as a shield for a Roman soldier that comes to life in the movie and a full-size copy of Rodin’s The Thinker. "ArtCAM is an essential tool that enables me to deliver props in an amazingly short period of time that knock my clients’ socks off,” Freeman concluded.
