When I lent my services to a collegue who was working on a film about 12 years ago, I was introduced to the world of cnc. I remember watching this huge machining centre milling out a slab of mdf and turning it into a fantastic set of gears. I knew that it would have taken me hours to achieve the same thing with traditional power tools. I decided then that I would invest in a cnc router for my own business Oxenham Design. At that time I could turn on a computer, but even to check email seemed like a crazy set of operations. I persevered and learned every piece of relevant software I could get my hands on. I am now fortunate enough to be using Vectric's ASPIRE software, and Techno cnc routers, which has helped us to create some amazing projects, both in part, or in full. I thought that this blog would be a great place to share "behind the scenes" adventures with the software, materials and equipment we use, as well as the projects we build.

Monday, 14 March 2011

Ships Ahoy, sort of.

Saturday was the start of another neat job. We were to supply a 4X8' panel that was to look like a section of an old weathered ship. Complete with rusty bolt heads and ring cleats. Another fun job with the cnc router! We started this build by picking up 20 or so pine planks. We got clear pine so there would be no knots that might fall out. What a disaster that would be for a ships hull! Our panel is smaller than it will appear in the final billboard ad. They will scale it in post to what size they want to use.  I started out by opening a new model in Aspire the size of 5 of our planks stacked edge to edge. Then I used a photograph of wood that I have, and imported it into my model.

I can scale the woodgrain image in Aspire as easily as any image editor, so this makes it remarkably simple. The next step is to convert this image to a component. A component in Aspire is just another name for a 3d model.
 When you convert an image to a component, Aspire changes the image from colour to a greyscale version. After this, the software assigns heights to each of the grey pixels in the picture. Black is the lowest in depth and white is the highest. All the other greys are in between those absolutes. This however can make the 3d model a little spiky. The trick here is to apply a smoothing filter on the model. I applied a maximum smoothing filter and then scaled my whole relief to .100". We were only using 1/2" pine, and wanted to make sure the planks wouldn't get to thin.
This whole process has really only taken me less than 5 minutes already. I then toolpathed the whole model with a 1/2" ballnose cutter. Our Techno cnc router has 3 high power servo motors that move the cutting head all around the 5X10' machine bed. By selecting a machine that uses servo motors instead of stepper motors, it allows us to cut with an accuracy of  .004" as well as run it at speeds of up to 800 inches a minute. This is essential as most of our deadlines are VERY short. The combination of using the biggest cutter that the model detail allowed, and running our machine full tilt, let us machine the 5 stacked planks in 13 minutes. 13 minutes X 4 sets of planks = 52 min in total. In less than 1 hour, all 20 planks had a weathered surface, identical to the picture we started with. The next step was to run a wire wheel over all the planks. This would give us the really fine tearout that weathered wood naturally has.
As Jody started the process of staining and colouring the planks, I started making the rusty bolt heads. I took wooden furniture plugs, then heavily textured them with various texture sprays. Next I was on to the rope tie rings. These started as steel eye bolts. As we wouldn't be on set the day of the shoot, I wanted everything that might have to move to be very easy for them to explore new positions with. I didn't want to drill a 3/8" inch hole through the panel for the eyebolts, if the eyebolts might not even stay. The holes however, would be permanent. I decided to cut off the threads to the eyebolts, drill a hole into the bottom, and screw in a cut-off trim screw. At least any holes left by these little screws, would hardly be noticable. The next part was the actual ring. I took 3/8" acrylic rod and heat bent it over a 3" tube. I then heated the acrylic until the surface started to boil. This would make it look VERY rusty and scaly.

The final step was to mount all the weathered planks to the 4X8 sheet of plywood. After that we inserted all our rusty bolt heads, added some rust stains to the planks and voila! a weathered wooden hull section. They will add the wooden rub rail and rings we made when they get it in front their camera lens. I will upload the final billboard ad as soon as they send me a copy in a couple of days.

1 comment: