My grandfather bought a 1966 Chevy bus and converted it into an RV, that my family used to take trips in every summer. I wanted to give him a model of this bus for Christmas, but since he had made so many modifications to it....I would need to create my own version in 3D and have it printed. This is my process.
A COUPLE NOTES
1. I won' t be going into step by step details on how to model in 3D with this instructable. There are plenty of great tutorials online.
2. Although this example is an automobile, many of these techniques can be used to model, print, paint anything.
Step 1: Tools You Might Need.
- 3DS Max or similar modeling program that will export .STL or the file format used by your printer.
- Photoshop or other image editing program.
- Blueprints if you can find them for the object your recreating. (I will go over how to make your own)
- Reference images (Google image search)
- Camera to take additional reference images.
IF you want to paint your 3D print, you'll also need:
- Brushes of misc sizes
- Model paint
- Paint thinner if airbrushing
- Airbrush - I used an old paasche double action I had.
- 3M Masking tape - low tack
- 3M Striping tape
- Exacto knife and blades
- Painting respirator
- Newspaper or cardboard to use as extra masking to cover everything.
- Old cardboard boxes turned on their side work great as mini spray booths.
- If spraying paint, do it in an open area that is well ventilated.
Step 2: Before You Start!
You want to do this to help determine the scale/size of your print, what material you will be using, and any other information they may be able to give you that will help with the model. Some printers will accept multiple water tight meshes that are intersecting, and they'll come out as a single piece. This would have saved me quite a bit of time, and I wouldn't have had to stitch all the different pieces together...as you'll see later.
Check to see if your printer has guidelines and tolerances list online. Some even have guides that would help you prepare your final .STL file
SCALE - HOW BIG IS YOUR PRINT?
Determine final print size early! By knowing how large your model will be, you will know what details you can exclude since they are just too small. No reason taking the time to build small details that you can't end up printing. Or you can size the details up so they are printable. Same thing goes for small attachment points, the reflectors I had on the front of the bus' fenders were just too small to work. I could have adjusted them, but I didn't realize it.
Size will also affect your final price for the print. You should be able to get a ball park price from your printer early on, but they will probably need the actual .STL file to give you a firm qoute. I wanted to print the bus at 19" long, but that was just too much money, so the final print was 12". You also have to take into account the maximum size the printer can handle.
You can see some parts of the model I really exaggerated, in hopes of getting a better print. I knew it wouldn't be able to hold all the detail (license plate for example) but I wanted to try. The "WARD" text on the rear end actually came out very nice on the final model. Many of the really small chamfers and rounded corners I had ended up being unnecessary at this scale though...
THINK ABOUT THE MODEL IN PIECES
Can you BUILD in parts? Like a plastic MODEL kit? If I did it again I would have probably built the model in several pieces and assembled the entire thing at the end, more like a scale model. I didn't know that you could actually glue this material easily. I found this out when they told me they had problems with the hitch, ladder, and racks on the top. Those parts were actually rebuilt and attached again by the printer.
If I had setup some of the parts to print separately I could have had the rack built horizontally instead of vertically and it wouldn't have needed any of the support structures they had to use to build it vertically.
Step 3: The More Reference the Better
When I started this model, I only had some old family photos that just happened to have the bus. I was able to get better reference the next time I went to visit my grandparents. If you're building something you won't have easy access to later, take a TON of photos, you never know which one will have just the angle or detail you need.
Use a telephoto lens and get far away from your subject when taking photos for blueprint reference. This will lessen the distortion you would get if you take a close up photo with a wide angle lens.
Step 4: Blueprint Reference Image
I used the wheels as a gauge to determine overall length and height proportions. To do this, I traced over the front wheel with a circle on a new layer in Photoshop. I made it partially transparent, and copied that horizontally and vertically.
I knew it was roughly 5 wheel widths for the wheelbase (distance between front and rear tires.) There was a small amount of front overhang, and 2 tires overhang in the rear. It was also roughly 3 wheels to the top, with another 1/3 or so for the rack.
You can use this same idea on anything you want to model in 3D. Find a part of it that you can use to create a grid over your entire object. If the part of the object you choose has a known size, that will help your determine the overall size.
I would have preferred to use a more straight on side view, but this got me started.
You can see the vertical yellow lines I have do NOT match the bus' perspective!
Step 5: Blueprint Making
I opened 3DS Max and created a circle spline at the size I needed in the side view. I then made a grid of circles, and I tried to draw in all the major elements of the bus. The circles give you a good idea where each body line, window, etc lies in relation to another. You will have to adjust for perspective, but this really helps. Its the same as using this technique for drawing from a photo: http://drawsketch.about.com/od/drawinglessonsandtips/ss/griddrawing_4.htm
Since the two sides are different, I finished one side, then modified it to work for the other one. And of course, then the front and the rear are done as well, taking care that everything lines up.
Step 6: Modeling - Overview
I also want to say the mesh is REALLY REALLY messy but it works for the print, and I was running out of time for Christmas.
Since I've done this model, I've heard from some printers they can take multiple water tight meshes in a single .STL file and print it. This would have saved me considerable work, but wasn't an option at the time. Make sure you know what the printer you use is capable of printing!!
Step 7: Modeling
I started by blocking out the biggest shapes first, then worked down to the smaller details. I find it easiest to start in the side view and get the body and hood done first. Everything can be built from a primitive shape, and then progressively refined. Cubes and cylinders were used over and over.
MODEL IN PIECES
The wheels, ladder, windows, etc were all modeled as separate pieces that I knew I would be later joining together. Objects like the windows that are identical to one another are only modeled once and duplicated. Many parts were along large flat surfaces so I would cut in the more detailed parts into a single quad or other polygon, which made it much easier.
Step 8: The 3D Print
To save money on print time and materials, I quickly hollowed out the model before sending off the .STL. You can see this in the last picture. Both ends are noticeably darker, as are the wheels. Again, check with your printer and see if they prefer to do this themselves, some printers can print some kind of low density honeycomb or matrix inside very thick areas to reduce time/costs. As always...consult with your printer.
Step 9: Painting
I was told this material should NOT be left in direct sunlight as it is UV sensitive, but painting it helps. I have other unpainted 3D prints that I've had for years, but they're a different material that is much more coarse. Some materials you can paint, sand, mill, etc. Make sure you know what paints can be applied before you start!
Make sure your paint is compatible with the printed material! I went to a model store and bought a range of colors I would need. I also bought some clear coat that was applied at the end.
I decided to first spray a white base coat. I masked all the windows first to leave them transparent. Make sure to read your instructions on the paint and thin it to the proper consistency so it will flow through your airbrush. I can't recall for sure, but I think I used 2 parts thinner to 1 part paint. I also had a pretty low pressure of around 20lbs. You should do some test sprays on cardboard before starting on the model. Spray thin coats and build up slowly to avoid runs in the paint.
Making sure to let the base coat completely dry, I then masked all the areas I wanted to remain white, knowing everything left uncovered would be painted blue. If you have some extra parts like the broken ladder I had, you can paint some of your base coat on that and check it with the masking tape before going to the model itself.
I then sprayed the blue paint. Let it dry, and removed all the masking tape VERY CAREFULLY. This took quite a bit of time, to not damage what was already sprayed.
All the details were then brush painted. I knew I could hold the model and paint the wheels, and then balance it on its top with a block in the center. The rack wasn't strong enough to hold the weight of the model by itself.
In the translucent area for windows, the pictures show residue from masking that had to be cleaned.