I'd also like to address some common concerns: I went with a 3 wheel design because I wanted the bottom part that held the wheels to be a single, solid piece and a piece for three wheels was the largest I could print on a Makerbot Replicator 2. As for comfort I used some craft foam and packing foam in the boot and on the footplate and between it and my normal skate I couldn't tell a difference. I didn't include a 'brake' on the skate because of size constraints (a separate piece could definitely be added) and I've never used them as I feel toe dragging is a better stopping method.
To make this project you will need access to a 3D printer, or a company like Shapeways, as well as some general CAD knowledge for the program you will use (the tutorials they offer should be plenty). For these instructions I am using Autodesk Inventor 2013. Also make sure to wear the appropriate safety gear and use caution when testing! Most importantly, have fun and be creative!
Updates: Since building I have made a seconds skate and found that the toe part of the boot and the tongue are essentially only for looks so I updated my design without those and just added a little toe guard to the end of the boot for safety. All the files will still be on the thingiverse page.
The files for all parts can be found on Thingiverse HERE.
Step 1: Parts List
Non 3D Printed Parts:
6 x 8mm or 5/16inch diameter bolts and corresponding nuts (2.5 to 3 inches in length)
6 x 3mm or 1/8 inch diameter bolts and corresponding nuts (around 1 inch in length)
6 x Rollerblade wheels (anything that uses standard bearings and has an 8cm diameter or less will work)
12 x Standard rollerblade bearings (these probably will come with the wheels)
2 x Shoelaces (string also works in a pinch)
A plethora of washers or other spacers (I've added a file on Thingiverse for 3D printed spacers that are the perfect size for the skates)
Some type of foam or styrofoam padding.
(Optional) 6x 'S' hooks for quick release lacing.
Step 2: Designing the Bottom Skate
All files can be found HERE.
Step 3: The 'Boot'
After testing the design I have found that the heel part of the boot is essential for good control, while the toe part mostly is there for protection. Keep this in mind, if looking just for functionality you could first try just printing the heel part and add the toe on at another time. The tongue also doesn't add much besides protection as well and so isn't completely necessary.
Step 4: Making the Custom Footplate
From this drawing you are going to make a simple sketch by drawing three circles on the outline of your foot: one at the heel, the middle of the foot, and the ball of your foot. Measure and record the diameters of each circle. You can see this in my drawing. Next draw a line between the centers of the circles and from the center of the last circle to the tip of your foot. Measure and mark these as well. Now open your CAD program and create a new drawing of the circles and lines that space them apart. To connect the circles use the 'arc' or 'curve' tool and draw lines following the shape of your foot and connect the circles together and create the curve towards your toes. You can see sketch of this for reference (ignore the little rectangular drawings on the side of mine). Once you are satisfied click 'Finish Sketch' and then click the 'Extrude' tool. Select the sketch you just made and make sure all parts of your foot drawing are selected. In the 'Distance' box enter 0.2 inches and click 'OK'. You now have a custom footplate! Feel free to make it more detailed than this, this was just the easiest way to describe the process. If you want to make it specific to your right or left foot change the curves a little bit and go for it!
Step 5: Designing the Sides of the Rollerblade
1. (EASY/LESS CUSTOM WAY) Make a new sketch on the top of the footplate and do the exact same drawing you did to make your footplate with the three circles and curves, but this time make the circles all 0.3 inches smaller in diameter. This allows for 0.15 inch walls on either side of your foot. Once you have this sketch extrude the thin section between the outside of your sketch and the outline of the footplate. Make it whatever height you want. It won't have very good hold on your feet but will be easy to do.
2. (HARD/COMPLETELY CUSTOM WAY) You will use the 'Loft' tool which essentially blends sketches together. To take advantage of this you will create a series of planes all parallel and spaced about an inch apart. You can do this by clicking the arrow under the 'Plane' button (circled in red in the pictures) and selecting 'Offset From Plane', select a plane parallel to the one you want to make and enter how many inches the new plane should be from the plane it is spaced from. On each plane you will make a drawing of what you want the boot outline to be at that height. I can't really help you with this since everyone has different feet and ankles. My advice is to get paper and use a caliper to take measurements and draw out a rough sketch before designing that layer on the computer. Then once you have drawn as many of these layers as you desire click 'Loft', select all the drawings, and click 'OK'. You now have a custom boot. You can see each of these steps in the picture. In my pictures you can see me lofting the upper part of my boot, but for the lower toe guard it follows the same steps, just uses different drawings.
Step 6: Adding Shoe Lace Holes
Step 7: Designing Mount Holes
This would also be a good time to cut out some material from the footplate to make the prints take less time and save plastic. Draw closed shapes and extrude them in the same fashion as the mounting holes. If you go back to Step 3 you can see how I've cut spaces into my design.
Step 8: Extras
Step 9: Splitting the Design for Printing
Step 10: The Tongue
Step 11: Print
Step 12: Assembly
Now, take all 6 bearings and place one in each side of the wheel in the circular cut-outs for them. Then grab the bottom parts of the rollerblade and your 6 larger bolts and nuts (8mm or 5/16inch). Feed one through each of the three holes on the bottom skate, the holes are drawn to a size that the bolts will need a crescent wrench to screw them into the part. If you want them to just slide through you can drill the holes out a bit. Once the screw is through one wall of the bottom part of the skate, slide on washers (or printed spacers), a wheel, and then more washers (or another printed spacer) in this order. You should have the wheel spaced right in the center by washers on both sides (you can see this in my pics). Then screw the bolt through the hole in the other wall and tighten the nut enough that it holds in place but doesn't stop the rollerblade wheel from spinning. Repeat this for each of the three holes on the first rollerblade, and then for the second. Your rollin'!
Step 13: Lacing and Padding
Alternately if you have S hooks (see pictures) you can use these and instead of criss-cross lacing just feed one side of the string up each side of the skate and place an S hook on the string between each hole on one side. The you can hook the laces together for a much faster way to get in and out of the skates. See pictures for clearer example.
The plastic is pretty uncomfortable in just a sock so it is a great idea to add some padding into the skate. I used regular foam and craft foam sheets. Cut out one piece using the template you drew for you foot and lay it on the bottom of the boot, you can use some glue to make it stick if desired, but mine fit snugly (you could also try a shoe insert). I also used a piece cut out to the shape of my heel and wrapped it inside the boot. This piece did require some glue. I added a little bit of thicker foam at the ankle and was set to go! After the foam it's quite comfortable and I had no pain while skating.