Creating a 2D textile cut pattern to match a specific 3D shape such as a prosthetic socket or hand
If you have a prosthetic socket that requires a perfectly fitting sleeve, or a prosthetic hand that requires a perfectly fitting glove - or if you have some other 3D shape you need to convert into a suitable 2D textile cut pattern: here is how to create a sewing pattern from your specific 3D shapes.
I will look at textiles, textures and patterns separately. This only addresses how to cut 'em up.
Shape modeling using newspaper and sticky tape was suggested by Dr. sc. nat. Sabine Klein who also carried out the manufacturing of two initial sleeves and gloves. I came up with a way to determine the best cuts for a 3D cover (see diagram below). Subsequent covers are sewed by myself (cow hide, ..).
As you will see the following method is explicit in how to get from 3D to a set of 2D shapes that actually works.
See the following image and subsequent description and example photos.
1. There is your 3D shape, let us assume it is a prosthetic socket.
2. Use newspaper (best), paper (works as well) or other material (maybe plastic or rubber?) to tightly wrap it around your 3D object. Use as much sticky tape to hold it, fix it, mount it, keep it in place. You will thereby create a perfectly fitting paper cover (gray). The more sticky tape you use, the stiffer your paper cover will become. Some stiffness is helpful for the subsequent steps.
3. Take the finished paper cover off.
4. Now that paper cover is a bit like a cast: it represents the 3D shape of your object, in this instance, a prosthetic socket. Now the idea is to cut it up - and through these cuts, the pattern is created. The first cut will be the first sewing line. Place it at your convenience. Then cut it (image: red line).
5. Place the cut paper cover onto a flat surface, such as a table. Let the paper cover lie on one side. You now want to find out how much of it can be approximated by a flat surface. To allow you to orient yourself better in the diagrams, I drew the initial cut line red in image 4 and all subsequent images.
6.The rounded paper cover will exhibit some part that you can lie down flatly onto the table (image: "FLAT"). Your fingers will be able to feel an imaginary line where the paper cover's roundness makes it stand up on the table. That line (image: DASHED LINE) is what we are after. It will serve us to separate the flat part (image: "FLAT") from the part that stands up above the table (image: STANDS ABOVE TABLE). If you look at the paper cover from the side, you will probably be able to see where the curved edge lifts off the table (see arrow). Spend some time using eyes to see and fingers to feel (image: FEEL) where that line would be located in your instance.
7. Use a pencil to draw out the line along the region that you identified in the previous step.
8. Cut the flat part away from your paper cover. That now represents a shape part that can be approximated with a flat part of fabric (or fur, or leather, or sheet metal, or whatever else). Continue with the remaining part in the next step (image: CONTINUE WITH THAT PART).
9. Place the remaining part of the paper cover in front of you. Use fingers to feel what parts can be pressed flat onto the table (image: FLAT) and what part still stands up above the table (image: STANDS ABOVE TABLE). Place an imaginary line between those two (image: DASHED LINE).
10. Draw out that line using a pencil.
11. Cut the remaining part of the paper cover apart.
12. You continue with the process by repeating steps 9, 10, 11 until you are done.
13. The resulting paper shapes are your pattern.
Results - 0: sewing pattern for my own prosthetic socket
Here are the parts we came up with that we then used for the socket sleeves, just for reference and to give you an idea:
Here are the parts for the Otto Bock system hand:
Results - 1: red artificial leather
The socket now was fitted with a sleeve, the Otto Bock hand was fitted with a glove.
To that purpose, the method outlined above was used. To obtain the glove sewing pattern, an old Otto Bock PVC glove was cut up (instead of doing the newspaper / sticky tape method - but that would have worked as well).
As you can see, the socket sleeve features curved seams. The shape is irregular cylindrical but almost perfectly matches the socket.
It also looks cool with the Becker Lock Grip hand: