Cosmetic gastrocnemius prosthesis printed on a 3D printer
Perhaps you are already familiar with our history of creating a functional mechanical prosthetic of the fingers and have seen the intermediate results of this venture, which has grown into a separate project. Recently, my experience of creating artificial limbs was replenished with one more case, this time our skills in 3D scanning, 3D modeling and 3D printing found their application in creating a cosmetic prosthetic gastrocnemius muscle.
This story began with a letter from the girl Olga. Olga has a very extreme hobby - parachuting. As a result of one of the jumps upon landing, Olga received an injury to the calf muscle of her right leg. Now the muscle tissue of the legs is almost completely absent. Visually, this is noticeable, which causes discomfort to the girl. For this reason, the need arose to create a cosmetic prosthesis. The prosthesis should be as individual as possible, with full consideration of all the anatomical features of the injured leg. On the advice of her friend, Olga turned to me.
')
We met with Olga and discussed all the details of the work. The action plan was as follows:
The first thing was to scan both legs: both damaged and healthy. For this, we used an Artec Eva scanner. Scanning involved design engineer Alexander Gorodetsky, who developed the body of this scanner. Conveniently, the scanner does not require calibration and the use of markers. It makes about 16 frames per second, which are automatically combined. We needed a scan of sufficiently high accuracy, so the work was carried out painstakingly, it was not done without repeated passes by the scanner.
Even the most thorough scanning does not mean that after this process is completed, you will receive an ideal and absolutely ready 3D model. Scan is only a good preparation, a cloud of points, over which it is necessary to work hard and “assemble” a solid body. Scanning with a coffee break took about two hours.
This stage of work was the most time consuming and laborious. This task was undertaken by my good comrade and experienced 3D modeler Valery Karaoglanian. He was faced with a new task for him - to create a 3D model of a cosmetic prosthesis from the existing two point clouds (scans of a healthy leg and an injured one), taking into account all Olga's wishes. There were no ready solutions for this task.
The first step is solid-state 3D modeling in SolidWorks.
When the solid-state 3D-models of both legs were ready, the model of a healthy foot was mirrored with height corrections, then a volume model of the damaged leg was “subtracted” and the tolerances were set for the skin to “breathe”.
At first the idea was that both the inner and outer surfaces would be mesh (and at some point both surfaces were). At Olga's request, only the internal surface of the prosthesis was made with a net, and the external surface was left solid, which led to additional changes in the external parts of the prosthesis.
To create a grid-like surface, we had to juggle a little bit with a 3D model from one program to another. At first, it was imported into ZBrush to make a UV scan and create a grid module, then the grid was overlaid on the Photoshop program, then the 3D model returned to ZBrush again. At this stage, there was a problem with giving thickness, ZBrush does not provide such an opportunity, so 3DS Max was also involved in the process.
In parallel, Alexander Gorodetsky was developing and 3D-modeling mounts in the program SolidWorks. When they were ready, they were “merged” with the main 3D model of the cosmetic prosthesis:
Of course, it took time to create a 3D model. What I described in the two preceding paragraphs is a brief and superficial description of the process. The designer had to apply all his experience and build an algorithm for creating such a 3D model from scratch, and this is not easy. As a result, we had a full-fledged model of a cosmetic gastrocnemius prosthesis on our hands.
3D printing is the finishing line to create a prosthesis. As a material for 3D printing, we chose white durable plastic PA 2200 (polyamide). Very durable and lightweight material perfectly suited for our purpose - to create a cosmetic prosthesis that will be used often. For the production of objects from this material, the technology of selective laser sintering (Selective Laser Sintering) is used, when in the bulk of the powder the laser sins the material in given places, “growing” the bulk model.
The stage was exciting: we waited with impatience for the whole team when it would be possible to pick up the finished prosthesis and move on to the next step - fitting.
The fitting of the prosthesis, as expected, revealed both its advantages and disadvantages, which were difficult to avoid in the first iteration. When assembling the prosthesis on the leg, the attachments worked as it should, and the body itself sat exactly along the leg.
It became clear that it was necessary to use some kind of soft material as a layer between the skin of the foot and the prosthesis itself, since the leg was sweating and the texture of the material itself was slightly rough to the touch. Perhaps, if the external surface of the prosthesis were also left netted, this would solve the problem with ventilation, and the foot would “breathe” better.
The fitting took place until Olga had the opportunity to actively use the prosthesis, since the summer was hot. So, the main tests of the cosmetic prosthesis are still ahead.
This was our first experience in creating a cosmetic prosthesis. In the process, we made a lot of mistakes, went around the circle several times, and performed unnecessary actions. But he showed us not only our shortcomings, but also our capabilities, he taught us a lot, now we know short ways and effective solutions.
The most important opinion in this story is that of Olga. She was pleased with the result, according to her, he met her expectations. She thanked us for the work and promised to share the results of further tests of the prosthesis.
A remarkable point in this whole story is that it is much easier to use industrial 3D printing technology than it might seem. Using professional equipment and knowledge, you can get the desired quality object - a prototype, a prosthesis, a figure, decoration, a functional part, a rocket engine, and practically everything that can come to your mind.
It is not surprising that the Internet is filled with articles that someone and somewhere created something with the help of 3D printing. It is also not surprising that opinions about the capabilities of this technology vary - someone is skeptical, someone is an ardent supporter of home 3D-printers, and someone does not miss the opportunity to talk about the advantages and disadvantages of additive technologies. But in my opinion, there is no need to extol or detract from the merits of 3D printing, you just need to use it to effectively solve problems like any other technology. If you have any interesting suggestions or ideas that you would like to embody, welcome to the comments, maybe we can create something interesting together.
The need for a unique cosmetic prosthesis
This story began with a letter from the girl Olga. Olga has a very extreme hobby - parachuting. As a result of one of the jumps upon landing, Olga received an injury to the calf muscle of her right leg. Now the muscle tissue of the legs is almost completely absent. Visually, this is noticeable, which causes discomfort to the girl. For this reason, the need arose to create a cosmetic prosthesis. The prosthesis should be as individual as possible, with full consideration of all the anatomical features of the injured leg. On the advice of her friend, Olga turned to me.
')
We begin to create a cosmetic prosthesis
We met with Olga and discussed all the details of the work. The action plan was as follows:
- 3D scan of legs
- 3D modeling
- 3D printing of cosmetic prosthesis
- Fitting
Foot scan
The first thing was to scan both legs: both damaged and healthy. For this, we used an Artec Eva scanner. Scanning involved design engineer Alexander Gorodetsky, who developed the body of this scanner. Conveniently, the scanner does not require calibration and the use of markers. It makes about 16 frames per second, which are automatically combined. We needed a scan of sufficiently high accuracy, so the work was carried out painstakingly, it was not done without repeated passes by the scanner.
Even the most thorough scanning does not mean that after this process is completed, you will receive an ideal and absolutely ready 3D model. Scan is only a good preparation, a cloud of points, over which it is necessary to work hard and “assemble” a solid body. Scanning with a coffee break took about two hours.
Creating a 3D model of a cosmetic prosthesis
This stage of work was the most time consuming and laborious. This task was undertaken by my good comrade and experienced 3D modeler Valery Karaoglanian. He was faced with a new task for him - to create a 3D model of a cosmetic prosthesis from the existing two point clouds (scans of a healthy leg and an injured one), taking into account all Olga's wishes. There were no ready solutions for this task.
The first step is solid-state 3D modeling in SolidWorks.
When the solid-state 3D-models of both legs were ready, the model of a healthy foot was mirrored with height corrections, then a volume model of the damaged leg was “subtracted” and the tolerances were set for the skin to “breathe”.
At first the idea was that both the inner and outer surfaces would be mesh (and at some point both surfaces were). At Olga's request, only the internal surface of the prosthesis was made with a net, and the external surface was left solid, which led to additional changes in the external parts of the prosthesis.
To create a grid-like surface, we had to juggle a little bit with a 3D model from one program to another. At first, it was imported into ZBrush to make a UV scan and create a grid module, then the grid was overlaid on the Photoshop program, then the 3D model returned to ZBrush again. At this stage, there was a problem with giving thickness, ZBrush does not provide such an opportunity, so 3DS Max was also involved in the process.
In parallel, Alexander Gorodetsky was developing and 3D-modeling mounts in the program SolidWorks. When they were ready, they were “merged” with the main 3D model of the cosmetic prosthesis:
Of course, it took time to create a 3D model. What I described in the two preceding paragraphs is a brief and superficial description of the process. The designer had to apply all his experience and build an algorithm for creating such a 3D model from scratch, and this is not easy. As a result, we had a full-fledged model of a cosmetic gastrocnemius prosthesis on our hands.
3D printing time
3D printing is the finishing line to create a prosthesis. As a material for 3D printing, we chose white durable plastic PA 2200 (polyamide). Very durable and lightweight material perfectly suited for our purpose - to create a cosmetic prosthesis that will be used often. For the production of objects from this material, the technology of selective laser sintering (Selective Laser Sintering) is used, when in the bulk of the powder the laser sins the material in given places, “growing” the bulk model.
The stage was exciting: we waited with impatience for the whole team when it would be possible to pick up the finished prosthesis and move on to the next step - fitting.
Trying a calf cosmetic prosthesis
The fitting of the prosthesis, as expected, revealed both its advantages and disadvantages, which were difficult to avoid in the first iteration. When assembling the prosthesis on the leg, the attachments worked as it should, and the body itself sat exactly along the leg.
It became clear that it was necessary to use some kind of soft material as a layer between the skin of the foot and the prosthesis itself, since the leg was sweating and the texture of the material itself was slightly rough to the touch. Perhaps, if the external surface of the prosthesis were also left netted, this would solve the problem with ventilation, and the foot would “breathe” better.
The fitting took place until Olga had the opportunity to actively use the prosthesis, since the summer was hot. So, the main tests of the cosmetic prosthesis are still ahead.
Summary
This was our first experience in creating a cosmetic prosthesis. In the process, we made a lot of mistakes, went around the circle several times, and performed unnecessary actions. But he showed us not only our shortcomings, but also our capabilities, he taught us a lot, now we know short ways and effective solutions.
The most important opinion in this story is that of Olga. She was pleased with the result, according to her, he met her expectations. She thanked us for the work and promised to share the results of further tests of the prosthesis.
Available technology features
A remarkable point in this whole story is that it is much easier to use industrial 3D printing technology than it might seem. Using professional equipment and knowledge, you can get the desired quality object - a prototype, a prosthesis, a figure, decoration, a functional part, a rocket engine, and practically everything that can come to your mind.
It is not surprising that the Internet is filled with articles that someone and somewhere created something with the help of 3D printing. It is also not surprising that opinions about the capabilities of this technology vary - someone is skeptical, someone is an ardent supporter of home 3D-printers, and someone does not miss the opportunity to talk about the advantages and disadvantages of additive technologies. But in my opinion, there is no need to extol or detract from the merits of 3D printing, you just need to use it to effectively solve problems like any other technology. If you have any interesting suggestions or ideas that you would like to embody, welcome to the comments, maybe we can create something interesting together.
Source: https://habr.com/ru/post/237141/
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