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Bones The main advantage of the orthopedical presurgical 3d printed models is the possibility to create an accurate model, which can be used for metal osteosynthesis premodelling - the surgeons can prepare (bend, twist, accommodate) the implants prior the operation. After a sterilisation (autoclaving, UV-light, gamma-ray etc etc), those implants can be used in the planned surgery, which will decrease the overall surgery time (in some cases with more than an hour) with all it's advantages, including a dramatic decreasing of the complication rates, the X-ray exposure for the patient and for the surgeons, the cost and the recovery rates etc etc. For this purpose, you need a smooth bone model, with clearly recognizable and realistic landmarks, realistic measurements and physical properties, close to the real bone. Traditionally, the orthopedical surgeons in my institution used polystyrene models, made by hand, now they have access to 3d printed models and they are better in any way. Here are some tips how to print that thing. 1. Method - FDM. The bone models are the easiest and the most forgiving to print. You can make them with literally every printer you can find. FDM is a strong option here and, in my opinion, the best method on choice.2. Matherial - PLA - it's cheap, it's easy to print, it's the bread and butter for the bone printing. Cool extruding temperature (195-200C) decrease the stringing and increases the details in the models.3. Layer heigh - 0,150mm. This is the best compromise between the print time, the quality and the usability of the models.3. Perimeters (shell thickness) - 4 perimeters. One perimeter means one string of 3d printed material. It's width depends on the nozzle diameter and the layer thickness. For Prusa MK3 with 0,4mm nozzle 1 perimeter is ~0,4mm. To achieve a realistic cortical bone, use 4 perimeters (1,7mm). The surgeons loves to cut stuff, including the models, in some cases I have to print several models for training purposes. 4 perimeters PLA feels like a real bone.4. Infill - 15% 3d infill (gyroid, cuboid or 3d honey comb). The gyroid is the best - it looks and feels like a spongy bone. It's important to provide a realistic tactile sensation for the surgeons, especially the trainees. They have to be able to feel the moment, when they pass the cortical bone and rush into the spongiosa.5. Color - different colors for every fracture fragment. If the model is combined with a 3D visualization, which colors corresponds with the colors of the 3d print, this will make the premodelling work much easier for the surgeons. Also, it looks professional and appealing. 6. Postprocessing - a little sanding and a touch of a acrylic varnish will make the model much better.7. Support material - every slicer software can generate support, based on the angle between the building platform and the Z axis of the model. You can control this in details with support blockers and support enforcers, which for the bones is not necessary, but it's crucial for the vessels and the heart.Conclusions - the bone models are easy to make, they look marvelous and can really change the outcome of every orthopedical surgery.
The last three weeks was a busy time for me. I purchased the best 3D printer of Fall 2018 - Prusa I3 MK3. I ordered it as a kit, the build itself took me 8 hours - my obsession with the electronics payed off - and immediately after that the printer was ready for some action. Prusa I3 is the most common 3D printer in the world - 70% of all printers are Prusa clones. Prusa MK3 is manufactured by the designer of the printer itself, Josef Prusa and most of it's parts are made by other MK3's in the Prusa's 3D printer farm. The printer is robust, tough, with very useful automatic functions and can print with most types of termopolymers (Polycarbonate included) with minimum layer thickness of 0,05 mm. Now I'm preparing an enclosure with automatic temperature and humidity control, Hepa and carbon filter and Octoprint upgrade for WiFi control. I bought cheap secon-hand server rack for this purpose (Fig. 4) - if it can keep a constant environment for the servers, it can do it for my printer, right? y first print was the object on Fig. 1 (what is the name of the organ?) Then I had more than 300 hours of unstoppable 3D printing and the printer doesn't made A SINGLE bad print. The only issue was the printing surface after print #12 - the next print didn't adhesed properly, so I had to wipe the printing surface with isopropyl alcohol. I was printing with PLA, now I'm starting with the first roll of PETG. My next step was to contact my colleagues from the orthopedic surgery clinic and to show them my first prints. They was exited by the result, so they provided a 1 mm. slide thickness CT scan of a Pylon fracture. Then I used the following workflow: 1. Slicer 3D, Resample Scalar Vollume to resample the set to 0,5 mm. 2. CurvatureAnisotropicDiffusion with 3 iterations. 3. Editor module for segmentation, model maker for the conversion to stl. 4. Autodesk Meshmixer for remeshing, editing and sculpting, Blender for smoothing. I prefer Meshmixer than Zbrush because it's much simpler and user-friendly. I'm also pretty good with it 5. I sliced the final stl with Slic3r, Prusa Edition and sliced the model on 0,150 mm slices, with support from the building plate, with 15% Gyroid infill (it looks exactly as a spongy bone), with Natural White PLA (17 euro per kilogram, from a local supplier) with the Natural PLA preset on the slic3r. 6. The print took 14 hours, the support was easy for removal (Fig. 2). 7. The orthopedical surgeons did their magic, first on the model (Fig. 3), then on the patient. They claimed, that the operation was very successful, thanks to my model and their skill. The chief surgeon is Dr. Preslav Penev MD PHD. My second project was a Pilon fracture of the ankle with multiple fragments, which I made with the same workflow. The patient is in operation right now. I also have two more projects, for a congenital aplasia of the talus with pes varus and for luxatio of the Lisfranc joint, so I hired two medical students and I'll teach them how to model (I already sent them Dr. Mike's beginners tutorial) for my future projects. I'm the first physician in Bulgaria, who performs preoperative 3D printing, which is very good for my career development. My colleagues called me a "pioneer" and I'm thinking about a 3D printing lab. I already ordered the Multimaterial Upgrade, which means SOLUBLE SUPPORT MATERIAL (I have to wait till January, it's in production right now). Jo Prusa's STL printer looks quite appealing too. Those printers are ridiculously cheap, considering how efficient never-stopping beasts of burden they are. I guest I should hit the vascular surgeons next...
Ultimaker just announced the new Ultimaker 3. It looks pretty awesome. My main interest is the use of water-soluble support material, which will allow manufacture of complex anatomic structures without having to worry about support removal. For example, a skull can be printed without having to rip out the support structures inside the cranium using tweezers or pliers. I want one!
If you are like me and have no real background in engineering or chemistry, keeping the different 3D printing technologies straight may sound daunting. In this post, I will attempt to give a simplified overview of the seven major types of 3D printing technologies and summarize the key advantages and disadvantages for each. I hope this information helps anyone who is interested in acquiring a 3D printer understand the different processes better and direct you to a specific technology that suits your needs the best. 3D printing is an additive process that creates volume by adding material one layer at a time following a predetermined pattern as opposed to milling, where material is removed from a raw block. The American Society for Testing Materials (ATSM) has defined seven major additive manufacturing processes, each represented by one or more commercial technologies. 1) Vat photopolymerization (Stereolithography, SLA) Invented over 30 years ago, SLA is the foundational technology of 3D printing. In this process an ultraviolet light is applied to a vat (large tub) containing liquid photopolymer (plastic). UV light is used to cure the liquid photopolymer (convert the liquid into a solid state). When a layer is completed, a leveling blade is moved across the surface to smooth it before depositing the next layer. This process is repeated until the model is completed. Support structures are needed which anchor the parts on the build platform and support overhanging structures. Once complete, the part is drained and excess polymer is rinsed off. A final cure in a UV oven is often required to further solidify the object. Advantage: - High resolution and accuracy - Allows production of complex geometries Disadvantages: - Durability; photopolymers are the weakest material 2) Material extrusion (Fused Deposition Modeling, FDM) This process is analogous to a hot glue gun where a printer melts a cable roll of raw material (usually plastic) and extrudes it through a nozzle. Through the use of a second nozzle, a support structure can be built using a different material. The melted material is laid down on the build platform layer by layer, where it cools and solidifies. Once complete, support material is either mechanically removed or melted away. The majority of commercially available desktop printers are currently of the FDM type. Advantages: - Multiple materials/colors may be used for both build and support - Affordable, easy to use, can fit in an office Disadvantages: - Relatively slow build times - Limited surface quality, fine details may not be realized - Care needs to be taken during design to optimize final object strength 3) Material Jetting (Multijet modeling) This process is analogous to inkjet printing, but instead of jetting drops of ink onto paper, a 3D printer jets drops of liquid photopolymer onto the build tray. Liquid drops are then converted into a solid state using light. Support materials are required which are either mechanically removed or melted away once building is complete. Material jetting can combine different materials within the same 3D printed model, in the same print job. Fully cured models can be handled and used immediately without additional post-curing processes. Advantage: - High accuracy and surface finishes - Can combine different materials within the same 3D printed model Disadvantages: - Durability, Photopolymers are the weakest material 4a) Powder bed fusion (Selective Laser Sintering, SLS) This process uses laser to selectively sinter (melt and fuse) a thin layer of powdered material. The build platform will then be lowered and the next layer of plastic powder will be laid out on top. By repeating the process of laying out powder and melting where needed, the parts are built up in the powder bed. Unsintered loose powder supports the object during build so no other support structures are needed. The loose powder must be removed from the completed object. Advantages: - Relatively rapid build time - No support material is needed - Can manufacture parts in standard plastics - Low cost Disadvantages: - Surface finish can be rough 4b) Powder bed fusion (Electron Beam Melting, EBM) This process is similar to SLS, but uses electron beam instead of laser to melt and fuse a thin layer of powdered metal into a solid object. Completed object is embedded in a block of loose powder, which must be removed. Advantages: - Relatively rapid build time - Material recyclability is often possible, reducing potential waste. - Useful in settings that require complex internal structures for metal components Disadvantages: - Relatively high cost for the systems and the knowledgeable operators required to run them - Surface finish can be rough 5) Binder jetting (Powder bed and inkjet head printing) In this process a print head moves across a powder bed, laying down a liquid binding agent that glues the particles together to create a solid object. The built parts lie in the bed of loose powder, so no support structure is needed. Advantages:- Relatively rapid build time - No support material is needed - Simple and inexpensive technology - Can print a wide range of materials in full color Disadvantages: - Objects are relatively fragile and require post processing to improve durability 6) Sheet lamination This process stacks sheets of materials using binding agents (adhesives) or other joining processes such as friction welding and then cuts the edges of each layer to create the desired shape. Advantage: - Does not require a controlled environment and can be run in open air - Can be used to join dissimilar materials Disadvantages: - Ability to produce complex objects is limited 7) Directed energy deposition (Laser metal deposition) In this process material is directly deposited by jetting the build material into the heated zone created by a laser, electron beam or an ionized gas. Advantage: - Can operate in open air and at large scale - Multiple materials can be used in the same process - Good at processing a high volume of material quickly and inexpensively Disadvantages: - Lower accuracy and reduced ability to create complex objects Now that you have some idea about the different 3D printing technologies, I hope you will get a 3D printer of your choice and print your heart out! Tatiana Kelil, MD Sources: custompart.net, mechanicalengineeringblog.com, additively.com, 3dsystems.com, Deloitte University Press