3D printing! It's big, it's exciting, and it's fun! It's so important that Microsoft made being 3D printing compatible a high priority for Windows 8.1. This book will help you get started in using Blender to make objects specifically for 3D printing. We will not recommend any particular printer or printing service. If you already have a 3D printer, you will know what you need to do for printing. If not, you'll probably be depending on someone else to do the actual printing and you'll need to know what they need from you, and what you need to keep in mind as you model in Blender.
In this chapter, we will look into general issues affecting 3D printing and give you a little background on what is going on so you understand why you may have to do things differently to make an object in Blender for 3D printing than you do for animation or a game engine.
The following are the topics we'll be covering in this chapter:
Opportunities to use your 3D printer
How a 3D printer works
Modeling dimensions, tolerances, and file sizes
Controlling printing costs
What materials can I use in 3D printing?
What types of printers are there?
A tour of a 3D printing service
3D printing is not the correct way to make everything. If you need to make a lot of copies of an object, 3D printing is too slow. 3D printing is also expensive. You have a limited choice of materials. You have limits on the size of objects and the quality of the objects you can make.
For example, think about making a bicycle completely with 3D printing. While I am writing this, it's impossible. The tires alone are impossible, with rubber, thread, and steel cords; the process is too complex for today's 3D printers. The size of the bike frame is still too large for almost all 3D printers; carbon fiber frames cannot be printed directly, titanium frames are very expensive, and the quality of steel you would be able to use in a 3D printer may not be right for a durable bike.
At the same time, you could easily make custom lugs to hold the frame together, custom light mounts, shifters, and water bottle racks. 3D printing can be used to create the mold for carbon fiber lugs or even a mold for a carbon fiber frame.
3D printing is best used for making prototypes and custom objects. As an exercise, I looked around to see what kinds of things I'd want to use 3D printing for. I came up with the following things:
Water bottle holder for my recumbent bicycle's oval-shaped frame
A clip that would let me mount my hydration pack to my recumbent bike and hold the hose securely next to my shirt, yet be convenient to move so I can drink from it, and it detaches easily in case of an accident
Replacement for the plastic table clamp of an old Luxo lamp
Replacement plastic foot for a camera tripod
Extension for my mouse to make it large enough for my hand
3D-printed business cards
Z-shaped key for an antique Chinese brass lock that had accidentally got latched, and for which there was no key. As seen in the following image, the new key was simple to make in 3D printing but difficult to make otherwise:
I'm sure that you have your own list. The great part about 3D printers is that they can make any shape you need, and they do it in a reasonable time at a reasonable cost. That's amazingly powerful. Look at the catalogs of the services linked later if you need more ideas.
You may want to use 3D printing as a part of a business. You could make prototypes of mechanical parts and objects architectural or theatrical stage models. You can sell what you make, such as jewelry, fantasy figurines, a smart phone case, custom coffee cups or vases, cookie molds in the shape of a cat, or whatever you think of.
3D printing is just getting started, so there is no telling how far it will go. A company named Made in Space is designing a 3D printer for use in zero gravity. They see that it will be far more efficient for many space-based repairs to just make parts up there, rather than having to carry a large number of spare parts into orbit. The OpenLuna Foundation is using 3D printing to build a model of their proposed lunar lander to show potential investors. Being able to touch and hold something is a powerful influencer in making a sale:
A 3D printer needs to take a description of a three-dimensional object and turn it into a physical object. Like Blender, a 3D printer uses values along the X, Y, and Z axes to determine the shape of an object. But where Blender sees an object as perhaps cylinders, spheres, cubes, or edges and faces, a 3D printer is all about layers and perimeters.
But you can get a better idea of how these layers stack up if you can see it interactively. I have provided an interactive illustration that allows you to see the dragon slice by slice. Scrolling through the frames, you can see how the walls of the dragon's body are built:
4597OS_01_LayersDisplay.blendin your download packet. Examine the thickness of the body at each layer.
Press Alt + A to play the animation. Press Esc to stop playing it.
You can also drag the current time indicator in the timeline back and forth to look at individual frames, or use the right and left arrow keys.
Note how the dragon starts as a series of islands. Look at the dragon's hands. The fingers start off floating in space until they are joined to the arms.
The exact method a 3D printer uses to print a layer varies. Some printers work like a pencil, drawing an outline of the shape on that layer and then filling in the shape with cross-hatching. Look at the left side of the preceding screenshot again.
The printer would first outline the tail, then fill it in. Next, it would move to one haunch, outline it, and fill it in, and then the other. And finally, it would outline and fill each foot. You can get a better idea of how this happens with this 3D printer's hot end simulator. The hot end is the printer's nozzle where the 3D printing material is extruded.
Other printers may use a print head much like an inkjet printer. The print head moves across the printing bed and deposits material where needed.
So what kinds of printers are there? How do they print and how are they different? The terminology is still a bit confusing. The American Society for Testing and Materials (ASTM International) recently came up with the following categories:
Material extrusion is also known as Molten Polymer Deposition (MPD), Fused Deposition Modeling (FDM), or Fused Filament Fabrication (FFF); these extrude a gooey material out in layers to build up the proper shape. This is the class of printers that includes most hobbyist 3D printers. They work like the simulator you just used. These can use plastic, metal wire, wax, sugar, frosting, chocolate, cookie dough pasta, pizza, and even corn chips.
Material jetting is also known as photopolymer jetting. Like an inkjet, this printer squirts liquid photopolymers at the right moment, which are cured immediately with ultraviolet light, layer by layer. The object being built is supported by a layer of gel that is also applied by the print head, so overhang is not a problem.
Binder jetting uses a two part system. A thin layer of composite material is spread across the print bed. Then, an inkjet-like printing head sprays a binder fluid and possibly colored ink, which combine with the composite material to produce solid colored and sometimes textured objects. This can be plastic, gypsum, or metals, such as copper, tungsten, bronze, and stainless steel. For metals, a second step is needed to make them solid. The binder is removed and metal is infused where the binder used to be.
Vat photopolymerization is also called Stereolithography (SLA). Photopolymerization printers use light to cure liquid material into the right shape. This process uses resins, wax, or liquid plastics for the material. It may use a laser or a high resolution DLP video projector similar to one you would hook up to your computer to give a PowerPoint presentation.
Powder bed fusion is also known as Granular Materials Binding. These printers use a laser or heat to fuse layers of powder into the right shape. These can use metal, ceramic, gypsum, or plastic powder. There are several subtypes of powder bed fusion printers.
Selective Laser Sintering (SLS) is used with thermoplastics, wax, and ceramic powders. A thin coat of powder is spread across the printing bed. Then, the printing head prints the layer by fusing selected areas with the laser. The printing bed then drops down. Another coat of powder is added and the laser prints the next layer.
Direct Metal Laser Sintering (DMLS) or Selective Laser Melting (SLM) is a subcategory of selective laser sintering. The laser beam melts the metal and makes solid parts with metal alloys like aluminum, iron, stainless steel, maraging steel, nickel, chromium, cobalt, and titanium alloys. In theory, it can be used with most alloys.
Directed energy deposition, also known as Electron Beam Melting (EBM), is similar to SLS, but uses an electron beam instead of a laser. The high heat generated by the electron beam allows use of pure metal powder such as titanium alloys, and can make high-detail, high-strength objects that do not need any postmanufacturing heat treatment.
Question: Earlier, I mentioned a company named Made In Space, which is making a 3D printer to be used in zero gravity. What kind of printer is it making?
Directed energy deposition
Powder bed fusion
Answer: Option 3, material extrusion is correct. Extruding a material avoids liquid or powder floating around in zero gravity.
As you have observed, there are a wide variety of 3D printers. But there are some parts they all have in common.
The printing head holds the laser, the printing jet, or the hot end of the extruder.
And then there are controls to position the printing bed and the printing head in relation to each other; one control for the X dimension, one for the Y dimension, and one for the Z dimension.
There are no hard and fast rules for which controls the printing bed and printing head have. The Cube printing head is controlled in the X dimension only and the printing bed is controlled in the Y and Z dimensions, whereas the MendelMaxPro puts X and Z controls on the printer head and controls the printing bed only in the Y dimension.
Generally, the answer is stepper motors. Stepper motors are motors that move in small discrete angles of rotation instead of spinning like most regular motors. This allows you to make definite, easily repeatable motions. It is also one reason why there are minimum sizes on the detail that you can make. A 3D printer can't make detail smaller than one step of the stepper motor.
Then, through wires, drums, gears, and threaded rods, the motion of the stepper motor is scaled to fit the medium that the printer uses. A hobbyist printer that uses a filament of the ABS or PLA plastic that feeds off of a reel will provide the kind of detail that those plastics can support. A high-end stereolithography printer may get much finer detail.
The next graphic is a diagram of the insides of a stepper motor. The rotor is in the center. It rotates and is attached to a shaft that pokes out of the motor. The stators are attached to the outer shell of the motor. They are wrapped with copper wire and an electrical current is run through the wire to give each stator a negative charge, a positive charge, or no charge as indicated in the next graphic. In the graphic, red represents a positive charge, the blue is a negative charge, and the grey has no charge.
The rotor in the center has 50 teeth. The stators around the outside have a total of 48 teeth. It's this imbalance in the number of teeth that allow the stepper motor's rotor to walk around step-by-step.
The positive charge of the rotor is attracted to the stator teeth that are negatively charged. In the following screenshot, you can see that the rotor teeth aren't well aligned with the uncharged stator that is counter-clockwise from the blue stator. To do a single step, the stepper motor controller changes the negative charge from the blue stator in the following screenshot to the stator just counter-clockwise to it. Then, the teeth in the rotor try to align with that stator. So, the rotor moves just a little, a step. To continue moving more steps, the stator with the negative charge keeps moving to the next stator, as follows:
To see how this works, open the interactive
4597_01_StepperDemo.blend file and follow the instructions.
The stepper motor is then attached to a control belt or a shaft with a screw thread to give the printer precise control of the print head and the printing bed. There may be one or more stepper motors controlling a single axis.
Well, I said I wouldn't recommend any printers, and I won't. But, the Peachy printer deserves a special mention in this book for three reasons. One, it has no stepper motors. Two, it's the only 3D printer I have heard of that actually uses Blender as the printer driver. Three, it uses the Blender files as object files.
It is a vat photo polymerization system. Instead of stepper motors, the laser beam is controlled in the X and Y axes by a sound form generated in Blender that moves two mirrors. The Z axis is controlled by a salt water drip system. The dripping is monitored to tell Blender which Z depth the printer is working on and the salt water is used to float the resin so that the resin rises to surround the part of the object that is being formed at that moment. It should be on the market as of April 2014.
You must know the maximum dimensions that the printer that you intend to use can print. If your object is too large, then you must break it down or find a larger printer. One printer may handle a volume of 10.16 x 10.16 x 10.16 cm (4 x 4 x 4 inches), another 22.86 x 25.4 x 17.78 cm (9 x 10 x 7 inches). A service may be able to do 100 x 45 x 25 cm (39 3/8 x 17 3/4 x 9 13/16 inches) in one material, but only 15 x 15 x 15 cm (5 15/16 x 5 15/16 x 5 15/16 inches) in another material. When you are planning your object, know what you will print it with. The links later in this chapter will help you figure out which printer(s) are big enough to make what you want to build.
Pay attention to the minimum size as well. Small parts get lost. You may want to attach tiny parts to a sprue, as used in plastic model kits, to keep them together. Most services will list the minimum size parts that they can work with.
Another thing to consider is the size of the polygons. There is a minimum size of detail that each printer can handle. It makes no sense to have polygons much smaller than the minimum detail size. The print won't be better, but the file size will be larger. It makes more work for the slicing program and the printer, which slows things down and may lower the print quality.
We like to imagine that when we make an object in Blender that everything will just be exactly the size we specified. But this is not always the case. 3D printers exist in the real world and there are a lot of things that can affect how precise your object is:
The size of the object
How well the printer is set up
The quality of the printer to begin with
Any sloppiness in the system
Whether the printer controls the X, Y, and Z dimensions equally well
How recently the printer was calibrated, and how well it was calibrated
How consistent the extrusion and material flow is
The ability of the software to control the system
How much flex there is in the printer
The ambient temperature of the room
These things can result in objects being stretched or squashed, holes not being round, objects that should fit not fitting, straight lines being wavy, gaps between the layers, and more. The burden of keeping these things under control falls to the person with the 3D printer, but it's important to keep in mind when you are designing your objects.
Most printers charge by the cubic centimeter of material made. Some may add a "handling" charge. So you, as a designer, want to minimize the amount of material used. A few things you can do are as follows:
Shop around for a printer who charges less.
Use a less expensive material.
Make your object smaller.
Hollow out your object.
Remove unneeded material, in the lunar lander, the fuel tank clusters were built as a single hollow object instead of individual tanks. The landing pad is not a solid block; underneath, it's like an upside down soda crate. The rocket motors are not solid.
Delete unneeded details.
Acrylonitrile Butadiene Styrene (ABS) is currently the most popular plastic for 3D printing. It is lightweight, shiny, easily extruded, strong, impact resistant, and heat tolerant. It's used for the interiors of cars, household appliances, and more. It requires high heat to extrude. While being extruded, it does give off fumes, so the printer should be in a well-ventilated room. ABS is not generally recycled.
Polylactic acid (PLA) is made from lactic acid, the same chemical that builds up in your muscles when you exercise hard. PLA melts at a lower temperature than ABS. The PLA objects are stronger and take wear better than ABS. PLA is used for things, such as plastic cups, fabric, and microwave trays. PLA is derived from natural sources, such as corn starch, tapioca roots, or sugar cane. It is recyclable.
Aliphatic polyamide (nylon) is a family of materials. Invented as a synthetic silk, some early uses were in ladies stockings and parachutes. Nylon is cheap, tough, flexible, and can be dyed. Nylon is less brittle than ABS and PLA, so it can take a beating. It's also somewhat self-lubricating, which is good for making gears. But nylon is also more prone to warping, and is stringier when printing than ABS or PLA. Nylon is recyclable.
Polyethylene terephthalate (PET), also known as Dacron or polyester, is often used for soda and water bottles because the plastic's chemicals don't leak into the food. It is strong and it takes a lot of wear, so it's used for recording and adhesive tape as well as "space blankets". PET is the most recyclable of the plastics.
Stainless steel, bronze, tungsten, and copper are used in binder jetting and mixed with a binding agent, which is later removed and replaced with metal.
Tool steel, stainless steel, cobalt, chromium, nickel, titanium, and alloys of these are used in direct metal sintering and directed energy deposition printing to make solid metal objects.
Since 3D printing is a new technology, there may be problems that we don't know about. ABS sometimes gives off fumes when being printed because of the heat, but seems to be stable afterwards. Other materials like PLA can be food safe. But there are a lot of variables; the object could be dipped in acetone to smooth the surface, or there could be other additives mixed into the materials. The more common problem is that 3D printing processes may not create a completely smooth solid surface, so germs can find nice places to live. Currently, the only 3D-printed materials considered food safe are glazed ceramics and polished metals such as stainless steel. For printing food, chocolate, frosting, and so on, you need to make sure that the materials and the printer itself are food safe.
It's a good idea to know at least a little about what happens between the time a 3D printing service receives your file and when you receive your object back. Here, Bart Veldhuizen, founder of BlenderNation, takes us on a tour of the Shapeways factory. It's very good for seeing all the steps involved in 3D printing:
You have learned a little about 3D printers and 3D printing. You discovered some opportunities for you to use your Blender design skills in 3D printing. We covered the fundamentals of how a 3D printer works and the different kinds of printers that there are. And you discovered that 3D printers can handle a wide variety of materials from wood, to plastic, to titanium. You learned a bit about factors to keep in mind when you are designing objects for 3D printing in Blender, such as the sizing and tolerances.
3D printing is an industry just taking off. It's time to join in the excitement and learn how to use Blender to make objects for 3D printing. Let's go!