Models of Everyday Things

Many databases of 3D-printable objects are available online. The Thingiverse ( www.thingiverse.com ), Youmagine ( www.youmagine.com ), Pinshape ( www.pinshape.com ), and Instructables ( www.instructables.com ) websites all feature a wide range of objects, from sci-fi figurines to parts for enhancing 3D printers. These models have been contributed by users and as such vary widely in the quality of their design both for printing and for their intended purposes.

Sometimes model creators will upload both the STL file for printing and the file in the original format of the software that created the model. That means if you happen to be conversant in the original program, you can start with an object and modify it. For example, in Thingiverse, when you click the Download This Thing! button, you get both a list of the available files and the type of license under which each is being made available. Sometimes the developer just wants you to credit them if you use it. Sometimes commercial use is not allowed. If you obtain something from one of these databases, be sure to look carefully at the requirements, particularly if you’re going to modify the object or sell something based on it. See Chapter 3’s notes on Creative Commons licenses.

Specialized Databases

Both programs have extensive documentation. They are freely available, but have some restrictions on commercial use.

The National Institutes of Health (NIH) in the United States maintains a repository of medicine-related models ( https://3dprint.nih.gov ). The Smithsonian ( https://3d.si.edu ) and other institutions are increasingly putting together “greatest hits” downloadable sets from their collections. Often, though, these files are huge and may have other issues. You will probably want to repair and decimate them — see the section “Repairing a Mesh” in Chapter 3.

Using a CAD Program

Most CAD programs will either save a file as STL directly or offer an option to “export to” STL. Which CAD program is the right one for the job? This section describes commonly used programs ranging in price from open source and/or free to quite expensive. The programs also vary in the steepness of their learning curves. In general, the more powerful the program, the longer it takes to be reasonably proficient in its use.

Some software packages are geared toward creating models meant to be viewed on a computer or theater screen (called 3D rendering). A “3D” movie normally does not contain the parts of the model that are not on the screen at that moment. Various tricks exploit the way your eyes perceive 3D and fool you into thinking you are seeing a 3D image when really all you are seeing is two offset versions of a 2D image.

If you are at a 3D movie looking at a 3D stereo image of the north side of a tree, that side was generated in a computer. The south side of the tree, the underside of the trunk, and some of the top, east, and west sides are not needed for the movie viewer to see the tree in 3D. However, all of that is needed for printing an object. Be sure the software you are looking into can export an STL file or a format that can be converted into STL.

Some programs have the user write computer-code–like instructions, whereas others require a lot of mouse use and more of an artistic bent. This is a quick overview of some of the available options; for the most part, the open source programs offer extensive documentation available for free download. The proprietary software programs typically offer training or have help available.

Options for Getting Started Quickly

If you want to go from “zero to plastic” as soon as possible, you might try Tinkercad ( www.tinkercad.com ) and OpenSCAD ( www.openscad.org ), both of which are free. Tinkercad requires registration; OpenSCAD is open source. Both have example files available that you can play with and use as guidelines for your own first project.

Tinkercad: Drag and Drop

If you want to use something simple that requires no programming knowledge at all, you will like Tinkercad. Tinkercad is a member of Autodesk’s suite of 3D printing productivity tools. The program is free as of this writing, although it requires the user to register. Tinkercad is a purely drag-and-drop program that supplies a lot of simple shapes such as rectangular solids, spheres, cylinders, three-dimensional letters of the alphabet, numbers, and so on. Printable objects are created by assembling them out of these standard virtual pieces.

Tinkercad requires a good Internet connection because the program is entirely cloud-based and frequently saves incrementally. If several people are using it on one wifi node, the result can be frozen screens and frustration. However, it’s a great way to develop something quickly just to test the end-to-end process of creating a model, slicing it, and printing it. Figure 6-1 shows a simple “star and Saturn” pendant designed by Joan in Tinkercad.

Tinkercad has extensive tutorials that are arranged into bite-sized brief walkthroughs of the key features, and there are a lot of examples that others have designed and put out there for you to play with and build upon. The classic project to try first on a 3D printer is a small keychain fob decorated with 3D initials or a few hearts. Most people can do a project of that scale in an hour or so starting from zero with Tinkercad. In Chapter 5, we suggest just printing a cube from Tinkercad as an end-to-end plastic “hello world.”

To get started in Tinkercad, follow the process at the Tinkercad home page, www.tinkercad.com . Autodesk also has special accounts for teachers to register their students; click the Learn tab for details. First, you will need to create an account (with Autodesk) to use the program. There are good tutorials on the site that appear by default when you go in for the first time.

When you feel comfortable, you can close the tutorial and click “Create new design” to open a new open build plate. You can drag the preexisting shapes onto the build plate, select two or more of them, and use the group icon to merge them into more complex building blocks. You can make any shape a hole (negative space) by selecting the shape you want to use as a hole and then clicking the “hole” graphic. By adding and subtracting shapes, you can build up fairly complex models.

Tinkercad also has features that are new as of this writing – scribble and a coding capability. We describe those in some detail in Chapter 11.

Save your model by clicking the Export button and selecting the option to download for 3D printing. Laser cutting is an option too, for models that can be made as a flat cutout.

You should now have an STL file in your downloads folder that you can import into your slicer of choice (see Chapter 3) and ultimately print. Tinkercad makes up weird, pseudo-Swedish names for models. You can make them something more memorable by clicking the name it made up and typing in what you would like to call it. Alternatively, you can take one of the public Tinkercad models and alter it a bit, if the model creator allows that, and then save it to STL. Remember to start small and simple—see the “3D Printing Design Rules” section at the end of this chapter about what makes a model “simple.”

Tinkercad also has the ability to model basic circuits and create enclosures for some electronics components in your 3D print. See www.tinkercad.com/circuits for details.

Note

There are a variety of other low-cost, school-oriented CAD programs, and more pop up all the time. Morphi ( www.morphiapp.com ) has a small cost per seat, but does not require a live wifi connection (which Tinkercad does). People sometimes try to use Inkscape ( https://inkscape.org ) for 3D printing, but it is not designed for it, and you will need to export your drawing to another program to extrude it into the third dimension. The result after all that will be better suited for a laser cutter.

OpenSCAD: A CAD Programming Environment

OpenSCAD follows the opposite philosophy from Tinkercad in that it is not drag and drop at all, except for adjusting how you view the model you have developed. OpenSCAD uses a programming language very similar to C to define geometrical shapes, translations, rotations, and so on.

The program has built-in functions for most common shapes, although the names can be a little misleading. For example, all the rectangular solids are called “cubes.” Figure 6-2 shows a simple file with three “cubes” assembled into a simple bridge by moving (translating) the top and one side of the bridge away from the zero point. Note that the cubes were designed to be slightly overlapping—because shapes with purely coincident faces may not have created a manifold STL.

To try out a simple model in OpenSCAD, first either click File ➤ New to start a new model or pick an example from the Example submenu. You can also type in the little example shown in Figure 6-2—the three lines shown are all you need for the model shown. As with any program, saving frequently is a good idea, which you do from the File menu. This will save the program in OpenSCAD format, not STL.

If you want to see what your model will look like, select Design ➤ Preview. This creates a quick visualization of your model without taking the time to calculate all the geometry.

Click and drag with your mouse in the preview pane to roll your model around and see it from different angles. This is also useful to give you a better idea of what the shape actually looks like in 3D.

If you like the looks of what you see in the 3D preview, you’ll want to render the model and create an STL. Go back to Design ➤ Render. This may take longer than the preview step (especially if your model is very complex or uses certain computationally-intensive elements), which is why the preview is available.

When rendering has finished, the preview pane will update. If you had used colors or certain other features, you may notice that they disappear, because they are not supported by STL and thus are only usable for previewing. Roll your model around in the 3D view again and make sure it still looks like you expect. If it does, go to File ➤ Export and then choose STL as the file format.

You can then take the STL file and run it through a slicing program (see Chapter 3) and you will be ready to print. OpenSCAD is particularly suited to modeling objects that can be built up out of geometric shapes. Complex objects are possible by starting with these basic shapes and rotating them. You can make impressive geometries with a little programming experience and the OpenSCAD manual. We have two books of 3D printed science and math models, all of which were created in OpenSCAD (3D Printed Science Models (Apress, 2016) and 3D Printed Science Models Volume 2 (Apress, 2017). Figure 6-3 shows a botanical model from the “Plants and their Ecosystems” chapter of the 2016 book.

Tip

It is helpful if you create an STL and export it in the orientation you expect to print it in. Consider minimizing support. One special case is thin objects with a lot of surface detail, like the models in Figure 6-3. In that case, you may want to print the objects standing on end, as these were printed. As long as the overhangs are manageable, this should work well.

Programs for Specific Applications

Tinkercad and OpenSCAD are great for beginners. If you are using your printer mostly as a hobbyist, in a classroom, or to make fun objects around the house, you can probably be happy for a long time with these programs. However, if you need to create professional-level sculptural models, or if you need dimensioned drawings, then these programs probably are not enough. Many, many design programs can either produce an STL file or a file that can be translated into STL. Most of these programs deserve (and in some cases have) their own book-length tutorials.

Generally speaking, you need to consider a few key attributes when selecting a design program. First, think about your own strengths: are you good at programming, or are you better at drawing with a mouse? Do you have decent hand-eye coordination and drawing skills? How much time do you have to devote to becoming proficient, and how much design are you really going to do? A program with a short learning curve but limited capability may be okay if you are only going to make a few complicated objects, but learning a more-capable program may be worth it if those features will vastly enhance your productivity.

Some software only runs on either Mac or Windows, not both. If you only have access to one or the other operating system, that may force a choice.

Next, consider budget. Free and open source software varies in quality; documentation can be uneven or incomplete for open source software. However, it is free. For pricey software, research whether demonstration versions of the software are available, and if so, try before you buy. If you are a student, check with your school to see whether any discounts are available to you.

With all that said, programs to create models for 3D printing need to serve various constituencies. Engineers, architects, industrial designers, mathematicians, and similar professionals need drawings with each part’s dimensions shown and great precision. Often, they will need to integrate 3D printed parts with traditionally manufactured ones and thus will need both the ability to create a file for printing and a traditionally dimensioned, human-readable drawing. Artists may want good drawing tools that allow them to sketch freely but not require as much precision. Different tools have evolved for these respective communities, as we will see next.

Using One Extruder for Support Material

If you are printing something with significant amounts of support material, you may want to simplify the removal of that support. Dissolvable support is made for this purpose. In this case, no extra steps are necessary prior to sending an STL file to your slicing program (Chapter 3). You will need to tell the slicer which extruder is using the support material.

Water-soluble support filament is usually relatively expensive, and may come in smaller quantities (both for cost reasons and because it can be ruined by leaving it out to absorb moisture from the air). For this reason, it can be advantageous to minimize how much of it you use. Most slicers now have the ability to configure the extruder used for the support interface separately from the rest of the support structures, which allows you to print the bulk of the supports with the cheaper print material and only use the soluble material for the interface between the supports and the part. Depending on the geometry and orientation of your part and of its support structures, this may allow the supports to just fall off, or some breaking of the supports might still be required to remove them, but it makes support removal easier and less likely to mar the surface of your part than using break-away supports.

If your printer has multiple extruders that share a single nozzle, you may find there is no way to use them for materials with different properties, or if you can, that it requires significant purging of the extruder to switch back and forth. Using a support material that is formulated to have similar printing temperatures to your print material will help.

Two-Color or Two-Material Prints

As mentioned, dual-extruder printers allow you to print objects in two colors or materials. It is still a little complicated, though. First, you need to create the STL files for each of the extruders separately, so that you can assign each one to an extruder. In the example here, we will be printing a red heart pendant with a light blue star and exclamation point. This entire object was created in Tinkercad, with the exclamation point, star, and heart all in the same file.

To create a two-color object, we needed to create two separate STL files. To create the first one, we turned the heart/pendant hook into a “hole” in Tinkercad and subtracted it from the merged item to ensure that the two shapes would not overlap. We then saved that much into what we will call STL number 1.

Then, to make the second STL, we undid the merging, turned the heart/pendant back into a regular object, and deleted the star and exclamation point so that we could export just that part as STL number 2. Remember to undo the deletion (or better yet, work with a copy of your original file) so that you don’t lose the ability to edit your file and try again.

These two STLs are shown in Cura 3 (Figures 6-4 and 6-5) as they look when they are dragged in separately. Note that some of the model in Figure 6-4 is just hanging in air, because the models need to have the same coordinate system as each other to begin with.

While making these two files, we were careful not to move anything around during this process so that the STL files would line up properly when we re-merged them.

The following directions assume you have two STL files that were created with a process similar to what we just described for our heart pendant—that is, two STLs created in a way that maintains the same coordinate system across the two files and avoids overlaps. If your printer has multiple nozzles, check your documentation for determining the offset between them and making sure that they are at the correct relative heights. For some printers, you will need to enter the correct offset values in the slicer; others carry this information in the firmware. The offset is the distance between the two extruder heads in the x and y directions.

In a pinch, you could measure from the center of one nozzle to the center of the other nozzle, but this is difficult to do and your manufacturer should have given you either a number or a means of determining the number from a print. Unless your printer has some method of moving the inactive nozzle out of the way, height adjustments will need to be made mechanically—otherwise, the lower extruder could collide with the plastic that came out of the other nozzle. Single-nozzle dual extruder systems do not have any offsets to worry about.

Cura’s Process for a Dual Extruder Print

As we note in Chapter 3, slicing software gets updated a lot. However, the general processes stay about the same. We are going to walk through the process of creating a dual print in Ultimaker Cura 3, since it is so tightly tied to the model generation. For the example here, we used a MAKEiT Pro 3D printer, which automatically handles the extruder offsets in firmware.

First, we brought both STLs into Cura 3 and selected the MAKEiT Pro M, which has two extruders. We selected each STL in turn and chose an extruder for it (Figure 6-7). Then we right-clicked one of the models and selected Select All Models and then Merge Models. The result is Figure 6-8.

Finally, under the Dual Extrusion settings (visible in Figures 6-7 and 6-8), we added a prime tower and an ooze shield. This figure highlights a single layer simulation in Cura, with the tower and shield (you have to select “show helpers” to see these) and the travel among them shown in light purple.

These features, visible in the photos in Figures 6-9 and 6-10 taken during printing, keep the extruder not being used from dripping plastic onto the print when it is supposed to be idle.

The prime tower can get a little uneven and get knocked off near the end; if that happens near the end of a long print, you can let the print finish just drooling over where the prime tower was as long as the prime tower wound up somewhere out of the way. Note that the wipe shield curves around the print and does not go straight up. Figure 6-11 shows the print after it has been removed from the platform and separated from the wipe shield.

Complexity Is Free: Hardware as a Service

One of the mantras of the 3D-printer community is that complexity is free. Because 3D-printed parts are built up one layer at a time, it really doesn’t matter whether that layer is one unbroken sheet or an intricate design. There are models that would be essentially impossible to machine, but people who know what they are doing can print them on a low-cost consumer printer.

Consumer-level printers have one more strong advantage: the opportunity to iteratively design something, see how it came out, and then change the design if necessary. When that became possible in the 1980s for computing (versus overnight batch jobs), there was a real change to the nature of creating software. We all hope the same thing is about to happen for making physical things!

This phenomenon is starting to be called hardware as a service (an analogy to software as a service), and the business models are still unclear. Resolution and materials are likely to continue improving, and all the pictures in this book will probably look primitive to anyone reading this a few years down the road. Chapter 14 speculates on how 3D-printing businesses may evolve toward short-run manufacturing or mass customization.

Speed vs. Customization

Complexity is not entirely free because the amount of material used (and the time it takes to print) is more proportional to surface area than to volume of the part. Complexity may matter less in 3D printing than in conventional fabrication, but complex prints may take a long time. Consumer 3D printers take a while to print anything out—it’s rare for a print of any size to take less than a few hours, and prints that take a day are routine. If you’re making one of something or a prototype for a mold, such a length of time may be competitive. The other option is a machinist or other professional making a prototype in a way that involves a lot of labor. But if the part is simple or you want a lot of them, a 3D-printed part is probably not the way to go. If you are happily creating injection-molded parts for something now, then 3D-printing that part is definitely not the way to go.

To narrow it down a bit more, consumer 3D printers may not be the best fit for your project if everything you do will require a lot of hand finishing after the fact. You might consider using a service bureau to do one of the more industrial processes. To put it another way, only the right kind of complexity is free.

3D printing has a role for items that are by their nature one-of-a-kind (or a-few-of-a-kind) and that work well with the technology. Time will tell what the best applications are. Our sense is that one key role for 3D printing is that it makes the front of the product-development process faster. People who would have made a computer model and then created a foam-core physical mockup as two separate chores are obviously better off with a 3D printer.

Other promising markets exist in industries that make custom parts for one-of-a-kind applications (or, even better, industries that should operate that way but cannot do so economically at the moment). The biggest market now, though, is a somewhat intangible one: allowing people to make stuff again just because they want to and can.