When 3D printing, especially with the level of tools that we have at Cogswell, it’s important to keep in mind that what is printed is not a finished product. Frequently, the printed model will require some additional work to look polished, or may need to be tweaked and printed again. The actual printing of the model is just a small part of the process, which normally involves designing, slicing, printing, and finishing to make a final product. That said, you can make some amazing things with the help of the 3D printer and a little bit of craftsmanship.
Every good project starts with a seed of an idea. This is no different with 3D printing, and keeping a few things in mind at the idea phase can save you hours of headache later down the road. The most important thing to remember is like any tool, it’s important not to put the cart before the horse. If you’re trying to think of things to make with a 3D printer, you’re likely to end up with a bunch of projects that you’re half invested in. Rather, try to think of 3D printing as a tool you can use to help you with things you already want to do. In the past, people have had lots of success using the 3D printer for making their modeling projects physical and creating pieces for games they created. Both just use 3D printing as a means to an end, rather than an end within itself.
Once you have a good idea of what you want to use the 3D printer for, the next step is to create a digital model. Before you even launch a modeling program, however, you need to determine what scale you’ll be working at. If you make anything smaller than 1 inch, it’s unlikely that any fine details will show in the print. Likewise, if you make anything much bigger than 6 inches on a side, you’ll have to split it up into multiple parts to be printed one at a time (the 3D printer is only so big.) If you’re creating an art piece, your scale will determine how much you should exaggerate features to make sure that they appear normal to someone looking at the final piece.
With scale in mind, you can now begin modeling. Depending on what your skillset is, you may choose to either use a 3D modeling or Computer Assisted Design (CAD) program. CAD programs work great with any scale, often allowing you to specify exact dimensions for every facet of your model. However, if you’re creating anything with an organic shape, such as a model of a creature, a CAD program will make your life a nightmare. Instead, it’s recommended you use a traditional modeling program. Maya and Z-Brush are available for use on the school’s computers, but do require a paid license to use elsewhere. Free programs, such as blender, can substitute in for these, albeit suboptimally.
While working on the model, it’s worth keeping in mind how your model will be printed. Fundamentally, all 3D printing works by creating a thin layer of material, then a thin layer on top of that, over and over again until the model is complete. Since these layers are stacked on top of each other, there is a sort of pixelation that occurs across the physical dimension. On Cogswell’s 3D printer, this pixelation is made up of steps 0.27mm tall. (About one-hundredth of an inch) Across the horizontal plane, however, the printer has much greater precision. This means that you will get greater detail on the sides of your model than the top or bottom. Working with this grain in mind is key for making smooth looking models.
Now that you have a 3D model for your project, it must be converted into instructions that the 3D printer can understand. This process is called slicing. Although most of the process is automatic, there are some important decisions to be made regarding how your model will come out of the printer. The first major decision to be made is whether you want to print your model as one contiguous piece or many small ones that must be assembled after the print. Printing as one piece can often mean that your model will have lots of overhang, which will result in more support material being printed (discussed later) and ultimately a longer print. Choosing a multi piece print means spending more time on modeling to split the model up, and more time after the print to assemble it, but can make a higher quality model for less cost. If you choose to print in multiple parts, it’s recommended that you split the model in spots that won’t be seen or rest on a joint. This will hide any unevenness in the two parts and ensure you don’t have to work too hard to hide the joint afterwards.
Once you’re ready to start slicing your models, the slicer will ask you what sort of support material you want on your print. Support material is used to keep overhangs in your model from drooping while the plastic it’s made of is still soft. If your model has any sections that jut out at a right angle, you should enable supports in the slicer. Keep in mind that the more support material you have on your print, the longer it will take to complete, just as if you had added them in your modeling program. You can get details on which slicing program is the best to use from whomever manages the 3D printer you’re using. For the Cogswell 3D printer, CES can usually run the slicing program on your model for you.
Once your model has been sliced, and the instructions sent to the 3D printer, there’s not much you can do but wait. Typically, a 3D print will take anywhere from 1 to 5 hours depending on the size of the print. Most slicing programs will give you an estimate of how long your print will take, accurate to about 10 minutes.
When your model has printed out, you’ll now have to spend some time finishing the model. At the very least, this means separating the raft from the model. The raft is a loose mat that the 3D printer will make under your model to make it easier to separate from the print bed in the 3D printer. If you let the model cool down before trying to remove it, the raft should come off more or less in one piece. You may have to scrape at the bottom of the model a bit to remove any small pieces that are still stuck to it. You’ll also have to remove any support material at this time. Support material is flimsy and fragile by design, so it should collapse and break off the model without much effort.
Now that the model is on its own, you can begin to smooth the surfaces of the model. Sanding is a quick method that works well for flat surfaces and joints that need to be superglued together, but it will be ineffective at smoothing down organic, curved surfaces. For this, it’s recommended that you try acetone smoothing.
Acetone smoothing is used to melt or dissolve the surface of your model in a controlled fashion, so the model losses the vertical pixilation that’s present in the print. When the surface of the model is melted, it will flow down the model, filling any texture and creating a smooth latex-like surface. Because this technique relies on the plastic dribbling down the sides of the model, the top surfaces are often left rough or made rougher by this technique. However, you can still finish those spots off with sandpaper after the smoothing to create a consistent texture across your model.
The key thing to remember when using acetone is that acetone is very good as dissolving plastic and it is very easy to overdo it. To smooth your model evenly and ensure it happens smoothly, you need to place your model in a small, closed container with acetone soaked paper towels. This way, the acetone will outgas from the paper towels and gently melt the surface of your model. Placing your model on a tray made of aluminum foil while in this container will prevent the bottom from melting excessively. Most models will take around 30 minutes to a few hours depending on size and the amount of acetone used. To make sure you don’t overdo it, check on the model every 15 minutes or so. Additionally, when you take the model out or check on it, do not touch the sides of the model. Usually these will still be tacky for some time after acetone treatment, but will dry with time.
Congratulations! You now should have a completed 3D model. If it was an artistic work, this might be where you paint the model or mount it on a base. If it was a piece for a game prototype, you might get feedback on the design, and do the whole process over again. Either way, it’s good to keep notes on what parts of the process worked and didn’t work for you. 3D printing is much more a craft that just a fancy way of printing. However, with a bit of practice, However, with a bit of practice, it can be a great asset in any project.