3D Printer Frame Design

Every part of designing a 3D printer is fascinating, from the linear motion system, to the electronic circuitry, to the software, designing a 3D printer offers Makers the opportunity to explore a wide range of technological areas and skills. But out of the many systems that must work together to create a high-performance 3D printer, I actually think the design of the frame is one of the most interesting.

On one hand, the frame can be seen as one of the simplest parts of a 3D printer. The frame is essentially just a platform for supporting all the electronic and mechanical components that do the actual work of printing objects. But on the other hand, designing the 3D printer frame gives Makers by far and beyond the greatest opportunity for creative thinking and problem solving. Despite the simplicity of its function, the 3D printer frame is among the most difficult parts of the 3D printer to design because there are probably a near infinite number of possible designs and different ways to build a 3D printer frame.

Of all the numerous (to say the least) 3D printers on the market today, it is often the frame design that makes each 3D printer different from the others. Just take a look at a selection of 3D printers that have been successfully funded on Kickstarter.

They all look pretty similar don’t they? In fact, if you could make the frames on each of these printers invisible, it would be very difficult to distinguish one 3D printer from the next. Underneath the frames, all of these 3D printers function exactly the same way and use almost exactly the same parts. You will have three stepper motors, connected to belts or lead screws, that move the build platform or hot end along linear motion rails. You will have a heated nozzle (hot end) and a filament extruder (cold end). You will have one of only a few different types of controllers and then you will have a spool of plastic filament. That is the bill of materials for nearly every 3D printer on the market. I’m not saying this is a bad thing, there is certainly still lots of room for innovation even using the same short list of parts for each 3D printer. My point is that much of this innovation comes from the design of the frame.

Most 3D printers on the market today, at least those that will stay on the market for any length of time, have at least a few novel features, like low cost, premium components, perhaps a new hot end design, but for the most part, the only thing that is different from one 3D printer to the next is the design of the frame. That shows just how important the frame design is; it probably isn’t the only thing that differentiates a 3D printer from its competition, but it is one of the biggest and the most visible.

3D Printer Frame Construction

Another, more technical, reason 3D printer frame design is so fascinating is the vast array of different construction/manufacturing techniques used to build the frames.

Member and Joint Construction

The simplest, most utilitarian frame designs use some kind of member a joint construction. The RepRap 3D printer designs have frames built using this technique, as well as all the 3D printers pictured above. Basically the frame consists of a bunch of straight members, like threaded rods or smooth metal rods, connected together by joints.

The construction of these frames is similar to the construction of truss bridges, and 3D printers built using a member and joint construction share many benefits with truss bridges. First of all, this type of construction is cheap. Threaded and smooth rods are readily available from many sources and because they are used for numerous applications in construction, they are inexpensive. Second, Second, this type of frame is relatively easy to design because of its simplicity. Third, also because of the frame’s simplicity, it’s easy to assemble this type of frame.

On other “benefit” to 3D printer frames build using member and joint construction, although it might be considered more of a feature than a benefit, is that the joints can usually be 3D printed. This means 3D printers using member and joint construction are partially self-replicating. This is, in fact, the purpose of RepRap machines; they can typically be used to produce a large portion of their own parts.

The most obvious downside to the member and joint constructed frames is that they simply do not look good. This is probably fine for a 3D printer used as an experimental platform, but it is a significant downside for 3D printers that will be sold to the public.

Another major concern for member and joint construction is safety. First, all of the belts, lead screws, and pulleys are usually exposed with this kind of frame. This creates a danger that objects could get caught in the linear motion mechanisms, including hair or loose clothing. Second, the hot end is also exposed, making it easier for objects to come into contact with the heated nozzle.

Laser Cut /CNC Cut 3D Printer Frames

Another way to design and construct 3D printer frames is with laser-cut or CNC-cut panels. The vast majority of the most successful 3D printers of only a few years ago were constructed from laser-cut or CNC-cut panels:  the Makerbots Cupcake, Thing-O-Matic, and Replicator 1, the Ultimaker Original, the Printrbots Simple and Jr., the Tinkerine Ditto, and many others were all made from laser-cut or CNC-cut wood, or sometimes plastic, panels.

There are a few very good reasons why building 3D printer frames using laser cutting and CNC cutting is so popular. First, this type of construction is very inexpensive. The material most commonly used for computer-cut 3D printer frames is MDF or plywood, both of which are very cheap. Second, designing laser cut panels is extremely easy and does not require specialized software as the design work is basically done in two dimensions. Third, building frames from computer-cut panels offers easy construction while also offering a fairly good-looking (but still mostly appealing to hobbyists) finished product. Fourth, 3D printers built with this technique are, in general, safer than those built with member and joint construction because the moving parts and the hot parts of the 3D printers are typically covered by the computer-cut panels.

Last, and this item may be one of the most important benefits on the list, the barriers to entry for making 3D printers with laser-cut or CNC-cut panels is very low. The design work can be done using free or low-cost image editing software. The material, as discussed above, is inexpensive. The technique is extremely popular in the Maker community and so a lot of documentation and help is available online. And many laser cutting services exist, like Ponoko, that offer affordable light manufacturing services that do not require tooling (more on tooling in the next section). These services mean 3D printer designers do not need to purchase a laser cutter or CNC machine themselves. All of this means that a Maker can easily design a 3D printer, and possibly start a business to sell it, with minimal upfront investment.

The low barrier to entry into the 3D printing market created by low-cost manufacturing techniques like laser cutting, coupled with the decrease in cost for electronics and stepper motors, is what has driven the explosive growth in the number of 3D printers on the market.

But, building 3D printer frames from laser-cut CNC-cut panels has its drawbacks as well. First, assembling 3D printer frames designed using this technique can be difficult; the frames end up being a bit like big 3D puzzles. Second, like anything build from wood, tight tolerances and precision manufacturing can be major challenges. Along the same lines, wood does not always offer a frame with the stiffness needed for high-accuracy 3D printing.

Last, and this is definitely a cultural observation rather than a technical one, consumer-grade products are not made from plywood (with the exception of furniture). If you went to the store, would you buy a TV made from plywood? Probably not. Even though it is certain possible to build a wooden TV, people would just not see it as a polished, finished product. 3D printers made from wood, or even acrylic, laser-cut panels are made to be sold to tinkerers, not to designers, and certainly not to a mass market.

Metal Framing and Injection Molding

This brings us to the last major design and construction technique used for building 3D printer frames, injection molding and metal fabrication. As 3D printing has evolved from a hobby only for tinkerers to a technology used by Makers of all kinds, by designers, and by businesses, the 3D printers themselves have evolved to use manufacturing techniques designed to deliver more consumer-facing end products. Another factor pushing 3D printer builders to more traditional manufacturing techniques and away from things like laser-cutting is the need for mass production. As 3D printers are rapidly becoming more popular and sales are growing, it is no longer feasible to manufacture 3D printers with laser cutting. Laser cutting, while it is great for prototyping and small-volume manufacturing, is just too slow and too expensive to produce 3D printer frames in large numbers.

The majority of the most successful enthusiast-level 3D printers today have frames constructed from metal with injection molded parts. Because a welded-together metal frame is not the prettiest thing to keep on a desk, again especially if you are talking about 3D printers for designers or businesses, 3D printer manufacturers will typically apply some kind of decorative facade on their 3D printer frame designs.