Why is Rigidity Important for 3D Printers?
One of the most important, and yet one of the least discussed, design considerations for 3D printers is rigidity. Every 3D printer product page lists things like layer height, linear speed, and build volume. These specifications are extremely important, but rigidity is more important still. Rigidity plays a critical role in a 3D printer’s accuracy and precision.
Most of the time, the design of the linear motion system gets all the credit for achieving highly accurate prints. It is true that a 3D printer’s linear motion system must be intelligently designed in order to get great accuracy, but a 3D printer frame lacking in rigidity can cause much greater errors in printing accuracy than problems with the linear motion system.
The Importance of Rigidity
3D printers are basically three-dimensional positioning systems. 3D printers are tricky to design though because they require fairly extreme accuracy. If you are trying to design a 3D printer with a positional accuracy of at least 0.1mm in any direction, the frame cannot flex at all or no matter how well the linear motion system is designed, the accuracy of the printer will suffer.
Take a look at the .gif below. The wooden 3D printer shown first is the PrintrBot Simple , and the second printer is the PrintrBot Simple Metal.
Although manually flexing the frame to move the extruder on the wooden Simple certainly represents an extreme case, you can see that the wooden frame allows the extruder to move around quite a bit. Even under the force exerted by the motors during printing – which is admittedly much less force than a person can exert on the frame – the frame will likely still move more than 0.1mm. This is why the accuracy of the PrintrBot Simple Metal is something like two or three times the accuracy of the wooden version, even though both prints have almost exactly the same linear motion system and components.
This is also why there has been a large shift over the past several years from 3D printers built from MDF, acrylic, or other laser-cut materials, to 3D printers made from metal or stiff composites.
Even though it is more difficult and more expensive for 3D printing startups to make their 3D printers from metal instead of wood or plastic, the metal frames offer a level of rigidity that MDF frames cannot match. This increased rigidity allows 3D printers made from metals or composites to be more accurate than older printers made from laser cut parts, even when the linear motion systems are almost the same.