Ball Screw 3D Printer – Fixed Bed / Moving Gantry
The original design goal of the Workhorse 3D Printer was to design a large 3d printer that used ball screw on the XYZ-axis and used a fixed bed setup.
- XYZ Ball Screw Driven Motion
- Fixed Bed – Moving Gantry
We later came to the conclusion that a larger 3d printer should be faster in order to reduce the long print times accumulated to print large objects. This conclusion led to the switch to high helix lead screw as the design evolved.
Reducing Moving Mass
Many earlier 3d printers kinematics use the classic “bed-slinger” design that originated from the early Reprap designs. As 3d printer builders and designers gradually pushed the limits of scalability, the classic y-axis traveling bed kinematics became more problematic. Although there are large scale 3d printers that work fine with this mechanical arrangement, they are often using industrial grade hardware such as linear rails and ball screws driven with high end servo motors to maintain print head position at all times, print beds that travel laterally, typically along the Y-axis.
While a simple and cheap solution for kinematics that works for countless desktop 3D printers, this potentially poses a challenge to a large-format 3D printer in that it’s putting a lot of moving mass on one of the two main axes engaged in travel during printing. A large moving mass consisting of the print bed, the carriage it’s riding on, and the increasing weight of the print being deposited on it means greater inertia to overcome with each direction change in that axis.
The timing belt tightness and the linear guides may be rigid enough to handle the inertia, but the frequent direction changes can leave artifacts such as ghosting on 3d printed objects. Not only this, a print that has poor adhesion to the print bed, moving vigorously back and forth through the Y-axis, can risk the success of the print.
These problems are not an issue for large-format 3D printers which use a static bed setup that is stationary and moving only through the Z-axis layer changes. While the motion system is more complex it can maintain the mechanical advantage compared to “bed-slinging” designs.
Large Scale 3D Printing vs Batch Printing
Large volume 3d printers can be considered as a great solution for batch printing, or alternate to multiple smaller 3d printers. A typical sized object or print job can be arranged and stacked for mass production. However, a print farm can complete a large quantity run or job quicker than a single object 3d printed as a batch of 3d printed objects are spread across a number of machines and can decrease the number of failed prints. Failed prints are isolated to a single machine without affecting the rest or potentially ruining the entire job.