There are multiple actuators that could be used to autonomously eject print jobs. I have researched different methods, all of which have their own pros and cons. I hope to give a brief synopsis of each design below.

Eject Part with Shear

3D print jobs can be ejected with a mechanical shear. A thin wedge can be gradually moved beneath the 3D printed object to remove the part from the print bed. A motorized shear is a relatively simple module to design and build. However, the shear is unlikely to work on large print jobs. The more contact area between the print job and print bed, the more force will need to be applied by the shear to separate the two. Therefore, print jobs with large footprints will be difficult to remove with a shear.

Some 3D printers already employ a pushing method to eject 3D printed parts. It is a common technique to push the print head of a 3D printer against a printed part. This method works for printed parts that have low contact area with the print bed, such as a thin bracelet.  

[Figure 1: Ultimaker Ejecting Bracelet]

With this method, users should be concerned by the amount of force being applied by the sensitive stepper motors. Additionally, the movement is likely to defect the calibration in that axis of the printer.

Eject Part by Compressing Plate

Many 3D printing companies are moving towards spring plate beds. To remove parts, users flex the bed to remove the print job. This motion can be automated with a robotic manipulator. The design of the manipulator would be significantly more complex than the robotic shear. Additionally, constant bending of the metal would gradually distort the shape of the bed.

[Figure 2: Spring Plate Part Removal]

Remove entire Build Plate

Many 3D printing factories automate part ejection with removable build plates. In this technique, a removable build plate is attached to every 3D printer. The build plate is generally held in place with magnets. After a 3D printer is finish printing a part, a robotic arm removes the entire build plate from the printer. The robotic arm then places an empty build plate in the printer and the 3D printer prints its next job. Workers are required to actually separate the printed part from the printer. While this solution does improve the efficiency of a fleet of 3D printers, it does not fully automate part ejection. Additionally, the print capacity of the 3D printers is limited by the number of empty build plates available. Furthermore, the machinery required to implement this solution is extremely expensive and requires a large footprint to operate in.

[Figure 3: Print Bed Removal with Robotic Arm]

Eject Part with Conveyor Belt

Instead of 3D printers printing parts on a static plate, parts can be printed on a conveyor belt. After a print job is completed, the conveyor belt can roll off the part and the 3D printer can start printing the next job. This solution allows a printer to print an infinite stream of parts. Additionally, the conveyor belt system can be compact and easily integrated into any 3D printer design. A conveyor belt mechanism is not overly complex.

The WorkHorse 3D Printer will use a conveyor belt system to automatically eject print jobs.