One of the benefits of 3D printing for industry and smaller scale makers alike is the ability to do rapid prototyping, simply by printing a copy of a design and then tweaking as necessary. A new kind of printing system speeds up this process even more, by allowing for designs to be edited on the fly – as they're being printed.

A team of Cornell researchers created what they call the "On-the-Fly Print system," that can be paused in the middle of printing an object so that it can be measured or tested. Any needed changes can then be added to the physical object while it is still in the printer.

The system uses a modified "WirePrint" printer, which is different from a conventional 3D printer in that it extrudes quick-hardening plastic meant to create a wire frame skeleton of a solid object instead of printing the whole thing, to assist in rapid prototyping. The Cornell system expands on the concept by allowing for "edits" or other refinements that can be made while printing is in progress.

The printer's nozzle can rotate to add surfaces to any side of an object and it also comes with a cutter to remove material and create cutaways from an object. An extended nozzle also makes it possible to reach beyond the wire-frame outline of an object to make changes within it. A pair of mist-cooling nozzles spray the extruded material as it prints to speed up the hardening process.

Perhaps most importantly, the removable base of the system allows an object to be removed, tested or measured and then put back in to resume printing. A magnet-based alignment system ensures the object returns to its precise original location before printing continues.

A companion CAD software plugin allows a user to work on designing and changing an object while it is printing at the same time.

Check out the video below to see how the system works, using a model of a toy airplane as an example. It begins to print the fuselage of the plane while the wings are still being designed in the CAD program. Once the wing design is ready, it is added to the printable area. After one wing is printed, the user removes it to check the design and then puts it back in the printer and begins designing the cockpit while the second wing is printed, and so on.

"We believe that this approach has the potential to improve the overall quality of the design process," said Cornell graduate student Huaishu Peng, who described the system in a paper presented at the 2016 ACM Conference for Human Computer Interaction.
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