Color switching for three-dimensional printing
By reversing the direction of a first build material fed into an extruder, the first build material can be wholly or partially evacuated from the extruder before a second material is introduced. This approach mitigates transition artifacts and permits faster, more complete changes from one build material to another.
1. A method comprising:
providing a three-dimensional printer having an extruder with a first input port, a second input port, an extrusion port, and a chamber coupling the first input port, the second input port, and the extrusion port in fluid communication;
driving a first build material through the first input port until the first build material extrudes through the extrusion port;
withdrawing the first build material through the first input port a predetermined amount, wherein the predetermined amount is selected to move a material transition region between the first build material and a second build material out of the chamber but not enough to completely withdraw the first build material from the extruder; and
driving the second build material through the second input port until the second build material extrudes through the extrusion port.
2. The method of claim 1 further comprising heating the chamber to liquefy at least one of the first build material and the second build material.
3. The method of claim 1 wherein the first build material is a different color than the second build material.
4. The method of claim 1 wherein the first build material is of a different type than the second build material.
5. The method of claim 1 wherein the first build material is a plastic.
6. The method of claim 1 wherein the first build material is one or more of ABS, PLA, and PCL.
7. The method of claim 1 wherein the predetermined amount includes an amount of the first build material displacing at least one half the volume of the chamber.
8. The method of claim 1 wherein the predetermined amount includes an amount of the first build material displacing at least the volume of the chamber.
9. The method of claim 1 further comprising withdrawing the first build material concurrently with driving the second build material.
10. The method of claim 1 further comprising withdrawing the second build material through the second input port by a second predetermined amount and driving the first build material through the first input port until the first build material extrudes through the extrusion port.