Techniques for force sensing in additive fabrication and related systems and methods

1. An additive fabrication device configured to form layers of solid material on a build platform, the additive fabrication device comprising:

a container;

a build platform;

at least one force sensor configured to measure a force applied to the build platform; and

at least one processor configured to:

form a layer of material in contact with the container, and in contact with the build platform and/or a previously formed layer of material;

determine, using the at least one force sensor, a plurality of force measurements during separation of the layer of material from the container;

determine a length of time taken between initiating a separation of the layer of material from the container and completing the separation based on the plurality of force measurements; and

control motion of the build platform based at least in part on the measured length of time taken to separate the layer of material from the container.

2. The additive fabrication device of claim 1 , wherein controlling the motion of the build platform based at least in part on the determined length of time taken to separate the layer of material from the container comprises positioning the build platform so that the layer of material is at a predetermined distance from the container.

3. The additive fabrication device of claim 2 , wherein controlling the motion of the build platform based at least in part on the determined length of time taken to separate the layer of material from the container further comprises waiting for a time period subsequent to positioning the build platform so that the layer of material is at a predetermined distance from the container, wherein at least one processor is further configured to determine the time period based at least in part on the determined length of time taken to separate the layer of material from the container.

4. The additive fabrication device of claim 1 , wherein the at least one processor is further configured to select a sequence from amongst a plurality of sequences of predetermined motions of the build platform based at least in part on the determined length of time taken to separate the layer of material from the container, and wherein controlling the motion of the build platform based at least in part on the determined length of time taken to separate the layer of material from the container comprises controlling the motion of the build platform in accordance with the selected sequence.

5. The additive fabrication device of claim 1 , further comprising a wiper configured to move through the container, wherein the at least one processor is further configured to control motion of the wiper based at least in part on the determined length of time taken to separate the layer of material from the container.

6. The additive fabrication device of claim 1 , further comprising:

an actuator arranged to move the build platform linearly in a first direction; and

a deformable mounting structure on which the actuator is mounted, the deformable mounting structure arranged to allow the actuator to move in the first direction when the deformable mounting structure deforms,

wherein the at least one force sensor is configured to measure the force applied to the build platform by detecting an amount of deformation of the deformable mounting structure.

7. The additive fabrication device of claim 6 , wherein the deformable mounting structure is mounted to at least one rigid structure.

8. The additive fabrication device of claim 7 , wherein the deformable mounting structure is mounted to at least a first rigid structure and a second rigid structure such that the actuator is mounted to the deformable mounting structure between the first rigid structure and the second rigid structure.

9. The additive fabrication device of claim 6 , wherein the at least one force sensor includes at least one inductive sensor.

10. The additive fabrication device of claim 9 , further comprising an inductive reference target attached to the deformable mounting structure.

11. The additive fabrication device of claim 6 , wherein the deformable mounting structure comprises a metal sheet.

12. The additive fabrication device of claim 6 , further comprising a threaded rod to which the build platform is coupled, and wherein the actuator is arranged to rotate the threaded rod about its axis.

13. The additive fabrication device of claim 1 , wherein determining the length of time taken to separate the layer of material from the container comprises identifying, using the at least one processor, a moment at which the layer of material separates from the container by identifying a spike in a plurality of force measurements taken over time by the at least one force sensor.

14. The additive fabrication device of claim 1 , wherein determining the length of time taken to separate the layer of material from the container comprises identifying, using the at least one processor, a moment at which the layer of material separates from the container by detecting when force measurements taken over time by the at least one force sensor are within a predetermined range of force measurements.

15. A method of operating an additive fabrication device configured to form layers of solid material on a build platform, each layer of material being formed in contact with a container in addition to the build platform and/or a previously formed layer of material, the method comprising:

forming a layer of material in contact with the container, and in contact with the build platform and/or a previously formed layer of material;

generating, using at least one force sensor, a plurality of force measurements during separation of the layer of material from the container;

measuring a length of time taken between initiating a separation of the layer of material from the container and completing the separation based on the plurality of force measurements; and

controlling motion of the build platform based at least in part on the measured length of time taken to separate the layer of material from the container.

16. The method of claim 15 , wherein controlling the motion of the build platform based at least in part on the measured length of time taken to separate the layer of material from the container comprises positioning the build platform so that the layer of material is at a predetermined distance from the container.

17. The method of claim 16 , wherein controlling the motion of the build platform based at least in part on the measured length of time taken to separate the layer of material from the container further comprises waiting for a time period subsequent to positioning the build platform so that the layer of material is at a predetermined distance from the container, and wherein the method further comprises determining, using at least one processor, the time period based at least in part on the measured length of time taken to separate the layer of material from the container.

18. The method of claim 15 , further comprising, selecting, using at least one processor, a sequence from amongst a plurality of sequences of predetermined motions of the build platform based at least in part on the measured length of time taken to separate the layer of material from the container, and controlling the motion of the build platform in accordance with the selected sequence.

19. The method of claim 15 , wherein measuring, using the at least one force sensor, the length of time taken to separate the layer of material from the container comprises identifying, using at least one processor, a moment at which the layer of material separates from the container by identifying a spike in a plurality of force measurements taken over time by the at least one force sensor.

20. The method of claim 15 , wherein measuring, using the at least one force sensor, the length of time taken to separate the layer of material from the container comprises identifying, using at least one processor, a moment at which the layer of material separates from the container by detecting when force measurements taken over time by the at least one force sensor are within a predetermined range of force measurements.

21. The additive fabrication device of claim 1 , wherein the plurality of force measurements are generated at least in a time period between initiating separation of the layer of material from the container and completion of said separation.