Filament feeding device having a capacitive filament displacement sensor for use in additive manufacturing system

Patent metadata

Field	Value
Publication number	US-10421268-B2
Application number	US-201615355441-A
Country	US
Kind code	B2
Filing date	Nov 18, 2016
Priority date	Nov 18, 2015
Publication date	Sep 24, 2019
Grant date	Sep 24, 2019

Abstract

A filament feeding device includes a drive mechanism and a displacement sensor. The drive mechanism is configured to feed a filament along a feed path. The displacement sensor is positioned adjacent the feed path and is configured to determine a velocity and direction in which the filament is fed along the feed path based on at least two capacitance measurements that vary in response to movement of the filament along the feed path.

First claim

The invention claimed is:

1. A filament feeding device for use in feeding a filament into a liquefier assembly of an extrusion-based digital manufacturing system, the filament feeding assembly comprising:
a drive mechanism configured to feed a filament along a feed path; and
a displacement sensor adjacent the feed path, the displacement sensor comprising a first sense electrode positioned adjacent the feed path in a first location and configured to sense a first capacitance, and a second sense electrode positioned adjacent the feed path in a second location spaced from the first location and configured to sense a second capacitance, wherein the displacement sensor is configured to determine a velocity and direction in which the filament is fed along the feed path based on at least the first and the second sensed capacitances.

2. The filament feeding device according to claim 1 , wherein the first sense electrode is a first parallel-plate capacitor and the second sense electrode is a second parallel-plate capacitor.

3. The filament feeding device according to claim 2 , wherein:
the displacement sensor comprises at least one excitation electrode; and
the first parallel-plate capacitor includes a first sense electrode and one of the at least one excitation electrode; and
the second parallel-plate capacitor includes a second sense electrode and one of the at least one excitation electrode.

4. The filament feeding device according to claim 3 , wherein the first and second sensed capacitances are spaced a first distance apart that is different from a second periodic distance between a repeating surface pattern on the filament such that velocity of the filament can be determined through quadrature analysis.

5. The filament feeding device according to claim 4 , wherein the first and second sensed capacitances vary in response to movement of the surface pattern on the filament along the feed path relative to the first and second sense electrodes.

6. The filament feeding device according to claim 5 , wherein the surface pattern of the filament comprises a series of detents in the surface of the filament having the periodic distance.

7. The filament feeding device according to claim 6 , wherein the drive mechanism comprises a filament drive having a textured engagement surface that engages the filament and creates the surface pattern in the filament having the periodic distance.

8. The filament feeding device according to claim 7 , wherein the filament drive comprises a drive wheel having teeth that engage the filament and create the pattern in the surface of the filament, and the drive mechanism comprises a motor configured to drive rotation of the drive wheel.

9. The filament feeding device according to claim 4 , wherein the first distance is different than a whole number of the second periodic distance.

10. The filament feeding device according to claim 9 , wherein:
the surface pattern comprises a series of valleys in the surface of the filament that are displaced from each other along the longitudinal axis of the filament; and
the first and second sense electrodes are displaced along the longitudinal axis such that when the first sense electrode is positioned at a location along the longitudinal axis corresponding to one of the valleys, the second sense electrode is positioned at a location along the longitudinal axis corresponding to a position in the pattern that is displaced from the valleys.

11. The filament feeding device according to claim 10 , wherein the first sense electrode is positioned at a location along the longitudinal axis corresponding to one of the valleys of the pattern when the second sense electrode is positioned at a location along the longitudinal axis between two adjacent valleys.

12. The filament feeding device according to claim 3 , and further comprising:
a housing having the feed path extending therethrough, the housing comprising first and second spaced apart openings in communication with the feed path; and
the first and second sense electrodes are suspended over the first and second openings in the housing.

13. The filament feeding device according to claim 12 , wherein the housing comprises a liquefier tube, wherein the liquefier tube includes a portion of the feed path.

Assignees

• Stratasys Inc

Inventors

• Batchelder J Samuel
• Swanson William J

Classifications

• B29C64/40

  Structures for supporting 3D objects during manufacture and intended to be sacrificed after completion thereof · CPC title

• B29C64/209

  Heads; Nozzles · CPC title

• B29C64/118

  using filamentary material being melted, e.g. fused deposition modelling [FDM] · CPC title

• B29C64/393

  for controlling or regulating additive manufacturing processes · CPC title

• B29C64/321 Primary

  Feeding · CPC title