Method for building three-dimensional models with extrusion-based additive manufacturing systems

• US 8,815,141 B2
• Filed: 09/22/2010
• Issued: 08/26/2014
• Est. Priority Date: 09/22/2010
• Status: Active Grant

• Current Assignee: Stratasys Incorporated
• Original Assignee: Stratasys Incorporated
• Inventors: Swanson, William J., Johnson, Kevin C., Hjelsand, Timothy A., Batchelder, J. Samuel
• Primary Examiner(s): Del Sole, Joseph S
• Assistant Examiner(s): Brown, II, David N
• Application Number:
  US12/888,098
• Publication Number:
  US 20120068378A1
• Time in Patent Office: 1,434 Days
• Field of Search: 264/308, 264/401, 425/174.4, 425/375, 425/385
• US Class Current: 264/308
• CPC Class Codes: B29C 2948/926 Flow or feed rate
• CPC Class Codes: B29C 2948/92876 Feeding, melting, plasticising or pumping zones, e.g. the melt itself
• CPC Class Codes: B29C 2948/92904 Die; Nozzle zone
• CPC Class Codes: B29C 48/05 Filamentary, e.g. strands
• CPC Class Codes: B29C 48/266 Means for allowing relative movements between the apparatus parts, e.g. for twisting the extruded article or for moving the die along a surface to be coated
• CPC Class Codes: B29C 48/2694 Intermittent extrusion
• CPC Class Codes: B29C 48/475 using pistons, accumulators or press rams
• CPC Class Codes: B29C 64/106 using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material
• CPC Class Codes: B29C 64/118 using filamentary material being melted, e.g. fused deposition modelling [FDM]
• CPC Class Codes: B33Y 10/00 Processes of additive manufacturing

Abstract

A method for building a three-dimensional model with an extrusion-based additive manufacturing system having an extrusion head, the method comprising depositing a consumable material from a liquefier assembly at an extrusion rate to substantially normalize a meniscus height within the liquefier assembly.

Claims

1. A method for building a three-dimensional model with an extrusion-based additive manufacturing system having an extrusion head, the method comprising:

depositing a consumable material from a liquefier assembly of the extrusion head at one or more extrusion rates while moving the extrusion head along a first portion of a first generated tool path;

reducing the extrusion rate from the one or more extrusion rates to a slower, constant extrusion rate at a predetermined point along the first generated tool path, the predetermined point being before an end point of the first generated tool path;

depositing the consumable material from the liquefier assembly at the reduced, constant extrusion rate while moving the extrusion head along a second portion of the first generated tool path, the second portion bounded by the predetermined point and the end point to substantially normalize a meniscus height within the liquefier assembly before or upon the extrusion head reaching the end point of the first generated tool path;

moving the extrusion head to a successive-layer tool path while substantially maintaining the normalized meniscus height and without performing a purge operation; and

depositing the consumable material from the liquefier assembly while moving the extrusion head along the successive-layer tool path.

2. The method of claim 1, wherein moving the extrusion head along the second portion of the first generated tool path comprises moving the extrusion head for a duration ranging from about 3 seconds to about 20 seconds.

3. The method of claim 2, wherein the duration ranges from about 4 seconds to about 10 seconds.

4. The method of claim 1, wherein the liquefier assembly comprises a stepped cross-sectional area.

5. The method of claim 1, and further comprising:

cooling down the liquefier assembly after the meniscus height is substantially normalized; and

heating up the cooled down liquefier assembly prior to depositing the consumable material from the liquefier assembly while moving the extrusion head along the successive-layer tool path.

6. The method claim 5, wherein heating up the cooled down liquefier assembly comprises heating up the cooled down liquefier assembly to an operating temperature within about 10 seconds.

7. A method for building a three-dimensional model with an extrusion-based additive manufacturing system having an extrusion head, the method comprising:

generating tool paths for building a plurality of layers of the three-dimensional model, wherein each of the generated tool paths comprises a start point and an end point;

generating a set point between the start point and the end point for at least a first tool path of the generated tool paths;

depositing a consumable material from a liquefier assembly of the extrusion head at one or more extrusion rates while moving the extrusion head along the first tool path between the start point and the set point;

depositing the consumable material from the liquefier assembly at a reduced and constant extrusion rate while moving the extrusion head along the first tool path between the set point and the end point to substantially normalize a meniscus height within the liquefier assembly; and

moving the extrusion head to a successive-layer tool path of the generated tool paths while substantially maintaining the normalized meniscus height and without performing a purge operation; and

depositing the consumable material from the liquefier assembly while moving the extrusion head along the successive-layer tool path.

8. The method of claim 7, wherein a location of the set point relative to the end point along the first tool path defines a time period of movement of the extrusion head ranging from about 3 seconds to about 20 seconds.

9. The method of claim 8, wherein the time period ranges from about 4 seconds to about 10 seconds.

10. The method of claim 7, wherein the liquefier assembly comprises:

a liquefier tube having an inlet end, and outlet end, and a first inner cross-sectional area;

a hollow liner having an outlet end disposed at least partially within the liquefier tube at a location between the inlet end of the liquefier tube and the outlet end of the liquefier tube, and having a second inner cross-sectional area that is less than the first inner cross-sectional area to define a shoulder; and

an extrusion tip secured to the liquefier tube at a offset location from the hollow liner.

11. The method of claim 7, and further comprising:

cooling down the first liquefier assembly after reaching the end point of the first tool path;

heating up the cooled down liquefier assembly prior to depositing the consumable material from the liquefier assembly while moving the extrusion head along the successive-layer tool path.

12. The method of claim 7, wherein the liquefier assembly comprises a stepped cross-sectional area.

13. A method for building a three-dimensional model with an extrusion-based additive manufacturing system having an extrusion head, the method comprising:

feeding a consumable material filament into a liquefier assembly of the extrusion head;

melting the consumable material filament in the liquefier to form a melt of molten material, wherein the melt defines a meniscus in the liquefier tube;

extruding the melt out of the liquefier assembly;

moving the extrusion head along a first tool path while extruding the melt;

restricting movement of the meniscus along a longitudinal length of the liquefier assembly while moving the extrusion head along the first tool path, such that a height of the meniscus within the liquefier assembly is substantially normalized upon reaching an endpoint of the first tool path;

moving the extrusion head to a successive-layer tool path while substantially maintaining the normalized meniscus height and without performing a purge operation; and

depositing the melt from the liquefier assembly while moving the extrusion head along the successive-layer tool path.

14. The method of claim 13, wherein the liquefier assembly comprises:

a liquefier tube having an inlet end, and outlet end, and a first inner cross-sectional area;

a hollow liner having an outlet end disposed at least partially within the liquefier tube at a location between the inlet end of the liquefier tube and the outlet end of the liquefier tube, and having a second inner cross-sectional area that is less than the first inner cross-sectional area to define a shoulder; and

an extrusion tip secured to the liquefier tube at a offset location from the hollow liner.

15. The method of claim 14, wherein restricting movement of the meniscus along the longitudinal length of the liquefier assembly comprises at least partially blocking movement of the meniscus with the shoulder.

16. The method of claim 15, and further comprising:

generating a set point along the first tool path; and

depositing the extruded melt at a constant extrusion rate while moving the extrusion head along the first tool path between the set point and the end point of the first tool path, wherein the constant extrusion rate causes the height of the meniscus within liquefier assembly to substantially normalize at the shoulder.

17. The method of claim 16, wherein the set point and the constant extrusion rate are determined based on a height of the shoulder along the longitudinal length of the liquefier assembly.