US 11,654,614 B2
Method of printing semi-crystalline materials utilizing extrusion based additive manufacturing system
Vittorio L. Jaker, Chanhassen, MN (US); Paul Leavitt, Minneapolis, MN (US); and Benjamin N. Dunn, St. Louis Park, MN (US)
Assigned to Stratasys, Inc., Eden Prairie, MN (US)
Filed by Stratasys, Inc., Eden Prairie, MN (US)
Filed on Jul. 23, 2018, as Appl. No. 16/42,568.
Prior Publication US 2020/0023574 A1, Jan. 23, 2020
Int. Cl. B29C 64/118 (2017.01); B29C 64/245 (2017.01); B29C 64/393 (2017.01); B33Y 70/00 (2020.01); B29K 71/00 (2006.01); B33Y 10/00 (2015.01); B33Y 50/02 (2015.01)
CPC B29C 64/118 (2017.08) [B29C 64/245 (2017.08); B29C 64/393 (2017.08); B29K 2071/00 (2013.01); B29K 2995/004 (2013.01); B33Y 10/00 (2014.12); B33Y 50/02 (2014.12); B33Y 70/00 (2014.12)] 24 Claims
OG exemplary drawing
 
1. A method of 3D printing a part with an extrusion-based additive manufacturing system, the method comprising:
providing a filament having a semi-crystalline material as a majority component of a polymeric matrix into a liquefier, the liquefier comprising a liquefier tube having an inlet end and a heated outlet end and an extrusion tip at the outlet end, the liquefier tube having an overall length between the inlet end and the outlet end, wherein an upper portion of the liquefier tube adjacent the inlet end has a first length and a first cross-sectional area substantially perpendicular to a longitudinal axis, a lower portion of the liquefier tube adjacent the outlet end has a second length and a second cross-sectional area substantially perpendicular to the longitudinal axis, wherein the first cross-sectional area is greater than the second cross-sectional area such that a first nominal distance from the outer surface of the filament to a first surface of the upper portion measured substantially perpendicular to the longitudinal axis is about 1.5 to about 2.5 times greater than a second nominal distance from the outer surface of the filament to a second surface of the lower portion measured substantially perpendicular to the longitudinal axis, and wherein the extrusion tip includes an extrusion port having a third cross-sectional area that that is less than the second cross-sectional area and the extrusion tip includes a downwardly slope surfaces that slopes downwardly to the extrusion port, and wherein a shoulder includes a downwardly sloping surface in a range from about 10° to about 60°, and a heating element positioned about the liquefier tube from proximate the heated outlet end to a location above the shoulder wherein the shoulder transitions the first cross-sectional area and the second cross-sectional area is located in a melt zone of the liquefier, wherein the melt zone extends substantially along a length of the heating element;
advancing the filament into the melt zone the liquefier at a selected rate based upon a desired extrusion rate;
melting the filament within the melt zone by imparting heat into the filament with the heating element to form a melt pool capped by a meniscus located above the shoulder during at least a portion of the printing of the part; and
printing the part in a series of layers by extruding the melted filament having a majority of semi-crystalline material from the melt pool through the extrusion tip along tool paths representative of the part by driving the unmelted filament into the melt pool at the selected rate to force the melted material through the extrusion port along the tool paths, wherein utilizing the liquefier tube with the upper portion above the lower portion causes the meniscus to be lower relative to a liquefier having a constant diameter such that shear forces are decreased proximate the meniscus allows the series of layers to be more accurately printed at varying flow rates relative to the liquefier having the constant diameter.