Extrusion method for three dimensional modeling

• US 6,998,087 B1
• Filed: 05/10/2004
• Issued: 02/14/2006
• Est. Priority Date: 04/30/2001
• Status: Expired due to Term

• Current Assignee: Stratasys Incorporated
• Original Assignee: Stratasys Incorporated
• Inventors: Batchelder, John Samuel, Bosveld, Michael David, Hanson, Jeffery J.
• Primary Examiner(s): Tentoni, Leo B.
• Application Number:
  US10/842,269
• Time in Patent Office: 645 Days
• Field of Search: 264/40.7, 264/308, 264/401
• US Class Current: 264/308
• CPC Class Codes: B29C 48/023 Extruding materials comprising incompatible ingredients
• CPC Class Codes: B29C 48/03 characterised by the shape of the extruded material at extrusion
• CPC Class Codes: B29C 48/05 Filamentary, e.g. strands
• CPC Class Codes: B29C 48/345 Extrusion nozzles comprising two or more adjacently arranged ports, for simultaneously extruding multiple strands, e.g. for pelletising
• CPC Class Codes: B29C 48/86 at the nozzle zone
• CPC Class Codes: B29C 48/865 Heating
• 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 30/00 Apparatus for additive manufacturing; Details thereof or accessories therefor
• CPC Class Codes: B33Y 50/02 for controlling or regulating additive manufacturing processes

Abstract

A multi-tip extrusion method and apparatus for building a three-dimensional object deposits modeling materials from distinct supply sources, each in a layerwise predetermined pattern, from dispensers having co-planar dispensing tips. The tip spacing is controlled so that a road of material extruded by a leading one of the tips will cool and shrink from the plane of the tips before a trailing one of the tips passes over the road. In this manner, smearing of the road by a trailing one of the tips is avoided.

Claims

1. A layered deposition method for building a three-dimensional object comprising the steps of:

providing a first thermally solidifiable modeling material to a first dispenser, the first dispenser having a first dispensing tip which has a downward planar face;

providing a second thermally solidifiable modeling material to a second dispenser, the second dispenser having a second dispensing tip maintained in a fixed vertical position relative to the first dispensing tip, the second dispensing tip having a downward face approximately co-planar with the face of the first dispensing tip;

dispensing roads of the first material in molten form from the tip of the first dispenser onto a base contained in a build environment having a temperature lower than an extrudate temperature of the first and second material, while moving said first dispensing tip in a predetermined pattern within a layer above the base;

dispensing roads of the second material in molten form from the tip of the second dispenser while moving said second dispensing tip in a predetermined pattern within the same layer; and

controlling the dispensers such that a trailing one of the first and second dispensers lags behind a leading one of the first and second dispensers by no less than a minimum transit time Δ

t, defined as the time for a road deposited by the leading dispenser to sufficiently shrink due exclusively to cooling so that the tip of the trailing dispenser does not drag across and smear the road.

2. The method of claim 1, wherein the minimum transit time Δ

t is given by the equation $\mathrm{\Delta <br><br>}<br><br><br><br>t=\frac{0.3<br><br>h^2}{K_e},$

where h is the height of the deposited road and K_e is the thermal diffusivity of the material forming the road.

3. The method of claim 2, wherein the dispensing tips accelerate and decelerate through paths comprising multiple vertices and have a minimum vertex velocity v_min and a maximum acceleration a_max, and wherein the dispensing tips are spaced apart a minimum spacing s characterized by the relationship $v_{\min }$

⁢

Δ

⁢

⁢

t+12⁢

⁢

amax⁢

⁢

Δ

⁢

⁢

t2≤

s.

4. A layered deposition method for building a three-dimensional object comprising the steps of:

providing a first thermally solidifiable modeling material to a first dispenser carried by an extrusion head, the first dispenser having a first dispensing tip which has a downward planar face positioned in approximately a z-plane;

providing a second thermally solidifiable modeling material to a second dispenser carried by the extrusion head, the second dispenser having a second dispensing tip maintained in a fixed vertical position relative to the first dispensing tip, the second dispensing tip having a downward face spaced apart a distance s from the face of the first dispensing tip and approximately co-planar with the face of the first dispensing tip;

moving the extrusion head at a controlled velocity in a layerwise predetermined pattern above a base contained in a build environment having a temperature lower than an extrudate temperature of the first and second material

alternately dispensing roads of the first material in molten form from the tip of the first dispenser and dispensing roads of the second material in molten form from the tip of the second dispenser while the extrusion head is moved in the predetermined pattern within a layer; and

controlling the velocity of the extrusion head such that a road deposited in the layer by a leading one of the first and second dispensing tips shrinks from the plane of the tips due exclusively to cooling before a trailing one of the first and second dispensing tips passes over the road, so that the trailing dispensing tip does not smear the road.

5. The method of claim 4, wherein the extrusion head is controlled so that a minimum transit time Δ

t elapses between deposition of the road by the leading dispensing tip and the passing of the trailing dispensing tip, wherein Δ

t is a function of the height of the deposited road the thermal diffusivity of the material forming the road.

6. The method of claim 5, wherein the dispensing tips accelerate and decelerate through paths comprising multiple vertices and have a minimum vertex velocity v_min and a maximum acceleration a_max, and wherein the dispensing tips are spaced apart a minimum spacing s characterized by the relationship $v_{\min }$

⁢

Δ

⁢

⁢

t+12⁢

⁢

amax⁢

⁢

Δ

⁢

⁢

t2≤

s.

7. A method for building a three-dimensional object in a modeling machine of the type which builds three-dimensional objects in layers by depositing thermally solidifiable modeling material as roads of molten material into a build environment having a temperature lower than an extrudate temperature of the material, and from an extrusion head that moves at a known speed in a predetermined cross-sectional pattern, the method comprising:

providing a first thermally solidifiable modeling material to a first dispenser carried by the extrusion head, the first dispenser having a dispensing tip which has a downward planar face;

providing a second thermally solidifiable modeling material to a second dispenser carried by the extrusion head, the second dispenser having a dispensing tip maintained in a fixed vertical position relative to the tip of the first dispenser, the dispensing tip of the second dispenser having a downward face spaced apart a distance s from the tip face of the first dispenser and approximately co-planar with the tip face of the first dispenser;

dispensing roads of the first material in molten form from the tip of the first dispenser, without using a planarizer to shape the roads;

dispensing roads of the second material in molten form from the tip of the second dispenser, without using a planarizer to shape the roads;

moving the extrusion head in a layer according to a predetermined pattern, wherein each of the first and second dispensers at different times act as a leading and a trailing dispenser; and

controlling the velocity of the extrusion head such that the trailing one of the first and second dispensers lags behind the leading one of the first and second dispensers by no less than a minimum transit time Δ

t, wherein Δ

t is the time for a road deposited by the leading dispenser to sufficiently shrink due to cooling so that the tip of the trailing dispenser does not drag across and smear the road.

8. The method of claim 7, wherein the minimum transit time Δ

t is given by the equation $\mathrm{\Delta <br><br>}<br><br><br><br>t=\frac{0.3<br><br>h^2}{K_e},$

where h is the height of the deposited road and K_e is the thermal diffusivity of the material forming the road.

9. The method of claim 8, wherein the dispensing tips accelerate and decelerate through paths comprising multiple vertices and have a minimum vertex velocity v_min and a maximum acceleration a_max, and wherein the dispensing tips are spaced apart a minimum spacing s characterized by the relationship $v_{\min }$

⁢

Δ

⁢

⁢

t+12⁢

⁢

amax⁢

⁢

Δ

⁢

⁢

t2≤

s.

10. A layered deposition method for forming a three-dimensional object, comprising the steps of:

moving an extrusion head at a controlled velocity in a layer, said extrusion head carrying first and second adjacent dispensers;

depositing a thermally solidifiable material in molten form in a road from a downward facing tip of the first dispenser into a build envelope having a temperature lower than an extrudate temperature of the material, while the extrusion head is moved; and

controlling the velocity of the extrusion head such that when the second dispenser trails the first dispenser, a downward facing tip of the second dispenser approximately co-planar with the tip of the first dispenser lags behind the tip of the first dispenser by no less than a minimum transit time Δ

t, defined as the time for the deposited road to sufficiently shrink from the plane of the tips due to cooling so that the tip of the second dispenser does not smear the road.

11. The method of claim 10, wherein the minimum transit time Δ

t is given by the equation $\mathrm{\Delta <br><br>}<br><br><br><br>t=\frac{0.3<br><br>h^2}{K_e},$

where h is the height of the deposited road and K_e is the thermal diffusivity of the material.

12. The method of claim 11, wherein the first dispenser accelerates and decelerates through paths comprising multiple vertices and has a minimum vertex velocity v_min and a maximum acceleration a_max, and wherein the dispensing tips are spaced apart a minimum spacing s characterized by the relationship $v_{\min }$

⁢

Δ

⁢

⁢

t+12⁢

⁢

amax⁢

⁢

Δ

⁢

⁢

t2≤

s.

13. The process of claim 10, wherein the extrusion head further carries a third dispenser adjacent the first dispenser, and further comprising controlling the velocity of the extrusion head such that when third dispenser trails the first dispenser, a downward facing tip of the third dispenser approximately co-planar with the tip of the first dispenser lags behind the tip of the first dispenser by no less than the minimum transit time Δ

t.

14. A layered deposition method for forming a three-dimensional object, comprising the steps of:

moving first and second adjacent dispensers at a controlled velocity in a a layer, said dispensers having downward facing co-planar dispensing tips;

depositing a thermally solidifiable material having a thermal diffusivity K_e in molten form in a road having a height h from the tip of the first dispenser while the first dispenser moves in a predetermined pattern, into a build envelope having a temperature lower than an extrudate temperature of the material; and

controlling the dispensers such that the tip of the second dispenser does not pass over the road deposited by the first dispenser until the road shrinks due to cooling from the plane of the tips, such that the tip of the second dispenser does not smear the road.

15. The method of claim 14, wherein the controlling step comprises trailing the tip of the first dispenser with the tip of the second dispenser at a distance of no less than s, wherein s is a function of the road height h and the thermal diffusivity K_e of the material forming the road.

16. The method of claim 15, wherein s is given by v_min$\Delta$

⁢

⁢

t+12⁢

⁢

amax⁢

⁢

Δ

⁢

⁢

t2,

wherein the first dispenser accelerates and decelerates through paths comprising multiple vertices with a minimum velocity at a vertex v_min and a maximum

acceleration a_max, and Δ

t is given by the equation $\mathrm{\Delta <br><br>}<br><br><br><br>t=\frac{0.3<br><br>h^2}{K_e}.$

17. The method of claim 14, wherein the controlling step comprises trailing the tip of the first dispenser with the tip of the second dispenser by a minimum transit time Δ

t, calculated as a function of road height h and the thermal diffusivity K_e of the material forming the road.

18. The method of claim 17, wherein the minimum transit time Δ

t is given by the equation $\mathrm{\Delta <br><br>}<br><br><br><br>t=\frac{0.3<br><br>h^2}{K_e}.$