Method and calibrating an inkjet based three-dimensional printing system

1. A three dimensional printing system for fabricating a three dimensional article of manufacture comprising:

an elevator mechanism for supporting a build plate;

a printhead assembly configured to scan over the build plate along a scan axis, the printhead assembly including a printhead and a planarizer arranged along the scan axis whereby the planarizer leads or follows the printhead during a scan, the printhead including an ejector face, the planarizer defining a planarizing plane that is offset downwardly from the ejector face by a trajectory height H T ;

a movement mechanism for scanning the printhead assembly across the build plate; and

a controller configured to:

(a) operate the printhead and the movement mechanism for eject a plurality of base layers of ink onto the build plate while maintaining the build plate at a fixed vertical height until a cumulative thickness of the base layers of ink reach at least a base height H B whereby the planarizing plane is at least proximate to an upper surface of the plurality of base layers;

(b) print a layer of a test pattern onto the base layers;

(c) increment the build plate downwardly by a layer thickness;

(d) repeat b and c for a plurality of test pattern layers until an alignment determination can be made;

(e) receive information based upon the test pattern; and

(f) update machine timing parameters to more accurately align the three dimensional printing system along the scan axis.

2. The three dimensional printing system of claim 1 wherein the planarizer begins to engage the base layers of ink before step (b).

3. The three dimensional printing system of claim 1 wherein the base layers define a support portion formed from a phase change ink.

4. The three dimensional printing system of claim 3 wherein the base layers include a plurality of layers of build material printed over the support portion.

5. The three dimensional printing system of claim 4 wherein the build material is formed from a phase change ink having a higher average melting point than the support portion.

6. The three dimensional printing system of claim 4 wherein the build material is formed from a UV curable ink.

7. The three dimensional printing system of claim 6 wherein the build material includes a phase change component.

8. A method of fabricating a three dimensional article of manufacture comprising:

providing:

an elevator mechanism for supporting a build plate;

a printhead assembly configured to scan over the build plate along a scan axis, the printhead assembly including a printhead and a planarizer arranged along the scan axis whereby the planarizer leads or follows the printhead during a scan, the printhead including an ejector face, the planarizer defining a planarizing plane that is offset downwardly from the ejector face by a trajectory height H T ;

a movement mechanism for scanning the printhead assembly across the build plate;

(a) operating the printhead and the movement mechanism for eject a plurality of base layers of ink onto the build plate while maintaining the build plate at a fixed vertical height until a cumulative thickness of the base layers of ink reach at least a base height H B whereby the planarizing plane is at least proximate to an upper surface of the plurality of base layers;

(b) printing a layer of a test pattern onto the base layers;

(c) incrementing the build plate downwardly by a layer thickness;

(d) repeating b and c for a plurality of test pattern layers until an alignment determination can be made;

(e) receiving information based upon the test pattern; and

(f) updating machine timing parameters to more accurately align the three dimensional printing system along the scan axis.

9. The method of claim 1 wherein the planarizer begins to engage the base layers of ink before step (b).

10. The method of claim 1 wherein the base layers define a support portion formed from a phase change ink.

11. The method of claim 3 wherein the base layers include a plurality of layers of build material printed over the support portion.

12. The method of claim 4 wherein the build material is formed from a phase change ink having a higher average melting point than the support portion.

13. The method of claim 4 wherein the build material is formed from a UV curable ink.

14. A non-transient storage device storing software instructions for a three dimensional printer, the three dimensional printer including an elevator mechanism for supporting a build plate, a printhead assembly configured to scan over the build plate along a scan axis, the printhead assembly including a printhead and a planarizer arranged along the scan axis whereby the planarizer leads or follows the printhead during a scan, the printhead including an ejector face, the planarizer defining a planarizing plane that is offset downwardly from the ejector face by a trajectory height H T , and a movement mechanism for scanning the printhead assembly across the build plate, when executed by a processor, the software instructions are configured to:

(a) operate the printhead and the movement mechanism for eject a plurality of base layers of ink onto the build plate while maintaining the build plate at a fixed vertical height until a cumulative thickness of the base layers of ink reach at least a base height H B whereby the planarizing plane is at least proximate to an upper surface of the plurality of base layers;

(b) print a layer of a test pattern onto the base layers;

(c) increment the build plate downwardly by a layer thickness;

(d) repeat b and c for a plurality of test pattern layers until an alignment determination can be made;

(e) receive information based upon the test pattern; and

(f) update machine timing parameters to more accurately align the three dimensional printing system along the scan axis.

15. The non-transient storage device of claim 14 wherein the planarizer begins to engage the base layers of ink before step (b).