Maintenance on a hand-held printer

1. A method of performing maintenance on a printer that is manually moved across a surface to print a user-desired output image, said method comprising:

generating print instructions for said user-desired output image that dictate when and where each of a plurality of nozzles will fire to print said user-desired output image;

determining, while printing said user-desired output image, which of said plurality of nozzles requires a maintenance action; and

including in said print instructions at least one instruction related to a performance of said maintenance action, said at least one instruction related to the performance of said maintenance action comprising including a print instruction that causes a nozzle to fire in a high density region of said image at least once to clear said nozzle with said maintenance action being performed during printing of the user-desired output image.

2. The method of claim 1 , wherein the step of determining which of said plurality of nozzles requires a maintenance action comprises determining if a time period between anticipated firings of a nozzle is greater than a predetermined period.

3. The method of claim 1 , wherein said step of determining which of said plurality of nozzles requires a maintenance action comprises assuming a minimal user printing speed to determine a time period between firings of each nozzle.

4. The method of claim 1 , wherein said step of generating print instructions occurs on an external device and said print instructions are transferred electronically to said printer.

5. The method of claim 4 , further comprising storing said print instructions on a computer readable media and inserting said computer readable media into said printer.

6. The method of claim 1 , wherein said step of determining which of a plurality of nozzles require maintenance comprises tracking a drop count for said plurality nozzles and identifying which of said drop counts exceed a predetermined threshold.

7. The method of claim 1 , wherein said at least one instruction related to a performance of a maintenance action comprises an instruction that causes a non-nucleating fire of a nozzle.

8. The method of claim 7 , wherein said step of determining which of said plurality of nozzles requires a maintenance action comprises monitoring a predicted thermal temperature of each of said plurality of nozzles.

9. The method of claim 1 , wherein said step of determining which of said plurality of nozzles requires maintenance comprises utilizing an algorithm for each of the plurality of nozzles as follows:

if(NozzleIdleTime> 15)

{

P = k 1 (p density ) + k 2 (p others ) + k 3 (p temp ) +

k 4 (p time );

if(P > 0.8)

{

FireNozzle( );

}

}

wherein P is a probability to fire a particular nozzle, p dnsity is a density of a swath firing around a dot location, p others is a number of other maintenance dots at that time, p time is an idle time of the particular nozzle, p temp is a parameter associated with maintaining a predetermined target printhead temperature, and k 1 , k 2 , k 3 and k 4 are weightings on said p dnsity , p others , p temp , and p time values.

10. A method of performing maintenance on a hand-held printer, said hand-held printer including a printhead with a plurality of nozzles and adapted to print a user-desired output image as said printer is manually moved across a surface, comprising:

generating a first set of print instructions that cause said hand-held printer to print said user-desired output image, said print instructions identifying a firing order for said plurality of nozzles;

analyzing, while printing said user-desired output image, said firing order for at least some of said plurality of nozzles to determine when one or more of said plurality of nozzles are likely to require a maintenance action; and

modifying said first set of print instructions such that said hand-held printer will perform at least one maintenance action as said hand-held printer is manually moved across said surface while printing said user-desired output image.

11. The method of claim 10 , wherein said step of analyzing said firing order comprises tracking a number of times each of said plurality of nozzles is fired.

12. The method of claim 10 , wherein said step of analyzing said firing order comprises calculating an estimated temperature of at least one of said plurality of nozzles as said image is printed.

13. The method of claim 12 , wherein said step of analyzing said firing order comprises calculating a thermal loss of at least one of said nozzles as a function of time.

14. A method of performing maintenance on a printer that is manually moved across a surface to print an image, said method comprising:

generating print instructions for said image that dictate when and where each of a plurality of nozzles will fire to print said image;

determining which of said plurality of nozzles requires a maintenance action as said printer prints said image; and

including in said print instructions at least one instruction related to a performance of said maintenance action, wherein said step of determining which of said plurality of nozzles requires a maintenance action comprises assuming a minimal user printing speed to determine a time period between firings of each nozzle.

15. A method of performing maintenance on a printer that is manually moved across a surface to print an image, said method comprising:

generating print instructions for said image that dictate when and where each of a plurality of nozzles will fire to print said image;

determining, while printing said image, which of said plurality of nozzles requires a maintenance action; and

including in said print instructions at least one instruction related to a performance of said maintenance action, said at least one instruction comprising including a print instruction that causes a nozzle to fire in a high density region of said image at least once to clear said nozzle.

16. A method of performing maintenance on a printer that is manually moved across a surface to print an image, said method comprising:

generating print instructions for said image that dictate when and where each of a plurality of nozzles will fire to print said image;

determining, while printing said image, which of said plurality of nozzles requires a maintenance action by assuming a minimal user printing speed to determine a time period between firings of each nozzle; and

including in said print instructions at least one instruction related to a performance of said maintenance action.

17. A method of performing maintenance on a printer that is manually moved across a surface to print an image, said method comprising:

generating print instructions for said image that dictate when and where each of a plurality of nozzles will fire to print said image;

determining, while printing said image, which of said plurality of nozzles requires a maintenance action comprising using, for each of the plurality of nozzles, the following:

if (NozzleIdleTime>15)

{

P=k 1 (p dnsity )+k 2 (p others )+k 3 (p temp )+k 4 (p time );

if (P>0.8)

{

 FireNozzle ( );

}

}

where P is a probability to fire a particular nozzle, p dnsity is a density of a swath firing around a dot location, p others is a number of other maintenance dots at that time, p time is an idle time of the particular nozzle, p temp is a parameter associated with maintaining a predetermined target printhead temperature, and k 1 , k 2 , k 3 and k 4 are weightings on said p dnsity , p others , p temp , and p time values;

and,

including in said print instructions at least one instruction related to a performance of said maintenance action.