Method of expelling ink from nozzels in groups, starting at outside nozzels of each group

1. A method of expelling ink from nozzles of a printhead module, the method comprising the steps of:

(a) providing a fire signal to nozzles at a first and nth position in each set of n adjacent nozzles in each row of a plurality of rows of the printhead module so as to expel ink from the nozzles, the rows being offset from each other in an intended direction of print media movement relative to the printhead;

(b) providing a fire signal to the next inward pair of nozzles in each set so as to expel ink from the nozzles;

(c) in the event n is an even number, repeating step (b) until all of the nozzles in each set has been fired; and

(d) in the event n is an odd number, repeating step (b) until all of the nozzles but a central nozzle in each set have been fired, and then firing the central nozzle,

wherein each nozzle is fired simultaneously with the nozzle or nozzles at the same position in at least some of the other rows.

2. A method according to claim 1 , the method at least partially compensating for errors in ink dot placement by at least one of a plurality of nozzles due to erroneous rotational displacement of a printhead module relative to a carrier, the nozzles being disposed on the printhead module, the method comprising the steps of:

(a) determining the rotational displacement;

(b) determining at least one correction factor that at least partially compensates for the ink dot displacement; and

(c) using the correction factor to alter the output of the ink dots to at least partially compensate for the rotational displacement.

3. A method according to claim 1 , the method including expelling ink from a printhead module including at least one row that comprises a plurality of adjacent sets of n adjacent nozzles, each of the nozzles being configured to expel ink in response to a fire signal, the method comprising providing, for each set of nozzles, a fire signal in accordance with the sequence: [nozzle position 1 , nozzle position n, nozzle position 2 , nozzle position (n−1), . . . , nozzle position x], wherein nozzle position x is at or adjacent the centre of the set of nozzles.

4. A method according to claim 1 , wherein at least a plurality of the nozzles in odd rows of the plurality of rows are fired prior to at least a plurality of the nozzles in even rows of the plurality of rows, or vice versa, the odd and even rows being offset from each other in both x and y directions relative to the intended direction of print media movement relative to the printhead.

5. A method according to claim 4 , wherein all the odd rows are fired before any of the even rows are fired, or vice versa.

6. A method according to claim 4 , wherein the odd rows, or the even rows, or both, are fired in a predetermined order.

7. A method according to claim 6 , wherein the predetermined order is selectable from a plurality of predetermined available orders.

8. A method according to claim 4 , wherein the predetermined order is sequential.

9. A method according to claim 8 , wherein the predetermined order can commence at any of a plurality of the rows.