Drop size control for a printer
View Patent ↗This invention relates to a printer whereby ink is printed by being discharged as dots from a plurality of nozzles by means of pulses. To ensure high quality printed images it is necessary to ensuring that the size of all dots is consistent. Therefore there is provided a method and apparatus whereby before printing of any dots, the temperature of the ink in each nozzle is sensed by Tsense, and a pulse insufficient to fire the ink from the nozzle, yet sufficient to heat up the ink, is fired to each nozzle in the same sequence as the standard print cycle, and the temperature of the ink is sensed. This process is repeated until the required temperature of the ink is reached, and printing is then inititated.
1. A method of printing from a microelectromechanical inkjet (MEMJET) printhead, whereby ink is printed by being discharged as dots from a plurality of nozzles by means of pulses, the number of nozzles being sufficient to produce about 1600 dpi, said method comprising the steps of
loading each nozzle with ink;
preheating said printhead by the steps of:
sensing the temperature of the ink in each nozzle;
if the temperature of the ink is at a required temperature, printing said ink;
if the temperature of the ink is below the required temperature, heating the ink by firing a short pulse to each nozzle, said pulses being insufficient to discharge ink from the nozzle, but sufficient to heat up the ink;
sensing the temperature of each nozzle;
repeating the steps of heating the ink and sensing the temperature of each nozzle until the required temperature is reached, said preheating lasting for a period of up to about 5 ms; and
printing said ink.
2. A method of printing according to claim 1 , wherein the steps of firing a short pulse and sensing the temperature of each nozzle, is carried out in the same sequence as the sequence of a standard print cycle.
3. A method of printing according to claim 1 wherein the sensing and heating steps are carried out while data is being transferred to the printer.
4. A method of printing according to claim 1 or 2 , wherein the transfer of data on the temperature of the ink is by Tsense.