Fountain solution thickness control system in a digital printing device using a drag force sensor

A method of controlling fountain solution thickness on an imaging member surface of a rotating imaging member in a digital image forming device, the digital image forming device printing a current image onto a print substrate, the printing including applying a fountain solution layer at a dispense rate onto the imaging member surface, the fountain solution fluid layer having a surface above the imaging member surface, vaporizing in an image wise fashion a portion of the fountain solution layer to form a latent image, applying ink onto the latent image over the imaging member surface, and transferring the applied ink from the imaging member surface to the print substrate, the method of controlling fountain solution thickness comprising:

• (a) transferring the layer of fountain solution from a fountain solution applicator having a fountain solution dispense rate onto a fountain solution carrier roller;
• (b) measuring a drag force of the fountain solution layer between a sensor head and the fountain solution carrier roller, with the fountain solution layer being a lubricant between the sensor head and the fountain solution carrier roller;
• (c) modifying the fountain solution dispense rate based on the measured drag force;
• and
• (d) printing a subsequent image by the digital image forming device using the modified fountain solution dispense rate.

A digital image forming device controlling fountain solution thickness on an imaging member surface of a rotating imaging member, comprising:

• a fountain solution carrier roller;
• a fountain solution applicator configured to apply a fountain solution fluid layer at a dispense rate, the fountain solution fluid layer being transferred onto the fountain solution carrier roller;
• a sensor including a sensor head adjacent the fountain solution carrier roller and in contact with the fountain solution fluid layer, the sensor configured to measure a drag force of the fountain solution layer between the sensor head and the fountain solution carrier roller, the fountain solution layer being a lubricant between the sensor head and the fountain solution carrier roller;
• and
• a controller in communication with the sensor and the fountain solution applicator to modify the fountain solution dispense rate based on the measured drag force,
• the fountain solution applicator configured to apply a subsequent fountain solution layer at the modified fountain solution dispense rate onto the imaging member surface for an image forming operation thereon.