Very Grainy Screens - Any Ideas?

[Joeutut]

My printer is an HP 3500 CP, Rip Wasatch 5.1, Image 4 color but does not matter cause even 1 color is grainy.
Ink HP UV
Have tried stoccastic and digital mezzotint screens, stoccastic is better.
I bought the printer very used so I had to download the drivers from HP.
In my printer list it says "HP Designjet 3000 (600dpi)
I have used numerous profiles and have tweak them also. It gets a little better but not sellable.
This is an old printer and I am doing ok with it except for this.
Any help would be greatly appreciated

 

[iCtP]

Grainy Image

Grainy Image

A grainy image can be caused by a number of reasons.

1) The dots are too large.
Because: You are telling the RIP to image a large dot....But, on the HP printer I do not believe you can change the dot size you are imaging.
Because: Your UV ink, is spreading before drying and effectively creates gain on the substrate resulting in a much larger dot (or dots that are close to each other are begining to join, and serpentine into larger dots). - Check if you can increase the curing power of your UV lamp to see if you can reduce dot size in this way.

2) The Head is not correctly adjusted...
Most common cause of Grainy images, is that the distance between the substrate and the printhead is too large. If your substrate is fairly flat, it should be circa 0.80mm - 1mm distances above this cause the ink to split in mid air, resutling ina grainy image.

Check the head is "Straight" and there is no BIAS that is incorrect.

3) You are running in a BI-Directional mode, and the timing for your ink type is incorrect. Try imaging in Uni-Directional mode, to see if the grainess improvess. If it does, then run a Bi-Directional calibration.


Hope this helps.