No Flow From Nozzle
If you’re seeing no flow from the nozzle, generally that means one of three things:
There is a small amount of ink that is exposed to your environment at the nozzle tip. This can sometimes dry out and form a very thin plug on the nozzle tip, called ‘skinning’.
A skin will never form in the middle of a print, only between print operations. If your last print was successful, but you are not getting any flow at the beginning of the next print, this is most likely due to skinning.
Inks contain volatile solvents, which are necessary for curing. Over time, ink at the tip of the nozzle can dry out and form a skin. For some inks, this can happen very quickly, while for others it might take hours or even a day.
Generally, a purge operation will clear a skinned nozzle. In extreme cases where ink was left out for days, you may just need to change the nozzle as no amount of purging with pressure will clear the skin.
Depending on the ink and how it has been stored or handled, sometimes the contents of the ink are just not suited for printing with nozzles below a certain size. You must match the right nozzle diameter and geometry to your ink properties to get good quality printing.
This issue can result in clogs at any time — at the beginning of a print, or during a print. If you have changed out a nozzle and are still seeing intermittent clogging, it is likely due to the particles being too large for the nozzle size. For a definitive answer, you can also test for agglomerates with a Hegman Gauge to look for large particles.
There are many potential causes. You could have filler particles that are too large, there could be dried ‘clots’ of binder material mixed into your ink from exposure to air, or the ink may be expired and just too viscous for that nozzle size.
If you have repeated clogging with a certain nozzle size, the only solution is to either increase the nozzle size, or change your material. Aim for a nozzle diameter that is six times larger than the size of particles in your material. If you suspect the clogging is due to expired ink, get a fresh batch of material, or talk to your ink manufacturer to help resolve the problem.
If your nozzle was damaged during handling, it may have restricted the flow.
Inspect your nozzle, and look for any signs of damage.
NOVA’s height control ensures that your nozzle should not crash into the surface. However, if there are unexpected 3D features, the nozzle can crash during travel. The most common cause of a broken nozzle is mishandling during the smart dispenser assembly or mounting, so be very careful with your nozzles.