I have been very good with my maintenance and before starting any job, I do a nozzle check and head clean if required. I find that I can do a maximum of about 5 white shirts before I need to clean again. If I am using the client’s shirts that they supply, I end up with a huge problem having to replace them every time. I am printing on 1440 X 1440, one pass. When I print on 720 X 720, 2 passes, the nozzles block even sooner causing even more rejects. I also have a humidifier that is permanently on next to the machine.
I seem to have exactly the same problem on coloured shirts. The white also prints about 5 shirts, and then one very bad one. I print coloured shirts at 720 X 720 with two passes of white and colour inks.
Focus is always checked in a consistent way while printing. I am using DTG inks and Print Pro. The machine is an HM-1C.
Re: Very high reject rate on white and black shirts
Colin,
There is a much higher risk when printing on customer supplied garments. I know several companies that will not do this type of work at all or that tell the customers that they have to provide a specific % of more shirts to cover potential mistakes.
As far as the printing, it sounds like you have a ink stravation issue - which means you start off good, but after a specific # of prints the ink flow is no longer at the point where it needs to be to get good prints. Some of the things for you to look at are put in this post - White ink fades out on large print. Just be careful if you decide to raise the height of your ink bottles. If you raise them too high, the ink will flow uncontrollably out of the print head.
Re: Very high reject rate on white and black shirts
The issue you are describing could be caused by bad ink. We had a bad batch of ink a while ago and it would do as you describe, slowly clogging the dampers until head cleanings would no longer solve the problem. Remove the dampers that are on the lines that seem to be starving and see if they are getting a buildup of ink particles in the screen, if this is the case you most likley have a bad batch of ink. Is this happening on the white also or just the colors?
Re: Very high reject rate on white and black shirts
I seem to be getting somewhere printing at 720 X 1400 on white, one pass, and will try it on black after this print run. It seems to work nicely so far with good colours. If this fails, I will try the tips as suggested above.
Re: Very high reject rate on white and black shirts
I did not notice that you were printing 1440x1440 - this puts down a lot of ink and it needs a full cure time to dry. The 1440x720 should help as long as you are happy with the coverage.
Re: Very high reject rate on white and black shirts
If you are getting ink starvation from 720-720 it still means you have an underlying problem with ink flow. Doing it in 1440 means you are just compensating for the lack of ink flow. I'd try to find and fix the problem now before it gets worse.
Very high reject rate on white and black shirts 
