CET K2-1000L flatbed with intermittent banding issues and nozzle fallout

Grimace78

New Member
Have a K2-1000L CET flatbed printer that has intermittent banding and nozzle fallout. I think that the issue is because the printer is exposed to too much fluctuation in temperature and humidity. It is basically in a small warehouse adjacent to a garage door that exposes it to the outside periodically through the day as shipments come and go.

The unit tends to have issues with banding when printing large areas of solid colors, and when shown to the lead tech he says it looks like the heads are losing nozzles.
IMG_20220519_163124464.jpg


When we run a nozzle test, it sometimes shows all nozzles and sometimes shows nozzle loss of nearly all a specific head (M4 recently)(will follow up with pictures as I get them). Often these tend to be one or two heads in particular but not always. We have purged the the ink through the heads, checked for air in the lines, bled the lines that lead to the affected heads (at the time of specific failures) and adjusted the negative pressure numerous times.

It seems like the printer will work for a while without issue, then when we get a heavy workload in will start banding when it has to print a large area of solid colors.

I don't know for sure if I am approaching the problem correctly or not, as I have about 6 months or so experience with the machine, and no experience with other large format printers before that.

The photo with the blue prints and the negative pressure setting of each print is also attached below. This is how I tried to approach the negative pressure settings for the prints.
IMG_20211126_103903203.jpg

I just picked the setting with the least amount of banding. The banding in the photos is hard to see unfortunately, but if I remember correctly we went with 5.2 at the time, which seemed a bit high to our technicians.

I would think though that if there was no blockage in the lines or heads that it would have to be the negative pressure not at the correct setting for there to be nozzle fallout, which I understand is directly affected by ambient temperature and humidity. The machine has been calibrated numerous times by the technicians from CET, and when its not banding will print the quality check print seemingly to perfection on high quality setting.

Here is an example photo of the banding. Red and blue colors seem to be the most problematic, with the M4 head showing most of its nozzles missing more often than the rest, followed up by the cyan heads. I will post more pictures when I get to work of the nozzle test etc. This has been particularly hard to nail down as the problem isn't always apparent.

The company I work for is also looking for a humidity and temp logger to monitor this. I think we need one that can plug into the pc via usb for monitoring purposes, likely one with alerts for when variables go outside of optimal ranges. There are so many options with a wide price range and I'm looking for suggestions for this as well. I don't want to get one that is more expensive than necessary but don't want to go so cheap that we get a crap tool. Here is a link of one I am considering, but am worried that it is just a cheap knockoff of what we actually need.

 
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DSGI

New Member
Have a K2-1000L CET flatbed printer that has intermittent banding and nozzle fallout. I think that the issue is because the printer is exposed to too much fluctuation in temperature and humidity. It is basically in a small warehouse adjacent to a garage door that exposes it to the outside periodically through the day as shipments come and go.

The unit tends to have issues with banding when printing large areas of solid colors, and when shown to the lead tech he says it looks like the heads are losing nozzles.
View attachment 159682

When we run a nozzle test, it sometimes shows all nozzles and sometimes shows nozzle loss of nearly all a specific head (M4 recently)(will follow up with pictures as I get them). Often these tend to be one or two heads in particular but not always. We have purged the the ink through the heads, checked for air in the lines, bled the lines that lead to the affected heads (at the time of specific failures) and adjusted the negative pressure numerous times.

It seems like the printer will work for a while without issue, then when we get a heavy workload in will start banding when it has to print a large area of solid colors.

I don't know for sure if I am approaching the problem correctly or not, as I have about 6 months or so experience with the machine, and no experience with other large format printers before that.

The photo with the blue prints and the negative pressure setting of each print is also attached below. This is how I tried to approach the negative pressure settings for the prints. View attachment 159681
I just picked the setting with the least amount of banding. The banding in the photos is hard to see unfortunately, but if I remember correctly we went with 5.2 at the time, which seemed a bit high to our technicians.

I would think though that if there was no blockage in the lines or heads that it would have to be the negative pressure not at the correct setting for there to be nozzle fallout, which I understand is directly affected by ambient temperature and humidity. The machine has been calibrated numerous times by the technicians from CET, and when its not banding will print the quality check print seemingly to perfection on high quality setting.

Here is an example photo of the banding. Red and blue colors seem to be the most problematic, with the M4 head showing most of its nozzles missing more often than the rest, followed up by the cyan heads. I will post more pictures when I get to work of the nozzle test etc. This has been particularly hard to nail down as the problem isn't always apparent.

The company I work for is also looking for a humidity and temp logger to monitor this. I think we need one that can plug into the pc via usb for monitoring purposes, likely one with alerts for when variables go outside of optimal ranges. There are so many options with a wide price range and I'm looking for suggestions for this as well. I don't want to get one that is more expensive than necessary but don't want to go so cheap that we get a crap tool. Here is a link of one I am considering, but am worried that it is just a cheap knockoff of what we actually need.

What print mode are you running in (what resolution and passes)?
 

GC Decor

Super Printer
First Go to Homedepot or a hardware store and grab a humidity gauge, a basic gauge is $15 - this will give you some insight on where your at. Normally they want these between 40-60 if I’m correct, might be a little higher. Without knowing any number your shooting in the dark but yes Humidity plays a huge factor with flatbeds.
Another factor is the amount of heads your running - 1,2 or 3 lines of color ?? What print heads do you have ??
From what it looks like you might be having ink starvation - we had this issue a few years back. Looks and sounds the same. When your laying down so much of one color - the print heads can’t keep up and will give you nozzle drop outs and banding - do a purge and wipe and they look great again.
Their are numerous fixes for this - check that all ink line filters are up to date on replacements.
Slow the print head down - custom print mode option. I’m not sure if CET has a flood option - we do and it really helps with solid color prints. More passes, more ink, slower head speed and smaller gaps is how the setting is set up.
Not an expert but always running into new issues with our UV printers.
 

chinaski

New Member
It looks like each pass is producing a gradient in itself. I've had similar issues with my Arizona in the past and resolved it by doing the following:

1) Change lamps settings. For me, only running trail lamps on high solved this.
2) Change RIP settings, Such as, 16-bit rendering, interpolation, rendering intent, screening, etc.
3) Add a delay to each pass and try Uni-directional printing.

I've had my printer both inside and outside of a climatized room and it has made no difference for me.
 

GC Decor

Super Printer
How many heads are you running 1 row or two ??
Program is the Same as our Fluidcolor - Topjet
 
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Grimace78

New Member
I am sorry I didn't follow up on this thread and all the responses. I had a ton of stuff fall on me and it is difficult to get time to post online where I work. I ended up having to run at 0.33 on the screen size to get the banding to be less noticeable. I also changed out all the secondary filters as suggested. I'm still not happy with it but at least we can produce the orders with large solid colors again. Thank you to everyone that post with troubleshooting ideas or suggestions. I will go over all of this as soon as I can.
 

DSGI

New Member
I am sorry I didn't follow up on this thread and all the responses. I had a ton of stuff fall on me and it is difficult to get time to post online where I work. I ended up having to run at 0.33 on the screen size to get the banding to be less noticeable. I also changed out all the secondary filters as suggested. I'm still not happy with it but at least we can produce the orders with large solid colors again. Thank you to everyone that post with troubleshooting ideas or suggestions. I will go over all of this as soon as I can.
I thought that would be the case, we can't run solid colors on our CET in larger screen values, basically it's too few a passes and the printer doesn't seem to be able to deliver the ink quickly enough to meet the demand which results in missing nozzles and ultimately banding. We run everything at .33 screen.
 
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