L26500 Print Quality Issue (Vertical banding, thermal maybe?)

[JoeBoomer]

The diagonal banding is actually a shadow, not in the print.

1 - What do you think the problem is here and what is the solution for future prints?

2 - Do you have any suggestions to get me through

I'm pretty sure my problem here is heat (too much maybe?) and excessive ink related but I need to match the print to existing panels and I'm afraid of limiting ink and having colors change on me.

I'm also afraid of doing a calibration and having colors change on me....



3M Control Tac v3
HP L26500 on 10 Pass
Heat Settings:

Drying 129
Curing: 241
Vaccuum: 25

Warm-Up Offset: 2
Heat Airflow: 40

 

[CES020]

Custom made profile or 3M's profile? What's "3M ControlTac"? I thought ControlTac was the adhesive used on a variety of their products, isn't it?

 

[JoeBoomer]

3M ControlTac (IJ 180cV3)

Standard 3M profile.

 

[CES020]

Wish I could help. I've seen that with custom profiles that didn't have the ink limits set right, but I haven't seen that with the factory profiles.

 

[FrankW]

Reduce the input tension (driver properties). If that don't help, reduce the vacuum.

 

[P Wagner]

Reduce the input tension (driver properties). If that don't help, reduce the vacuum.

Vertical banding can be a chore to resolve, and I would echo Frank's recommendations above. Softer and thinner medias (cast medias for example) will tend to deform in the print zone more readily than a stiffer media might (calendared media perhaps), and this non-flatness can cause vertical banding artifacts on some medias. Reducing the amount of vacuum can significantly reduce this and often times eliminate it entirely.

 

[AF]

Both vacuum and airflow can distort the material on the print platen. What are your settings for that media?

I would expect settings of 15nm tension, vacuum 25 and airflow 30% would work to eliminate the banding. A print head alignment using the affected media would be a good thing to do as well.

 

[danno]

My thoughts would be to increase the passes and reduce the heat a bit. If you have access to an IR temperature gauge, I would check the actual temperatures.

 

[AF]

From the HP troubleshooting guide

Vertical banding

If vertical bands of different colors (and sometimes of different graininess) appear in the first 200 mm of the
print, this is probably caused by the curing process of the previous print, which may have distorted the
substrate. In this case:

1. Set the extra bottom margin to 100 mm.
2. If the problem persists, set the extra bottom margin to 200 mm. This margin will apply only to jobs that
start printing when the printer is idle, and when the cutter is disabled.
3. If the problem persists, decrease the warm-up drying temperature in steps of 5°C.
​

If vertical banding affects the whole of the print, the drying temperature may be too high.

1. Reduce the drying temperature in steps of 5°C, down to a minimum of 40°C.
2. If the problem disappears but then there is bleeding, coalescence or not enough durability, try using
more passes or less ink.
3. If the problem persists, restore the drying temperature to its original value and select unidirectional
printing in the RIP.
​

 

[jason_hamilton]

Late to the game....as usual...

HP recommended that I move the temp. offset to 9 when I was having some issues. Also, as others noted, increase pass and lower the temp.

 

[JoeBoomer]

***update***

I am slowly getting through my issues here and thought I would update everyone.


• I lowered the drying temp by about 8ºc and that seemed to help.
• I adjusted my ink levels which for some reason were all at 100. They are now in the 80-90 range (roughly).

• I noticed after all that, the first part of my print was still showing problems while the rest was clearing up. So, I adjusted my drying offset to 2º.


• I am noticing some coalescence and horizontal banding in my prints now (in dark colors), so I am going to adjust my heat settings and try to work that out.

I'll keep you posted.

go team!

 

[chafro]

Less ink, less speed.

 

[danno]

I have custom created an 8" leader to give the heads/heating units time to "warm up". It solved many problems with the first few inches.

 

[SignLogic]

I've had this problem with my 26500 and the problem ended up being humidity in the shop.

 

[AF]

Just a thought, if one of thermal sensors is malfunctioning it could cause the printer to run either too hot or too cold.

 

[JoeBoomer]

I've had this problem with my 26500 and the problem ended up being humidity in the shop.

I just noticed the humidity in my print room is @ 62%! I totally forgot to look at that. I usually pay attention to it better and keep my temp @ 72 and my humidity around 20 or 30%.

I'm going to get my trusty dehumidifier out and running again. I'll update with results.