Low Spots or Skip Outs

[tsfx]

Good Day,
We are a flexo print facility and have been having some low spot issues recently. We have liquid pour plates and a WH Press. I have put a question out to my vendor for assistance but figured I'd double-down and head to the forums for confirmation. In the attached images you can see the low spots printed on our press.

The plates have been reviewed prior to sending to the press department. This issue was not recognized during the review.
After printing, we can see the issues and it is felt within the plate. This is something that could possibly have been missed during the review. But I feel this is happening too often for so many plates to be missed.

I just wanted to know if anyone has seen anything similar and if they might have an idea of what could be the cause.
In my experience, I have seen low spots. But nothing quite like what is seen in images 06 and 07.

Thanks for any feedback.

 

[SteveSuffRIT]

Are these photos inked, on plate or substrate (#4 is)?
A low spot can occur at 0.002"-.003" and you will never see this in an un-inked plate.
Don't forget, the impression pressure is the total combination of plate, sticky back tape, plate cylinder or sleeve, and impression drum. In the first 3, it's location will not move.
#6 & 7 do have a harder edge, which would be the plate.

 

[tsfx]

Are these photos inked, on plate or substrate (#4 is)?
A low spot can occur at 0.002"-.003" and you will never see this in an un-inked plate.
Don't forget, the impression pressure is the total combination of plate, sticky back tape, plate cylinder or sleeve, and impression drum. In the first 3, it's location will not move.
#6 & 7 do have a harder edge, which would be the plate.

Thanks for the feedback.
These are on substrate. I will have to investigate if this is in the same location when it does happen.
Thanks for the info on 6 & 7, as well as the rest.

 

[tsfx]

Are these photos inked, on plate or substrate (#4 is)?
A low spot can occur at 0.002"-.003" and you will never see this in an un-inked plate.
Don't forget, the impression pressure is the total combination of plate, sticky back tape, plate cylinder or sleeve, and impression drum. In the first 3, it's location will not move.
#6 & 7 do have a harder edge, which would be the plate.

To add to this. I have reviewed how the plates were made and the process of the platemaker.
The only thing I can see, that might have been an issue with their process is when the plate backing is lied down with the liquid resin in between. There may have been points in which the backing was not coming out as straight as possible.

I believe this may have caused wrinkles. And therefore causing a low spot during the curing process. And being that they are new, they probably missed this prior to sending plates out to press.

Would you say these hard-edge, low spots could be created from this?

 

[ar17]

i am also encountering low spots, although i am using a digital thermal plate. any advise how to get rid of this concern?

thanks

 

[tsfx]

i am also encountering low spots, although i am using a digital thermal plate. any advise how to get rid of this concern?

thanks

The only thing we could see that ended up being the solution to this issue; was to ensure that when the backing substrate was being laid out, to ensure it does not bubble or crease.

As I watched our platemaker perform their duties, I saw that they would place the substrate in the carriage but not ensure that it was straight.
As the carriage would move to the right, the substrate would come out crooked. Not immediately detectable unless you were looking for it. But easy to see.

As the lid to the exposure unit was closing, I would assume, it'd push that bubble/wrinkle from the back to the middle of the area. At the same time and in some instances, it'd create more wrinkles.

Once I informed them to look out for this and to ensure everything on the unit is flat, straight, without bubbles, and had proper settling times, this issue seemed to go away. Or for the most part, we haven't had this issue since.

What I feel caused the questioning of the issue is that I have not seen anything like this before and made the assumption that the operator was performing everything correctly. Especially since it was happening on some and not all plates.

What I feel was the thing that helped resolve the issue was to have someone experienced, watch and perform the duties and see where the operator was having issues. During that time, I made multiple plates and had no issues. This lead me to user error and not machine error.

I was able to see that instead of looking over all sides of the machine during its operation and reviewing any possible issues. The operator was performing the bare minimum.
Placing materials in the machine and standing in one area expecting the machine to do the work and not realizing they have to review the process to ensure the machine would perform as expected. And that the user does not hinder the machine's performance.

Hope this helps.