New printer shipped with LCD protective plastic?

[Helotech]

I have complete about 5 or 6 print jobs with my Mars 2 Pro. There were only a couple print issues that I chalked up to my inexperience.
I just finished printing 2 tall tubular pieces for a Star Wars blaster on my Mars 2 pro, and when I went to check on it the last few layers were very irregular. After removing the piece I started to pull out the resin tank for cleaning and noted that it was stuck a bit to the LCD screen. I was able to get the resin tank out, but now realized that the FEP screen had gotten damaged during printing and some resin had leaked out and cured to the LCD screen in two thin circles.

After wiping up the resin I used a razor blade tool (for cleaning glass stove tops) to try and gently scrape the circles off the screen. As I scraped and very gently pried at the circles, I noticed that they were pulling up what looked like a plastic layer that was on top of the LCD.

I thought I had damaged the surface of the screen as it looked like glass layers were separating.
As I pried a little more an entire rectangular sheet came up. 
This loosened the sealing tape along the edges and I had to scrap it.

Now I have this plastic sheet, which looks like FEP with two circles on it.

I went on Elegoo's website and looked at the video for LCD screen replacement. It shows a person removing 2 plastic layers before installing the new screen.

Is it possible that Elegoo is forgetting to remove this plastic protective sheet when they install the LCD? Seems kind of crazy!
Does this protective plastic screw with printing clarity?

Now I have to source some of the black sealing tape....

[cliffyk]

It is entirely likely they left the protective film on the LCD shutter--IIRC there was one on the LCD GUI screen as well--most products having LCD displays are shipped with a protective film--often with a small tab to assist in its removal. It couild indeed mess up the printing process as it could diffuse the curing light.

IN the future do NOT go at the LCD shutter with a razor blade--many here and elsewhere on the web have ruined theirs by doing so.

[Helotech]

It is entirely likely they left the protective film on the LCD shutter--IIRC there was one on the LCD GUI screen as well--most products having LCD displays are shipped with a protective film--often with a small tab to assist in its removal. It couild indeed mess up the printing process as it could diffuse the curing light.

IN the future do NOT go at the LCD shutter with a razor blade--many here and elsewhere on the web have ruined theirs by doing so.

Thanks.
Is there any way to remove cured resin from an LCD if a FEP leak happens again and I have no protective film on the screen?

I have seen on other forums people stating to use a razor to clean off the screen. Guess they were wrong...

I've also read some people do use after market LCD screen protectors to prevent damage to the LCD's.
Only reason I really tried the blades is I thought I had completely ruined the screen and there were none available any where. I thought I had nothing to lose.

[cliffyk]

I have used a single-edge razor blade to remove cured resin from the LCD shutter, however I have found over the years I tend to do such things with a great bit more finesse than others, and procedures that work fine for me are like handing others a loaded and cocked gun. Many go at things such as this like a bull in a China shop (these are the ones that need after-market protectors). If you feel competent to do so that's the way to do it--AFTER--fingernails and plastic scrapers have failed!

The easiest thing to do of course is to not get resin on the screen in the first place. I now remove the resin vat after each print job and make 110% certain it is not leaking...

[Helotech]

Thanks. I get ya'
I am very meticulous due to experience as an aircraft mech and my hobby of model building. I have a gentle touch

I clean the resin tank religiously after every print.
The FEP leaked as I built built two tall 5" blaster barrel tubes at the same time. I'm thinking the repeated up and down in the exact same spots stressed the FEP.
Good news is Elegoo got back to me in less than 24hrs when I asked a question on their main page. I sent them pics of the sheet I peeled off.

I'm finding it hard to locate the sealing tape (OEM or after market) for the LCD screen edge. Maybe Elegoo will toss some my way!

Anybody use a substitute for the tape?
Truly appreciate the help.

[cliffyk]

You will be OK with the blade then. Aircraft mechanics understand that "Bring it in again tomorrow and we''l see what we can do." is not an acceptable outcome.

I was plant engineer for a manufacturing company years ago and one of my mechanics was lamenting that when he told people he was a mechanic they asked "at what dealership?" and were less than impressed when he told them he worked in a mill. I told him to next time tell them he "repaired multi-million dollar machines that had to run 24/7 for the next 6-12 months when he was done--not cars". 

Re: the tape, as a substitute I'd use UHMW tape like this stuff. It has good adhesion and nothing sticks to its outer surface. I keep a roll on hand and find more uses for it than you'd think.

[Helotech]

LOL. Exactly.
When I say I'm an aircraft mechanic, they think I am like a car mechanic. I have toe explain that when something goes wrong with your aircraft in flight at 20,000 ft, you simply can't pull over and call triple A.

I got another email from Elegoo customer service. very fast on the responses!

"This plastic film should be a polarizer and LCD screen should be damaged."
My screen looks completely brand new, but looks more like very clean glass rather than clean glass covered with clean plastic sheet, if you know what I mean.

So, according to them there is supposed to be a plastic "LCD polarizer film" on all the LCD's. Anyone else confirm on their printers? I googled this and it is apparently a thing that I never knew about.
https://www.youtube.com/watch?v=jHiM4ph6kUI

The polarizer in attached video seems to be two layers, a clear and tinted. Mine is just clear, so there may be another layer stuck there. The sheet this guy pulls off the large LCD screen looks like what I pulled off mine.
If I could figure out how to attach pics here I would.

Anyways, the company offered to ship me a brand new LCD, so I'm happy.

I am just wondering if when I install the new LCD and pull off the protective plastic sheet, if it will look like the sheet I pulled off.

Anyways, more to follow!

[cliffyk]

I have had a number of email exchanges with Elegoo support, several of which became confused due to our language barriers. There is a clear plastic protective film on a new screen (I just went to my shop and verified this):

this is the clear protective film--the pull tab is shown:


As to polarizing layers, they are essential to the LCD function, should not be removed, and are in general not easily removed.

An overly-simplified explanation of how the LCD shutter works may be in order here:

There are three essential layers to its assembly; two passive and one active. Passive are the lower and upper polarizing layers, with the active liquid crystal layer in between.

The lower polarizer orients the curing light to a certain polarity, however as the upper polarizer is oriented out of phase with the lower it blocks the light from passing through the assembly--this is where the active layer kicks in.

In their normal non-energized state each cell of the liquid crustal layer passes the light with no changes, leaving its passage through the entire assembly blocked by the upper polarizer. However when the LC cell is energized the "liquid" crystal twists, and changes the polarity of the curing light so that it can now pass through the upper polarizer.

I believe the "language barrier" part kicks in as their (Elegoo support) implying the polarizer is a possibly removable "film" rather than in integral part of the LCD assembly.

If you removed the upper polarizer and not a protective film then the LCD is damaged with repair unlikely. I have seen other videos of people trying to accomplish something (???) by peeing their LCD apart, though I have not seen any thast resulted in anything but a damaged beyond repair LCD.

[Helotech]

All good to know.
The stuff I peeled off accidentally does not have the tab, so it is almost definitely the polarizing layer.

Company is shipping me a new LCD, so I will try and source a polarizing film if I can find one. Not sure if this is possible but worth a try.
I'd hate to throw away a perfectly good LCD for the lack of a small piece of special plastic sheet.

[cliffyk]

All good to know.
The stuff I peeled off accidentally does not have the tab, so it is almost definitely the polarizing layer.

Company is shipping me a new LCD, so I will try and source a polarizing film if I can find one. Not sure if this is possible but worth a try.
I'd hate to throw away a perfectly good LCD for the lack of a small piece of special plastic sheet.

A new LCD will have the top polarizing layer--if not it is incomplete. A new LCD is only worth $30 (I keep two on the shelf) or so don't spend too much time looking for a kludgy solution to a cheap problem...