Partially failed models and a wobbly (overexposed?) bottom layer

[tlactar]

Hello!

Until a few days ago i've been a happy owner of a new Mars 2 Pro. Been printing dozens of succesful prints until those happened:









I did not change any settings in between the last succesful prints and those, i've been using the same bottle of resin, room temperature is (subjective...) the same and the printer is printing in a dark room. Anycubic Grey Resin. I had to clean the VAT after every try as there's now pieces of that wobbly layer and failed parts attached to the FEP and had'nt had a succesful print since then. Here is my Chitubox settings:


Prints now got 2 main issues: First that wobbly thing attached to the buildplate in places where the Mars shouldn't expose at all (it extends beyond the rafts where no model is placed) and secondly the models are randomly missing parts that should not be missing, like this:


- as if someone took a bite out of it 

Help!  

On a sidenote: this is the 2nd usb pen i'm using as the original one died on me after a few days. Out of curiosity: is that covered by warranty? 

[tlactar]

No idea how those should look, but it seems it does kind of expose a complete "horizontal line" when there's a model, see the elegoo letters and the area besides the raft in the first picture and this result of my latest try...
No idea though what might be causing this...

[cliffyk]

How many hours of printing time would you estimate? I had the LCD on one of my Mars units fail after just 11 hours (it got universally dim and required 25 to 30 s exposures to print anything). Elegoo replaced it at no charge...

[DDLLC]

Hi,

I don't know if any of these comments are directly applicable since I'm using the Elegoo Gray Resin and a Mars printer, but I've spent the last several months trying to accurately characterize the effects of print parameters on achieving optimal accuracy and minimal distance variations from the design.

One observation is that room temp and exposure time are very important on base layer to adhesion to the plate. I did some preliminary screening of exposure time and it suggested lower base exposures might give better accuracy and be sufficient crosslink the resin enough for adhesion(some problems with this data that will be in a different post later today or tomorrow). I started a larger scale set of experiments upon that premise and quickly found that using 40s (again this is not a Mars 2) base exposure resulted full release or lifting corners of a set of nested rectangles. The earlier tests were done with a room temp in the 81F range, but the second set had room temps in the mid to upper 70's. I restarted my trials using 50s for the base and then seemed to have adhesion failures when the temp dropped to 68. From that info I set the temp to be controlled at 73 F. I think I might have had one of the rectangles occasionally lift a corner or fall off, so it might be best at more like 75F.

Bottom line is that temperature is very important in conjunction with exposure time for base adhesion.

Also if I have adhesion problems, I will clean first with acetone and then follow with the alcohol. I can't definitively say it works, but I'm slowly convincing myself it might.

Lastly as to that filmy region that extends beyond where I think your raft is ending, might be due to over exposure. That seems to contradict the preceding part that suggests you had inadequate adhesion in some places, but I found that be extending exposure time I would see an increase in layer thickness (up to some time) at some particular time and then it wouldn't grow much at all (this was done without the build plate, i.e., printing on the FEP directly). That suggests that the free radicals that cause the bonding can diffuse through both the liquid resin and bonded acrylic, which is not surprising. My increases in width and length were not nearly as large as in your picture however.

I have had a lot of difficulty in keeping the build plate parallel to the LCD (look for my post thread about the layers shifting). If this happened to you at some point likely early during the base print, you might have some reflection off that plate.

On the line issue it could be a failure in the LCD screen, but it is nothing I' experience (yet!)

Greg

[cliffyk]

^^^ GOOD info...

[tlactar]

Hey, thanks for the advice, seems really useful. I'm looking forward to the rest of your results!

Unfortunately i think it's not what is happening with mine. I've not had adhesion problems with prints before with those settings.

Main problem for me are these extending lines of resin i think. Here's more pictures with tests i did - the wobbly stuff perfectly matches those lines visible when putting the paper on the screen (i can't compare to a working machine, so i'd love some feedback if those lines should be there at all!)





here is a video of the area flickering - is that normal, too?


https://imgur.com/a/2WbBqC4

and an even more obvious test setup:






no square = no horizontal line = no wobbly film there

[DDLLC]

Have you opened up the base and inspected each of the connectors? One may be loose somewhere or damaged. I can't imagine those stripes are intentional.

I'd reach out to elegoo. It seems many folks have had some good responses from them (but not me).

Greg

[cliffyk]

Something it not correct with that LCD--it may be it's connections, could also be a problem with it's power supply. Your best bet is to contact Elegoo; I am among those that have had timely and productive communication with them.

[tlactar]

Something it not correct with that LCD--it may be it's connections, could also be a problem with it's power supply. Your best bet is to contact Elegoo; I am among those that have had timely an productive communication with them.

Will try that! What way did you have the best success? Mail? Facebook?

[cliffyk]

Email has worked for me: 3dp@elegoo.com--they have been very responsive. You have to remember they are in China, so it may take 12-15 hours for them to respond...