Circles are not Round [Mars 2 Pro]

[SHack]

Moin! (We say in north Germany)

My elegoo mars 2 pro doesn't print circles in the right shape. The model has some decent failures all over.

I have attached a picture to show what I mean. 

Anyone has an idea to fix this? I'm using the ABS-like resin from elegoo at the standard settings in chitubox.

Greetings from Germany 

SHack

[cliffyk]

I see no photo?

What slicing software are you using?

If Chitubox, are the machine settings correct for the Pro 2's 1620 x 2560 resolution? Chitubox's "default" settings are 1440 x 2560.

[SHack]

Updated the pic

[cliffyk]

It looks like quite a bit of distortion, try increasing the normal layer exposure thime, I feel Chitubox's 2.5 s is a bit aggressive--try 2.75 or 3.0...

[SHack]

Moin!

So i tried 2.8 and 3.

2.8 looks better then before:



The circles look way better. But there are still many failures in it. Its not plane and the corner isn't a straight line. So I tried 3 seconds exposure:

That even got worse...

It got a big bow and at the end it has some big shifts.

Don't know what to do now. I can't print directly on the plate cause of elefant foot and not getting it off. 

Hope there is someone with solutions for these problems. 
Thanks for helping!

Greetings from Germany 

SHack

[Lobo09]

Servus SHack,

i'm still a beginner in resin printing myself, but maybe i can help you.

I also have an Elegoo Mars 2 Pro and have made prints with the gray ABS-like resin from Elegoo.
I dis some test prints of the Ameralabs Town and had the best result with 2.5 sec.
This is also the exposure time recommended by elegoo (link) for both, grey and white. So I think with 2.5-3.0 sec you are in the right spot.
I would try to orient it steeper to reduce the cross section and suction forces.

If you want to print something flat on the build plate, you a few options to get rid of the elephant foot:
1. Try to reduce the bottom layer exposure. The standard 35s are way to high in my opinion. 6-8 time your normal exposure should be enough. I usually use 15s with the gray resins of Elegoo, Nova3D or eSun even on bigger prints.
2. Use bulgebuster or UV Tools to dimm a few pixel of the outer border of the bottom layers, so they don't get overexposed.

I hope this helps a bit

[cliffyk]

Servus SHack,

i'm still a beginner in resin printing myself, but maybe i can help you.

I also have an Elegoo Mars 2 Pro and have made prints with the gray ABS-like resin from Elegoo.
I dis some test prints of the Ameralabs Town and had the best result with 2.5 sec.
This is also the exposure time recommended by elegoo (link) for both, grey and white. So I think with 2.5-3.0 sec you are in the right spot.
I would try to orient it steeper to reduce the cross section and suction forces.

If you want to print something flat on the build plate, you a few options to get rid of the elephant foot:
1. Try to reduce the bottom layer exposure. The standard 35s are way to high in my opinion. 6-8 time your normal exposure should be enough. I usually use 15s with the gray resins of Elegoo, Nova3D or eSun even on bigger prints.
2. Use bulgebuster or UV Tools to dimm a few pixel of the outer border of the bottom layers, so they don't get overexposed.

I hope this helps a bit

^^^ all good advice.., experiment is the key--in my experience lighter colour/translucent resins are the most sensitive to the parameters "Lobo09" brought forth--i have intentionally avoided them...

[earthball]

Looks to me like it might be under-supported. If the part is pulled free of the supports before you touched it, the peel forces may be higher than the support strength on the edges. At that point, all the remaining layers will be warped, depending on how the part flexes when it is pushed back against the FEP. You could try increasing the angle of the part to reduce the peel forces and/or increase the number of support points. Thin edges like that are often hard to support when they are on the bottom.

[cliffyk]

Looks to me like it might be under-supported. If the part is pulled free of the supports before you touched it, the peel forces may be higher than the support strength on the edges. At that point, all the remaining layers will be warped, depending on how the part flexes when it is pushed back against the FEP. You could try increasing the angle of the part to reduce the peel forces and/or increase the number of support points. Thin edges like that are often hard to support when they are on the bottom.

I find it helpful to keep in mind that in SLA printing what are commonly called "supports" are actually hangers--because our systems printer things from the "bottom-up" but do it upside down. I.e. the bottom of the model--which is printed first--is physically at the uppermost point and that the hangers ("supports") suspend the remainder of the model from it's base.

In FDM printing, those which are call and actually are "supports" support the model against gravity and are compression loaded columns.

Our hangers are loaded in tension and must be individually strong enough to not tear apart or tear away from where they anchor to the model or raft; they also must be sufficient in number to tear the just printed layer away from the FEP without breaking or pulling away from their anchors.

Inter-layer lift speed is directly related to the tension force the hangers must withstand--the faster the lift, the higher the load, on the hangers--and vice versa. Curing time is also a factor as longer exposures = more complete curing = stronger hangers.