3d printing errors

[hegedusmj]

I am a newby to 3d printing. I have had a number of prints come out with a 'tear' as shown in the attached. This is the base of a stone building without a roof. The printer is an Anycubic Photon Mono X using Anycubic's slicing software and their plant based resin. The example in the photo was printed in the orientation shown, upside down of course. I have had similar results tilting the object with a supporting structure provided by the software although none as bad as this.  I hesitate to start manipulating the many variables available because each iteration takes 3-4 hours print time. I question whether the wall thickness is causing me difficulties (5 mm throughout and up to 12 mm at the chimney closest to the lens, but I'm just flailing around.

 

Any thoughts out there?

 

 

 

  

[njee20]

You need vent holes in any closed box (which that appears to be), otherwise the pressure will do that. 
 

That wall thickness is colossal though, you’ll just be using loads more resin than you need, and you’ll never cure the middle, which could cause leaching or other issues. I use 1mm by default, I upped that to 1.5mm for larger scale items. 

[Royal42]

Hi Mike,

I have the same machine as you and would agree with njee about the vent holes.  When you get to the stage just before slicing, there should two icons in the toolbar top left stating 'hollow' and 'punching'; use those to hollow out the inside and then make some punch holes underneath to allow the unused resin to drain out after printing.

 

Mike

Edited September 6, 2021 by Royal42

[DGO]

The 12mm wall thickness is probably the clue, it will be trying to stay attached to the FEP as the plate moves upwards causing the print to effectively tear, try to keep your wall thicknesses to under 2mm and either make the wall hollow or do it in several parts and fit them together after its cured

[Quarryscapes]

Slow lift right down, if you can raise it up so the interior is vented thst will also help.

[hegedusmj]

I hollowed the walls. That didn't resolve the problem. I still got the tearing effect. I even sliced the model open to make sure that the hollowing was performed. The walls had enough hollowing and hole punching that there was a solid matrix within the walls but no liquid resin. I'll try Quarryscapes pointer next. 

In the meantime I thought trying another building might give a different perspective. I picked every modeler's favorite, at least in the US, the outhouse. It looks like the privy roof printed OK even though it is several mm thick It is only about 8mm square overall though. 

[njee20]

Hollowing the walls is a bad idea, any hollowed solid needs drain holes, or the pressure will cause failure anyway. What do you mean about the solid matrix? Did you use infill? If so, avoid that. 
 

If the lack of vent holes wasn’t the cause here it was the suction I’d suggest. That seems odd if rotating it didn’t solve the problem though. Unless it was simply the combination of the two; big surface area and high suction. What are your lift speeds?
 

I’d definitely thin your walls (don’t hollow them), it’ll cause you more problems having them so thick, and is just using unnecessary resin. 

[JimFin]

I think your orientation is a significant part of the problem The job is splitting as the suction force is greater than the adhesion due to the cross sectional area being printed at each layer. Solutions would generally be to angle it at 45 degrees to reduce the cross section of each layer, reduce the lift speed possibly and a longer light off time. Difficult to be definitive without knowing your settings.

 

[hegedusmj]

On the next round I reduced the retraction speed from 2mm to 1mm/sec as suggested by Quarryscapes and continued to hollow walls and punch about 20 drain holes. The results were just terrific.

 

One of the replies suggested that orienting the model base at 45o to the build plate. I had tried that just before starting this thread and had perhaps the worst result in terms of tearing and planes being printed as warped surfaces. Conceptually it makes too much sense not to keep using it though. On this last iteration prying the model from the build plate was VERY difficult.

 

Thanks to all for the help.

[JimFin]

6 hours ago, hegedusmj said:

On this last iteration prying the model from the build plate was VERY difficult.

There is a trick to lift a corner with a Stanley type razor scraper or similar ( https://www.uktoolcentre.co.uk/products/stanley-tools-razor-edge-scraper-with-5-blades.html?sku=946048&gclid=Cj0KCQjw4eaJBhDMARIsANhrQADe_bEpoqzC4UMmz2ce1tiSAopg--4auGu-7cUCvmTTnd8DDtK03ygaAhhhEALw_wcB )  and then use the large scraper, A soon as the corner is lifted, it becomes very easy to slide the large scraper under and lift it off.