Precision in Printing (SLA)

[Hole in the ground]

Greetings all. I am having some issues with my prints and was wondering if I could borrow your combined wisdom and intellect.

 

I am trying to create a model of Beardmore's (yes that one) Aviation Ship. Which should look something like this, when Im done:

 

 

The part I am having issues with at the moment are the twin superstructures. Which should look like this:

 

  

 

But are coming out like this:

 

 

 

Has anyone got some hints on what I might be doing wrong and some tips to correct?

 

Cheers

[Bonhoff]

I'm not a user of 3D printing (Yet) but my view would be to do the funnel as a separate part and perhaps more supports depending on the part orientation when printing?

 

Kind regards

 

IanJ

[Hole in the ground]

Bonhoff, thanks for the response. Im not convinced that the funnel is an issue here. I've had a play with the supports (added about 5 times as many as originally) as well as upping the exposure time per layer by 25%. This seems to have produced a reasonably good tolerance part. But I am not sure that it is really necessary to have a support every mm. So I think there is still some more tweaking to be done.

[ICMF]

Unfortunately, you can't just magic up any shape you want with a 3D printer.  You need to design for the medium.  The steps I'd take to troubleshoot, from least to most work/lowest to highest chance of success...

 

Calibrate your resin with a RERF to find the best exposure time.

Print the file straight off the build plate, if you can, rather than using supports.

Add a ton of supports under the overhangs.  These areas will never be perfectly flat, due to the 'tentpole effect', but the more supports, the closer they'll be.

Add a hole to the side of the stacks.  As it is, you're printing suction cups; a small hole in the side will allow airflow and eliminate the suction.

Thicken the thin walls at the front and back of the model.  Adding supports to their sides for lateral stability will also help.

Consider revising the model, to remove the thin, flat overhangs.  You could easily skin these areas with styrene sheet instead.  This would get you closer to your original design. 

[Hole in the ground]

Yes, I'd like to think of myself as reasonably proficient at designing for FDM but SLA is another set of requirements. All good learning though. 

[ICMF]

Just remember, you can do a reasonable job bridging in FDM, but you can't really bridge in SLA - at best, the first layer is a floppy film of resin that's half the thickness of a sheet of paper ; at worst, it'll be a floppy, thin film of resin that simply tears off the part, sticking to the FEP.  This is the 'tentpole effect' - it's like a sheet of fabric being held up by tentpoles, sagging in between them.  This is why the surface facing the build plate is never as crisp as the surfaces facing away from it.

[Hole in the ground]

With a fair amount of post processing, I've managed to get a couple of good superstructure pieces. More learning to be done I'm sure!