Modelling support structure for 3d printing

[Drewpan]

Hi All,

I am having a few issues with the automagic support structure from

the Slicer and my model. I have tried several different variations using

Prussa and the AnyCubic slicers but they both create these huge chunky

supports that take almost as long to print as the model does and they

are incredibly difficult to remove without destroying the model.

I have done a bit of research and there are a couple of suggestions I want

to try. One of the Slicers suggests "Tree" Supports that seem to be like a

little tree (as the name suggests) that have a small footprint and widen as

the layers are printed so that they are fully supporting the model structure

when they need to.

The AnyCubic Slicer that suggests it says that supports are not needed for

the model but so far every print without supports has failed. I have tried

tweaking the AnyCubic Slicer settings but no luck so far. It will not build

tree supports, just the chunky ones.

Option two is model the supports myself. I have given this a try but so far

with mixed results as it is difficult to know how much actual "support" each

part actually needs.

My question is really about what advice others may have for this problem?

If I was to model supports myself then the main issue is how big are they?

I obviously need to remove them after the print without too much damage

to the model. What size "pad" should I use and what shape so it will easily

break off but still give the filament bridge for an almost horizontal print in

space? Would the support shape matter with these Blades that need the

support? The Leading and Trailing Edges of the blades are razor sharp so

avoiding support at all if possible is preferred.

As you can see the Blades are getting hammered when I remove

the supports and the rear hub gets filled up and is very difficult

to remove.

There is some delicate structure on the model and it is easily damaged

but the print is to see the detail well enough to know it is correct when

it is sent to be CNC milled. What I need is a print that is "good enough"

to see not actually bolt onto something and use.

Cheers

Andrew

[billbedford]

You have to understand that 3D printing produces objects with five 'good' sides and one which is less than perfect.

I suggest that you redesign this fan and print each blade individually, with a separate hub. This will enable you to print the blades vertically and on the build plate. The quality of the edges of the blades will then be dependent on the resolution of your printer. 

[Drewpan]

Hi,

Redesign isn't possible for this project. The fan is only 148.5mm diameter so it is already

very small. It wasn't originally made for 3d printing it is to go directly to CNC machining.

The idea of the 3d printing is to get a visual on how it will look to make sure there are no

gross errors in it. It doesn't have to be perfect, just usable. Sometimes it comes out really

good on the blades just not all blades at the same time.

Some slicers say I don't need supports but I haven't had a good print without them. Each

print takes 6 hours for the model and anything up to another 8 hours for the supports. We

are using an AnyCubic Kobra 2 Pro Max and a new Kobra 3 Max. The K3 only has support

on the AnyCubic Slicer right now but the K2 I have a profile for it on Prussa.

I don't expect good resolution on the edges of any of the blades. When CNC done you could

ACTUALLY shave with them they are so sharp. I wouldn't try though you'd come out looking

like a slasher movie.

Cheers

Andrew

[billbedford]

I'd say that almost 6in diameter for a fan would be pretty big, but there you go.

You don't say what size nozzle you are using. If it is too big, making the layer height more than the thickness of the blade edges, then you are going to get the gaps in the edges that show in the photos. You could try using a 0.2mm nozzle, but printing the blades vertically is the best solution. Since this is going to be a visual test model, why can't you model a section of the hub into each blade and then glue them all together after printing? 

I'm certain I could print this fan in this orientation on one of my resin printers, as the layer height is 0.05mm, and the point size of supports near the blade edges would be 0.2-0.3mm. 

[bwalker145]

It might be worth looking into contracting a third-party for a SLS print, if you're having issues with FDM.

That's what I've done in a few cases for prototypes when FDM just couldn't provide the product detail/quality I needed. Much better looking parts with the SLS, and still fairly cost-effective.

[wersy]

The print result was to be expected.
This would require a dual-filament printer that prints water-soluble support material.
I always design in such a way that support is never needed. To avoid support, I split up the construction accordingly.

Fifteen years ago, I designed a special surface propeller that was shown to customers for advertising purposes. The propeller was detachable and could be stored in a space-saving manner when traveling.

Your propeller could be divided in a similar way and the blades printed vertically as well.