FDM 3d printing vs. SLA resin-based 3d printing for waterproof parts

[DreiFish]

Hi,

I'm a noob when it comes to 3d printing, but considering purchasing my first printer to make various parts like zoom gears, ports/port extensions, and floats. From reading through some of the threads here, there seems to be a theme that making anything that needs to be waterproof like ports/port extensions and floats require quite a bit of experimentation to identify right printing material and settings for FDM printers.

 

My question is whether going down the SLA resin-based printing route eliminates this concern? Are resin-based prints inherently better at resisting water intrusion and achieving better structural resistance to water pressure?

[Isaac Szabo]

First a disclaimer: While I have some knowledge on resin printing, I don't actually have any experience using it yet (though I've been considering buying one). 

 

I believe resin prints are inherently watertight, unlike FDM prints, so that's a plus. They're also better at reproducing fine details. However, resin materials are generally weaker and more brittle than FDM materials, and I'm guessing they're more susceptible to degrading under harsh outdoor conditions. Also, resin printing seems to have more annoyances/frustrations due to the mess of the resins (which are health hazards), the washing/curing steps, etc. 

 

My experience is that most people choose FDM for functional prints. Resin printers seem to be more popular for things like miniatures where fine details are more important than strength/durability. 

 

That said, just as there are numerous types of FDM materials with different properties, there are many different types of resins, some of which are "tough" resins that are designed to have more strength/durability for functional parts. My impression is that they still lag behind the best FDM materials, but that doesn't necessarily mean they're not good enough for our purposes.

 

To sum up, waterproofing is the challenge with FDM, though some people have been able to figure that out. On the other hand, strength/durability is the challenge with resin, and I'm less sure if that can be figured out for underwater parts that need to withstand high pressure, saltwater, sunlight, etc. 

Edited June 25 by Isaac Szabo

[Mathieu Cornillon]

I've had some (little) experience with resin printing for small parts, that are used outside the housing, and don't need to be watertight : I designed and printed knob extensions for my housing, so that some buttons get easier to manipulate.

 

So far, I found resin printing to be more prone to "breaking", there is strictly NO flexibility, so if your printing tolerances are too tight, you can't force it, otherwise it would break.

 

I've made about 10-15 dives with them, and I have not seen any degradation so far, it seems very stable & durable.

 

Here are examples:

 

 

 

Edited June 25 by Mathieu Cornillon

[DreiFish]

3 hours ago, Isaac Szabo said:

First a disclaimer: While I have some knowledge on resin printing, I don't actually have any experience using it yet (though I've been considering buying one). 

 

I believe resin prints are inherently watertight, unlike FDM prints, so that's a plus. They're also better at reproducing fine details. However, resin materials are generally weaker and more brittle than FDM materials, and I'm guessing they're more susceptible to degrading under harsh outdoor conditions. Also, resin printing seems to have more annoyances/frustrations due to the mess of the resins (which are health hazards), the washing/curing steps, etc. 

 

My experience is that most people choose FDM for functional prints. Resin printers seem to be more popular for things like miniatures where fine details are more important than strength/durability. 

 

That said, just as there are numerous types of FDM materials with different properties, there are many different types of resins, some of which are "tough" resins that are designed to have more strength/durability for functional parts. My impression is that they still lag behind the best FDM materials, but that doesn't necessarily mean they're not good enough for our purposes.

 

To sum up, waterproofing is the challenge with FDM, though some people have been able to figure that out. On the other hand, strength/durability is the challenge with resin, and I'm less sure if that can be figured out for underwater parts that need to withstand high pressure, saltwater, sunlight, etc. 

 

Thanks for the input, Isaac! Sounds like FDM may be the way to go, at least for initial learning curve, and consider resin later down the line. Are there any FDM printers you (or others) would recommend to start out with, especially with the mindset that it should have the flexibility to print materials that can be waterproof? Budget is $1000.

 

Another thought -- how about adding SLS technology to the comparison? Is it the best of both worlds for the use cases outlined in original post? Or would an SLS printer be completely out of budget and thus not worth considering?

 

(I just found out I have access to a CNC machine at work -- no idea about 3d printers --  so maybe I'll stick with with FDM for now and buy some time on our CNC machines for more interesting metal or derlin projects once I have the design worked out)

[Dave_Hicks]

I've made some waterproof parts with my 3d printers. To the best of my knowledge, you can't expect any 3d printed plastic to be fully waterproof under pressure. You need to do some post printing process to treat and seal it. Acetone smoothing, resin, etc. 

 

I've successfully created and tested a Nauticam m87 & m60 port float that can add about 10 ounces of buoyancy to my rig. I printed it in PLA+ on my Bambu P1S and on my earlier Creality Ender 3 S1. I printed with 5 walls perimeters, 8% infill. To finish and seal the print I painted it with a layer of epoxy resin. This has worked great and has been tested up to 80-90 feet and used on about 5-6 dives so far. I plan to add a carbon fiber wrap to it soon for better durability.

 

If you plan to spend $1000 you should buy a Bambu P1S Combo (w/AMS) no question. Get 3 colors of PLA and 1 on PETG to get started. Maybe a TPU later on for specialty objects. The P1S will get you going fast and work great. I started with the Creality last year as it requires more tweaking, tuning, and trail/error, but I learned a lot. I replaced it with the Bambu and it's so much better in every way. 

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Pictures:

 

Edited June 25 by Dave_Hicks

[DreiFish]

Thanks David! I guess I could stretch the budget a bit to the Bamboo X1 Carbon also if there's a point. It's currently on sale for $1049. 

[Isaac Szabo]

3 hours ago, DreiFish said:

 

Thanks for the input, Isaac! Sounds like FDM may be the way to go, at least for initial learning curve, and consider resin later down the line. Are there any FDM printers you (or others) would recommend to start out with, especially with the mindset that it should have the flexibility to print materials that can be waterproof? Budget is $1000.

 

Another thought -- how about adding SLS technology to the comparison? Is it the best of both worlds for the use cases outlined in original post? Or would an SLS printer be completely out of budget and thus not worth considering?

 

(I just found out I have access to a CNC machine at work -- no idea about 3d printers --  so maybe I'll stick with with FDM for now and buy some time on our CNC machines for more interesting metal or derlin projects once I have the design worked out)

 

Like Dave said, for FDM it’s hard to beat Bambu Lab’s printers right now. They have a range of options, starting with the very capable A1 at only $340 (or $490 with the optional multi color/material unit). 

 

That said, if you happen to see a good deal on a used Prusa MK3 or MK3S, that’s the printer that I have developed a waterproof print profile for and could probably share it. The Bambu Lab printers are certainly newer/nicer, but you might have to do quite a bit of experimenting to find good waterproof settings. I have a Bambu Lab A1 too but haven’t developed a waterproof profile for it yet.

 

I’d personally recommend skipping PLA and going straight to PETG for functional parts. PLA has a lower softening temperature (parts may soften/warp in a hot car for example), is not as durable in the elements, and is more brittle. PETG has been just as easy to print for me, and it’s just as cheap, so I see no reason to use PLA.

 

Yes, SLS printers are still well beyond the range of hobbyists as far as I’m aware. However, you can always get your designs printed by print companies that have expensive SLS printers. 

 

Lucky you to have access to a CNC!

 

1 hour ago, Dave_Hicks said:

To the best of my knowledge, you can't expect any 3d printed plastic to be fully waterproof under pressure. You need to do some post printing process to treat and seal it. Acetone smoothing, resin, etc. 

 

It’s certainly possible. I print fully waterproof ports and other parts that require no post processing. I’ve been using them for 3-4 years. So far I have tested the ports to over 100m/330ft. 

[Dave_Hicks]

34 minutes ago, Isaac Szabo said:

It’s certainly possible. I print fully waterproof ports and other parts that require no post processing. I’ve been using them for 3-4 years. So far I have tested the ports to over 100m/330ft. 

Please share a profile or setting for how you do this. 

 

I found that to get a good balance of weight vs buoyancy and strength to not implode, printing with 4-5 walls and minimal infill provides enough strength. Epoxy takes care of the waterproofness for minimal cost in weight. 

[Dave_Hicks]

58 minutes ago, DreiFish said:

Thanks David! I guess I could stretch the budget a bit to the Bamboo X1 Carbon also if there's a point. It's currently on sale for $1049. 

These is very little difference between the two unless you have very specific requirements. After consideration I saw no advantage of hoping up to the X1. I am very happy with the P1s. 

[Isaac Szabo]

12 hours ago, Dave_Hicks said:

Please share a profile or setting for how you do this. 

 

I found that to get a good balance of weight vs buoyancy and strength to not implode, printing with 4-5 walls and minimal infill provides enough strength. Epoxy takes care of the waterproofness for minimal cost in weight. 

 

The profile I've developed in PrusaSlicer for my MK3 is not directly applicable to a different slicer/printer. However, the main settings that come to mind are:

 

PETG filament

0.4mm nozzle

0.10mm layer height

for ports, solid prints composed entirely of perimeters/walls

for hollow items like a float, designs probably need a minimum wall thickness of around 3mm

random outside seams and staggered inner seams

extrusion multiplier/flow ratio around 20% higher than normal

 

And then there are other tweaks to temperature, speed, linear advance, etc to improve print quality. Bambu's slicer is simpler than Prusa's and may not have all the necessary options (such as staggered inner seams), so using another slicer such as OrcaSlicer may be preferable. No matter what it will likely take a fair amount of experimentation to find a sweet spot between watertightness and acceptable print quality. 

 

You also need ways to test if the prints are actually waterproof and capable of withstanding pressure. I print a small test chamber that I can pull a vacuum on and monitor a pressure gauge to see if it holds a vacuum indefinitely or if leaks over time. If my print settings pass a vacuum test and I print a real object such as a port then in addition to a vacuum test I also I test it in a hydrostatic pressure chamber to ensure that the design will withstand the pressure that I need it to. 

 

Of course, if post processing prints with resin is working for you and you're happy with that, then there's no reason you need to do anything differently. I can see how that could work well for something like a float, but it's not ideal for something that requires more precision such as a port with an o-ring groove. 

[CaolIla]

2 hours ago, Isaac Szabo said:

I can see how that could work well for something like a float, but it's not ideal for something that requires more precision such as a port with an o-ring groove. 

I builded a snoot with o-ring to sealed the inner part containning a diaphargm an some lens.   

PETG with Epoxy resin and O-Ring it works well .
 

[Isaac Szabo]

35 minutes ago, CaolIla said:

I builded a snoot with o-ring to sealed the inner part containning a diaphargm an some lens.   

PETG with Epoxy resin and O-Ring it works well .

 

Nice. Of course it can work. I just said that it's not ideal when precision is needed since adding epoxy resin is imprecise. I used to add epoxy resin to o-ring grooves. It worked but sometimes I added a bit too much or not quite enough. I also personally just prefer to have prints waterproof straight off the printer and not have to put more work into them. But by all means do what works for you. 

Edited June 26 by Isaac Szabo

[Dave_Hicks]

4 hours ago, Isaac Szabo said:

 

The profile I've developed in PrusaSlicer for my MK3 is not directly applicable to a different slicer/printer. However, the main settings that come to mind are:

 

PETG filament

0.4mm nozzle

0.10mm layer height

for ports, solid prints composed entirely of perimeters/walls

for hollow items like a float, designs probably need a minimum wall thickness of around 3mm

random outside seams and staggered inner seams

extrusion multiplier/flow ratio around 20% higher than normal

 

And then there are other tweaks to temperature, speed, linear advance, etc to improve print quality. Bambu's slicer is simpler than Prusa's and may not have all the necessary options (such as staggered inner seams), so using another slicer such as OrcaSlicer may be preferable. No matter what it will likely take a fair amount of experimentation to find a sweet spot between watertightness and acceptable print quality. 

 

You also need ways to test if the prints are actually waterproof and capable of withstanding pressure. I print a small test chamber that I can pull a vacuum on and monitor a pressure gauge to see if it holds a vacuum indefinitely or if leaks over time. If my print settings pass a vacuum test and I print a real object such as a port then in addition to a vacuum test I also I test it in a hydrostatic pressure chamber to ensure that the design will withstand the pressure that I need it to. 

 

Of course, if post processing prints with resin is working for you and you're happy with that, then there's no reason you need to do anything differently. I can see how that could work well for something like a float, but it's not ideal for something that requires more precision such as a port with an o-ring groove. 

Cool. Thanks for sharing. 3mm is not much more than what I used, but I have not tried upping the extrusion multiplier. I also stayed at a standard 0.2mm layer height. I will consider your formula when I try a new project. I need some better arm floats for the heavier HF-1 strobes, so I may have another project shortly. 

[Cromagnon]

I have run various 3d printers in a R&D lab using SLS, SLA, and FDM.  For the casual user the SLA would produce the smoothest, highest fidelity print with the lowest learning curve.  There are many resin additives available to provide durability to the print for the environment that it will be used in.   Water can be used for some post processing cleaning, depending on the resin that is selected.  Disposal of the cleaning solutions for any of the resins I have used involved placing the solution in the sun or curing chamber for a day and filtering the solids while reusing the liquid.  The solids are disposed of as plastic waste.  Some are recyclable.

 

FDM would probably be the cheapest but for close tolerance fitting it is an exercise in patience and perseverance.  We did have success milling surfaces as a post processing solution for fitment.

 

SLS is the cats meow but the cost is probably outside the scope of the casual user.  They print jet engine bleed air ducts using that process and it is AMAZING.

[Isaac Szabo]

1 hour ago, Cromagnon said:

For the casual user the SLA would produce the smoothest, highest fidelity print with the lowest learning curve.  There are many resin additives available to provide durability to the print for the environment that it will be used in.

 

Can you recommend any affordable resins or additives to try for printing ports that might stand up to diving pressure, saltwater, UV, bumping into rocks, etc?

[Cromagnon]

I have had very good results with Phrozen's Impact Plus resin.  https://phrozen3d.com/products/impact-plus-resin

 

The finish and resolution has been true to my renderings and I have drop tested from 1 meter on a marble slab without breaking or cracking.  I have not done any water immersion testing.

 

I do not have any interests in the Phrozen company, I just use their resins.

[shokwaav]

On 6/26/2024 at 12:06 AM, DreiFish said:

Another thought -- how about adding SLS technology to the comparison? Is it the best of both worlds for the use cases outlined in original post? Or would an SLS printer be completely out of budget and thus not worth considering?

 

AFAIK, SLS prints are made from nylon (PA12) which is not suitable for underwater immersion. 

Source: https://xometry.pro/en-eu/articles/3d-printing-water-resistant/

 

The best material to use is probably PETG, PC or ASA.