LW-PLA for buoyancy?

[ChrisMBC]

I just stumbled across the existence of LW-PLA, a 'foaming' version of regular PLA with much less density. I'm wondering if this could be used to 3D print (with 100% infill) buoyant components, such as floats for camera arms. Obvious questions would be the compressive strength, as well as the rate of moisture absorbtion when foamed. Curious if anyone has any experience with this material?

 

[Ryan Wininger]

From what I understand. PLA is biodegradable, I wouldn't use it for anything important that will be exposed to water for any length of time...

 

[kammel78]

From what I understand. PLA is biodegradable, I wouldn't use it for anything important that will be exposed to water for any length of time...

I've had PLA in the water for plenty of time and would consider it fine for non-critical stuff. Also bear in mind, manufacturers can call filament whatever they want, PLA, PETG but the actual content can vary wildly. These are more or less very generic terms and one of the many reasons why PLA from Overture prints differently than eSun, for example, on the same printer.

The bigger issue in my mind with any filament, is how much water ingress are you going to have at depth which will cancel out the potential buoyancy?

 

[ScubaToneDog]

I don't think you would gain anything from this filament. What little you would gain in less weight, you would lose in stability of the part.

Its perfect for RC Aircraft though.

 

[kammel78]

I don't think you would gain anything from this filament. What little you would gain in less weight, you would lose in stability of the part.

Its perfect for RC Aircraft though.

It's not about less weight, it's about adding buoyancy. You're not replacing negatively buoyant camera bits with lighter ones, you're trying to add things that are positively buoyant to offset the heavy camera gear. Same reason you have some sort of bc.

In the OP's use case, stability doesn't come into play. They're floats, under min stress and non-moving (other than ambient pressure). And you can get really great structural results from just about any material if you design and print them properly. There are plenty of reasons why PLA might not be a good choice, but stability isn't one of them in this case.

I say all this because I've seen way too many people (myself included) try to fight with more exotic filaments thinking PLA isn't good enough, when in the time it took to try to get PC, ABS, etc to print reliably, they could've printed, tested, and refined their design with PLA (which is cheap and easy) and then determined whether they needed a different filament. At that point, you've proven your design and can pay a fraction of the cost to have someone else print it in something exotic for you.

I've got a knife sheath that I was going to eventually print in PC or Nylon, but started testing the PLA version, and damn if it hasn't been on a couple of hundred dives and I'm pretty sure I'd have to run over it with a car to break it. Think I have 20 or so out there being used and none has ever broken.

 

[ScubaToneDog]

It's not about less weight, it's about adding buoyancy. You're not replacing negatively buoyant camera bits with lighter ones, you're trying to add things that are positively buoyant to offset the heavy camera gear. Same reason you have some sort of bc.

Less weight in the part would add buoyancy in relation to the water the part is displacing. Making parts or a float out of this filament would add a minimal amount of added buoyancy with less stability in the part.

I agree about PLA, people have this vision of it instantly dissolving in contact with water.

 

[kammel78]

Less weight in the part would add buoyancy in relation to the water the part is displacing. Making parts or a float out of this filament would add a minimal amount of added buoyancy with less stability in the part.

I agree about PLA, people have this vision of it instantly dissolving in contact with water.

You're missing my point. He's not replacing parts, he's adding parts.

Curious what you're basing the "less stability" on. Seems a generalization with no real bearing on OPs use case. Aluminum is softer than steel, still lots of things made out of aluminum. It's all about the use case.

 

[ScubaToneDog]

This particular filament expands when printed which is why the flow rate is around 50%. Its intended to print single walled parts with designed infill bracing which makes extremely light parts. There are some great videos on Youtube for using it. Its not for any load or stress.

 

[kammel78]

This particular filament expands when printed which is why the flow rate is around 50%. Its intended to print single walled parts with designed infill bracing which makes extremely light parts. There are some great videos on Youtube for using it. Its not for any load or stress.

Sorry, but I disagree with most of this, especially the single wall prints part. I think the default min wall settings for most slicers is 2. Why in the world would you not want to print multiple walls?

I also take issue with the over-generalization of PLA is not designed for "any load or stress". It's all about what kind of load, how much stress, where and how those forces are applied as well as the design.

But regardless, you haven't addressed the OP's use case. Floats will not take any load or stress, so PLA would be fit for purpose by your definition.

 

[ScubaToneDog]

Sorry, but I disagree with most of this, especially the single wall prints part. I think the default min wall settings for most slicers is 2. Why in the world would you not want to print multiple walls?

I also take issue with the over-generalization of PLA is not designed for "any load or stress". It's all about what kind of load, how much stress, where and how those forces are applied as well as the design.

But regardless, you haven't addressed the OP's use case. Floats will not take any load or stress, so PLA would be fit for purpose by your definition.

You absolutely can do single wall prints. Vase mode in Prusaslicer is a great example.

2-3 walls is the default setting for a 0.4 nozzle on various slicers, resulting in a wall thickness of about 1.2mm(depending on layer height setting). Personally, I am a 10 wall guy resulting in 4-4.5mm thick walls for everything I make no matter what my infill setting is. For floats or anything that needs reduced water intrusion that would affect buoyancy, 10 walls is the way to go.

I wasn't generalizing PLA at all. I am referring to the LW-PLA the OP is inquiring about to make buoyant components and floats. LW-PLA is a Specialty PLA formulated, that when extruded, it increases its volume about 3 times reducing its weight 50% by the varied density. For instance, to get a 0.4 wall thickness with LW-PLA, you have to adjust flow down to 50% or less and vary the nozzle temp. At normal flow at a higher temp your wall can end up 1mm to 1.2mm with a single wall count. LW-PLA is a specialty filament that takes a bit of fiddling with design and settings to get right. LW-PLA's intended use is for thin, lightweight, single wall parts for model planes, car bodies and cosplay costume pieces. the parts are are not structurally sound and will only take light loads and stress. So you might get a light part, but it wont withstand any water pressure at depth. Regular PLA is a much better choice.

As I stated earlier in my original statement that "this filament would give no benefit". What I thought was implied was "LW-PLA offers no benefit over regular PLA or any other filament of choice". Hope that clears things up for everyone.

The LW-PLA is really cool stuff. Check out YouTube for instructional videos on settings, design and what people are making with this filament.