Stuff your 3D printer has made today...

[Screwdriver]

What are the general differences between PLA & PETG, in regard to suitability for certain types of item?

I haven't used PLA since I got the machine. My understanding is that PLA might be a bit stronger or tougher because it will yield. PETG is harder and "better" for practical working parts/mechanisms, has a higher heat tolerance and a lot less susceptible to UV degradation.

 

[fractured]

Does your printer have Marlin firmware?

I really wouldn't know, it's basically how I unpacked it - appart from building of course!

 

[PhillipM]

I haven't used PLA since I got the machine. My understanding is that PLA might be a bit stronger or tougher because it will yield. PETG is harder and "better" for practical working parts/mechanisms, has a higher heat tolerance and a lot less susceptible to UV degradation.

Entirely the other way around, PLA is harder, stiffer and more brittle. PETG less so so it it's a bit better for toughness and where heat resistance is needed. (Although worth noting, PETG exhibits quite a lot of rate-dependent behaviour, almost non-newtonian, if you hit it hard/fast enough it'll stiffen and shatter)

 

[Screwdriver]

Entirely the other way around, PLA is harder, stiffer and more brittle. PETG less so so it it's a bit better for toughness and where heat resistance is needed. (Although worth noting, PETG exhibits quite a lot of rate-dependent behaviour, almost non-newtonian, if you hit it hard/fast enough it'll stiffen and shatter)

We can agree to disagree.

 

[Onoff]

What are the general differences between PLA & PETG, in regard to suitability for certain types of item?

If you make a phone holder from PLA for the car it'll go all floppy and bend in hot weather. When you come back having forgotten to put it in the shade, it'll have dropped down the dashboard. If you remake in PLA...it'll do it again!

 

[ajlelectronics]

We can agree to disagree.

He is correct though.

 

[PhillipM]

I mean we can, or we can look at datasheets for the facts, it's really easy

 

[Screwdriver]

We can go into the deep tech and perfectly describe "strength" and "brittleness" etc. and if you do a quick Google it will tell you that PLA prints are more brittle for example. But that is referring to poor layer adhesion, not the fundamental properties of the plastic.

Models printed in PLA can withstand higher forces because a good print will yield, whereas a PETG model will break. One of the problems PLA has though is that of creep. It might not break and it might be "stronger" but over time it will "flow", buckle and distort. PETG is harder (though I do not have the data for that) and does not suffer from creep. Since a PETG print will crack and break before it yields or distorts, I use the term "brittle" to describe how a model behaves in the real world, not just on Google.

I assume my undefined use of the word "strength" is causing the issue here. If you disagree regarding temperature stability and UV resistance you'll be dead wrong.

For those who suggest my comment is obviously "wrong" please define what YOU mean by strength and how you would measure it...

 

[ukracer]

I have grabbed couple of rolls of the wedge3d website. I believe is flexible but can be used on a bowden printer.

So I might be checking in soon.

 

[Screwdriver]

FWIW the old Ender3 can print flexible filament quite happily. At least it does with <whatever it was> that I bought. I imagine it will depend largely on the precise type of flexible filament you get. Good luck!

 

[ukracer]

FWIW the old Ender3 can print flexible filament quite happily. At least it does with <whatever it was> that I bought. I imagine it will depend largely on the precise type of flexible filament you get. Good luck!

It's flying out as its closing Thursday. There is only beige left in what I grabbed.
I got brown green and white

 

[PhillipM]

We can go into the deep tech and perfectly describe "strength" and "brittleness" etc. and if you do a quick Google it will tell you that PLA prints are more brittle for example. But that is referring to poor layer adhesion, not the fundamental properties of the plastic.

Models printed in PLA can withstand higher forces because a good print will yield, whereas a PETG model will break. One of the problems PLA has though is that of creep. It might not break and it might be "stronger" but over time it will "flow", buckle and distort. PETG is harder (though I do not have the data for that) and does not suffer from creep. Since a PETG print will crack and break before it yields or distorts, I use the term "brittle" to describe how a model behaves in the real world, not just on Google.

I assume my undefined use of the word "strength" is causing the issue here. If you disagree regarding temperature stability and UV resistance you'll be dead wrong.

For those who suggest my comment is obviously "wrong" please define what YOU mean by strength and how you would measure it...

Dead wrong? PLA is more UV stable than PETG (it's not recommended for outdoor use because of degradation from heat and microbial attack, and the PLA dyes fade rapidly in UV usually, not because PLA isn't UV resistant).
PLA is stronger than PETG. PLA is harder than PETG. PLA is more brittle than PETG.
In the real world and in datasheets. I say that as someone that's printed about 50kg of various PETG for production, structural parts in end-use environments.

It's very simple, it's all very easily available information. I'm not sure what you define strength as but for it to be the way around you suggest, it must be a whole lot different to what anyone else does.
Want an example here's Prusaments as-printed datasheets, PLA:

And PETG:

PLA is harder, stronger, stiffer and more brittle.

 

[PhillipM]

If one source isn't enough, colourfab PLA:

vs PETG:

Same trends. You'll note I picked black all the way through for consistancy too, as colours affect the properties.

 

[Dr.Al]

My understanding is that PLA might be a bit stronger or tougher because it will yield. PETG is harder and "better" for practical working parts/mechanisms, has a higher heat tolerance and a lot less susceptible to UV degradation.

That sounds wrong to me - it's PETG that will yield and PLA that's brittle and will snap. PLA is hard so good under compressive loads, but brittle so not as good in working parts.

 

[clift_d]

What are the general differences between PLA & PETG, in regard to suitability for certain types of item?

A big difference for me is workability after printing, e.g. sanding, filing, etc. In my experience you're limited in what you can to PLA without risk of chewing up the surface.

 

[Screwdriver]

In the real world and in datasheets. I say that as someone that's printed about 50kg of various PETG for production, structural parts in end-use environments.

OK thanks. I'll have a good look at those data and get back to you. It will take some time and I'll have to reexamine where I got my information from.

 

[PhillipM]

There is unfortunately a whole lot of misinformation around in the 3D printing world from people that don't really have much idea and then it gets parroted around everyone because half the sites and forums all rip off their info from everywhere else and it goes around and around in circles.
A whole lot of people print PLA far too cold to make it easier to print and underextrude slightly to make sure it looks pretty and then claim it's a low strength material when it falls apart - the reality is it's because they haven't bonded the layers together properly and the print is full of voids. It's entirely on bad printing practices, not really the material, it's one of the stronger common materials for printing.

 

[m_c]

I had it in my mind that PETG is stronger, but usually fails via snapping, versus PLA that will usually bend/deform and is more prone to environmental degradation.

However the main reason I use primarily PETG is for it's chemical resistance and stability.

 

[pint]

A whole lot of people print PLA far too cold to make it easier to print and underextrude slightly to make sure it looks pretty and then claim it's a low strength material when it falls apart - the reality is it's because they haven't bonded the layers together properly and the print is full of voids. It's entirely on bad printing practices, not really the material, it's one of the stronger common materials for printing.

I've made dimple dies in PLA and i've been amazed at what it'll survive in the press

not so good out in the weather and sun though.

 

[PhillipM]

PLA snaps too. What's sold as PLA+ (Or often HT PLA, although there's one or two exceptions) doesn't, but that's not PLA, despite the name - it's a hybrid with a large amount of PHA in it, or sometimes entirely PHA.