3D printing plastics – PLA vs ABS in practice

Welcome on my blog! Today, we are going to go on with the differences of the most common 3D printing materials, the ABS and PLA plastics. The most desktop 3D printers can work with these materials, last week’s post was about the main characteristics of the two filament types, today it’s going to be about some special aspects of use in practice. I want to discuss some important things about these 2 materials, I mean the shrinkage factor, rigidity, bio-degradability and heat resistance.

Rigidity

A fact is a fact: PLA is a much more rigid material compared to ABS. If you compare ABS and PLA by applying a progressive force, ABS will start to bend and finally will break; while ABS is bending, PLA on the other hand will hold it’s shape (it’s very rigid and doesn’t flex). Actually, this one is the reason for the design fail of the plunger construction of the MakerBot Replicator 2. The guys at MakerBot have set the old plunger construction used in the Replicator1 and other RepRap 3d printers. But those all work with ABS filament, which is . as mentioned above – not as rigid as PLA. After 100 hrs of 3D printing with my new Replicator2 desktop 3D printer, the filament has cut a hole in the plastic cap of the plunger. It’s okay – I thought – and I have tightened the screw on the plunger a little. I got another 100 hrs of 3D printing, but after that, another hole has appeared. There is a much better – a spring loaded – construction for that, you can download the upgraded plunger form Thingiverse and 3D print your own.

PLA is more rigid and its surface is harder as well. When applying more force, after a certain point it will eventually break before bending. You often need more force to break a PLA part than an ABS one especially if you have a thick part.

Something about the shrinkage factor of PLA for 3D printing

Fact: PLA has a much lower shrinkage factor than ABS. Usually it means that it is MUCH easier to use in the most common desktop FDM 3D printers: unlike ABS, PLA deforms definitely less and suffers from very little layer detachment leading to a much higher success rate on your 3D prints. I’ve 3D printed my most beautiful parts all with PLA, ABS isn’t the right choice for fine surface finishes.

With ABS, even a relatively small part will deform when printing if you don’t have a heated bed and/or a heated building environment. With the RepRap machines like the Felix or the Prusa model, it is really hard to get a tempered 3D print environment, because the working area of the 3D printer isn’t closed. (I’ve never managed it to heat it up to 100 Celsius as suggested, my maximum of bed temperature has been 80 Celsius with my RepRap.) With the more expensive desktop 3D printers like the MakerBot Replicator 2X it would be better: the tempered chamber of the 3D printer allows you to control the temperature of your prints immediately.

Are you interested in painting of your 3D printed plastic parts? I have really good news for you: both usual 3D printing materials – PLA and ABS – can be painted and post processed (sanded) if needed. First thing is first… Preparation. There are some Items that you need when prepping the plastics to paint. This first step is really important, because if you missed it, the primer didn’t bond well with the ABS plastic and tended to flake off.

Bio degradability

PLA is a bio degradable material. This means it will resist for very long in indoors use and occasional outdoors use but permanent exposure to the elements will eventually start to degrade it. It is not suitable, for example, for parts that need to stay outdoors 365 days a year; for these applications ABS is preferable.From what we’ve seen over the years we’ve been selling 3D printers there are 3 very specific cases where ABS is preferable over PLA:

Outdoors use

I’ve had a customer a couple of weeks ago who has asked me to 3D print build enclosures for electronics modules that were going to be left outside for many years. In that case ABS was the better choice because it’s not biodegradable, so it is more durable for outdoor use.

Flexible parts

Another customer needed to build supports for DIN rails. The support needed to flex enough to fit into the DIN rail. I have 3D printed the same part in PLA and ABS. PLA, caused by its rigidity, wouldn’t flex so ABS was the right material because of its flexibility. In the last couple of weeks, some flexible PLA materials have appeared on the market as well; I’ve already ordered some spools for testing but I haven’t got any experiences with them yet. I’m looking forward to see the results.

Temperature and heat resistance

Fact: ABS has a higher melting temperature so if you need plastic parts that need to deal with high temperatures (about 100 Celsius or more), than ABS is also preferable over PLA because of its higher melting point.

 

My conclusion: all in all PLA is not a “one size fits all” but it will meet the needs of 95% of the 3D printing enthusiasts and – from experience – it is so much easier to 3D print compared to ABS.

That’s it for today, I hope this posts helps clear out some questions about the right choice of material for 3D printing. In my next post, I’m going to write about some really special, experimental materials which can be 3D printed as well, just think about some wood or sandstone 3D printed things. It sounds awesome, doesn’t it?

 

Some facts about the most common 3D printing materials: PLA vs. ABS

Hi there, it’s me again. Today we’re going to discuss some myths and truths about the most common 3D printing materials used in FDM (Fused Deposition Modeling) technology, which is applied in the usual affordable desktop 3D Printers like my MakerBot Replicator2, Cube, Solidoodle, RepRaps, uPrinters and so on…

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Honestly I felt – based on your questions and feedback – that it would be really necessary and important to clarify some key facts about PLA (Polylactic acid) and also the pros and cons, I mean the the advantages and disadvantages of PLA vs ABS (Acrylonitrile butadiene styrene) when used on FFD printers (such as the Makerbot Replicator2, Thing-O-Matic, Cupcake, Mendel, Felix, Rostock, UP!, etc.).

At first, I really would like to say that PLA is an absolutely strong and very durable material for 3D printing.

There are a couple of myths around this great material (PLA):

Some of you think that PLA will dissolve in water and/or will degrade in moist or wet environments. That is totally false. The 3D printable plastic, which is often used as a support material with dual extrusion 3D printers and which dissolves in water is PVA (Polyvinyl alcohol), not PLA.

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Another fake myth is the durability of this great material. Some people – even some 3D print enthusiasts – are afraid from PLA, because they think that it will self destruct and simply become undone in a matter of months, just because PLA is biodegradable. I have to repeat myself, again, not true.

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“Biodegradable” means – in my opinion and literally as well – that the product is strong and performs its function very well but when you throw it in a landfill or soil it will ultimately break down, of course not instantly, it takes a couple of years to complete the biodegradation process.

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This is actually much more environmental-friendly comparing to ABS which takes over hundreds of years to break down. In addition PLA is made from natural resources such as corn starch or sugar cane, which makes this great material the right choice to create plastic parts at home. Just think about it, what if it will be true and the revolution of additive manufacturing and desktop 3D printers was going to escalate, everyone would like to be a designer and will print the own ideas day and night. We should be more responsible for our mother nature and not 3D print too much ABS junk. (Although we have to recognize, that ABS and PLA could be recycled as well.)

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Some people claim that ABS is much stronger than PLA. That’s a little bit more complex, because the sentence mentioned above is absolutely true. This is the most recurring myth in the PLA vs ABS war and it’s also absolutely inaccurate: if you compare injection molded parts, ABS parts are pretty much stronger than it’s PLA counterparts; however we’re doing our 3D printed prototypes layer by layer, not injection molding and this changes things considerably:

A 3D printed part in PLA is MUCH stronger than a part printed in ABS. This is because PLA has much stronger layer bonding than ABS.

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Let me tell you some words about layer bonding: unlike injection molding, FDM printers  3D print layer by layer so layer bonding is what determines the part strength.

If you are familiar with 3D Printing you’ll know that the strength of a 3D printed plastic part changes depending on the direction: if you pull perpendicularly to the Z axis – I mean vertically – (where layers are deposited), they will detach; if you pull in any other direction the part is much stronger. It behaves a bit like wood, this kind of anisotropy is really characteristic for natural wood products, and for 3D printed wood as well.

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Because PLA has much stronger layer bonding it’s almost as strong in all directions (even when pulled in the Z axis).

ABS on the other hand, will detach layers much faster and much easily than PLA, making 3D printed ABS parts less strong. (they aren’t weak either; PLA parts are just stronger).

In my next blog entry, I want to discuss the PLA vs ABS thing in practice; there will be a lot of useful information about the shrinkage factor, rigidity, post-processing/sanding and melting temperature, so stay tuned;)