Hobbyist Forums banner

3d printing for models,PLA or ABS?

6K views 48 replies 12 participants last post by  charonjr 
#1 ·
What's the better choice?
 
#2 ·
Found this at all3dp.com:

PLA (PolyLactic Acid) is a biopolymer, i.e., a biodegradable plastic. It is made from renewable raw materials such as cornstarch or sugarcane. Aside from 3D printing, it is typically used for packaging material, plastic wrap, plastic cups and plastic water bottles. It is considered to be more ecologically friendly than ABS – after all, it’s made from plants.

ABS (Acrylonitrile-Butadiene Styrene) is an oil-based plastic. It is a tough material that can be used to create robust plastic objects for everyday use, for example in cars, electrical equipment or even in the popular Lego bricks.



PLA is more brittle and has a higher surface hardness. It is more prone to break when bent. Objects made from this material can be cut, filed, sanded, painted, and bonded using adhesives; treating them with acetone (for improving surface smoothness) is not possible.

When printed at the temperature recommended by the filament producer, ABS exhibits a superior layer bond. Objects 3D printed this way will be stronger and more impact-resistant. Therefore, it is better suited for mechanical parts and for objects that need to be weatherproof. Moreover, ABS parts are more flexible than PLA parts and tend to bend rather than break when under pressure. Also, ABS is better malleable, postprocessing is easier: The printed object can be cut, filed, sanded, painted, and bonded. And they can be treated with acetone to get a smooth and shiny surface or to weld two objects together.

To me, ABS seems to be the better choice.
 
#3 ·
ABS requires a heated printing surface (bed).
It also smells worse than PLA when printing.

I've used PLA for model parts and it works fine. It's harder than styrene, sanding it can be a pain but the dust is non-toxic. Gluing it is not as easy as styrene as well, no way to fuse parts together, I've used gorrilla glue and CA glue and they work fine, or epoxy if you want it to hold forever.

I printed parts to make a sub kit look like the one my dad was on in the 50s, he was on a heavily modified guppy, see the build thread here:

http://www.hobbytalk.com/bbs1/170-military-aircraft-models/424734-guppy-sub-conversion.html

I haven't printed with ABS yet, but I will be trying it out at some point now that I've got a house with a basement where I can put a fan in a window for ventilation. Right now I'm getting stuff set up for learning airbrushing so I'll be busy with that for a while.
 
#4 ·
Non-3D printer user here reminding that given the nature of the materials it's probably a real good idea to make SURE you've got good, constant ventilation going on. If nothing else buy a cheap small fan to keep the air moving. Luckily it's the time of year where most every store has a variety of fans available, esp. the small 'clamp on' kind sold for student's dorm room.
 
#5 ·
ABS is harder to print than PLA usually, but easier to work with afterwards. It is much easier to sand and finish.

I have had success gluing PLA with Plastruct Plastic Weld and Tenax and, depending on the PLA, regular old Testor's glue. CA and Gorilla Glue work as well.
 
#6 ·
ABS is harder to print, but you can use acetone vapors (carefully!) to smooth out the print steps on the outer surface. You can also use acetone (or regular model glue) to glue the parts together. You can also print with HIPS (High Impact Poly Styrene) which is a bit softer but otherwise identical to ABS when it comes to printing.

I've been having success printing ABS on a Monoprice Mini Select 3D with a PEI build surface and the bed set to 80C. For ABS, you do not want cold (or cool) air hitting the extruder. I use a 50 gallon clear plastic tub over the printer to keep the air currents to a minimum and keep styrene fumes in the box.

PLA is easier to print than ABS or HIPS, but getting rid of printing artifacts requires priming and sanding. I haven't found any glue that works well with PLA, other than epoxy or CA.
 
#7 ·
I havent sprung for a 3d printer as of yet, but I always read/hear calibration is the hardest part to master (set) with them.

Does the choice of PLA or ABS factor into calibration maintenance?

Can you switch back and forth on the same calibration settings?
 
#8 ·
There are different calibration settings. One is based on the printer parameters (how many steps per millimeter on each axis, the temperature sensor specs and the heater element specs and calibration). You usually do this once, or when there are changes to the printer (new motors, heaters, thermistors).

The second set of calibration code (that doesn't change much) gets executed right before printing and right after. For instance, as the head heats up, some material will ooze out of the printer. I have a "wipe" step where the head prints a long, flat line on the build surface to clean the head and prime the extruder with molten plastic right before it starts printing the object. After it finishes printing, the code turns the heater off, turns on the cooling fan on the head for a few minutes and parts the extruder head (to get it out of the way).

A third set of commands is embedded within the code generated for the object you want to print. This changes depending on the material. PLA and ABS print at different temperatures and require different settings, like retraction distance and speed (how quickly and far the printer pulls back on the filament to avoid/reduce stringing) extrusion amount, etc. When I switch filaments (which can be a PITA all by itself) I'll print a test object to make sure I have the settings dialed in. These settings are changed in whatever slicer program you use (for instance, Cura or Slic3r, both are free) and are saved with the object.
 
#10 ·
I won't print parts in PLA and then glue them on my model. On the other hand, I *do* print parts in ABS and use them in my models.

For me, I am very picky about materials that go into my models, so I don't trust PLA. It's bio-degradable, can be brittle, and may not hold up to the environment (i.e. changes in temperature and/or humidity) over time. It is not guaranteed to be dimensionally stable. It can warp at not-so-hot temperatures. All these characteristics make it unsuitable for use in models IMHO. What it *can* be useful for is making master patterns that will be molded and cast in some other material.

In contrast, I do trust ABS. It is a heavy-duty engineering plastic and many of the parts in your car are made from this material. ABS is strong and somewhat flexible. It is dimensionally stable over time and better able to resist the environment.
 
#11 ·
That's being serious level picky, the only real issue listed is that it will deform at a lower temperature that polystyrene. If you are worried about leaving your model in a hot car on a sunny day don't use PLA. Although even then I've made GPS and phone holders for the car out of it and only had one deform on me because it had electrical tape wrapped tightly around it applying constant pressure.
 
#13 ·
Hi, I have yet to convert my Witbox in to one with a heated build plate. It has borosiicate glass for the plate, on which I used Scotch blue painters tape, a little glue stick(lightly applied) and hairspray on top of that (also fairly lightly applied. I have all the corners of the Witbox case covered with painters tape to hold the heat in, otherwise it will not make a successful print in the winter! I also have learned to level the plate more finely while printing a large brim around the base of the object - you can CAREFULLY! dial in the bed screws until you see the brim printing with flattened filament. For PLA, I use a temp of 220C. I have had very nice prints at 100 micron (0.1mm) layers.

I started using ABS recently and had trouble with layer bonding at 235C (recommended temp by the manufacturer). My Witbox goes up to 250C (no higher as there is a teflon (PTFE) tube in the hotend to facilitate filament movement without significant friction - above that the tube will soften and clog the head!). ABS at 250C printed far better. At 235C it managed to build a cylinder successfully up to about 3 inches tall, but as the tube started narrowing at that point, the head (set at a certain speed) was too fast for the ABS layers to bond with each other. I ended up with a nice small ball of melted filament! I increased the temp to 250C and slowed the print speed from 30mm to 20mm. The rounded cone on top of the cylinder printed perfectly! There is still some lifting on the bottom of the print, despite the brim. I am going to try "ABS slurry/juice" to see if that will help. Otherwise, I will have to compensate by telling the printer to use a raft under the part. I am current using Cura 2.1 and Slic3r.

I am not a programmer, as my head doesn't like doing really linear thinking. But, it is possible to master the g-code made by the slicing program to change things like heat, layer thickness and speed, at different levels of the print. I have NOT learned to do this yet. Yet!
 
#15 ·
I am not a programmer, as my head doesn't like doing really linear thinking. But, it is possible to master the g-code made by the slicing program to change things like heat, layer thickness and speed, at different levels of the print. I have NOT learned to do this yet. Yet!
Yes, it's pretty easy to insert new commands into the file created by the slicer, it's just a big text file and all the g-codes are well documented.

Cura has a plugin to tweak settings at a Z height of your choosing, so you might want to look at that. Looking at it in the version of Cura I use (15.04.6) it looks like you can change print speeds, temperatures, fan speeds, but not the layer thickness.

It would be very hard to change the layer thickness mid print, the number of layers is calculated based on the model size, you would have to create all new slices from that point up if you changed the layer thickness. Flow of plastic into the extruder is also calculated based on layer thickness and print speed.

Wait, how are you doing ABS without a heated plate? I didn't think that was possible...
 
#16 · (Edited)
MartyS, right now, it seems to be mostly heat related. I think the issue of having a heated plate is only to keep edge curling from cooling too fast from happening. It looks like the first 3mm contains the entire amount of curling. As long as I had it at 235C, the print worked nicely, using Scotch blue painters tape, glue stick and hairspray, the bottom 3mm exhibited some curling. But the rest of the print went nicely until it got to about 3 inches height, where it began to print a narrowing cone (Bussard Collector). At a certain point, the ABS just would not stick to the lower layers, because head movement was too fast and the temperature was not high enough. Ended up with a glob stuck to the top of the print (luckily not around the nozzle itself!). Raising the temp to 250C and slowing the print speed 30% took care of this issue. Now, that I have Windows running again, I will get some pics from my phone ported over to show here.

I should mention that the Witbox is fully enclosed. It's one flaw is that it has to enormous fans to draw air out of the enclosure. I haven't yet tried disabling and covering the fan orifices to increase the warmth of the enclosure. I have read that letting the hotend preheat the enclosure for half an hour would warm the plate as well, but I have not tried that.

Slic3r announced a plugin for variable height layers, but it is supposed to be reserved for a particular printer. I have not tried yet, to see how that works.
 
#17 ·
I read this thread mainly because I'm interested in what the technology can do (because HOW it works is like a photocopier to me, basically magic. "OK, see, you put the paper here, there's a bright light and you have a copy..." :) )

But amid the complicated tech talk about this and that, I am somehow encouraged by the 'down and dirty' solutions like blue tape, glue stick and hairspray. It ain't pretty but it works, right? No Robot or rogue A.I. trying for that Revolution deal is going to figure THAT formula out!
 
#18 ·
But amid the complicated tech talk about this and that, I am somehow encouraged by the 'down and dirty' solutions like blue tape, glue stick and hairspray. It ain't pretty but it works, right? No Robot or rogue A.I. trying for that Revolution deal is going to figure THAT formula out!
There are more expensive ways to get the first layer of melted plastic to stick to the build plate, but the first home 3D printers were build by tinkerers, so the idea of "what do I have around the house that might work" is how people came up with stuff like painters tape, hairspray, glue stick, etc.

And frankly, the more expensive options don't work all that better, so if something cheap works just as well why not stick with it. Although I do cringe with buying painters tape, it is way overpriced for what it is...
 
#22 ·
I glued a sheet of PEI (Polyetherimide) to the build plate on my Monoprice MP Select Mini 3D Printer. PEI is a hard, heat resistant plastic. When heated to 80C ABS sticks to it like glue. When I'm done printing, I wait for the build plate to cool off and the ABS part pops off - often on its own. PLA is even easier. I'll give the PEI a quick wipedown with acetone every few prints, but that's all the maintenance it needs. Worrying about plate adhesion is a thing of the distant past now.
 
#23 ·
These are the ABS Bussard Collectors (one with a flashlight in it), you can see how the lack of temp caused the upper layers to not adhere and glob up. The last is a Ghost Destiny I made for a friend out of PLA, paint, magnets and an LED.







 
#26 ·
These are the ABS Bussard Collectors (one with a flashlight in it), you can see how the lack of temp caused the upper layers to not adhere and glob up.
I don't think it's a layer sticking to each other issue since there are plenty stuck together below the problem.

Was the extruder clicking a lot when in "blob" mode? I've seen that happen if I set the current to the motor too high, the motor slowly heats up and gets weaker, then starts skipping steps since it can't create enough pressure to push out the melted plastic. Prints start out fine and then go to spaghetti or blob. When you raise the temperature you lower the pressure needed to make the plastic flow out of the nozzle, that lets a heat weakened extruder motor keep going longer.

My latest printer design I built the extruder so the fan that cools the cold zone on the hot end also blows air over the stepper motor to keep it cool. (yeah, I've used the one printer I bought to build others, but I'm down to 2 now...)
 
#25 ·
That's the thing that seems to be a delicate balance issue. You need to vent the air, circulate it, get those fumes away, yet the kind of air movement that would do that would also likely cool the platform and the filament resulting in uneven building.

Enclosing the machine completely seems the best solution with a powerful vent fan that you run to clear the area when you open the door to the print platform.

it seems a series of trade-offs.
 
#27 ·
MartyS - I just thought that since the print was getting narrower there, it meant that the head was moving too fast and the volume at that height was cool enough to stop the layers from adhering to each other. When I slowed it down and raised the head temp, I thought it had solved the issue. The Witbox stepper motor does have a fan attached directly to it. I will do a test print to see if the fan has stopped working. Also, I usually have the fan run at 10% speed during the first 30 layers (3mm) to let the laid down material cool off more slowly, then it goes to 100%.

If the extruder stepper motor is heating up, could this be an indication that it should be replaced?
 
#28 ·
MartyS - I just thought that since the print was getting narrower there, it meant that the head was moving too fast and the volume at that height was cool enough to stop the layers from adhering to each other. When I slowed it down and raised the head temp, I thought it had solved the issue. The Witbox stepper motor does have a fan attached directly to it. I will do a test print to see if the fan has stopped working. Also, I usually have the fan run at 10% speed during the first 30 layers (3mm) to let the laid down material cool off more slowly, then it goes to 100%.
The travel speed should actually be slower when printing small areas because acceleration doesn't have a chance to kick in. Unless your slicer is weird and is increasing movement speed in small areas.

I would expect since you are not using a heated bed that is the reason you've got to print slower for longer at the start.

If the extruder stepper motor is heating up, could this be an indication that it should be replaced?
Not if it hasn't been overheated too much, too much prolonged heat will weaken the magnets inside the motor and then it would have to be replaced.

If it is the motor getting too hot see how to adjust the current and lower it a little. It's a fine balance, you need enough current to push the plastic out the nozzle but not so much that it overheats the motor.

Is this the only model that has the problem? Is it always at the same height? I've had stl files that had issues that would cause the slicer to skip a layer, look at that area in layer view mode in the slicer to see if all the layers are properly sliced. A lot of downloaded files have issues like that, I've gotten in the habit of always scrolling through the layers before printing a new one.
 
#29 ·
I've only used ABS once and since I sold my house and for now live in an apartment, I have nowhere to vent the fumes, besides, I've had very good luck with PLA. I find it easy to work with, it's easy to get great prints and I don't need to vent..... I have a Raise3D N2 printer and PLA works consistently and I also use 3" wide 3M blue painters tape on the build plate, love the stuff.....:thumbsup:



 
#31 ·
I just had a phaser rifle prop printed in PLA I believe--I wonder about the cost difference between PLA and ABS. For an object this large it seemed VERY inexpensive to print it in PLA, but the quality is very uneven. Flat surfaces look great and it seems as light and strong as styrene, but on curves the striation is very course and when you sand it the fibers start pulling apart. Makes me wonder how stable it would be over time:

https://www.facebook.com/jeffc.bond...otif_t=feed_comment&notif_id=1493593251147518
 
#33 ·
I have no idea--I had it printed by an outside party, but I can probably find out. All I know is if I had something this large printed at shape ways I would think it would have cost me about a grand. So in the short term the quality issues don't seem that big a deal--I would assume it they would be ironed out over time or by using a different material.
 
#35 ·
There are a lot of new formulation PLAs out there that are better than the original brittle PLAs available in the early days of 3D printing.

I used eSun PLA+ (sometimes called PLA Pro, too) when I built my 1:350 Klingon D7. (Thread here.) It is still tough to sand, but it prints very, very well for me.

Today I printed out a 1:350 SS Botany Bay to display next to my Big E. I printed it at my printer's highest resolution so I will likely be able to fill most of the layer gaps with Rustoleum Primer 2 in 1 Filler & Sandable.
 
#39 ·
Hi MartyS - Usually, I use Cura. Other times, Slic3r. When I use Slic3r, gaps show more prominently in the 3D view mode, but not in its layer mode. Cura seems to have more difficult problem displaying missing layers. Just downloaded 2.5, which has color keys for layer mode, though my quad core pc seems to have difficulty moving the layer mode around in 3D layer view. I don't really like Cura's raft, but I do like Slic3r's raft. I tend to use it for that. I have found that in PLA, a brim will work fine at hold the bottom layers down on the plate. But, since ABS exhibits some lifting, I am planning on doing a test print using it's raft.

As far as models having printing issues at that height, this is the first that I have printed that is 113mm tall. The increased heat/slower speed took care of the issue, but I don't know whether it is a consistent issue in either PLA or ABS. These to prints in ABS are the first time I have used it. Also, this is printed in 100 micron layers. Being thinner, I would think each layer would cool much faster than 200 or 300 microns.

Further experimentation might reveal more answers for us both.
 
#40 ·
I know that PLA is not stable in high heat. I have read that if you leave a print in a hot car, it will deform. I don't know if that depends on how small or big a print is. I would think a phaser rifle might be more resistant to deformation by 130F+ heat. But, polystyrene kits will also deform and shrink in that kind of heat. ABS is supposed to be much more stable and resistant to heat. But without actually experimenting with a large vs small set of pieces, I can't say with absolute certainty how PLA will react to heat inside a car in the Tucson desert at the height of summer.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top