3d printing for models,PLA or ABS? - HobbyTalk
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post #1 of 49 (permalink) Old 04-21-2017, 07:28 PM Thread Starter
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3d printing for models,PLA or ABS?

What's the better choice?
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post #2 of 49 (permalink) Old 04-21-2017, 11:29 PM
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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 Ė after all, itís 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.
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post #3 of 49 (permalink) Old 04-22-2017, 12:15 AM
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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:

Guppy Sub conversion.

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.
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post #4 of 49 (permalink) Old 04-22-2017, 12:56 AM
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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.
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post #5 of 49 (permalink) Old 04-22-2017, 04:12 AM
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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.
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post #6 of 49 (permalink) Old 04-24-2017, 07:43 PM
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Originally Posted by Fozzie View Post
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.
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.
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post #7 of 49 (permalink) Old 04-24-2017, 11:29 PM
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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?
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post #8 of 49 (permalink) Old 04-25-2017, 12:40 AM
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Originally Posted by Milton Fox Racing View Post
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?
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.
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post #9 of 49 (permalink) Old 04-25-2017, 01:29 AM
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Thanks! That makes it sound a lot simplier than the "its to hard faction".
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post #10 of 49 (permalink) Old 04-25-2017, 05:42 PM
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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.
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post #11 of 49 (permalink) Old 04-25-2017, 06:28 PM
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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.
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post #12 of 49 (permalink) Old 04-25-2017, 06:47 PM
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I put a tremendous amount of time and energy into my projects and I build them to last. So, no, I won't take any unnecessary chances using materials I don't know from experience will hold up over time.
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post #13 of 49 (permalink) Old 04-25-2017, 08:12 PM
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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!
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post #14 of 49 (permalink) Old 04-25-2017, 08:18 PM
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ABS can be a challenge. An enclosed printer works best. Even then, a friend had fits with his, probably because it was in a chilly basement. He got it to work using PEI sheet on the bed and coating that with purple Elmer's glue stick.
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post #15 of 49 (permalink) Old 04-25-2017, 10:29 PM
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Quote:
Originally Posted by charonjr View Post
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...
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