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Posted by NumberSix 
August 15, 2011 09:11AM
Hi all,
Some questions about plastics:
When printing a new RepRap which printer parts are best printed in ABS and which in PLA?
In general, are repraps being printed in ABS or PLA? Is it just the "PLA bushings" that are typically printed in PLA?
What characteristics of each material make then suitable for certain components or objects over others?

Also, if not too much to ask, could people give some every-day examples of when you might choose one plastic over the other and reason for the choice. This may help me and others understand these materials better.

I have read the reprap wiki pages on each material ( [reprap.org] and [reprap.org] ) but would love some real world examples of when each material prooved to be a good or bad choice for a particular item you printed.


Re: PLA vs ABS
August 15, 2011 10:15AM
It is only the Prusa bushings that are better printed in PLA due to it being harder. The rest of the parts are best made from ABS because PLA goes soft at the temperatures you find around the motors and the extruder, particularly when printing ABS.

The main advantages of PLA is it is easier to print and biodegradable. Although it is hard, that also makes it brittle and it seems to creep more than ABS.

Re: PLA vs ABS
August 15, 2011 12:29PM
abs is more durable as far as dropping, and handling. you can throw parts on the floor and not much will usually happen. PLA is a bit harder and can break easier. that being said, either works well for reprap. IF you use PLA you will want walls to be thicker, infill to perhaps be higher and more plastic overall, and lots of fan cooling to keep down creep or warping of parts from mechanical stress of nozzle moving in above layers.

As for quality of prints PLA is more accurate and allows higher resolution builds as long as your machine is capable of pushing PLA.

PLA allows higher print speed, more accurate placement of material with proper cooling (it does not shrink as much) and also thinner build heights because of less resistance from the plastic coming out the nozzle, where abs even at high temps (252C) is still sticky and has high viscosity.

So my take on what to use is if you need to make a model or small part to show and it will never be exposed to heat cyces. use PLA. If you need to fix something or use the part for something where it will have mechanical stress. make it out of ABS.

This is of course assuming these are the only plastics you use.

Also this is my opinion from personal experience. other people experience different things...
Re: PLA vs ABS
August 15, 2011 05:37PM
I print exclusively in PLA. If you use PLA for extruder parts then fan cooling is a necessity. I use a Greg's Accessible Extruder in PLA and cooling with a small fan have no issues. However, if you are going to be printing in ABS I would recommend an ABS extruder, especially with a heated bed.

I have had no issues with creep or warping on my PLA Prusa after many days worth of printing, including several 8+ hour prints.


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Re: PLA vs ABS
August 15, 2011 07:36PM
And of course the other big advantage of PLA is it doesnt stink of burning plastic like ABS does. Although some say that is the smell of making.
Re: PLA vs ABS
August 16, 2011 11:08AM
If you want to print large parts, then you'll want to put your printer inside a box like Nophead did. For this, you have to use ABS for the printed parts. PLA will get soft around 50 C.
Re: PLA vs ABS
August 16, 2011 11:44AM
Thanks guys,
That's excellent feedback and many practical perspectives on the two materials. It puts a good 'real world' view on them both for me, and hopefully will be of value to other readers also.

I've done some printing in PLA and now look forward to testing out some ABS, but as the advice seems to advise, not in the house! smiling smiley
Thanks again,

Re: PLA vs ABS
August 16, 2011 12:49PM
There is a big difference between different makes of ABS as to how much it smells. Makerbot's smells a lot stronger than Reprapsource's. I have heard that both PP3DP's and BFB's ABS does not smell at all, but they are twice the price.

Re: PLA vs ABS
August 17, 2011 06:36AM
Does the difference in PP3DP's ABS also explain why they are able to print without heated bed or chamber? Does anyone know what allows this to work? The plastic parts for my RepRap came from an Up! printer, and except for a slightly warped large gear for the extruder, the print quality is pretty decent.

.: repraponaut.blogspot.com :.
Re: PLA vs ABS
August 17, 2011 07:35AM
I think it has something to do with it and also how well support works. I bought some but have not had time to make a 1.75mm extruder to try it out.

They do have warping problems with bigger objects I think, but not as much as one would expect with ABS and no chamber. They do use a heated bed though and rafts. We use heated beds without rafts.

Re: PLA vs ABS
August 17, 2011 12:32PM
ABS warps and cracks a ton more than PLA does, even with a heated build platform (it's nearly unusable without one). If you print large objects or do print jobs that take hours, you will struggle to prevent the corners of your ABS prints from curling and individual layers from pulling away from themselves causing cracking. If extreme heat on the printed part isn't an issue, I'd go with PLA 100% of the time if your printer can do both. I find it to be much nicer in nearly every way.
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