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Edu_B

Best materials for functional prototipes?

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Posted · Best materials for functional prototipes?

Hi!

I am using Ultimaker 2+ for prototyping components of machines. These parts are not geometrically complicated nor have fine details, but I want these prototypes to be more or less functional, so the priorities are:

- Dimensional stability (the lowest warping)

- good mechannical properties (specially critical is the layer adhesion).

 

Up to now, I have used PLA, which has a good dimensional stability, but its mechannical behaviour is not so good, and ABS, which is quite stronger but only works well when the pieces doesn't have long and straight faces or walls (contraction issues: warping and interlayer cracks).

 

I have also tried HIPS, whose contraction is a bit lower than ABS, but still warps quite a lot if the piece has a high infill and straight walls (besides, its adhesion to the build plate is very soft).

I wanted to try nylong, but it requires managing humidity...

 

According to your experience, which material is the best for functional prototyping?

 

Thanks in advance

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Posted · Best materials for functional prototipes?
24 minutes ago, Edu_B said:

 

According to your experience, which material is the best for functional prototyping?

 

PLA.

 

I'm not sure why you think ABS is stronger than PLA.  Here is a chart I created that shows two "strength" properties of many thermoplastics.

 

http://gr5.org/mat/

 

The vertical axis is strength.  For example if you used the filament as a rope, the higher up in the graph the material is, the more weight the rope could pull before breaking.  This is a linear relationship (twice as high strength handles twice as much weight).  It's a very good way to think about strength but more specifically it's "tensile strength".  Note that both axes are log.

 

If you use the material for a beam, then "strength" is more complicated and you need to know how flexible it is.  More flexible but with the same tensile strength will be stronger because now the beam can bend a bit before breaking.  ABS has a reputation for being a little more flexible but with typical additives you can see in my chart that modern PLA filaments are just as tough (flexible) as ABS.  Nylon is the next level up - it's much more flexible.  Sometimes too flexible.

 

So it matters what kind of parts you are building.  If they are like links in a chain where it is mostly just tensile force then most of the materials are about the same.  If it's bending forces that sometimes shatter the part then nylon is superior.  If it's hardness that you want - like teeth on a gear - then most of the materials are the same but CF filled filaments are superior.

 

Yes Nylon takes more steps (you have to keep it super dry) but after you've printed 100 parts in Nylon you think "what was the big deal again?".

 

I keep my spool of nylon in a zip lock with rechargable dessicants and "unzip" the bag just enough to let the filament out and into the feeder.  If I screw up and leave the spool of nylon out or don't recharge the dessicant I can "fix" the nylon by putting it on the heated bed overnight at 80C.

 

Nylon is not going to print as dimensionally accurate as PLA.  PLA is the superior material in most ways which is why it is so popular.

 

If you go for a CF or GF (carbon/glass fibers) you will want to get a ruby nozzle (I sell them by the way) and a bondtech feeder.  CF and GF are a pain to deal with but if you are printing larger parts they can be significantly stiffer and stronger.  I personally like Xstrand PA6-GF30  (nylon with 30% glass fiber fill).

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Posted · Best materials for functional prototipes?

For ABS I use ABS-X from 3DFilaprint (this is link to black, but other colours available). It has excellent mechanical properties, and boasts 'Zero Warp' technology, which I find to be true.

I have successfully printed many functional prototypes using this material.

 

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Posted · Best materials for functional prototipes?

I print most models in PLA (95%), and they are functional: good enough for use in the hospital, and good enough for mould making. But they can't stand the heat of a car interior, even not in mild spring or autumn weather: then they will deform. And of course desinfection has to be done chemically, not by autoclave.

 

Also, PLA is very hard to drill into, or tap threads into, because it melts. Functional items that need flexing, like carabiners or snap-fit locks, will break over time: PLA is not flexible enough, and it hardens over time.

 

Creep is also a factor in PLA: if tightened fast, it will permanently deform over time. This is also why threads in PLA don't work well: they tend to dislodge. Now I use nylon nuts and screws, or glue, to fix PLA models.

 

If more flexibility is required (e.g. for snap-fit locks or carabiners), or for in the car, I use PET. I haven't tried nylon, PU, or PC yet.

 

The cream carabiners below are PLA/PHA (colorFabb) after some time of daily use and flexing. You see where they crack and deform. The green one is PET, which is flexible enough for this application. However, when pulling very hard, the PET snaps before the PLA. So it all depends on the exact application.

 

DSCN6060.thumb.JPG.0ed9fccc0d06ae587a27c4d8dcc31579.JPG

 

DSCN6055.thumb.JPG.c9f2aa4f551f913408727e004905b944.JPG

 

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