How durable are 3d printed objects?

[Reacher]

Hello everybody, this is Reacher from Italy.
I'm thinking about buying my first 3d printer. It would be something like a Prusa I3.
I've seen a lot of things on thingiverse that I would like to print. I mean things like small plastic tools, smartphone covers, rc cars parts, spares and upgrades for the 3d printer etc...
Would it be possible to print everyday objects durable enough to withstand actual use? With a printer this cheap? (obviously after a correct set up and learning...)
Thanks in advance for any answer

[curious aardvark]

Yes.

It can depend of what material you use, but even cheap abs and pla is extremely durable. For seriously strong stuff you can use petg, polyflex polymax and flexible materials.

But yes - parts are as good as commercially produced parts, in many cases stronger and lighter.

To a large extent for fdm machines it depends on the orientation you print them in.
So the same part can be printed in different orientations and one will be weak and break easily and the other will be strong, flexible and hard to break.

Getting really good 3d printed parts is as much an art as a science.

[zakeen]

Aardvark said orientation you print makes a huge difference. I can't stress that enough. Something so simple. Let's say I print a link in a chain and I print it standing up, bottom to top will be a far weaker link if I printed the the link laying flat on the print bed. Printing it laying flat will have the layers in the direction of the stress.

[classone]

Yes i agree with curious abs and pla can be quite durable. If you want to use other materials check that the printer you are buying can actually take the material you want to print but a lot of cheaper 3d printers recommend either pla or abs or both.

[Davo]

It absolutely depends on the material AND the design.

And there are even more durable materials - it depends on the environment (temperature, humidity, pressure forces, acidity, rapid temperature changes) in which they need to perform.

[Reacher]

Thanks for the answers. I wanted to know if these printers were suitable to produce usable parts. Now I think I'm gonna buy one soon.

[Ama-fessional Molder]

On the subject, you guys think a PETG subframe could be designed to support 300+ lbs from 4 attachment points?

My original intent was to use internal aluminum tubing, but if I can make something that's totally printed, that would be great.

[curious aardvark]

stick with the aluminium. cheaper and stronger.

You probably could make it from pet. But pretty sure aluminium would be cheaper and easier to use.

petg while stiff, is Nowhere near as stiff as aluminium. You would get way too much flex.

300lbs ?
what the hell are you making

[Ama-fessional Molder]

A subframe for a motorcycle. I only weigh about 220, add another 10-15 lbs with gear, and then assume there will be bumps in the road.

I still intend to print the bulk of it, just reinforce it with aluminum. It will all be visible, and custom is cool. Plus I need to do up all sorts of brackets and stuff for wires, tail light, various electrical control bits, battery, and all that.

I see no problem just designing it with a channel all the way around to just drop in square aluminum tube from the bottom, then have the printed part just "sit" on top of it.

[Graham]

A subframe for a motorcycle. I only weigh about 220, add another 10-15 lbs with gear, and then assume there will be bumps in the road.

I still intend to print the bulk of it, just reinforce it with aluminum. It will all be visible, and custom is cool. Plus I need to do up all sorts of brackets and stuff for wires, tail light, various electrical control bits, battery, and all that.

I see no problem just designing it with a channel all the way around to just drop in square aluminum tube from the bottom, then have the printed part just "sit" on top of it.

A couple of observations:
First, if you have a design payload of 250lbs, I think you need to design for 500-750 lbs minimum. That "bump" in the road could easily cause a 2G force making you weigh 500lbs for a moment.
FDM printing is inherently weak in certain directions as it is dependent on the tensile and shear strength of the interlayer bond, which is significantly less than that of most of the materials we use.
Tensile strength along the build's Z axis is almost non existent except for very large areas.
Compression directly along the build's Z axis will perform at or near the material specifications where directly supported, however, the beam strength (i.e. bending resistance between supports) is also reduced due the the weak interlayer bond.
IMO, FDM (at least with our hobby machines) is not suitable or safe for any kind of structural requirements in the ranges you need. It would be fine for enhancing the aesthetic appeal of an otherwise strong and well built aluminum structure that is properly designed to support all the loads.
Graham