CNC Router vs 3D Printer

[DampRobot]

Originally Posted by EricH

You're not really up on what 3D printing is currently used for in the real world, are you?

First, let me set something straight: "3D printing" can refer to any one of 5 processes. Yes, 5--FDM, SLS, DLD, ULA, and Objet are the acronyms. At least 2 of those 5 can print metal--I've seen them, I've handled the parts they've produced (Selective Laser Sintering and Direct Laser Deposition). 4/5 processes have very expensive machines, think 6-7 figures for the price tag, per machine. I know for a fact that at least a couple of those 4 can produce parts that will take anything you can reasonably throw at them--otherwise, the aerospace industry would throw them out and do something else. It might take a couple of days or so--but if you're comparing to several weeks, the 3D printer is downright fast--and it can do some things that would be VERY difficult to do on any other machine. (Trust me, I walk by my company's SLS unit every day--it's got some fun stuff in the window, but the machinists would freak out if it was handed to them to build.)

What you're talking about is one specific type of 3D printing. The 5th process won't work with metal, but because it doesn't use a laser (the other 4 do) it can be made relatively cheaply and sold to just about anybody. This process, which is known as FDM (Fused Deposition Molding, or something of that nature), is what most people will think of when you mention a 3D printer. It's basically a hot glue gun, only with plastic.

This process is, shall we say, under iteration. The thing about most of the users, at least of the RepRap model types, is that they will monkey around with build parameters if they can to get the best result they can. Some companies are playing around with different materials to see if they can get something better than current. I've seen several robot teams with 3D printed parts--I believe 207 printed wheels for their robot a year or two ago, with excellent results, though I don't recall what process they used.

You're right, I was referring to that type of 3D printing. We've got an early model MakerBot, and I've played around with parts off other machines too. That process in specific is very weak in my experience, because you're left with a bunch of layers weakly joined together, like a wood grain. We've made a few sensor mounts and stuff like that, but they're fairly inaccurate and shatter into layers very easily. As far as I know, there's no 3D printer within an average teams budget that doesn't use this process, so my comments were mainly in regard to printers of that type.

I've also gotten some stuff printed online through an SLS process, and it was quite weak too. Instead of layers being fused together, it was grains. I was very pleased though with a part I ordered cast in silver from a 3D printed mold (of course, I can't think of any reason a team would need to make something like that). I've never handled metal SLS parts, but I'd imagine that they'd suffer from weakness in the same way that SLS plastics would, because they're still composed of fused grains.

I have heard hype about 3D printed titanium or aluminum through SLS, but for the moment I'm inclined to believe that this is has yet to break though to traditional manufacturing or even mainstream prototyping. We're certainly not 3D printing replacement car parts yet. I'm very interested to hear that aerospace companies are making parts through SLS, but I suppose that with the kind of performance they'd require, they could afford to be an early adopter.

Maybe by the time I'm out of college, well be seeing cheap metal 3D printers in the wild. At that point, I'd become very interested. However, I think we're still a little bit before the time when 3D printing can really break through into the mainstream.

[EricH]

Originally Posted by DampRobot

We've made a few sensor mounts and stuff like that, but they're fairly inaccurate and shatter into layers very easily. As far as I know, there's no 3D printer within an average teams budget that doesn't use this process, so my comments were mainly in regard to printers of that type.

Funny, I've not seen those issues. Maybe you had a bad printer, or a lousy parameter set (the only problems I've seen tended to stem from lousy parameters in the build). Or, as you note, it's an early model and some bugs may not have been worked out.

I've also gotten some stuff printed online through an SLS process, and it was quite weak too. Instead of layers being fused together, it was grains.[...] I've never handled metal SLS parts, but I'd imagine that they'd suffer from weakness in the same way that SLS plastics would, because they're still composed of fused grains.

Yes, they are composed of fused grains. Name a single metal that ISN'T*. Just some are more fused than grains. I'm not an expert in SLS, but there is one who hangs out on Chief Delphi. Suffice it to say that the strength--from what I've seen--is pretty reasonable compared to a solid piece, though certainly not 100%.

I have heard hype about 3D printed titanium or aluminum through SLS, but for the moment I'm inclined to believe that this is has yet to break though to traditional manufacturing or even mainstream prototyping. We're certainly not 3D printing replacement car parts yet.

Actually, you're right. Most of the manufacturing I've seen, in large scale at least, is DLD, which is a VERY similar process. This includes parts for a Formula SAE car. P.S. 3D printing is not traditional manufacturing, by any stretch of the imagination.

I'm very interested to hear that aerospace companies are making parts through SLS, but I suppose that with the kind of performance they'd require, they could afford to be an early adopter.

Or the amount of time they don't have, or the costs they need to drive down. I've heard that a part that could take months to get done via conventional methods (machining and molding) lost to an SLS part that could be done in a week, mainly because it was needed the previous week.

Maybe by the time I'm out of college, well be seeing cheap metal 3D printers in the wild. At that point, I'd become very interested.

I doubt that, at least on the metal side. Most of those use a laser. Guess what happens to need a lot of shielding, which costs money? Just something else for someone to work on.


tl;dr: While the layer structure or grain structure may appear weak, it can actually be quite strong if built properly. Proper building may take some time to achieve; once achieved, it should stay that way for a while.


*All metals have a grain structure. Whether you notice it or not is another question. If you go into mechanical engineering as a career, you'll hopefully get a lab on materials which includes looking at grain structures in a microscope. It's quite interesting. Sometimes you can see it in a fractured section of metal.