CNC Router vs 3D Printer
 

For several months I have been considering purchasing either a CNC Router or a 3D printer. I have been doing research into both categories, and wanted some help making final decisions. Currently, I am leaning towards a 3D printer, but the right router could sway me. I'll first outline my use case, design requirements, and similar info to ensure that we're all on the same page. Sorry in advance for the long post…

Use Case:
At this point, I envision myself using the device as a tool for personal and school projects (I'm a junior in college), as well as possibly for FRC. I would like a personal router or printer as opposed to using the tools at my college's machine shop because I would like to have unfettered access. That is, I want to be able to use it for projects outside of classes without having my motives questioned, so to speak.

General Requirements:
The requirements of course differ for each machine, but a few are shared. First, my max price is $4000, but I would prefer to keep it in the $2000 to $2500 range. Second, because I want to use these for projects and not have the tool be the project in and of itself, I would prefer to use a well-developed kit or a turnkey system.

Machine specific info:
CNC Router:
Minimum area of 2x3 feet, would primarily be cutting aluminum sheet/plate.
I have currently priced out two options, details for which can be found in the attached Excel document. My main concern with a router is both size and mess: as a college student, I don’t have too much room to store a router, and machining would create messes that are potentially hard to contain and clean up. This is the primary reason I am leaning towards a 3D printer at this point.

3D Printer:
The primary requirement here is material strength. Again, I want to be able to use the parts it produces for projects, not just for pretty models. I have experience with the Dimension/Stratasys uPrint SE and found that it produces very durable parts (made a decent number for my team’s robot my last year as an FRC student). After this, my priorities are build area then surface finish.
After doing some research, I have been considering the Makerbot Replicator 2 and 2X and the Solidoodle 3rd Generation printers. This is a website that has aggregated information about 3D printers that I found very helpful. If you have experience with any of these, I would love hearing about it. Also, if you would suggest a different printer model, I would also be interested.

Well, that’s it. That’s what I have in mind at this point.
Thanks in advance for all the help!

Re: CNC Router vs 3D Printer
 

The budget doesn't leave you a lot of options. It really depends on the type of work you plan to do. I have access to both, and the router sees far more practical use, however, I'm not a fan of doing aluminum on a router. It's a real mess, and painfully slow compared to a mill with rigidity, horsepower, and flood coolant.

Re: CNC Router vs 3D Printer
 

Still a very useful machine. We did all of our gussets and a good deal of large plates on our 2012 bot on it.

For the 2013 bot we did all our gussets, and nearly all of our tubing.

It's a workhorse in our shop, certainly orders of magnitude more useful than a 3d printer.

Re: CNC Router vs 3D Printer
 

I'd agree with Adam, if you're interested in making stuff that's more versatile, go with a router.

At least at this point in their development, most 3D printing systems don't produce parts that are very strong at all. Sure, they do require little human input once they're running, but they're slow and I would not trust any of their parts structurally. If you like making little plastic parts to show concepts or as models or something, go with a 3D printer. Otherwise, a router is the way to go. In my experience, you can make basically everything you'll need for macro scale personal projects and for FRC on a 2.5 axis CNC machine like a router.

Lots of people are making a huge deal out of the "3D printing revolution," but the truth of the matter is 3D printers are only good for very small run, complex, non structural plastic parts, like trial electronics cases or miniature sculptures. There will be no real manufacturing revolution (as some reporters and politicians are hoping for) unless 3D printers start printing much more durable materials, become much much faster, or become able to print electronics as well as plastic materials. For the moment though, I'd prefer using a subtractive CNC tool (like a router) any day of the week.

Re: CNC Router vs 3D Printer
 

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.


Now, I haven't played around with any CNC routers. I have played around with 3D printers. If I was looking for a large build area, I'd pick up an inDimension3 Glacier Steel unit (if they happened to be available--they're currently out of stock), partly due to the 12" square build area (they can go bigger, but that goes out of your budget) and partly because the company is experimenting with better materials. (And partly because they're a new incarnation of a company I've dealt with for 3D printers in the past with excellent service.)

Re: CNC Router vs 3D Printer
 

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.

Re: CNC Router vs 3D Printer
 

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.

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%.

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. :D P.S. 3D printing is not traditional manufacturing, by any stretch of the imagination.

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.

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.

Re: CNC Router vs 3D Printer
 

His point stands. There is zero practicality in looking at SLS, SLM, or EBM in FRC. You couldn't even afford the powder for one of those machines with the budget OP is looking at.

Sure, it's good for a prospective engineer to understand how those technologies work and the applications they're good for, but FRC isn't one of them.

Re: CNC Router vs 3D Printer
 

I would argue that saying that "most 3D printing systems don't produce parts that are very strong at all" is what most folks would call a "hasty generalization". It's not the same as "most 3D printing systems that would work for FRC don't produce parts that are very strong at all", not by a long shot. It just happens that most, if not all, 3D printing systems that produce strong parts would be illegal for use in FRC--which is another matter entirely. Lumping all 3D printing systems together is like lumping all milling and lathing machines together--and then saying that they're all lousy because you happened to get a cheap mill/lathe combo that broke after the tenth use.



The other factor, as I briefly mentioned in an earlier post, is that there have been FRC teams who used 3D printed parts, of the FDM variety, in high-stress applications. See http://www.chiefdelphi.com/media/photos/38032, which has the machine in question listed in the comments, http://www.chiefdelphi.com/media/photos/38033, and http://www.chiefdelphi.com/media/photos/38034.


Basically, he's taking results from an older-model machine and applying the results to current technology and saying they're the same. I maintain that the results have gotten better, due to the continual development. (This is something that is pretty common across almost all new-ish technology.) Taking a 1st-run RepRap Mendel model and comparing it head-to-head with a 2011 Mendel or some of the spinoff companies' units is apples and oranges and bananas. The printers have improved multiple times. So have the control systems. And the price for something in that range hasn't gone up much if at all.

Re: CNC Router vs 3D Printer
 

I own the following personally:

Heavily modified SoliDoodle 2 ($400) and an Up! 3D printer ($1,600).
A ShopTask Mill/Drill/Lathe with CNC retrofit (my own tinkering).
A small gantry router I cobbled together myself years ago.
Several small X/Y/Z axis robots made from Intelligent Actuator linear systems.
2 LPKF Protomats (older series with paste injectors no auto tool change).

If your goal is to make 'normal' parts out of aluminum you can use the 3D prints to make molds and pour aluminum into the molds. Cast aluminum...real cast aluminum...is quite durable. Though metal forging seems to have made it's way out of most school metal shops Mount Olive High School did have a casting sand forge until it was removed. That forge was used to educate high school students so I know it is age appropriate. I decided to take it upon myself to build my own forge at home. It really is not all that hard to make a standard small forge but it is an art and the tools are not as important as the technique. Luckily I know a very talented metal worker and she has been helping me out. In reality you can liquify aluminum cans on a barbeque just to make ingot. I am constantly tinkering on a vacuum forge as well but for the moment I can only liquify steel in small quantity.

As far as the durability of the 3D prints themselves. I disagree that they themselves are not durable. If you are clever you can make working gears with a 3D printer. There are many restrictions to this but it can be done. I find this device as invaluable as a tool for making oddly shaped parts for brackets and the fella I bought my Up! printer from was a NYC photographer who used it to make crazy mounts for the film industry in his quite normal 8th floor apartment.

The rigidity of most bridge (ShopTask), turret (Bridgeport style) and some knee mills is usually desirable over the gantry when milling aluminum is the core achievement. However the work handling size of a gantry mill makes them a perfect fit for larger and professionally production wise softer pieces. Odds are you wouldn't want a piece of 4'x4' metal sticking out the front and back of your bridge mill on an unsupported keyway so it only makes good sense. Also a grantry mill is a nice gateway to a plasma cutter table or sometimes the other way around. If hot jagged metal everywhere is an issue for you you might consider where you plan on using these tools.

As someone that contributes to the RepRap project and the SoliDoodle if you want something 'out-of-the-box' that just prints you will be spending more than $1,500. If you want something out of the box that could print something really properly high end in the industry right now you'll be spending easily more than $5,000. This is why making firearms on a 3D printer out of: nylon, polycaprolactone or ABS is sort of silly. You could easily buy the firearm for *way* cheaper than the printer most people are designing those plans with. So that is really more FUD than practical application.

I will say that if you want to learn how to build a 3D machine the basics can be learned from a 3D printer kit. You've got: slicing, G-code, M-code, backlash, injection rate, friction and PID loops. All sorts of things you can learn. All sorts of things you will be learning or your print outs will be: warped, twisted, ovoid and otherwise defective. My Up! printer is the sort that 'just works'. I rarely need to do more than level it and keep it in an enclosure I made for it. In fact sometimes I use it to modify my SoliDoodle printer.

Ways to contain the mess from routers and plasma cutters. Plasma cutter slag assuming the actual cutting arc issues are considered and dealt with are sometimes controlled by cutting on a water table. Plasma arcs will easily flash off any water that gets in the way of the torch. So yes you could be pouring 240VAC and 50A into a plasma cutter system with a torch moving above a piece of metal laying in a pool of water. Doesn't that sound comforting? Your work volume is small for your router so may I suggest an enclosure with a shavings tray you can remove at the bottom? Think of it like a bird cage with a metal eating bird.

I am personally quite serious about making plans for a CNC gantry mill with axis driven by FIRST CIM motors in a closed loop and compatible with a PC based CNC control like EMC2 or Mach3. I know it can be done and I intend to do it and produce plans to help others turn their old robot parts into robot making tools. I am not going to commit to an immediate time frame on this. Team 11 just got a Haas mill and for the moment my more immediate goal is to get them going with it and potentially a CNC lathe. If anything I will use the CNC gantry I am constructing right now as a gateway tool for them and potentially a starting reference for what I would like to make.

Re: CNC Router vs 3D Printer
 

What kind of projects do you expect to be working on while you finish up school? Do you usually design more 3D parts than you do 2D (or tubing)?

Hard to weigh in without totally understanding what you want to create for your projects, but for prototypes of mechanical systems, I would think a router would be a good way to go. As we've seen before, you can cut out your own plate sprockets and such, and cutting chips on the router would still be faster than waiting for something to print (usually). Also, don't forget about being able to prototype in plastics and wood! I think the decision also depends on what machine at your school's machine shop is usually more readily available.

Personally, I love FDM printers and have used printed parts on many occasions, and the kids on 11 got to use a few critical printed parts on this year's robot as well. I think our parts were all printed on a Dimension 1200, but I don't recall exactly. The ABS, when printed correctly with the correct parameters, was really great for my applications as well as 11's (gears, spacers, couplers, collars, dog-bone linkage on 11, sensor mounts, etc). Nothing was in high load, just parts that we didn't have time to have sent out for conventional machining, or it was a bit too complex to machine easily.

Just a thought - if you do end up with a CNC router, I would think that modifying a bed and adding a 3D printing head would be a decently easy project for when you have some free time. You could, in the long run, make a hybrid machine with swappable heads, no? Or is that a silly idea? Probably a silly idea :)

Re: CNC Router vs 3D Printer
 

No it is quite doable. Just remember though to add a heated bed to the printer.
Both machines use G-code and M-code. All you need is a head and to list it as the spindle with perhaps a temperature controller which you can get or easily make yourself.

Heated beds are really as easy as a resistor, nichrome wire, or Inconel welding wire. Just put it under the work area with a proper temperature control that you could also use to control the head. An Arduino and temperature sensors like: thermistors, 2N2222 transistors or Dallas Semiconductor temperature sensors is all you need to make a multi-channel temperature controller (you can also buy them off E-Bay). Just make it so you set the temperature from another interface and turn the heaters on and off from the CNC control (this is actually really easy to do). If the entire machine is already enclosed to control swarf the heated bed will work just fine. All the work bed needs to be is a piece of aluminum covered by Kapton sheet or a sheet of glass.

You will want a heated bed for anything larger than 2" on the bed. It will reduce the warping that will start as layers build.

Re: CNC Router vs 3D Printer
 

Your point about the mess and noise of a CNC router - in a college dorm environment - cannot be ignored, and it is not trivial. Plus, CNC routers tend to be heavy, several hundred pounds perhaps.

So simply from a "where can I put/use this thing" point of view, a 3D printer is your better option.

Some different opinions on several 3D printers in your price range: http://kronosrobotics.com/3d/index.shtml

Re: CNC Router vs 3D Printer
 

Assuming you are printing ABS.

OP, I own a Replicator 2X and it has truthfully been a colossal pain in my rear... of course, we own the same one at work and it seems to be configured properly. I think I need to tinker with it more.

For FRC parts, I would agree that the raw printed plastic is simply not strong enough for anything more than sensor mounts. However, if you are not averse to casting some components it should work well for making masters for silicone molds and pouring urethane casts.

Personally, I went with the 3d printer due to the fact that I don't have a garage of any sort at this point in time. If I did I'd probably have gone with a small CNC mill or a mid sized router capable to handling aluminum. In fact, if I ever do get a place with a garage I will most likely be purchasing the router.

Re: CNC Router vs 3D Printer
 

I missed the information about the dorm room.... That's a gamechanger. A router of any real work ability is not happening in a dorm room.