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Desktop CNC options Hello, Im fairly new to the forums, but I'm looking at investing in a small desktop CNC for myself for home use this summer. I'm just graduating out of a Mechanical Manufacturing program, so as for programming and software and such I'm fine, but selecting the right mill is a tough decision for me.
Budget: Under $4k CAD.
Options:
Currently I'm looking at purchasing a Sherline 2000 model kit ready for CNC implementation [$1495 before tax and customs duties] that includes a bunch of the basic tooling things I will need to get myself started, endmills, collets, etc. From here I am thinking of a 4 axis servo kit from IMService ($1205 US before duties and taxes).
So already I'm sitting at $2700, servo based machine, with 4th axis capability when I need it.
Now, besides the computer that I'm going to have to source myself. Is there anything that I'm missing here? I still have access to my school's shop and large machines, so I will be milling my own sacrificial plate and creating my own stand for everything.
The next investment after I was set up would definitely be some sort of air cooling system, or liquid if it is even possible (I still have to look into it). And then a magnetic relay to control the on/off of the spindle with M3/M5 codes.
Any input on the system I am thinking of, better options, or just general advice would be greatly appreciated.
Thanks!
-Colin W
Servos really aren't necessary in a machine the size that you're talking about. Most small machines use stepper motors and work just fine. Steppers also have the advantage of being easy to setup (no servo loop to tune) and low maintenance (they're sealed and brushless).
I would recommend a 3 or 4 axis stepper kit from CNCRouterParts.com, significantly less expensive and the steppers will bolt directly onto the Sherline.
I like the idea of having a closed feedback loop with the servos is a good thing for me. I'm planning on having some pretty long setups and I would like to have the loop to keep everything accurate, as well as they should give me faster rapids. Do you have any experience with Sherline mills yourself? I'm really just trying to decide if there is a better option out there.
As I understand it most (if not all) controllers in your price range are not going to do anything with the feedback from the servos besides possible e-stop the job, which means that going closed-loop is not going to get you any benefit over closed-loop for long jobs.
There are lots of people on this forum running steppers in pretty serious applications, after building 2 and running machines myself and hanging around the forums for many years I have yet to see a good reason to go with servos over steppers for a small machine...
If you were looking at a machine that was 5x10' or something then that would be a different matter.
I haven't used or owned a Sherline, but I've run a lot of long jobs on my router (6+ hours) using steppers with no problems... If you're losing steps or having other issues then those are most likely underlying mechanical issues that will bite you even if you're running servos.
I see what you mean, I'll take another serious consideration to steppers.
I just read back over my last post, I'm kind of impressed you got anything from that at all. .. I must be a little tired.
Don't take my word as gospel, but definitely don't write steppers off without looking hard at them.
Having a CNC machine in your house is awesome! Definitely worth the effort that goes into getting it all set up.
I hope so! Its just about getting the right machine at the moment, between this Sherline and something like an X2 or an X3.Originally Posted by aarongough
You might want to look at the HiTorque Mini Mill from LittleMachineShop.com
There is a good conversion kit for the X2 sold by CNCFusion.com and they make a version for the HiTorque Mini Mill. Going that way will work out slightly more expensive than the Sherline, but you'll have a lot more capacity.
That's what I was thinking, as long as its still accurate and I can run my servo setup I will be much happier. Having the larger tooling capability is really, really nice. I can definitely see ATC in my future.
If you have access to a machine shop I'd suggest getting a larger cast iron machine and do the conversion yourself. With the savings you can invest in better hardware like nice ball screws. More so I'd look real hard for a used machine to do the conversion on to save even more.
In my opinion none of the small machines commonly available are optimal for CNC use. Be it a Sherline , X2 or whatever they are all originally designed for manual use. The fact that some convert well doesn't mean they don't have short comings. I would tend to suggest looking at the larger machines as they should be easier to convert and are more flexible.
As to the suggestion of a larger machine, you first need to consider what you will be machining or making. A small mill can certainly do the job for many users but you do run into size limitations faster. This requires a lot of thought on your part because the counter argument is that buying to much mill {is that even possible} can also be counter productive. Remember it isn't just the part but the fixturing and tooling you need clearance for. Further different materials can benefit from different spindle capabilities. Aluminum for example can benefit from much higher spindle speeds that aren't available on Chinese mills.
Stepper aren't bad at all if sized and driven properly. The far greater issue is that of bad CNC code / operator error or tool damage ruining a part. Due to the expense of a real servo setup I'd reccomend building a stepper based system with the eye towards a servo update in the future if you really think you need it. I really don't think you will need it given reasonable efforts to size the steppers. Better to save the money involved in servos for a future larger machine.
If you have access to tools and tooling there is a lot to be said for going DIY all the way in a small machine. This is especially the case if you are good at E-Bay, online searches, auctions and the like. With a bit of effort you could DIY a small but extremely capable mill, with linear ball slides and other goodies, in the price range you are talking about. You may be able to put something together that is a far better machine that you will be able to buy and it can be tailored to your needs. This takes a lot of scrounging, some engineering and a willingness to modify purchased components. Visits to scrap metal dealers can turn up all sorts of machine making goodies.
While it obviously can't deal with very large parts, there are many good reasons to get a desktop mill. Many people are working on projects, like jewelry or model railroading, that require small parts, which can certainly be done on these mills. Others simply don't have the space (or strong-enough floors) for a huge machine. While retrofitting a big old cast-iron mill can be an interesting adventure, not everybody's equipped for that, and even if that's the ultimate goal, having a small machine can make the process of producing mounting plates, etc a lot easier.
While the small Chinese mills need a lot of work before they can be used in CNC mode, and usually have slow spindles with plastic gears, the American-made machines like Taig and Sherline are easy to convert, with motor mounts, controllers and stepper motors supplied by the manufacturers. Their belt-drive spindles go up to 10,000 RPM, which make them effective tools for cutting aluminum. But if you want a Sherline, I'd suggest the 5400 model over the 2000 for CNC use. The 2000 has a lot of tilts and adjustments which are handy for making odd-angled holes and slots, but those also make it less rigid and harder to tram, and those tilts aren't very useful in CNC mode.
Andrew Werby
ComputerSculpture.com — Home Page for Discount Hardware & Software
Thing is....
By the time the servos have to correct (because they are closed loop)
your part is probably already ruined.
I agree, steppers for the win, especially if you are just getting started.
Properly setup, steppers will never miss a step, don't get sucked into the
industry hype.
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