Hobbyist: Buy or Build

As a newbie to the CNC world, I would appreciate credible advise to my research on whether to buy or build a woodworking CNC router. I am a mechanical engineer and an accomplished woodworker / woodturner, so building a machine is not out of the question. I would like to add to my shop a CNC router, aprox 25" X 25" X 5" (min) for general hooby application. I have looked at the General Industries router and liked the fact I do not have to tie up my computer in the shop while running, limit switches, pause feature, deadman switch, and ACME screws. Did not like that it was built in Taiwan, a proprietary router, noisy, no vacuum PU, and small dim Y axis. I looked at the Shark Pro HD, but did not like tieing up the laptop, no limit switches. Liked that it was built in America (Cleveland, OH)I have looked at K2 machines - just a little too much to spend for what I want to do: signs, woodcarving, some antique part reproduction for personal use. I definitely want screw movement (ACME)machines, not rollers, belts, or other movement mechanisms.
I mentioned the above so you have some kind of idea what I am looking at and approx price.
Question: Is there a comparable CNC kit out there to the Shark ProHD- OR- a comparable DIY plan or kit for a serious hobbiest at the size I am looking for that will not break the bank and meet my design considerations?
Thanks in advance for your help.

Hi, here is my 2 cents worth: Acme screws = backlash, Ball screws= no backlash. Study the difference between: stepper motors and servomotors with encoders, Open or closed loop. Remember that small motors may work, but may overheat! Personally, I wouldn’t go smaller than nema34 motors, which has a ½” drive shaft, on anything. Spindles that turn 6,000RPM or more should have some kind of cooling, either air or water. If you buy used, make sure there is no positioning problems, as there is a huge chance of that in the “step & direction” world. Even if you use a closed loop servo drive, with Mach3 software, you are only shooting steps at the drive, unless things have changed, the software has no way of knowing if your tool actually went to where it was suppose to go. Do a lot of research before you buy. Ideally, all wires should be shielded, and the logic wires should be as far away from the big power wires as possible. If you don’t use a dedicated computer, you may be opening yourself up to certain problems. (While your cutting, your computer may want to go on line for updates, or whatever, and mess up your work piece) If you buy from a dealer, you are probably OK, but if you buy a homebuilt, you could get a really sweet machine or a problem, which will be hard for you to solve. If you build it yourself, in the future, you will be able to fix it yourself. Good Luck :cheers:

As far as tying up the computer I would say it's a non issue. Plenty of free or VERY low cost computers around that are very capable at running some thing like LinuxCNC. My neighbor had an old Dell P4 machine in his basement, had very little ram and a badly abused windows XP install on it, could barely boot up. Took it home, put in an extra stick of ram I had around and loaded the Live LinuxCNC distro on it. Had steppers spinning in less than a couple hours.

As for building or buying, that's up to you. Do you want the fun and experience of building your own machine or do you just want chips to fly?

If you are a mechanical engineer then I think you should build your own. The experience will greatly help you to be a better engineer. Nothing worse than an engineer who has never had to suffer working on the equipment they designed.

Thanks for the help. I will probably build my own- somewhere between work and having fun with 9 grandchildren. I just want to make sure that their is not a nice kit out there that I haven't seen that might save some time and expense. Not really impresed with the "hobby cnc routers" that are out there.

to springlakecnc:
Agree on the NEMA 34 motors. Good tips on electrical/electronics. I have 2 electrical engineers for sons- they are handling that portion of the system. Allows me to spend time with their kids while they rack their brains out on the problems. Good point on shielding- I did not consider that. I will research the movemnet mechanisms per your suggestion. Thanks

You've got to get over the idea that you can only have one. And a laptop's not really well-suited to running a CNC machine anyway - they have too many power-saving features (that make it quit working when you need it to) and rarely have parallel ports (which most CNC control programs require.) Get an old beater desktop, strip off everything that's not needed for CNC operation, and dedicate it entirely to running your machine.

As for the ballscrews - it's not true that every ballscrew has no backlash, or is more accurate than every acme screw. Ballscrews do have less drag than regular screws, but that's all they have in common. Some ballscrews were designed for simple motion-control tasks, like opening garage doors, which require little accuracy. They can be shockingly imprecise, and have a lot of backlash. There are precision-ground preloaded ballscrews that are very accurate and don't have appreciable backlash, but they tend to be quite expensive. And there are spring-loaded anti-backlash nuts that can be used with acme screws that will eliminate backlash (at least until you overpower the spring.)

You say you're a hobbyist, but haven't specified the limits of that. If your hobby is building machinery, then sure, you definitely should try building a CNC machine. Even if it doesn't work too well, you'll have had fun and learned a lot. (Of the plans that are available, I like the MechMate best: MechMate CNC Router - Build your own with our detailed plans ) But if you're mostly interested in making wood chips, then just purchasing a machine that works makes more sense.

Andrew Werby
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