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Author Topic: Grizzly G0519 to a CNC  (Read 4390 times)

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Grizzly G0519 to a CNC
« on: July 26, 2009, 12:39:33 AM »
I’m looking at getting a small mill like the Grizzly G0519 and want to convert it to a CNC but before I spend some money I want get an idea of the total cost and get the right parts I want to go with Ball screws and servo motors so here the big questions 

 1    belt drive or direct drive for the servos I would like direct better but?? if belt what ratio
 2    what size and torque of servos
 3    what size ball screws pitch dia and length 

 Any help would be great or put me in a better path

 This is for a home RC Heli hobby shop cutting Carbon sheets and making small alum 3D bearing blocks need to be accurate
thanks aging
Atv

Offline Dan13

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Re: Grizzly G0519 to a CNC
« Reply #1 on: July 26, 2009, 01:39:49 AM »
Hi Atv

Personally I would go with a belt drive. I think it is easier to make properly and more technically correct. The ratio has to be reduction and has to be calculated based on your speed and load requirements.

To determine the motors power have a look here http://geckodrive.com/support.aspx?n=493148
But I think they are missing the friction element in their formula (though may be it is taken into account in their normalizing constant), so I'd add to the heaviest weight 15% before putting it into the formula.

The ballscrew pitch, again, has to be calculated based on your speed requirements and has to be suited to the belt drive ratio and motor performance.

I'd say start with the motors you can find (not sure you have to be using servos for a small machine, unless you are willing to spend more money and time on servos), and then choose the right belt drive and ballscrews to achieve the performance you want.

Daniel
Re: Grizzly G0519 to a CNC
« Reply #2 on: July 26, 2009, 05:21:02 PM »
thanks for your input and link that helps  ;D

 why I choose servos I wanted a closed system to get rid of any miss steps if its only a few more $$ but if you think a stepper would work with out any miss steps I have to look more into it

 I just want to do right the first time buying a stepper system then getting a servo system the same goes with ball screw I don't want to fight the acme threads backlash or am I just way off and inspecting to much from these little machines  ???

thanks aging
Atv

Offline Hood

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Re: Grizzly G0519 to a CNC
« Reply #3 on: July 26, 2009, 05:30:01 PM »
The most important thing whether its a servo or stepper is that you get motors that are big enough for your machine. I have steppers on my bridgeport  but if I was to do it again I would fit AC Servos, not because of any problems with accuracies but rather the slow speed and slow acceleration of steppers in comparison to servos. My Lathe and the Beaver mill I am doing at the moment both have AC Servos.
I prefer to have servos driven 1:1 via a belt. If you need to gear a servo then in my mind the servo is too small.
 Ballscrews are the only way to go if you want accuracy amd they also have way less friction.
Hood

Offline Sam

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Re: Grizzly G0519 to a CNC
« Reply #4 on: July 26, 2009, 08:17:43 PM »
And....you can get rolled ballscrews for a fraction of the cost of ground ones, if cost is a concern. There is of course a slight trade-off with accuracy, but still way better than lead screws. With such a small mill, I wouldn't think speed would be as big of a concern as it is to a larger machine like Hoods. If this is your first machine, or cost is a factor, I would not discount the idea of steppers.
"CONFIDENCE: it's the feeling you experience before you fully understand the situation."

Offline simpson36

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Re: Grizzly G0519 to a CNC
« Reply #5 on: July 27, 2009, 07:45:50 PM »
You may want to rethink the mill you are selecting for the work you want to do.

For several years I built and flew RC helicopters, eventually designing and building my own control schemes. So I am familiar with the carbon fiber sheeting you plan to cut and what you need is a router, not a big mill.

Even an X3 would be overkill for making RC heli parts. You might consider getting a smaller and more accurate mill and look into a high speed spindle, or plan on hanging a high speed spindle outboard on the head.

For small cutters, I have a block to mount my Dumore die grinder spindle on the mill head. I think it is in the 28,000 RPM neighborhood. My mill spindle tops out around 7,000 . . . great for cutting aluminum, but not fast enough for routing.  






« Last Edit: July 30, 2009, 11:57:55 AM by simpson36 »

Offline simpson36

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Re: Grizzly G0519 to a CNC
« Reply #6 on: July 30, 2009, 11:58:23 AM »
FWIW . . Digging for a different old project, I came across this page on the RC heli design I mentioned. From October of 2003.

Man, do I ever miss flying these things!

http://www.thecubestudio.com/helipage.htm


« Last Edit: July 30, 2009, 11:59:58 AM by simpson36 »