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Author Topic: Whats that Sharp milling machine on the home page?  (Read 4528 times)

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Whats that Sharp milling machine on the home page?
« on: October 21, 2006, 09:56:29 PM »
Im looking on the main page of this site, scroll down a bit.  Theres a picture of a bridgeport style Sharp mill with a laptop connected to it.  I see that it has motor attachments that look similar to a prototrak.  Are those custom made?  Where can I get something like that?  I just bought a bridgeport and I am thinking of how I can convert it to CNC!
Re: Whats that Sharp milling machine on the home page?
« Reply #1 on: October 22, 2006, 11:36:57 PM »
Im converting my bridgeport now. I have the x/y stepper mounts done ( size42) I have cad drawing for the mounts if your intrested.
I will be building the z axis drive for the quill next, and im working on an automatic tool changer.

Offline chad

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Re: Whats that Sharp milling machine on the home page?
« Reply #2 on: October 23, 2006, 12:40:56 AM »
Let me know what you come up with for the tool changer. i have been thinking about it for my bp clone too..


Chad
Re: Whats that Sharp milling machine on the home page?
« Reply #3 on: October 23, 2006, 01:00:51 AM »
Im converting my bridgeport now. I have the x/y stepper mounts done ( size42) I have cad drawing for the mounts if your intrested.
I will be building the z axis drive for the quill next, and im working on an automatic tool changer.

How does such a stepper setup compare to a closed loop ballscrew setup like a prototrak?   Are you going to install preloaded ballscrews?

thanks,
Mike
Re: Whats that Sharp milling machine on the home page?
« Reply #4 on: October 23, 2006, 06:01:05 AM »
The ballscrews are from Rockford Ballscrew. Its a retrofit kit and comes preloaded. (Mcmaster Carr $750.00)

http://www.rockfordballscrew.com/preload-bridgeport-clonemill.htm

The tool changer is currently stuck in design mode for the tool holders. The commercially available quick change ones are expensive and they dont recommend heavy loading.

And most stepper systems are not closed loop.

Offline chad

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Re: Whats that Sharp milling machine on the home page?
« Reply #5 on: October 23, 2006, 06:01:43 AM »
HI,
Like everything else it all depends on the performance vs. money.
A stepper system with the stock acme screws will have good performance with some amount of backlash and the possibility of steppers sticking if you try to go to fast or take too big of a cut.
Servo systems with ground ball screws will cost much more but will be faster and not loose steps. It will also have very little back lash.
It all depends on what you want to do with it, how much money you want to put into it, the resolution you want to get out of it, and how fast you want to do it.

Servo system:
figure
 $5000 for ac servo motors, drivers, cables.
$1200 for precision preloaded ball screws.
$3500 for prebuilt x,y,z belt and motor mounting.
$750 for VFD
$400 for mis. stuff.
total= $10850

This will get you 300+ ipm, the power to take cuts that will surpass the capability of the spindle and motor and .0003 backlash.

Stepper system:
BIG steppers, say $350 each =$1050
stepper drivers, 150 each = $450
power supply, $200
Misc aluminium, belts, pulleys, cabinet, wire, bolts and other stuff $ 550
total=$2250

This will get you around 100 ipm or so. on the order of up to .01 backlash depending on the shape of the acme screws and a lot of money left in your wallet. 

So $8600 more will get you, almost no back lash, fast rapids, state of the art (for a bp retro) and a pro level retrofit in a more or less bolt on conversion.

These are all ballpark numbers just to illustrate a point. There are lots of configurations from little money to lots, it all depends on what you want.  :D

Chad


   

 
Re: Whats that Sharp milling machine on the home page?
« Reply #6 on: October 23, 2006, 11:54:38 AM »
mach3 doesnt seem to support closed loop at the moment, so what software would u use?

Hood

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Re: Whats that Sharp milling machine on the home page?
« Reply #7 on: October 23, 2006, 01:13:11 PM »
Mach 3 isnt closed loop but the servo drives have encoder feedback so will fault out if a positioning error is detected.
Hood

Hood

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Re: Whats that Sharp milling machine on the home page?
« Reply #8 on: October 23, 2006, 01:15:33 PM »
BTW
 I did a Bridgeport manual mill with steppers and ballscrews and it worked well. I now have a series 1 CNC Bridgeport with the same steppers and it too works well. The cost of the CNC Bridgeport retrofitted was £1500 ($3000approx) and that was including the price of the mill.
Hood