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Author Topic: Bridgeport extrak retrofit  (Read 9033 times)

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Hood

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Re: Bridgeport extrak retrofit
« Reply #10 on: November 29, 2006, 06:27:12 PM »
Yes, just go into the homing and limits page (from config tab) and enter your max and min for each axis.
  I just have a single switch on each axis which is in the middle of the travel and is activated by stops at either end. That way I have +ve, neg and home from one switch. It is also possible to use only one pin for all axis by connecting all your limits in series.
Hood

Offline Chip

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Re: Bridgeport extrak retrofit
« Reply #11 on: November 29, 2006, 09:15:45 PM »
Hi, Rogerbsstt

As Hood stated, 1 pin will do it all, series wired normally closed switches, gives you Home and -X ,-Y and Z.

Then setup Soft limits will cover the rest.

You'll really like the extra Z spindle feature.

Thanks, Chip 
Re: Bridgeport extrak retrofit
« Reply #12 on: December 03, 2006, 09:21:38 PM »
Just a note to say I have installed two gas struts ( like that which holds up the boot ar bonnet of your car) at 220 lbs force each, on to the knee. I found the force required to raise the knee screw shaft dropped by about half, but, I got an increase in the force needed to lower the knee. As I reasoned this was due to friction, not weight, I adjusted the knee gib to be loose and lubricated the slide. The force needed to raise the knee dropped by heaps and that needed to drop the knee was only slighlty less than the up. As I havent got the motors wired up, I cant judge the effect on the motor drive on the knee, but a 1700oz/in stepper at 2 to 1 should put 3400oz/in force on the knee screw shaft, as my rough testing indicates a force of approx 220 to 350oz/in is needed I would think the motor should have heaps. The only down side is that stepper motors loose torque with revs, and maybe at high rapid rates the motor does not generate enough torque ?????
I will inform you of any other prgress made as I complete the conversion.
rogerbsstt
Re: Bridgeport extrak retrofit
« Reply #13 on: December 20, 2006, 08:08:35 PM »
Hi
just a note to say my Z (knee axis) conversion seems to work OK. The two 100 kg force gas struts plus a counterweight of 80 kgs allows the knee to move at 30" per min, as displayed in the Mach3 window.Im more than happy with that speed.
Here is a generic torque chart for a 1200 oz/in motor. this will give some idea as to the rev/ torque ratios.

Cheers,  rogerbsstt

Offline Chaoticone

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Re: Bridgeport extrak retrofit
« Reply #14 on: December 20, 2006, 08:41:41 PM »
Thanks a lot. I needed that chart. Sounds like you are on your way. ;D
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Re: Bridgeport extrak retrofit
« Reply #15 on: December 21, 2006, 05:30:15 PM »
I have scales on X, Y and Z (Knee) on my supermax. My knee has an airassisted ballscrew to take some of the load off it. I can rapid the knee at 120ipm!

The only problem is that with the scales I have (Heidenhain 20um with 5x interpolator for a ultimate quad res of 1um) is I can easily go faster then the parallel port can read the scales in rapid. There are 25400 lines per inch with quadrature and that figures out to 10.5khz at 100ipm.

Dosent really matter to me though. I am just keeping the scales for when I use the machine manually.

Offline Chaoticone

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Re: Bridgeport extrak retrofit
« Reply #16 on: December 21, 2006, 05:33:54 PM »
What are you driving the knee with? Servo? What size? What gearing?
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My guard dog is not what you need to worry about!
Re: Bridgeport extrak retrofit
« Reply #17 on: December 21, 2006, 05:40:52 PM »
Servo. Big Servo! 12:40 ratio. 1/4" pitch ballscrew. 2500lpr encoder. Glentek Analog Servo Drive interfaced with a Skyko Pixie.

Ive got to do something about that ratio. It comes out to 133333 1/3 steps per inch. I wanted a 10 tooth but they dont make a 10 tooth L size timing belt pulley in anything wider than 1/2". I may jump to 16 or 20 tooth.

Heres my little project log with pics on cnczone:

http://www.cnczone.com/forums/showthread.php?t=28668

Offline Chaoticone

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Re: Bridgeport extrak retrofit
« Reply #18 on: December 21, 2006, 05:54:56 PM »
Thanks a lot for the info. Nice looking machine.  ;D

Brett
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My guard dog is not what you need to worry about!