Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: rogerbsstt on November 22, 2006, 08:37:31 PM

Title: Bridgeport extrak retrofit
Post by: rogerbsstt on November 22, 2006, 08:37:31 PM
Hi, I have just purchased Mach 3, and am in the middle of retrofitting a bridgeport eztrak mill. I am fitting a stepper motor to the knee as the Z axis. The quill (old Z axis) has a glass scale on it and I want to use this as a manual setting point for machining and drilling. I have read the Mach 3 manual, but it doesnt give enough details as to connecting the scale, and using a 4th DRO (A, B, C) as a readout only. Can someone assist. Many Thanks  rogerbsstt.
Title: Re: Bridgeport extrak retrofit
Post by: Chip on November 23, 2006, 01:30:35 AM
HI Rrogerbsstt

Haven't try-ed this but I'll give it a shot.

First goto Config, Port's Pin's,Motor Output's Enable A axis leave the Pin's and Port's 0, click Apply.

Now click on Encoder MPG's Tab, Set  Enable MPG # 1 Set A-port to 1, B-port to 1, then use 2 unused pin's on port 1 for your A, B, encoder input pin's,

Pin's 10-13,15 are the only one's you can use, Set the Count Unit's to 1 - 4, probably, 4 to calibrate, Click on Apply again then OK.

Now goto Config, General Configuration, Angular Properties, un-check A-Axis is Angular Click on OK

Then Hit the Tab-Key for Screen Pindent, Select Jog Mode to MPG, Click on Alt A, Click it till it is on A axis.

That should Work, There is Probably a better way to do this more perminant, Just a start to get you going.

Infact you can use the spindle to MPG your X,Y,Z, axis's. By selecting them, Pretty Scary HU.

Be Care-full, Chip

Title: Re: Bridgeport extrak retrofit
Post by: Hood on November 23, 2006, 02:55:04 AM
I had glass scales connected to my mill for a while, I used the Encoder inputs on the Ports and pins page and they worked great. If you want it to display on the DRO on the main page you could easilly enough change the DRO which is for the fourth axis to the OEM code for an encoder DRO. You would do this in screen 4 and it would only take you a few seconds to do ;)
 One thing I would say though is to take a good look at using the knee as the fourth axis as without some sort of counterbalance you are going to have to gear the knee motor quite a bit and it will be slow.
Hood
Title: Re: Bridgeport extrak retrofit
Post by: rogerbsstt on November 23, 2006, 03:21:39 PM
Thanks for the info,
  Hood,  I have fitted a counterbalance system which gives me a total knee weight on the drive of 25 kgs. This appears to be enough to stop backlash and with the job weight on the table, should work.  We,ll see.
Rogerbsstt
Title: Re: Bridgeport extrak retrofit
Post by: Chaoticone on November 23, 2006, 03:54:34 PM
Have you got any pictures? I would love to see some close ups of the countrweight set up.
Title: Re: Bridgeport extrak retrofit
Post by: rogerbsstt on November 26, 2006, 05:32:08 PM
As soon as I complete the setup and tidy up the work area I will post some photos of the counter weight setup.  rogerbsstt
Title: Re: Bridgeport extrak retrofit
Post by: Chip on November 27, 2006, 09:46:53 PM
Hi, Rogerbsstt

Disregard my earlier Post on this, Hears a better way, I Think.

Hear is a screen .set I modified just a little, You need to set under, config, ports & pins, Encoder/MPG's, Encoder 4 to your A,B output to this.

Enable Encoder 4 Set A-port to 1, B-port to 1, then use 2 unused pin's on port 1 for your A, B, encoder input pin's,

Pin's 10-13,15 are the only one's you can use, Set the Count Unit's to 1000 - 4000, probably, 4000 to calibrate for .001 div., Click on Apply then OK.

Just make sure there outputs are no more than 5 Volt's.

Under Operator, Click on Auto/Calculator this will give you a Pop-Up window to Zero it, it works on other items also really nice.

To Zero the Quill Z click on DRO, Use,  Calc. Window to edit, You can pre-set to most any value.

Or use keyboard  to edit, Don't forget to hit enter Key.

Don't think I left anything out.

Oo, copy the set file to your Mach3 Folder, load-it give it a try.

Helps, I Hope, Chip.
Title: Re: Bridgeport extrak retrofit
Post by: rogerbsstt on November 29, 2006, 05:10:11 AM
thanks Chip,
when I get to that point I'll try it .
rogerbsstt
Title: Re: Bridgeport extrak retrofit
Post by: Chip on November 29, 2006, 01:02:31 PM
Hi, Rogerbsstt

I have a series 2 Bridgeport, just starting conversion, It has a Z table with stepper also, they used an air cylinder assist for counter balance (shop air), Will allow 1000 Lbs on table.

Has a Quill-master Z spindle (air / hydraulic) 8 position adjustable stops, not sure I'll leave it or not. Encoder will be added ether way.

Hope your conversion is going well.

Thanks, Chip
Title: Re: Bridgeport extrak retrofit
Post by: rogerbsstt on November 29, 2006, 05:51:04 PM
Chip,

I originally used two chains over idler sprokets with lead weighted counterbalances, but before I got it completed I picked up a pair of gas struts (220 lb force ea), and am now adapting them to the knee. If that doesnt work, I can always go back to the counterbalance weights.
The only real problem I have is I have not been able to get an accurate weight of the knee assy, so Im guessing a lot. I have been given 600lbs, down to 450 lbs. Does anyone actually know ??? please tell me if you do. Unfortunately I dont have air available, so thats out. Thanks.   rogerbsstt

Another question. My machine is set up to only have a limit switch at the end of each axis, that is used for a limit and a home, I think. Can I use this setup to home the machine to these limit switches and then somehow enter a work area size in Mach 3 to specify the working limits of the machine? This would reduce the number of switches and pins needed.

Thanks rogerbsstt
Title: Re: Bridgeport extrak retrofit
Post by: Hood 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
Title: Re: Bridgeport extrak retrofit
Post by: Chip 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 
Title: Re: Bridgeport extrak retrofit
Post by: rogerbsstt 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
Title: Re: Bridgeport extrak retrofit
Post by: rogerbsstt 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
Title: Re: Bridgeport extrak retrofit
Post by: Chaoticone on December 20, 2006, 08:41:41 PM
Thanks a lot. I needed that chart. Sounds like you are on your way. ;D
Title: Re: Bridgeport extrak retrofit
Post by: macona 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.
Title: Re: Bridgeport extrak retrofit
Post by: Chaoticone on December 21, 2006, 05:33:54 PM
What are you driving the knee with? Servo? What size? What gearing?
Title: Re: Bridgeport extrak retrofit
Post by: macona 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

Title: Re: Bridgeport extrak retrofit
Post by: Chaoticone on December 21, 2006, 05:54:56 PM
Thanks a lot for the info. Nice looking machine.  ;D

Brett