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Need a way to zero my part
« on: July 29, 2013, 11:38:46 AM »
I have a big lot of parts to do.  Originally I wanted to just take them to the mill so I can clean up the side I want to zero them all on so they will all have the same zero.  But before I do that I want to know if here is a way that before the program begins the table to goes to a preset point and leaves the spindle running so I can jog to touch the cutter on that edge, now I have X zeroed.  then after hitting a button like cycle start or something it goes to a different preset point and I can Zero Y.  I need this to use safe Z's so that while the table is moving the cutter is at +.010 in work coordinates and when it reached it's point it is back to -.5.  

I don't mind going to the MDI screen for this if necessary.  Its just that when I commanded G0 Z.01 Y-.2 X-.190 to touch off on the X axis and G0 Z.01 X.2 Y.19 to touch off on the Y axis.  all the axis's moved together.  I would have been happy if first Z axis moved and then XY moved.  My cutter is 3/8 and I want it center to the upper left hand corner of my work piece.  I have this problem where the tool paths are good but when the machines rapids in and out of a cycle, I lose a few steps.  At this point I suspect either my PID loop or  electronic interference.  I don't want to waste time with it until I upgrade to better parts and I won't have tuning issues or interference issues.  
Re: Need a way to zero my part
« Reply #1 on: July 30, 2013, 11:52:49 AM »
seems like my game plan will have to be set my XY zero to upper left hand corner of part.  When I am about to start a part hit go to zero
then change over to MDI screen G0 X-.080 Y-.125 hit enter, G0 Z-.4 F5 hit enter and start jogging till I touch and set that to X zero with the appropriate .0625 offset (  I am using .125" end mill).  Next MDI G0 Z0 hit enter, next G0 X.125 Y.080 hit enter G0 Z-.4 hit enter and touch off again and offset for Y axis.  Then I hit G0 Z0 X.125 Y.125 hit enter and then change over to the program screen and hit cycle start.  That comes out to a total of 6 MDI screen entries.  I hope they all get saved and I can execute them in order like that for each consecutive part.  I know this is teh stone age way of doing things and am dying for some one to come along with a better way of doing things.  preferrably from within the program.  After I get this run of parts done I am seriously upgrading to components so that zero means zero, not lost steps.

Offline BR549

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Re: Need a way to zero my part
« Reply #2 on: July 30, 2013, 02:23:08 PM »
Are you using a fixture? Vise? to hold the part?

(;-) TP
Re: Need a way to zero my part
« Reply #3 on: July 30, 2013, 02:35:39 PM »
using a vise and a workstop.  You see, my machine profiles within +/-.001 or better, couldn't ask for anything more.  At the end and beginning of every program there is a rapid, and usually it loses a few steps there.  So what happens is that zero is within +/-.015.  Now lets say that my .125" end mill whos radial depth of cut is .007" and considering that error if we are at .022 radial then with speeds and feeds tuned to .006 rad DOC SNAP!!.  I need to rezero for every part. 

I am using a C32 board ESS and dugong DG2S16035 drivers.  After these parts are made some one will be getting a nice deal on 4 26 in/lb SEM servos a Bridgeport power supply C32 board 4 drivers 3 brakes, and all the controller components for $2500 and I will be upgrading to absolute closed loop controller, on the fly tuning AC servos motors.  I have had it with what I have.   

Offline BR549

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Re: Need a way to zero my part
« Reply #4 on: July 30, 2013, 03:09:44 PM »
Change that rapid to a G1 and try it.  (;-) or lower the rapid speeds

You really need to fix the machine and with what you have I don't see a reason why it will not work correctly. The drives are closed loop it should error out with a loss of position. You may have a loose coupler or pulley allowing it to slip.

IF you insist on re zeroing the fixture each time then simply Ref home the machine and apply the proper offset to zero the fixture to user zero on XYZ at program start add in a G28.1 to ref home.

Just a thought, (;-) TP
Re: Need a way to zero my part
« Reply #5 on: July 30, 2013, 04:34:48 PM »
If you are really wanting to re power your machine I would be interested in buying the drives, servo motors, power supply and other hardware you may have

Adam
Adam
Re: Need a way to zero my part
« Reply #6 on: July 30, 2013, 07:32:50 PM »
If you are really wanting to re power your machine I would be interested in buying the drives, servo motors, power supply and other hardware you may have

Adam

Sit tight, that I will do.  

Nothing is loose, and the limit switches don't use a quadrature pulse so homing doesn't save the day either.   My servos are rated at 4000 rpm I am feeding them 108VDC (If I knew how to straighten out the taps on the main transformer they would be getting 130VDC like they were meant to get)  they are rated for 112VDC.  Anyways 180 IPM is not too much to ask at 9 I/S/S accel rate.  

I just wanna get these parts made and get a new controller package.  

Offline BR549

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Re: Need a way to zero my part
« Reply #7 on: July 30, 2013, 09:50:00 PM »
Limits have nothing to do with quad pulses. Limits will set a ref position if you are using them. If not then manually ref home the axis to create a point of reference.

I think you are a bit confused on how things mach work. You cannot cut at 180 IPM so what is the point.

Just a thought, (;-) TP
Re: Need a way to zero my part
« Reply #8 on: July 31, 2013, 02:45:48 PM »
Good quality components or professional level components use the quadrature pulse on the encoder to determnine home position after the axis has rapided to the home or limit switch.  Then teh axis moves slowly off the switch and looks for that pulse.  This business of strictly relying on snap action switches for home is very unprofessional.  At 180 IPM I am talking about rapids.  Some of my cutting goes up to 70 IPM with teh right end mill.  I am not confused as to how things work. I am just disgusted with my last vendor, and those like him, who sold me hobby grade junk when I told him I want to get work done.  Then when the problems come pouring he is never available or send me on a wild goose chase after grounds and some other nonsense that never was the problem. 
    Anyways we are way off topic.  I was wondering if there was a way to get a program to go to a zero have it pause and then I am able to jog and touch off teh cutter and reset zeros in teh dros.  Both dros and jogging are inaccesible after cycle start until the program is completed or stopped.  At least that is my experience.

    BTW, I am working within +/-.001" tolerance

Offline BR549

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Re: Need a way to zero my part
« Reply #9 on: July 31, 2013, 07:35:55 PM »
You normally do any positioning/referencing BEFORE the program starts and for good reason. It is very simple jog X to the ref point then press zeroX same for Y. Or adjust the dro to the offset of you tool.

Or you could use G92/G52 to offset the fixture.  

Or you can use #vars in place of real values where then you can vary the values .

Don't discount the accuracy of a decent home switch many can equal or better the accuracy of the machine it is installed on. +/-.001 would not be a problem for most.

 Most real CNC machines use an absolute encoder that always knows where it is +/- 0.00002.


SO do you want to do this at the start of every program as part of the master program  or just when you want/need to as a seperate process such as a macro or seperate Gcode program?

(;-)TP