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homing accuracy
« on: September 03, 2008, 02:13:20 PM »
Hello,

I am back to the frustration level. I thought everything was going well. I have been spending the past several weeks trying to get a lathe (2-axis) ready for production use. I was able to make about 200 parts ( I need to make about 2500/week) during which time the both the spindle motor and the servo motors had "seizures". Re-zeroing the servos seemed to take care of the control part but the spindle motor, I have no idea. I have put a surge protector on the computer power. The lathe power is 220V single phase I will put a sola there as well.

I went back at trying to run the lathe again this week after the holiday and I can't make a single good part. I loaded the same program I was using, I zeroed everything the way I have been I checked calibration and motor tuning settings. No luck.

Is there a way to write the program in encoder counts rather than inches or millimeters? I assume zero on the encoder is at same location all the time? Maybe I am really not getting everthing back to the correct offsets? It seems everytime I use the machine I have to tweak the program to get good parts. What am I missing?

We have an Applied Motion system that is about 5 or 6 years old now and the program is bullet proof. You can shut it off in the middle, pull the plug anything and when it powers up it is back and ready to go. Since it is getting old we are setting the Mach up as a back up/ replacement if the Applied Motion does quit.

B.E.N.

Offline Hood

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Re: VFD and noise questions
« Reply #1 on: September 03, 2008, 02:34:11 PM »
How do you home? Do you have turret if not  how do you change tools? Got any pics of the lathe to let us know what we are dealing with?
Hood
Re: VFD and noise questions
« Reply #2 on: September 03, 2008, 04:14:13 PM »
I am not using home switches. I zero on gauge pins then tell the drivers to go a dimension as a home. Find attach some photos.
« Last Edit: September 03, 2008, 04:42:50 PM by Chaoticone »
Re: VFD and noise questions
« Reply #3 on: September 03, 2008, 04:16:42 PM »
Two more pictures.
« Last Edit: September 03, 2008, 04:41:55 PM by Chaoticone »

Offline Hood

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Re: VFD and noise questions
« Reply #4 on: September 03, 2008, 05:05:26 PM »
Your repeating after a shutdown will only be as accurate as your homing. If you tell the machine to move to a point then set up a dial gauge then move away and go back to that point again does it go there time after time? If yes then your repeatability is ok and it has to be your homing that is at fault. If the repeatability is not there then you will have to find out why, if that is the case then tell us a bit more about the motors, drives, gearing etc and also attach your xml.
Hood
Re: VFD and noise questions
« Reply #5 on: September 04, 2008, 10:30:09 AM »
Hello,

I have done the repeatability test. I wrote a simple program to cycle between two points on y-axis 0.120 apart. The dial indicator always came to the same spot. I did this with G01 about 50 times repeat every time. Then I went to G00 and I ran about 15 cycles and the axis quit. The program kept going. I will try this again with a slower velocity on the motor tuning.

Sounds like I have a homing issue. The manual I have talks about pressing "Set Home" is that a keyboard input or a screen icon or a drop down menu or the REF ALL HOME? Or, would I use the gauge pin zero points as the G28 settings?

Obviously, I am a little confused about the homing issue. Do you still need my XML file?

B.E.N.

Offline Hood

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Re: VFD and noise questions
« Reply #6 on: September 04, 2008, 02:05:47 PM »
B.E.N.
 What you need to do is move your axis to a predeterminined point and then press the Ref All button. Another way is,  for the Z axis on a lathe you can often do away with referencing it as normally your zero position will be the end of the stock, you can just move to very slightly beyond the face of the stock and zero the axis then take a faceing cut. You can do similar to the X axis, just take a cut and measure then enter that dimension into the X DRO. However its not the best idea especially if you have multiple tools that you can place in a repeatable manner, what I mean by that is if you have a turret or a quick change toolpost.
 Its not a difficult thing to add home/limit switches and the optical ones I use on my mill are fairly cheap and very accurate so it might be an idea to think about adding some home switches.
Hood
« Last Edit: September 04, 2008, 03:06:44 PM by Hood »

Offline Hood

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Re: homing accuracy
« Reply #7 on: September 04, 2008, 04:54:48 PM »
Quote
Thanks for info about REF ALL HOME. I still can't seem to get back to making parts. I had the machine running today to tweak it in and after about 20 cycles the Y axis just quit. The DRO continued to run for Y but no movement. Can't even get it to go with the jog function. I have shut the drive down still nothing. Is there some kind of error log that might indicate what happened? I will restart Mach 3 and see what happens. I don't have the Sola on the drive supply yet.

B.E.N.
Do you have servos or steppers? what make of drives do you have, sounds like your problem is a hardware issue and your drive is playing up or there are loose connections. Mach will continue to run if a drive faults unless you have an input to Input 1 to tell Mach the drive has faulted.
Hood
Re: homing accuracy
« Reply #8 on: September 04, 2008, 05:11:34 PM »
Hood,

I have stepper motors with Gecko drives and a Sound Logic control. I will look into the Input 1 setup.

B.E.N.

Offline Hood

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Re: homing accuracy
« Reply #9 on: September 04, 2008, 05:17:22 PM »
OK but if your axis will not move then you need to find the problem, check for loose connections on both your breakout and your drive, if you have a voltmeter check the power supply is putting the correct voltage to the drive when you try and jog. You can also check at the Step and Direction Inputs on the breakout to make sure the signals are getting to it, if they are then check on the drivewhile trying to jog. When checking on the Step pin you will need the meter in mili volt range , voltage is not important as long as you see something when you jog and zero when you stop. For the Direction pin you should see 5V when you jog one way and zero the other.
Hood