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I have a JM325 mill with a delta 20 control.
I have all the associated manuals for the drives, controls, etc including full schematics.
Having trouble getting my Y axis servo lag to spec.
I have an oscilloscope with memory function that I could use to see exactly whats going on but I'm note sure where to connect the leads to obtain the signal.
The scope is powered by an isolation transformer so no risk of a ground occurring.
Thanks in advance
...Mode Select> (5)Setup> TM4 Lag Display was available... I think on D20's.
Yes...I know how to display the lag...I want to watch the Y motor voltage trace on the scope so I can see exactly where the issue is.Quote:
Originally Posted by machinehop5
The one of my documents shows sample graphs and outlines exactly how to correct problems to obtain the "normal" graph....
Nitrochuck,
Are these Servo Dynamics drives? If so, there should be a small header with short pins next to the pots. What you typically want to watch is the tachometer output, that is normally what the response graphs show in the manual and this will tell you what the motor shaft is doing. Your manual should specify the tachometer pin, in my case it is TP6 on my Delta 60M. Connect your scope to the tach pin and observe the response to a step input to the drive.
RT
Yes Rt...Quote:
Originally Posted by cngbrick
SD1525-10.... great...I believe my tach pin is the same...ill attach the probe there and see if I can get it better tuned....
Besides the lag reading being higher than suggested the motor growels when using the rotary know on the pendant to jog and occasionally stops out of position during a program causing it to stop...no alarm or trip but sits waiting for the IP signal
Nitrochuck,
You will need to supply a step input to the drive signal input to calibrate the drive, are you set up to do this?
You should also check the brushes on the motor and possibly the tachometer if you haven't done so.
RT
Can I use the rotary pendent on the machine set to the .0001 scale to provide the input signal ??Quote:
Originally Posted by cngbrick
You'd have to put a scope on the drive signal input to see if this is produces an actual step input and if it's loon enough for the motor to reach steady state speed.
In my case I disconnected the drive signal coming from the controller and used a 9V battery. Start by putting a 1 to 5 kOhm resistor between the signal input (pin 2 in my case) and signal common (pin 4) so that the control has a zero movement command. Confirm that there is no motor movement, if there is then adjust the balance pot to stop the motor. You can now apply connect the 9V battery momentarily (do not clip the battery in or better yet, use a switch) to the signal input and signal common pins to generate the step input. Be careful, the motor will accelerate at maximum rate in a direction dependent on the polarity of the battery so make sure the machine is in a position to move in either direction. Remove the battery to stop the motion, switch the battery polarity to switch the motor direction.
Again: make sure the axis you are calibrating can safely move in either direction at full velocity before applying the battery! If you are unsure about this have someone stand ready to push the e-stop in case things get out of control.
Does this help?
RT
Ok...so for the graph to have similar structure to the examples in the manual with all the rise and fall features it needs a distinct momentary pulse to get the motor up to full speed with no conflicting fluctuations in input signal....Quote:
Originally Posted by cngbrick
So full speed is not going to be limited to the software's 300 IPM restriction its going to be dependent on the servo cards output voltage and the
time at voltage...probably dangerous fast
Nitrochuck,
Your question prompted me to have a look at my manual as it's been about 8 years since I had to tune a servo on the mill.
The manual states "Apply a small step input command signal and watch the tach output as observed on an oscilloscope on TP6. Observe the tach output as the motor stops." It sounds like you should be able to do this test with a smaller voltage if you are concerned about attaining a high speed. In that case you can substitute a 1.5 V AA cell and see what happens. I'd still recommend you take the same precautions about positioning the axis so that it can go either way without danger and prepare to hit e-stop if necessary.
RT
Great..ill start with the lower voltage on a pushbutton....
I may get some electrical cleaner first and trying cleaning the motor in place...I've read the Y motor is in the path of coolant dripping quite often and suffers from it....
I was told by a knowledgeable tech that the tach wires are very very fine and it's not advisable to try and service it myself.
Hopefully cleaning and tuning will get me where I need to be...thanks
This thread might be helpful:
https://www.cnczone.com/forums/tree/...-software.html
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