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Author Topic: G84 tap cycle spindle not turning random error  (Read 3290 times)

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G84 tap cycle spindle not turning random error
« on: July 02, 2015, 12:25:03 AM »
I'll do some more testing on this problem, but maybe you have some experience with it already.

I have a job where the PM45CNC with WIndows Vista & USB motion controller & normal (not variable/VFD motor) is tapping about 160x  4-40 holes, all in a row, 90 rpm spindle speed via gearbox.

It uses a G84 cycle and Mach3 is configured to wait about 1.5 seconds in between spindle reversals to allow the spindle to coast to a full stop before turning on again (in either direction). I have checked that even after the machine is very warm (longer coast down times), it always comes to a full stop before reversing in either direction.

I may actually have two problems.:

1) G84 is a modal cycle with 160 x-y tapping coordinates following it.
After some amount of holes ..could be around 70, Mach3 will throw an error "Spindle not turning clockwise" ...and so it pauses, if I hit F5 to turn the spindle CW , I am able to continue, and it will continue for many cycles as it should. This seems like a Mach 3 issue as there is no feedback to Mach 3 from the mill for it to know if the spindle is turning. It could only "know" the spindle is not turning because it did not command the controller to turn on...but why did it not command the controller to turn on after many cycles of normal behavior.....buffer problem or such maybe?

2) Other times , I will get a sever "buzzing" noise from the motor when it turns the motor CW...I think it only fails in the clockwise start from zero rotation, not CCW. (need to do more tests) . It may buzz for a few cycles in a row, but eventually it will trip the breaker.

I am experimenting with electrical fans on the motor as it may be heat related....or time related...However with #1 happening sometimes I think it may be a software problem with the Mach3 to the controller, my gut says it may be trying to rapidly tell the motor to go clockwise then counterclockwise rapidly...So far I have not noticed any problems with the earlier holes only the later holes (with respect to run time,not line number)...and it if it does occur and I restart the cycles without either a cooldown or a reboot it does seem to recur sooner than from a fresh start.

I'll do a lot more testing but....maybe someone has experience with this already
« Last Edit: July 02, 2015, 12:40:35 AM by damo green »

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Re: G84 tap cycle spindle not turning random error
« Reply #1 on: July 02, 2015, 02:50:52 PM »
The  G84 cycle was NEVER a fully finished,fully debugged canned cycle. It has always had glitches in it . You would be better off just coding the cycles or using a SUB program to create them. Are the holes in rows or randomly placed ?

Is the spindle motor a single phase or 3 phase motor ??  A lot of motors cannot handle vast amounts of starts/stops in a duty cycle time period they tend to overheat and can shut down due to thermal overload(IF equipped). OR be damaged.

(;-) TP
Re: G84 tap cycle spindle not turning random error
« Reply #2 on: July 02, 2015, 02:57:13 PM »
This morning I tested and noticed that the CCW contactor would have a lot of arc-flash when releasing/off (flyback?) THis is in sync with the buzzing noise.

I talked to Matt at Precision Mathews and he informed me that capacitor start type motors are not rated for nearly as many starts per hour as I am attempting.

Currently I am drinking coffee and reading this:  https://gearmotorblog.wordpress.com/2010/01/26/hotrodding-capacitor-motors/ 

It is more ideal for me to rebuild my reversing tapping head anyway, so I will get on it sooner than later now. 

I would say this question problem has been answered.

Also thanks for the G84 info : "The  G84 cycle was NEVER a fully finished,fully debugged canned cycle. It has always had glitches in it . You would be better off just coding the cycles or using a SUB program to create them."

Is their a list somewhere of "Iffy: use at your own risk G/Mcodes?"
Re: G84 tap cycle spindle not turning random error
« Reply #3 on: July 02, 2015, 04:57:56 PM »
The  G84 cycle was NEVER a fully finished,fully debugged canned cycle. It has always had glitches in it . You would be better off just coding the cycles or using a SUB program to create them. Are the holes in rows or randomly placed ?  

Is the spindle motor a single phase or 3 phase motor ??  A lot of motors cannot handle vast amounts of starts/stops in a duty cycle time period they tend to overheat and can shut down due to thermal overload(IF equipped). OR be damaged.

(;-) TP

...the holes are in various rows, I like the idea of a MODAL canned cycle or a MODAL sub program, but I guess i can do a lot of text editing to make a subpogram work if it can't be modal.....?

also I am going to use a reversing tapping head i add the motor information link (previous post) just for " edumacational" interests.
« Last Edit: July 02, 2015, 04:59:34 PM by damo green »

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Re: G84 tap cycle spindle not turning random error
« Reply #4 on: July 02, 2015, 05:41:48 PM »
For a tapping head to work well you need a FAST retract cycle to work the clutch dependably and you need plenty of head room for the Z axis. The advantage is the tapping head can be faster than a tapping cycle with less wear and tear on the spindle.

How to program the PART depends on several things. One being are you making 1 or 1000 of the same part ?? another being how complex is the arrangement of elements such as hole locations.  Another is does the controll have dependable canned(modal) functions.

 IF ( there is NOT in Mach3, BUT there IS in MAch4) there was a Modal Sub or macro it would be much easier ESPECIALLY if you could link a CSV file to the MODAL function(;-) .

CAD/CAM would be your friend here as well.

(;-) TP

Re: G84 tap cycle spindle not turning random error
« Reply #5 on: July 02, 2015, 07:15:10 PM »
I am making MANY of these  parts..forever... so it is worth the time to optimize for efficiency.

I am making so many, I will eventually automate the loading/unloading of the stock into the mill.

If not now (or for other projects) I would love any leads on how to link csv files into CNC programs...I was actually wondering if this was sometimes done..
Re: G84 tap cycle spindle not turning random error
« Reply #6 on: July 26, 2015, 03:23:42 AM »
Hi,
a single phase motor is not the way to go despite being plentiful.
Most capacitor start motors have a centrifugal switch inside so the star winding is active on start up but disconnected
once the motor runs up to a couple of hundred rpm. If the switch does not connect at start time the motor will just
tremble and get hot real quick!
A VFD controlled 3 phase motor is a much better option. The VFD manufacturers tend to say that you need special motors.
They are probably right at high speeds but at lower speeds I don't think so much of a problem. I run a 1hp 3 phase motor
thru a VFD and no smoke has leaked out yet!
I bought a 2nd hand 750W Vfd for $100 of ebay. Some of the el-cheapo Chinese units are pretty poor, the smoke is just dying to get out.
Hitachi seem to have a good rep but a little dearer.
My wife left with my best friend...
     and I miss him!
Re: G84 tap cycle spindle not turning random error
« Reply #7 on: July 26, 2015, 03:37:35 AM »
Whoops,
posted before I was ready...
Should be able to get a 3 phase motor for a box of beer...
Most industrial electrical places have fan motors lying around. Look for one that does a little under 1500 rpm if you live in a 50Hz country
or a little under 1800 rpm in 60Hz countries. That would make them 2-pole-per-phase, slower but twice the torque. 1 pole-per-phase
motors have speed rating of 3000 or 3600 rpm respectively.
You may get lucky and find a 3 or 4 pole motor (1000 or 750 at 50Hz, 1200 or 900 at 60Hz) slower again but grunty as hell for tapping.
If you want quick accel- deacccel then you will need an outsize VFD and fit it with a big braking resistor.

Craig
My wife left with my best friend...
     and I miss him!