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Offline pumpa

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Need Answers!!!!
« on: November 19, 2007, 05:55:54 AM »
 
Hello all, I am new to this forum and very green when it comes to cnc stuff but i found it so interesting that i thought i would give it a go.
Looking through the posts it seems like a fantastic and very knowlegable community that are willing to help the novice
like myself.
I gathered a few bits and peices and put my first router together as cheap as i could seeing it was just a hobby thing.

I purchased a lic for mach3 and finally got it to go, but there are quite a few questions that i need answer to in order to move forward with it all.
Just a breaf discription of the setup may help others give me a more acurate answer to the folwing question or troubles
if you like.
It is roughly box tube frame i tig welded together aprox 1200 by 800mm
xyz all ball screws a axis 6" vertex rotary table
drivers kinling 50v 4.2 amp per phase
power supply i built using tordial transformer 35v @ 12 amps.
steppers: all 4 the same kinking 425 oz nema 23.

Q1 when machine is powered up and no cade has been comanded should the the steppers produce a hissing sound
very simmilar to an air leak from a compressor and should the steppers have any holding torque at that instance.


Q2 what would be the effects on the system if the power supply did not run a bleed resistor across the caps.

Q3 why does mach3 constantly keep tripping a reset after half a dozen lines of code when running a program, reset and it,s
good for another dozzen lines.

Q4 when running the roadrunner program and it runs to the end of the last line of gcode, should'nt the machine return to home automaticlly or do you have to command it home, and if so what is the gcode command to home all axis.

That's about all at this stage, i am sure i will be posting a lot more silly questions in the future just till i get my head around
this wiered and wonderfull world of cnc.

Cheers.

Offline Hood

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Re: Need Answers!!!!
« Reply #1 on: November 19, 2007, 12:02:10 PM »
Q1 when machine is powered up and no cade has been comanded should the the steppers produce a hissing sound
very simmilar to an air leak from a compressor and should the steppers have any holding torque at that instance.

Yes it its quite normal for steppers to make a noise when sitting still, some drives make things quieter than others but the main thing is that your motors dont get too hot to touch. Yes the steppers should have their holding torque as soon as they are powered whether moving or not.



Q2 what would be the effects on the system if the power supply did not run a bleed resistor across the caps.

 Dont have a bleed resistor on my mill and never had a problem.


Q3 why does mach3 constantly keep tripping a reset after half a dozen lines of code when running a program, reset and it,s
good for another dozzen lines.

 Sounds like you have noise in your limit switches, try going to generalĀ  config and setting the debounce up a bit, try 2000 and if it helps then try lowering until you start getting problems again.
 Also run the drivetest.exe (in Mach folder) and check that the line is fairly smooth with no huge spikes.

Q4 when running the roadrunner program and it runs to the end of the last line of gcode, should'nt the machine return to home automaticlly or do you have to command it home, and if so what is the gcode command to home all axis.

This depends on what you are meaning by home, normally the homing or referencing of the machine is done at start up and thats it until the next time you start the machine. Once referenced you can then jog to any position on the table and zero the axis and this will be your work offset. If you press the Go To Zero button the machine will go to the X, Y, Z, A zero position. If you want the machine to go to the zero position when it finishes the code just put a line or two of G Code in to do that, normally you would raise your Z axis first then the next line would take the rest of your axis to your zero position.
 Also worth mentioning is you may want to set a safe Z height so that when you press Go to Zero button the Z will move up to your safe  Z first then the X and Y will move to zero and then finally the Z will move down to zero.
Hood

Offline docltf

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Re: Need Answers!!!!
« Reply #2 on: November 19, 2007, 05:48:48 PM »
pumpa

try getting your power supply squared away first .if you have a step motor energized and you can feel it hum ,your dc power is not smooth enough.
you will be generating a strong and weak power wave,it is not nice to ask your motor to take a strong step on a weak wave.
the bleed resistor is more for your saftey than the caps.

Offline pumpa

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Re: Need Answers!!!!
« Reply #3 on: November 21, 2007, 08:24:20 AM »
Thanks for your prompt reply guy's, much appreciated.
Hood i do not have any limit switches hooked up at  the moment, I am just using the auto limits function in homing and limits, so that may rule out noise in the limit switches.

If i have reference my machine and then run a program like the road runner or just simply jogged around the table and the
press go to zero the machine will not home to zero, it does nothing however if i go to the MDI screen and place code
G0 x0 yo0 it will return to it's home possi.

I have run the driver test and according to the video it all seems fine with a fairly good signal, but i will look at general config and have a play around with that debounce setting  you mentioned.

Finally today a new problem has cropped up that had me a little stumped with the jogging of the machine and the DRO's.
If i try to jog around the table with the arrow keys or the jog pop up menu on or off line the DRO's only increment or decrement by 00010" every time i hit the arrow key on all axis, yet if i command say G0 X10 Y10 Z -5 they all wok fine at
good speeds, maybe it is something that is silly that i just can't put my finger on and any suggestions would be greatly appreciated.

Docltf, I don't understand what you mean by squaring up my power supply, could you please describe how to do this, as I was led to believe that the caps would smooth any ripple from the tordial before it was rectified but i might be wrong as i don't have a very strong understanding of electronics.


Cheers Lou.

Offline Chaoticone

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Re: Need Answers!!!!
« Reply #4 on: November 21, 2007, 08:43:10 AM »
Lou, sounds like you are in step mode rather than cont. jog mode. Pull the MPG screen by hitting your tab key and see if it is in cont. mode.

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!

Offline moxy

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Re: Need Answers!!!!
« Reply #5 on: November 22, 2007, 04:38:47 PM »
Hi Pumpa, from what you say I think that you have your caps in the wrong place. Your toroid output should first go to the rectifier and the caps are wired across the resulting dc voltage. Be careful that you get the polarity of the caps right or you will have a bad smell in your workshop and a lot of cap innards all over the place. I'm surprised that the caps never blew anyway because they really don't like ac power.

Good luck
Les

Offline pumpa

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Re: Need Answers!!!!
« Reply #6 on: November 22, 2007, 07:09:26 PM »
Thanks for that Brett, that's all it was.
 Les, thank you also for the advice, however the power does go up to the rectifier first then through a couple of caps.
 What i was trying to say was that the caps absorb the voltage fluctuation caused by BEMF if that makes any sense.


Cheers Lou.

Offline Chaoticone

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Re: Need Answers!!!!
« Reply #7 on: November 22, 2007, 09:43:58 PM »
No problem Lou, glad you got it.

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!