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Charge Pumps
« on: June 16, 2007, 09:54:25 AM »
Hi Guys,
Will a charge pump in Mach3 be any help in eliminating missing steps.
I am using Win 2000 and the hardware is HobbyCNC Pro board.
If so are there any macro's around that I could "borrow" that would fit my setup.

Bill Files
Re: Charge Pumps
« Reply #1 on: June 16, 2007, 09:59:59 AM »
Another after thought,
I have 200oz steppers.
My computer is ACER 1.6  CPU
750 meg Ram .
Not a monster but is it big enough for Mach3.

Bill Files
Re: Charge Pumps
« Reply #2 on: June 17, 2007, 04:34:00 PM »
Hello Willie,

Do you have the possibility to use an oscilloscope to view your pulses. Check if there is not to much RC-delay on the pulses or something like that. Especially if you think your machine should run faster then it does.

Kris.
Logic takes you from A to B, imagination takes you anywhere
Re: Charge Pumps
« Reply #3 on: June 17, 2007, 05:19:56 PM »
Willie,

How about some more info from regarding the missing step problem.  What are you cutting?  Router?  Plasma?  Lathe?  What about Specs on your DC power supply?  Maybe with some more info we can help more?

Regards,
Sid
 
Re: Charge Pumps
« Reply #4 on: June 18, 2007, 09:13:42 AM »
Hi Sid,
I have just rebuilt my gantry router to increase table size.
I am cutting AIR at the moment.
My power supply  is 32 volts to the board
All the settings on the HCNCPRO board are within the specs for the board.
I have the Vrefs set to .36 volts
Motor tuning is 1000mm per min and acceleration at .4 to .6.
Lead screws are 2.5 mm pitch.
200 oz Hobby CNC motors.
Jogging is smooth in all directions.
Run a routine and steps are missed. I can actually hear the motors change when steps are skipped.Not always in the same direction.
After a sound change I stop the machine and hit the GOTO Z and it will be up to 15 mm out.
I realiise this could be a tuning problem but the machine worked OK for a few months at these approximate settings.
The one consolation , a friend suggested that I sell my PhotoVcarves as abstract art,genuine one offs.

There is a funny side to everything, I am still looking for one.

Bill Files
Re: Charge Pumps
« Reply #5 on: June 18, 2007, 10:06:55 PM »
Bill,

I'm not at my shop right now so it's hard for me to test those settings but, I have a couple of thoughts... the first thing you mention is that you just rebuilt to increase table size.... what is happening with your linear motion devices (Bearings, wheels, etc.)  Is there perhaps something binding somewhere?  Seems like you should have have enough voltage to run things without missing but just for giggles why not try changing your steps per min to see if that stops the missing step problem?

HTH,
Sid
Re: Charge Pumps
« Reply #6 on: June 19, 2007, 01:46:16 AM »
Sid,
I am using Linear ball bearings on Hardened shaft.
My lead screws are 16mm diam 2.5 mm pitch
IWith the power off I can turn the lead screws with my fingers.
When jogging there is no variation  in the sound from one end to the other, that would indicate binding.
The lead screws have a ball  bearing on each end.
It seems to loose the plot on sharp changes of direction.As in PhotoVcarving.
9 times out of 10 it will mill a rectangular pocket without missing a beat, and the same goes for cutting a circular pocket.
I did try slowing right down to 500 mm but the motors got very rough.
Increasing the acceleration did improve things but waiting for it to change direction was like watching grass grow.


Bill

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Re: Charge Pumps
« Reply #7 on: June 19, 2007, 01:50:37 AM »

Binding may be an issue as Sid suggested.

If that is not obvious then what I would try first is drop the max speed and acceleration to about half what is is now.

That acceleration you now have is pretty high. It would need to be a very strong machine to handle that.

If it then does not lose steps, try increasing it by a small amount until it does. Then back it down again about ten percent.

Greg

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Re: Charge Pumps
« Reply #8 on: June 19, 2007, 01:57:37 AM »
When I enter those numbers into Mach this is what I get.

I expect that acceleration is most likely too high.

Greg

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Re: Charge Pumps
« Reply #9 on: June 19, 2007, 02:15:39 AM »

If I have got that right. That's what you said in post #4   :)

Then try something more like this. Then you can increase it bit by bit and see how it goes.

Greg
« Last Edit: June 19, 2007, 02:22:07 AM by Greolt »