Re: [CAD_CAM_EDM_DRO] Re: Dial indicator say machine is accurate in MDI screen. But out when

Peter:

>>The only thing that I did do differently from yeserday was that today I was only cutting out 2mm at a time and yesterday I was cutting 5mm at a time. So this begs the question of missed steps.

This can happen quite easily form the router. A 2mm cut doesnt draw the current and the brushes dont spark as much as with a 5mm cut.. Im thinking router noise is sounding likely when high current is drawn.. More testing I think..

Thanks,
Art
www.artofcnc.ca

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----- Original Message -----
From: Apalais
To: CAD_CAM_EDM_DRO@yahoogroups.com
Sent: Wednesday, September 13, 2006 1:20 AM
Subject: Re: [CAD_CAM_EDM_DRO] Re: Dial indicator say machine is accurate in MDI screen. But out when


I ran 3 test runs this afternoon. I clamped the dial indicator on here like this.
http://i90.photobucket.com/albums/k259/peterapalais/Dialindicator.jpg

I then jogged the gantry up untill the dial indicator was 0. Set the DRO's in Mach to 0,0,0.
Then I ran a basic program of a 35mm cicle.

The first time was with the router off.
The second time was with the router on in the air.
The third time was with the router on, actually cutting the MDF. Cutting at 2mm per pass, 1500mm/min.

The result. After every program, I went to the home position and every time the dial indicator showed 0.
Also the hole was pretty much 35.00mm in ID.

Funny, it did not do this yesterday. I will have to cut a longer bit of wood. I have a digital vernier, but it only goes up to 200mm. So I will draw up a rectangle that is 200mm long and cut that out. Then I can accuratly measure it with the vernier down to 0.00 accuracy. If that works out good. Then I guess the next step is to cut say 1000mm and measure that. Problem is though that the only thing that I have to measure such a large distance is a plain old tape measure. Unfortunatly they do not have 0.00mm accuracy.

The only thing that I did do differently from yeserday was that today I was only cutting out 2mm at a time and yesterday I was cutting 5mm at a time. So this begs the question of missed steps.

If I start at 0 on the dial indicator, and run a cutting program and I do loose steps. When I go back home to 0,0,0, the dial indicator would have to show another number other than 0, wouldn't it?

Moving on to electrical noise, I have taken a better photo of the power supply and motor drives etc. Which can be seen here.
http://i90.photobucket.com/albums/k259/peterapalais/Powersupply1.jpg

Caudlet, so are you saying that I should put all this stuff into a metal box/case?
I used the MDF because at the time that was all I had on hand.

What if I was to cut another longer bit of MDF, and space everything out more. So that the power supplies and capacitors are a foot away from everything else. Then have the motor drives spaced out evenly so the the wires can run in nice straight organised lines. Would this help, or not really?
Also I have used no sheilded wire, should I?

All help is greatly appreciated.

Peter
Australia

----- Original Message -----

From: caudlet
To: CAD_CAM_EDM_DRO@yahoogroups.com
Sent: Monday, September 11, 2006 7:24 AM
Subject: [CAD_CAM_EDM_DRO] Re: Dial indicator say machine is accurate in MDI screen. But out when

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "apples0_17" <apalais@...> wrote:
>
> Dial indicator say machine is accurate in MDI screen. But out when
> cutting.
>
> Okay. So I have been mucking around with my plasma/router machine. I
> am trying to get some positional accuracy out of it. It is maily just
> a CNC plasma table. I put a router in it so that I could take more
> accurate measurements, as measuring a plasma cut part has other
> factors to deal with.
>
> So I have been cutting MDF. I tell the machine to move 100mm but it
> will be out. I clamped my dial indicatior to the frame set it all up
> at 0 etc. Went into the "Set axis steps", the automatic thing. I
> tell the machine to move 5mm. After a few goes I get it spot on!
>
> I can then go into the MDI screen and tell it to move 5.00mm and it
> will move the 5.00mm. Then I can go forward another 3.54mm and it
> will do that fine. Then tell it to go back to 0, and the dial
> indicator will be spot on the 0 mark.
>
> But. I go to cut a bit of MDF with the router 100mm long and it will
> be the incorrect length.
>
> What bugs me is that it is working in the MDI screen, ie move 10mm it
> will. Even move 300mm and then back to the 0 the dial indicator will
> be on 0. I was impressed with this.
>
> So, after a bit of reading here ther and everywhere, I decide that it
> could possibly loosing steps when the router is cutting. So I slow
> the acceleration down. This has no effect. I'm using two 1200oz/in
> steppers slaved one either side, then they are belted down. I am only
> cutting at about 500mm/min at a depth of 5mm. So there is plently of
> torque from the stepper motors etc etc. So I think that I can rule
> out the missing stepps theory.
>
> But could it possibly be electrical interference causing my troubles?
>
> Have a look at this picture, this is my power supplie, breakout board,
> stepper drivers etc. It is very messy... etc etc.
>
> http://i90.photobucket.com/albums/k259/peterapalais/electronics1.jpg
>
> http://i90.photobucket.com/albums/k259/peterapalais/electronics2.jpg
>
> What are the chances that this birds nest is causing me trouble? ie
> 20% 40% 60% chance of electrical noise etc.
>
> If so, what is the solution. Make up a new board and space everything
> right out so that things are further apart? Should I use sheilded
> wire etc? If so for what connections.
>
> Cheers
> Peter
> Australia
>

Dry run the program (Router off cutting air) and check. If it's noise
from the stepping/power supply then it should show up there. Your
motor output wiring is wrapped around your low level input (DB25) so
is a place you would need to address if you are getting lost/gained steps.

If the noise source is the router motor itself, then typically it's
conducted noise (something across a shared ground connection) The
radiated noise should be easier to block. A wooden case does nothing
to block EMI and RFI in either direction. Simply enclosing the
electronics in a metal structure can block most of the radiated noise,
but could actually amplify the crosstalk of all the internal components.

Noise suppresion at the source is good but it's better to address both
parts of the equation (source and receivng end).

Chasing and finding noise is a like chasing a phantom. Things that
work for safety grounding and 50/60 hz work poorly or not at all for
high frequency.

The only "real" ground is a solid gold rod driven to the center of the
earth!

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