[Newbie] Cnc Questions

What are You using ? as machine , please.

Controller for hw, and feedback mechanism, and update rate on scales.
Whats the scales sped in kHz ?

Whats the actual approx. positioning accuracy ?
 
My machine is an Eagle (made by Topwell) 10x54 knee mill. It started out life as a 2 axis machine with an Anilam M controller.

It now has a Galil DMC-1846 motion controller, the original DC servos on X and Y. I built the Z axis drive myself. It has a NEMA 34 stepper on it. The mag scales are Renishaw LM10IC001AA10K12, 1 micron, rated at 4MHz, 4M/second. The controller is rated at 22 MHz per channel. I wrote my own software.

Actual position accuracy is - 5 micron when moving, and +/- 1 micron when stopped. When I do the conversion on my lathe I expect the same results. My router has the same hardware, and will hold +/- 5 micron.
 
I really, really, *really* like Your scales.

And the fast update rate is why it works so well for You.
I read that I need fast scales (Cslabs comment), and the common cheap ones thus wont work for position feedback.
Current speed is 500 kHz, and with 10.000 count encoders thats about right, for me.

According to the servos, position error is zero, of course some mechanical error is always present.
Servos are both step/dir and analog, and I use step dir.

Any chance for ballpark pricing or source for the fast scales ?
 
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The good news with this whole thing (besides discovering this really might be the best thing since sliced bread) is that I have a good idea of what I am going to do.

The bad is I am still kind of in the dark with the lathe- with the mill making it manual/CNC is straight forward, but what would I do with the lathe in order to pull this off? Are there motors that would allow me to connect the wheels on the backs of them?
 
Dual shaft motors are very common. I have seen it done that way, seems to work OK.
 
JimDawson said:
The read heads and mag tape I bought were from an Ebay vendor, and are no longer available. The read heads were US$85, and the tape was US$80 / meter

As far as I know, this Chinese vendor has equivalent devices. https://dcoee.en.alibaba.com/product/60416907705-212994889/magnetic_scales_with_digital_readout.html
Click to expand...

Let me know when you do, did you use these to make your cnc closed loop? is it as simple as telling the scales to output a pulse every ___um and mach3 accepts it on an input or was there wizardry involved?
 
Yes, I used those to make a closed loop. But.......Mach3 has no capability to close the loop on it's own. In order to do that, you need to use a motion controller interface that Mach3 will talk to and that will accept a quadrature input from the scales.

http://machmotion.com/cnc-products/parts-accessories/motion-controllers-parts.html

http://www.machsupport.com/software/plugins/

I use Galil products http://www.galil.com/

When you get to the point of specing out a drive system, I'll help you wade through specifications.
 
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