Re: [CAD_CAM_EDM_DRO] Re: Replacing Anilam Controller with EMC?

another_roger wrote:

>--- In CAD_CAM_EDM_DRO@yahoogroups.com, Matt Shaver <mshaver@e...>
>wrote:
>
>
>>On Saturday 20 December 2003 00:05, another_roger wrote:
>>
>>
>>>For
>>>position feedback, it uses linear encoders mounted directly to the
>>>axis.
>>>
>>>
>>I hope there is no backlash (or flexability) between the motor
>>
>>
>shaft, drive
>
>
>>belts, leadscrews (ballscrews I hope), nuts, and mounting hardware.
>>
>>
>I suspect
>
>
>>that if your present setup worked that you are OK in this respect.
>>
>>
>
>The servo's are set up in a velocity loop between the drive and motor
>with tach feedback. I had a good bit of backlash when I first got
>the mill, the motors would run a speed proportional to the error. If
>there was a 0.0005" error, the motor would run at a slow constant
>speed the other direction and wouldn't stop until the error was
>removed. I'm guessing that the analog output of the controller
>should consist of a velocity command minus the error. Perhaps I
>could set I and D gains to zero. Does EMC support velocity
>FeedForward?
>

Yes, it does! And it works VERY well to compensate for finite gain of
the servo amp. It won't fix backlash, however.

>>Matt
>>
>>P.S. If you live near Baltimore, I can come take a look.
>>
>>
>
>Is Southern Illinois close enough? Come on over :-)
>
>I plan to start saving $$$ for the STG board and getting the mating
>connectors for the 3 scales and the control. I'll also try to get
>the pinouts for the scales from Anilam, I think I have the control
>interface schematic already.
>
>
>

I'm in St. Louis, and have done a round-ram Bridgeport with an analog servo
system. Although I don't have handwheels on this machine for mechanical
reasons, you can reach in and turn the pulleys and see the position display
move. And, it doesn't lose position when you have to hit estop,
although the
position reference can be affected if you have a real crash.

I use shaft encoders on the ends of the leadscrews, so I don't face the
backlash
problem. I have pretty good ballscrews, anyway. If you'd like to see my
machine, I'd be glad to have you over, and show you what I've done,
how it works, and even do some handholding with getting EMC working
the way you like it.

Jon