Re: Suggested velcotity params for servos?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "AbbyKatt" <cnc@a...> wrote:

> Can anyone recommend velocity params for servos? I've got the big-

big

> servo motors from Dan Mauch's site (I can't remember which ones they
> were, but they cost $199/each) and I'm running these with geckos at

60v

> in a 1/3 timing belt setup on my mill/drill. I'm running with

TurboCNC

>
> My max reliable (without faulting) speed is 35Khz
> That's pretty easy to guage.. But I was wondering about the starting
> frequency and acceleration?
> I know steppers can have a high start frequency, since they

effectively

> "hop" to the first position with a high torque, but what about

servos?

>
> I'm really not sure here.. Any good way to derermine?
> I'm worried that I'll be accelerating too fast, or starting too

fast and

> sacrificing accuracy as the servo lags behind just far enough not to
> affect the signed 8-bit lock (128+- count) of the servo. But at the

same

> time, I don't want to enter 0 as the start rate if I can do better.
>
> Any suggestions? Good ways to check (without a DSO?)
> Thanks!
> ~Abby

Setting up your parameters is a very important step in ensuring
operation without step loss.
It is however a lengthy process covering several days of retesting.

Start out with your Max Pulse rates.
Set your Acceleration to a very conservative setting when testing.
A very noticable Acceleration setting that will ensure the motor
wont be inhibited by this maybe 2-4 seconds to reach top speed should
be fine.
Program long enough moves for testing so top speed can be reached.
Now increase the Max Pulse rate for the axses untill you get into a
stall condition. Reduce the setting about 10 percent.
Repeat with all axes and keep notes of the settings you come up with.

After the Max Pulse rates for all Axses are established test with all
axes moving together at max rates.
May add some weight to the table to simulate a load.
Note when 2 Axses of same resolution are moving a 45 degree angle
may be programed to ensure both run at Max capacity.
You may need to ajust your Max Pulse rate down again for this test
because your Powersupply will likely not be able to provide the same
amount of current when all motors are running.
The last phase of this test has to happen first thing in the morning.
You want to repeat this test after the machine has cooled of and the
oil in the slides has thickened overnight because this will add to the
resistance of the slides to move.
If your machine passes the test your parameters should be fine else
reduce and try again the next day.

Now you can begin setting Acceleration deceleration.
Basicly the same sequence as before just using the acceleration
Parameters.
Few people like to run there machines close to the maximum
acceleration settings posible a stiff machine puts a lot of
wear and tear on all components.
The settings you will come up with are just pices of info what is
possible.
When a axes locks its Error register has overflowed +-128 pulses it
would be good advise to Lower the setting significantly to get a
lesser following error.
There is a great deal of personal preference where you want your
final settings to be.
Most like to see a noticable Acceleration deceleration lasting for
maybe a second or so, this makes for smuther transitions and causes
less wear.
Lower settings also make a system less sensitive to increased masses
of tools or parts.
A properly setup machine will be much less likely to lose steps even
under the least favorable conditions, contrary bad setting can cause
problems under some conditions that will be hard to pinpoint and
toubleshoot.
Good Luck