Re: [CAD_CAM_EDM_DRO] Re: Thanks - was: Things to check? is now: RUNNING~!

Weyland wrote:

>On Saturday 20 September 2003 02:51 am, Jon Elson spake:
>
>
>
>>OK, if you have EMC up and running, and can read the .ini file, you can
>>figure out how fast the pulses are coming out. First, you need to look
>>in the .ini file, and see what it says in the axis section, on the line
>>that reads INPUT_SCALE = nnnn. This is the number of steps per user
>>unit (inch or mm). I will assume it is set up for inches. Assume the
>>INPUT_SCALE = 2000. Now, when jogging at 25 IPM (as set in
>>the left-hand slider bar for the jog rate) and with the feed override
>>at 100 % (right hand slider bar) EMC will send 25 * 2000 pulses
>>per minute. that is 50,000 pulses per minute in this case. Divide by
>>60 and you get 833 pulses a second.
>>
>>So, you can very easily tell what pulse rate EMC is putting out.
>>
>>
>
>I seem to get my best motion (not ragged, not stalling)
>with the axis speed set to 25, and the feed override set to 35.
>So, using your example, 25IPM multiplied by 35% = 8.75.
>And being set at 4000 on the input scale, comes out to 35000.
>Divided by 60, it would seem I'm getting 583.333 pulses per second.
>
>This is only for jogging the axis', though....
>
>

Well, that seems pretty slow. You should be able to do much better.
By the way, why did you use a 2:1 belt reduction. This is almost always
counterproductive with steppers. You'd double your speed immediately
by going to a 1:1 ratio.

But, let me give one data point, the closest I've got. I have Gecko 201A
drives on my minimill, which I got mostly for demos at NAMES. I have
size 34 motors on it, with a 4 A rating. I demoed it running at 90 IPM
at NAMES. (I had some binding in the non ball-bearing Y bracket.
Why the minimill has 2 ball bearings in the X axis, and a sleeve bearing
with the hand-wheel as the thrist bearing for Y, I can't fathom. After
fixing this with ball bearings, it runs again at 90 IPM.) This is
running the
motors at 1440 RPM! Obviously, this is pushing old-style 2-phase
steppers about as fast as they can go. That is feeding 45,000 steps/second
to the G201A, which doesn't have the step multiplier. You probably can't
do this with software step generation, but 25,000 steps/sec is not generally
a problem. You are quite far from there at the moment.

So, what happens when you go faster? Does it rattle, or just stall out?

Jon