On Thursday 24 April 2008, [EMAIL PROTECTED] wrote:
>> Gene Heskett wrote:
>>> A bit rough on an obvious newbie, John. In this case, and reading
>>> between the
>>> lines, I'm guessing that the terminology and format of the questions
>>> stepconf
>>> is asking are in effect, swahili to the OP, they are quite concise
>>> because of
>>> the gui's limits. When I ran it the first time, there were several items
>>> I
>>> didn't get right as the wording was somewhat ambiguous.
>>
>> I'll admit I was a bit rough, and I apologize. But...
>>
>>> He will in time learn, if we are willing to help, but first we need to
>>> know
>>> which question the OP is attempting to derive the answer to.
>>
>> EXACTLY!
>>
>> He didn't say "I've done steps 1, 2, and 3, but I'm stuck on step 4".
>> He said "give me the numbers". And when John Thornton asked him "Which
>> number", he said "all of them".
>>
>> I am more than willing to try to help. But the person asking for help
>> has to put in some effort too.
>>
>> Regards,
>>
>> John Kasunich
>>
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>I've tried putting numbers in like 400 steps per rev .5 micro stepping
>and the machine only travels half the distance that you tell it to. Also
>the Y and Z axes run backwords and I can't figure out where to go from
>here. any help would be greatly appreciated.
>
If they are running backwards, you can use a minus sign in front of the scale
value, or you can interchange the ends of one winding only either at the
motor or at the terminals of the driver package.
I don't recall now if you stated what driver package is used, and I'm not
familiar enough with the Sherline to know that. If they were xylotex drives,
they are setup to default to 8 microsteps, others may be more, or less.
This all goes into figuring out the scale value to be used, and it sounds like
the driver is set for twice as many microsteps as the software is. The more
microsteps, the smoother the motor will move, particularly in its self
resonant range, it can make a huge diff in the working torque at those
speeds, in favor of the microstepped motor.
Here are some 'rules of thumb'
1. 99% of the stepper motors used for this need 200 full steps for one
revolution.
2. If the driver microsteps the motor by a factor of 8, then the motor will
need to see 200*8=1600 steps for a full turn. Scale this according to the
number of microsteps your driver is doing.
3. If the motors are directly driving the screws, and I'm reasonably sure
Sherline is, then this 1600 needs to be multiplied by the number of threads
per _your_ unit of measure. Eg, if you are running in inches, and the
leadscrew in the mill is a 20 tpi screw, then 1200x20=32000 for the scale.
4. Then for MAXVEL, until you know what the machine can actually do, pick
something safe like maybe 3, and set a somewhat lower limit for MAXACCEL, 2,
2.5 maybe. Exercise that using the stepconf test facility by giving it a
range over which it is to move the motor, say 2" each way, and hit run. If
it moves ok, but seems slow and you can hear the motors slowing down and
winding up to speed at each end of the moves, increase MAXACCEL and MAXVEL by
half a point & retry. At some point the motor may freeze and buzz or sing,
if the move is well under way when this occurs, reduce MAXVEL by a full point
so you have a safety margin under load, but if it does this just as its
reversing, then MAXACCEL is too high, reduce it a full point, and move on to
do the same thing with the next axis.
Practice may find that these will still need to be tweaked one way or the
other, but that should get you at least playing in the ballpark.
I hope this helps.
--
Cheers, Gene
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Somewhere, something incredible is waiting to be known.
-- Carl Sagan
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