RE: [CAD_CAM_EDM_DRO] Re: Lost steps

Jerry,

I have seen odd results with regard to acceleration and backlash in EMC if
you are running in an area where the motors are already a little weak. On my
machine it happens as the RPM gets pretty high and the motors are dropping
in torque. On your machine it could be happening at a much slower speed as
the 150 in/oz motors combined with acme screws is a pretty weak combination.

Slightly of topic, I may be having some 550 in/oz NEMA 34 motors with
encoders for sale. They are currently on my machine, but if I like the
servos better once I get them installed I will probably be looking to sell
the big steppers.

Another problem you may be seeing is that EMC adds 1/2 of the backlash
setting to the first move of an axis and then adds the full amount on axis
reversal. I don't know what happens when you zero the axis.

Here is the procedure I use:
move the table to take out the backlash.
Now set a dial indicator on the table.
Move a set amount in the previous direction to make sure the distance is
appropriate without any effect from backlash (I use the jog command and set
it to move .100")
Now move in the opposite direction. If you previous movement in the
direction you went to remove backlash was proper, the difference from the
indicated move and the commanded move is your backlash.

Let us know what your results are.

Tim
[Denver, CO]

> -----Original Message-----
> From: Ozzie@... [mailto:Ozzie@...]
> Sent: Monday, August 14, 2000 11:07 AM
> To: CAD_CAM_EDM_DRO@egroups.com
> Subject: [CAD_CAM_EDM_DRO] Re: Lost steps
>
>
> Thank-you,
> I will try lowering the acceleration and see what happens.
>
> The software is set for 8000 steps (half steps) per inch which was
> set
> by Tim Goldstein and as far as I can figure is correct.The commands
> I'm giving are in 1/2" increments so I wouldn't think that an error
> could occur from partial steps being needed.
>
> My proceedure is to run the machine into the indicator, stop
> set the indicator to zero
> home the EMC to Zero
> run the machine away to .5"
> run the machine in to Zero.
> I figure the indicator reading should be the backlash!
> First run I get .002
> I repeat the process without changing anything and I figure I should
> get .002" again but I get more or less,i.e. no consistency.
> Same on another axis.
>
> Can motor damage cause this? These motors are not new.
> How about iffy connections? When I first plugged in the Y axis motor
> I
> could see it stutter. I pressed the plugs together harder and it
> smoothed out the motion but maybe the connection is not what it
> should
> be?
>
> Also, if the accelleration setting is the culpret would the defect be
> erratic?
>
> Thinking while writing,
> Jerry