Re: "Y" axis problem

[rehenry <rehenry-at-up.net>]

Joe

I believe that I'd try reducing the acceleration a bit.  It won't really 
slow down the move that much but it will change the angle of the ramp 
that the motion stuff is using to see if the axis is where it ought to 
be.  Try 2 or 3 in there and see if that helps.

Backlash from the pinion running in the rack might also cause the 
problem.  You could test this by bringing up the emc, set up an indicator 
on y and hand crank the y axis motor back and forth just until you get 
some change in the position display.  You could set this value as 
backlash but you may have a problem with homing.

I'm guessing that you could also set this value of backlash as deadband.  
Set more than half the value in the ini for y axis and it should satisify 
the motion planner with a close enough for me reading.  

You can also attack the following error directly by multiplying the 
values for the y axis by some value.

HTH

Ray



On Wednesday 06 February 2002 10:29 am, joe bury wrote:
> List,
>   I'm working on a two axis wood routing machine. It has a stg8 model 2
> card. Each axis is driven by a rack and pinion. Each pinion is driven
> by a series of two cog belts.
>   I have an encoder with a resolution of 2048, but it has to travel
> about three and a half inches to complete one revolution. This gives me
> a resolution of about 585 per inch.
>   On the "x" axis the encoder is coupled with the cog belt drive. This
> axis work fine.
>   On the "y" axis the encoder has it's own rack and pinion making it
> more accurate as far as the Poisson of the router. My observation is
> that emc sends the dac a signal and before the amp can ramp up and move
> the axis enough to get some encoder counts it gets get a fowling error.
> After that the emc releases control of the axis and there is a small
> hop of the axis. I have hooked a meter to the dac so that I could watch
> the signal. I have applied voltage in place of the computer to the dac
> and the axis and encoder run smoothly.
>   This machine was designed to move quickly three horse power on each
> axis and with out a high degree of accuracy. I may be way off on these
> observations but in any case I think you can get the idea of the
> problem. I would appreciate any input on this matter,I have no idea on
> what to try next.
>                                               Joe
>
>
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