Re: [CAD_CAM_EDM_DRO] What should I expect with CNC

Matt,

I am using the 97 oz in, Nema 23 Frame motor part number 23-019, from Camtronics. The driver board it the 2amp 3 axis Bipolar Chopper driver from Camtronics. Both can be found at
http://www.seanet.com/~dmauch/

I don't have much spec on the steppers, other then they are Bipolar with 8 leads.

The transformer is a unit I pulled out of a copy machine. It had a 3 amp fuse in line with it, which I changed to 2 amp fuse. Input is 120 v with 2 secondary. The first which I am using for the
stepper motors, had a output of 25 v. The second, which is not in use yet, but I plan to use as the voltage for the electronic of the driver board, is rated at 15 v. Presently I am driving the
electronic side of the driver board at 12 v with a bench Tri-output power supply.

The 25 v is fed into a 400 v, 4 amp, full wave bridge rectifier. The output of the rectifier is feed into the 10,000 cap which pumps the voltage to 34.8 v. The 34.8 v is fed into the driver board
for the steppers. The only other item is that a Tokin noise filter is in line with the power cord before it reaches the transformer. The noise filter was with the transformer, and I left it in
thinking less noise on the line is a good thing. I could remove it easy enough.

I am unable to measure the current directly, as I only have mA on my DVM. I can only say I am suppose to be in the 2 amp range, or not too far from it. But I have no easy way to verify it.

The ~34.8 volts with no load is measured at the cap. It drops to ~31.8 v with one motor running and down to ~27.1 when all three motors are going.

I am thinking the problem is mechanical, and I am going to post the mechanical side of this problem at the Sherline group. I know it can be hard to diagnose electronic problem without actually
seeing the problem and I appreciate your opinion. Do you see anything I have explained here that would put me off target ?

Thanks
Bruce




Matt Shaver wrote:

> On Tuesday 17 September 2002 12:02 am, you wrote:
>
> > The last time I posted, I was having problem getting the current to the
> > steppers. I have now built a power supply that is providing 35 v at
> > idle, to 29 v when all 3 steppers are moving. I am using a 10,000 mfd
> > cap. I am thinking this is enough. ??
>
> The formula (generally) is:
>
> (uF) = (80,000 times I) / V
>
> Since I don't know I (amps), I can't tell if it's enough, but my guess is
> that it is. That said, a 20% drop from no load to full load isn't good. I
> need to know how the voltage was measured, the specs of the motors, and what
> parts are in the supply to figure out anything more.
>
> > My observation is that while at the
> > extreme of each axis, I have notice an increase in resistance. Using
> > Jog, on the X axis, I can not exceed much more then 25 mm and 215 mm,
> > by the scale on the machine. On the Y axis, I am limited to 0 to
> > 120mm. At the 0 side, I can usually jog the machine to this machine
> > without any problems, but I have noticed an increase in resistance by
> > hand. The Z axis, oddly enough, doesn't seem to loose any steps. It
> > works from 0 - 160 mm. The only limitation is at 160 mm, is my own as I
> > am afraid of running the slide off of the lead screw. More on this
> > later.
> >
> > My question. Is this normal for the Sherline ? Or should I need to
> > adjust something ? Or, should I work around the stiffness by allowing
> > less working area in the G-code. Did I get the right size (oz)
> > steppers ?
>
> What you need to do (if you've used the factory motor mounts) is to remove
> the motors, loosen the two screws that connect the motor mount to the
> machine, run the table all the way out in the Y (Y+max) and to the left
> (X+max) and then retighten the screws. That'll fix the misalignment that
> causes the binding.
>
> I'm guessing the motors are OK.
>
> Matt
>
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