Martin
I am having a little trouble picturing your mill. I have a mini
mill about 125lbs and a small mill about 350lbs. The Rong Fu's I have
looked at (Square Column) weigh about 750. Can you post a picture on
your Blog? However, the fact it has ball screws is a very definite
plus. Also the fact that it is currently working is another plus. Do
you have access to an Oscilloscope? It definitely sounds worthy of
further investment if necessary. You didn't mention the Z axis. It can
sometimes take a heavier motor or higher ratio gearing. The 6.5 ohms
per winding sounds High. For example look at the motor's here
http://www.kelinginc.net/ To get an idea of what a lot of DIY projects
are using. I personally use a Gecko G540 driver which is a 4 axis
driver with integral breakout board that will drive up to 3.5 amps per
motor with up to a 50 Volts supply. But normally we use motors with
much lower resistance than yours seem to have.
200 ipm at 10 motor rotations per inch indicates a motor rpm of 2000 It
seems low for servo but somewhat higher than expected for a stepper with
6.5 ohms resistance. I personally do not have experience with servos as
I am using steppers so I could be wrong there. I took a closer look at
your Blog. I got the impression the driver board is the one that has
chop2 etched on the board, but did you have a picture of the reverse
side, or is it covered with a plate as a heat sink attached to
transistors. I also looked at your pinnout pdf. Where did you come up
with the labels? Yea, I am having trouble getting my head around this
one.
Why are you wanting to change to emc2 when it sounds like it was
working? How much hardware are you willing to change?
I am sorry I keep coming up with more questions than answers.
Hubert
Martin Pinkston wrote:
> Good evening or morning,
> The milling machine is basically a benchtop mini mill import. Looks
> exactally like a Rong Fu. And I have seen a Jet name brand setting at a
> Tractor Supply that was an exact copy. In fact I ordered hand wheels from
> Jet for this unit and they worked. Weights about 400 lbs. Capacity is 14 x 7
> x 4. Ball screw on X & Y that are 5 turns per inch. Current drives are set
> up on a cog belt with a 2:1 ratio to the screw. The machine had very few
> hours when I got it and I may have put an additional 300 or so on it in the
> two years I've had it.
> I do have to admit that the stepper motors are very weak. It is a delicate
> balance between keeping the gibs adjusted tight enough to eliminate
> unnecessary movement but yet loose enough to keep the steppers from
> miss-stepping. Rapiding the X or Y axis too fast is the greatest contributor
> to loosing a step so I keep rapids movement to around 200 ipm and then keep
> the over ride at about 50%.
> It is a decent machine for what it was intended for and I have made a number
> of parts for my locomotives on it and plan on making more over the winter.
> Since I don't have a workshop "YET" at my home, I keep this little mini mill
> setup in the corner of a spare bedroom (den / mancave) in the house.
> So there you have it.
> Thanks,
> Martin
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