RE: [CAD_CAM_EDM_DRO] Recommendations

P.J.

You don't say what kind of computer is driving your machine. But here's
something to think about. I am also using a Sherline 2000 mill and am
running TurboCNC on a DOS based machine. I first attempted to use my Zenith
Z-Star EX notebook computer, which is a 486 DX-2 50 Mhz machine. I found
that the stepping was quite unreliable. Each axis would drop steps on a
supposedly random basis. Then, I tried the same experiment with my Sony
Pentium-III 450 Mhz. machine. The difference in performance was dramatic.
Where the Zenith had problems moving the X Axis at 1000 pulses per second, I
can get 4500 pulses (steps) per second with the Sony.

So, I put an oscilloscope on the step line of one of the motors. What I
found with the Zenith is that the step line pulsed correctly, but had more
dither (variation than the motors could handle while the Sony provided a
rock solid pulse train. If you're trying to get by with an older machine,
this could be your problem. Remember, nothing really happens at random with
these machines. When you talk about about 1/5 the distance of the "bar" in
an "A," that's too much distance to blame on backlash in the Sherline.

Hope this helps you find the underlying problem.

-- Carol & Jerry Jankura
Strongsville, Ohio
So many toys, So little time....

| -----Original Message-----
| From: P. J. Hicks [mailto:hickspj467@...]
| Sent: Thursday, November 08, 2001 1:48 PM
| To: CAD_CAM_EDM_DRO@yahoogroups.com
| Subject: [CAD_CAM_EDM_DRO] Recommendations
|
|
| Gentlemen,
| First my position - I have the basics+ of ac/dc/electronics
| knowledge. I am
| a self-taught machinist. I am retired so have limited resources.
|
| My problem - I purchased a Sherline 2000 which I ran by hand for a while
| then retrofitted with a Maxnc retrofit kit 145oz steppers and
| w/4th axis as
| I knew not of this list at that time. I use BobCad/Cam to draw
| parts and as
| I learn more it seems to handle my needs OK. In looking at
| software I got a
| demo copy of Flashcut which I now use to verify tool paths and edit cnc
| programs created with BobCad. I have never been able to get reliable cuts
| from the system. I loose or gain(?) steps randomly. Example; while
| engraving a letter 'A' the horizontal bar was displaced to the right by
| aprox 1/5 the bar length ( as a way to express the displacment as
| it varies
| with size). This has also happened on the y and z axis at times as well. I
| have tried all the mechanical remedies I know and have seen here on the
| list. Do I need more powerful steppers, should I change to servos and how
| much of my present system would be usable in that case? I also seem to be
| at a crossroad where the Sherline MIGHT be too small/frail and I
| should look
| at a bigger machine?
| While I am willing to learn I do not wish to become an expert in
| steppers/servos, more I would like to produce useful parts for my various
| hobby projects
| PJH
|
|
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