RE: [CAD_CAM_EDM_DRO] Bridgeport Series 1 conversion and other st uff

Hi Jon,

To measure backlash on the machines that don't have power I was going to try
to uncover the stepper motor shafts and either mark them or attach a clamp
to them such that I could rotate the shaft one way, back to start and then
the other way and back to start using a dial indicator to see the difference
in readings on returning to the start position from different directions.
If the table moved when I pulled on it I'd be surprised. How much backlash
would be expected in a good ball screw/nut? How much should be considered
"no-go"?

Thanks for the pointers on checking the ways and spindle ....

What is "EMC"? I have seen a lot of discussion about it on the list but I'm
unfamiliar with it.

I have BobCAD V17 and the documentation is terrible (also the "movies" don't
work for me). It took me hours and hours to figure out that the dashed
lines shown in the pocketing example actually meant something to BobCAD! I
also have trouble getting the correct contour identified (especially with
lots of lines in the area) and it wasn't until I called tech support that
they told me that right-click could be used to end a contour. They now have
"training materials" available for $195 that includes an extra license
"seat". That's a steep price to pay for documentation you should have
gotten in the first place and I can't use the extra license because I'm a
one man operation. They said that if I ordered the manuals to check them
out I couldn't return them and they couldn't lower the price by removing the
extra license .....

One thing I do like about my (minimal) CNC conversion on my lathe is that I
can still use it in "manual" mode. This comes in handy since it's the only
lathe I have :-)

I was thinking of maybe adding a ball screw at the rear of the lathe saddle
and mounting the nut in a carrier that could be locked to the saddle when I
wanted CNC mode and unlocked for manual mode.

Regards,

Chuck Hackett
Omaha, Nebraska

-----Part of Original Message-----
From: Jon Elson [mailto:jmelson@...]
Sent: Tuesday, December 19, 2000 6:41 PM
To: CAD_CAM_EDM_DRO@egroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Bridgeport Series 1 conversion and
other stuff

....

> 2) Are there things I should look for on these machines prior to
> purchasing? I'm currently looking at overall condition, backlash (how

much

> is too much? can they be adjusted?), etc. If at all possible I'll try to
> check the machine under power. If they don't have power can I get to the
> axis's to pull them over by hand to check backlash?

Wear on the ways is a lot easier to SEE than wear on the balls and nut.
Detecting backlash by hand is almost impossible. You might be able to
mount a dial test indicator and push the table back and forth to detect
backlash, but it would be very tricky to do so. Wear on the ways and
ball/nut wear would likely be correlated unless the screws were sent out
for refurb without any work done on the ways. If the ways look absolutely
fine (even in the central region where wear would normally be worst)
then you have a high probability that the ballscrews are also fine.
Run the table to one extreme and look up with a flashlight at the frosting
on the ways on the underside of the table. Also, run the saddle forward and
back to the extremes of travel, and try to check the central part of the
ways
on the top of the knee (but the saddle kind of covers the very center).
Check for excessive "dropped tool" damage to the Y ways here, too.
Power up the head and listen to the spindle bearings. If not possible,
disengage the direct drive clutch (if var speed, there should be a hi-N-low
selector, put in Neutral) and spin the spindle as fast as you can with a
flip
of the fingers, and listen for bad noises. The spindle bearings can cost
almost as much as you mention the whole machine going for, so a bad
set of bearings could be a nightmare. Other wear can be lived with unless
it is quite bad.

> 4) Any other pointers before I jump into this conversion?
>
> As I mentioned, I use software from AHHA which is DOS based. It has it's
> good points but I would like to find driver software that is Windows-based
> or that will run in a "DOS Box" window. I'm aware that there has been
> discussion on this list of the relative merits of Windows, DOS, etc. as an
> OS. My desire for Windows is due to: 1) The ability to network with the
> other systems in my home where I do design, etc. 2) The ability to switch
> back-and-fourth to other programs like CAD to modify a part geometry and
> then back to the indexer software without having to re-boot, etc. 3)
> Software (if well written) has a consistent "look and feel". I'm aware

that

> a multi-tasking OS like Windows does not lend itself to real-time but this
> is my goal.

You might also look into EMC, which runs under a real-time version of the
Linux operating system. It has all the features you mention, including
letting you
run other applications while machining is being done. You may be able to
run
Windows CAD software under the VM-ware Windows emulator.

....

> 2) I'm looking for a program to aid in creating G-code from DXF

files.

> Recommendations? I have BobCAD but I'm VERY frustrated with it. For the
> development sequence I currently use TurboCAD, BobCAD and AHHA Artisan.

I use Bobcad/CAM V16.1 Yes, it took a good while to figure out how they
do things. Not the way I would have done it. But, once you get used to it,
it
works pretty reliably, and can do almost anything I've thought of so far. I
have
had a few problems with complex intersections of curves, but most cad
software
has quirks in that area, until you spend over $20 K.

> 5) What approaches have people used to add CNC to the longitudinal

feed

> of a lathe? I currently drive the right end of the screw cutting lead

screw

> and engage the 1/2 nuts to use CNC but this is probably not a good

long-term

> solution (lots of backlash I always have to account for). My lathe has a
> separate shaft to drive "power feed" but I didn't think that the pinion &
> rack could be counted on to be linear.

I have a good ballscrew for that, but I'm waiting for a good, small
ballscrew & nut
to show up for the crossfeed. Then, everything related to the old leadscrew
goes! No QC gearbox, no gear trains, reversing tumblers, crossfeed power
engagement, half nuts, threading dial, etc. Basically, all the guts come
out of the
apron, maybe the whole apron gets swapped for a bracket.

Jon



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