Re: [CAD_CAM_EDM_DRO] Bridgeport Series 1 conversion and other stuff

eGroupsCDH wrote:

> Hi List,
>
> Since this is my first posting to this list I thought I would start with an
> introduction: I heard about this list from the ModelEng list where I have
> been a member for several years. My application is Home Shop centered
> around 7.5" gauge Live Steam railroading but my interests range far and
> wide. I have an Electrical Engineering degree but my field is software
> development.

This is excellent background, as there is much more software involved,
and not much real electrical engineering, if you use commercial modules,
such as axis control cards, stepper drivers or servo amps, etc.

> I have only read this list for about a week. I have been very
> interested in the intelligent/passive (better than smart/dumb ;-) ) driver
> discussion and I understand the issues but I'm afraid I'll be able to
> contribute little since my "hands on" EE theory knowledge is 1970's vintage.
>
> Among other things I have an Enco 9x42 Bridgeport clone that I have added
> "Home" CNC to (X and Y only so far, Acme screws) and an Emco Maier Super 11
> lathe that I have also adapted to CNC (again, no ball screws). I use an
> AHHA 4 axis driver and their Artisan software.
>
> I have found 5 Bridgeport Series 1's (Boss 5 & 6, one 7) in the area with
> prices down to $1,000 and I've been thinking of getting one, throwing away
> the tape-based controller and substituting the AHHA driver/software.
>
> Questions:
>
> 1) Can you tell me the drive current requirements of the steppers on a
> Series 1? (I have 6 amp drivers)

6 Amps is close, I think they run 8 nominally. But, you need a lot of voltage,
as the stock motors have a lot of inductance.

> 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.

> Keep in mind that I'm probably a "beginner" compared to a lot of members of
> this list but ... my thoughts on the intelligent/passive box "line of
> demarcation" is that it would be best to put as little "hardware" in place
> as possible (enhances flexibility) but that it should include enough
> hardware help (interrupt and position buffering, etc. within reason) to
> allow a non-real-time OS to achieve smooth contouring, etc. (keep in mind
> I've only read a weeks worth of messages here so this may have already been
> hashed out ...). In my situation I value flexibility over speed but I
> realize that situations/preferences vary.

Well, EMC DOES use a real-time OS, so it takes care of the smoothness
problem the serious way!

> 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