Re: [CAD_CAM_EDM_DRO] cnc lathe - threading - alternitive method? (more-info, please read)

If that were possible all of the machine manufacturers wouldn't have wasted all that money and time on all those gears, shafts and levers for synchronized feed systems. All of the old-timers could've calculated it, the things we do on calculators, they did in their head. The problem with this idea: There is no way of calculating an accurate spindle RPM other than by real time mechanical or electronic means. If the lathe is at home and its summertime, the central unit kicks on, the RPM changes because of intermitent voltage/current drop. The RPM changes under load as well. This would be a very complex challenge to even get CLOSE to the actual RPM. It's impossible. If it's for turning a helix in a lampbase, it's do-able in one pass. If for machined anything of precision, forget it.

Ron

Russ Waters <mycncworld@...> wrote:

That is a very good point you made.... so, lets say one wants to turn a spiral (wood) using a thread theory in that the spindle speed needs to be coodinated with the z feedrate.... you would think there would be some sort of equation for spindle rpm, number of spirals per inch, and z feed rate and the x depth.....

Just a thought,
Russ

ps To all of those people who answered with a feedback type of control, this is what I am trying to work AROUND,,,,,not with.

Jon Elson wrote:

Russ Waters wrote:

>Hi to the group..... I need to pick your brain on this one!
>
>I would like to come up with a alternitive method of threading with a cnc lathe,,,,, not using a feedback system with conjuntion of the G33 code, but would it be possible to cordinate the spindle speed with the feedrate of the z axis to do threading? I think it could be done, has anyone tried this, or have a theory on how it could be done????
>
>

Yes, but....

The problem is that there will be no precise relation between the
spindle and
the Z axis feed, so the thread will be an APPROXIMATION of the desired
thread
pitch! If your spindle speed were held within 10%, then you'd get a
thread pitch
that was somewhere within 10%. So, for a 32 TPI pitch, you'd get
something within
29 and 35 TPI. IS that good enough? I suspect not, for most purposes.

Secondly, you would have no way to make multi-pass threads. Every
thread would
have to be cut in a single pass. Think you can cut an 8-TPI thread in
one pass?
Hmmm, I'd like to see your lathe!

So, these are the reasons why feedback is used.

Jon



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Addresses:
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FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
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Moderator: pentam@... indigo_red@... davemucha@... [Moderators]
URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO

OFF Topic POSTS: General Machining
If you wish to post on unlimited OT subjects goto: aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if you have trouble.
http://www.metalworking.com/news_servers.html

http://groups.yahoo.com/group/jobshophomeshop I consider this to be a sister site to the CCED group, as many of the same members are there, for OT subjects, that are not allowed on the CCED list.

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