Real CNC question

The introduction of CNC lathes has eliminated the need for many traditional attachments and accessories such as taper turning
attachments, ball turning attachments, compensating split-nut/leadscrews, polygon turning attachments, and metric transposition gears.
In looking at the old lathe books, I notice an attachment for relieving or backing off formed mill tools such as B&S type gear cutters and taps.
My question to the money players in the group -- do you machine anything that requires backing off or relief, and if so, are you able to program your cnc lathe to do this? Is this for the single point generated profile, or to cycle the form cutter in and out in sync with the spindle like the mechanical versions?
I don't recall seeing any "canned" back-off/relief cycles for lathes.
Unka' George [George McDuffee] ------------------------------------------- He that will not apply new remedies, must expect new evils: for Time is the greatest innovator: and if Time, of course, alter things to the worse, and wisdom and counsel shall not alter them to the better, what shall be the end?
Francis Bacon (1561-1626), English philosopher, essayist, statesman. Essays, "Of Innovations" (1597-1625).
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On May 26, 6:59pm, F. George McDuffee <gmcduf...@mcduffee- associates.us> wrote:

I've used thread relief many times while chasing threads.
CC
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

George you're obviously new(ish) here, these guys only want to slang CAD/CAM/CNC and the respective programs, they don't know how any of it works. Take a look back in time and you will see what I mean.
dj
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

<snip>
<snip>
============Both RCM and AMC are like gold mines. You have to shovel a ton of "stuff" to find a few nuggets, but it's worth it!!!! :-)
The real money players seem to know their stuff and their information, insights and suggestions on CNC are valuable, and the OpEd, social/cultural commentary and blog content is at least as good on AMC & RMC as the "stuff" you get in the papers or see on TV, its free, and you can talk back, without interruption like down at the donut shop.
The type of lathe attachment I was referring to as relieving or back-off can be seen at http://www.csparks.com/VanDervoort/index.xhtml http://www.lathes.co.uk/rivett34/page6.html http://www.star-techno.com/cfever00.htm {about 1/3 down} http://members.tripod.com/Geoffrey.Brown/id33.htm and many more google on <lathe attachment relieving OR back-off>
Where I am going with all of this is that it appears that a PC controlled CNC home/hobby shop lathe should be *LESS* expensive than a traditional engine lathe, especially when the cost of the necessary attachments/accessories for full utilization are included.
Even larger savings should be attainable through modernization of materials and design such as the elimination of the massive head/bed castings with the substitution of polymer concrete bases and concrete filled weldments, elimination of the lead screw gear boxes/gears, longitudinal and cross feed shafts, and possibly the compound/top slide and graduated dials, threading indicators, etc. It would seem that a plate type bed such as a Hardige, possibly with square rather than dovetail ways for easy/cheap adjustment with shims rather than gibs and scraping would be a good choice.
As shipping costs are becoming more significant, I could see a lathe where the new owner fills the sheet metal stand forms and bed with locally purchased pre-mix sackrete after getting everything in position.
Indeed, low cost tool change could be included by increasing the cross slide travel as is done on the "gangturn" production machines. This would also allow the easy upgrade to a stepper motor controlled Y axis to provide horizontal CNC milling capability, particularly with a "gap" bed design to allow the Y axis slide to go several inches below the nominal ways.
Most likely ball screws/nuts & servos would not be cost effective or required, but it appears that good quality rolled thread acme screws with easily replaceable low friction / low wear "half-nuts" such as moly filled nylon and "micro-step" stepper motors would be more than adequate for home/hobby and even more importantly educational use.
There appears to have been some consideration of this [google on "electronic lead screw"] but no real effort/effect on the order of open source software like linux, to re-engineer the lathe and other machine tools.
Other areas of investigation for cost reduction/value analysis [in the good sense of the term] would be the real/actual need for super precession [and super cost] antifriction ball/roller bearings, or has progress in materials such as UHMW polymers and teflon compounds like Moglice made their use unnecessary or can less expensive commercial grade heavy duty bearings such as front wheel bearings for HD trucks or FWD be used? The question being *NOT* is it good, but is it good *ENOUGH*.
Other possible areas would be the replacement of the existing traditional gears, pulleys, belts, gears, cams, toggles, and levers in the drive system with a VFD motor with possibly a single 3 or 4 step pulley for the spindle drive. This would also allow easy cnc control of motor speed for constant SFM where this would be helpful, e.g. facing and cut-off.
Unka' George [George McDuffee] ------------------------------------------- He that will not apply new remedies, must expect new evils: for Time is the greatest innovator: and if Time, of course, alter things to the worse, and wisdom and counsel shall not alter them to the better, what shall be the end?
Francis Bacon (1561-1626), English philosopher, essayist, statesman. Essays, "Of Innovations" (1597-1625).
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
tpow wrote:

Yeah. You got it! We don't know which end of a machine is the top!
KG
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

George, To answer your question, this feature would only be available on a CAM- TURN type lathe. In these machines, the x axis can be programmed to follow an eccentric shape in sync with the spindle. These are specialized lathes and are not cheap. The speed at which this can be done is limited by the design of the x-axis mechanism and the electronics controlling it. This is commonly used in piston manufacturing to produce the ovality needed. They are also used to produce -- You guessed it -- cams, hence the name.
--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 27 May 2008 15:23:38 GMT, Anthony

========Our money players come through again.
Thanks for the insight.
Unka' George [George McDuffee] ------------------------------------------- He that will not apply new remedies, must expect new evils: for Time is the greatest innovator: and if Time, of course, alter things to the worse, and wisdom and counsel shall not alter them to the better, what shall be the end?
Francis Bacon (1561-1626), English philosopher, essayist, statesman. Essays, "Of Innovations" (1597-1625).
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.