Gun Barrel Manufacturing

CNC Rifler

JerrySharrett said:
Me too Joe. I've been heavily involved in NC and CNC since 1968....AC current problems???
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Joe and Jerry:

The mechanical rifler indexes, and twist based on a gear or gear setting. The only variables are due to wear and flex. A CNC indexes by numeric control, ie: electric motors, gears and ball screws. The manufacture and engineer said that his sine bar rifler would hold .0003" tolerance in a million stokes in a 30" barrel. I have been told a CNC motor controlled indexer and/or it's ball screws would not hold those tolerances. I have seen one US manufactures CNC barrels the rifling examined under 25 power magnification shows what appears to be ratchet like edges on the rifling. The ones where the marks are consistent with all the opposing lands would indicate a hard spot in the metal. The feather like edges on single rifling would indicate fluctuation with the cutter head or inconsistencies in the rod pulling the cutter. Inconsistencies in the rod would be coming from motor harmonics or slop in ball screws. We all know motors, transmissions, and bearings develop harmonic vibrations. We all know voltages and the frequency provided varies from day to day.
Nat Lambeth
 
Rustystud said:
Joe and Jerry:

The mechanical rifler indexes, and twist based on a gear or gear setting. The only variables are due to wear and flex. A CNC indexes by numeric control, ie: electric motors, gears and ball screws. The manufacture and engineer said that his sine bar rifler would hold .0003" tolerance in a million stokes in a 30" barrel. I have been told a CNC motor controlled indexer and/or it's ball screws would not hold those tolerances. I have seen one US manufactures CNC barrels the rifling examined under 25 power magnification shows what appears to be ratchet like edges on the rifling. The ones where the marks are consistent with all the opposing lands would indicate a hard spot in the metal. The feather like edges on single rifling would indicate fluctuation with the cutter head or inconsistencies in the rod pulling the cutter. Inconsistencies in the rod would be coming from motor harmonics or slop in ball screws. We all know motors, transmissions, and bearings develop harmonic vibrations. We all know voltages and the frequency provided varies from day to day.
Nat Lambeth
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Nat,

I'll try to keep this simple but it won't be easy. CNC technology has come a long way, especially in the last few decades. The problems you are citing are from times long past. Ball screws are used on a linear axis. The idea behind a ball screw is to try to eliminate the backlash. Modern machine tool builders will even stretch the ball screw under tension and preload the bearings to eliminate any backlash. The leade screws/gears on a non-CNC type machine likely have much more backlash in them.

Jumping ahead to the "indexer". The term indexer used on a CNC is referring to a more crude technology than what is commonly available. Indexers are designed to move to a position and reach that target within a given tolerance. The motion from degree A to degree B may not, (and probably isn't), up to the accuracy you require. For accurate rotary motion control we refer to what we call a rotary axis. A true rotary axis is designed to give precise near infinite positioning. The position the rotary is in is measured by a device called an encoder. As an example, one of the newer rotaries I have worked with has an encoder that reads four million positions in one motor revolution. The motor has to turn many times for the rotary to revolve 360 degrees.

The common rotary designs I see today use a precision worm drive. These worm drives can be adjusted to eliminate any mechanical backlash. They ride in a sealed chamber in a bath of synthetic oil. They have a great deal of longevity and if any wear does occur, it can be adjusted out.

The voltage and frequencies do not vary from day to day on modern CNC controls of quality. Line voltage yes, but newer controls run the line voltage through a transformer first, then they convert the AC to DC. This smooth out any line fluctuations. The control operates the motors on continuously varying current anyway. If an axis sees a resisting load such as a tool entering a cut, the control must see the motors actual position is lagging behind the commanded position and increase the current to overcome the resistance. It's the controls job to maintain the synchronization of the axis and your resulting machine accuracy is likely a reflection of the quality and capability of your control and motor components.

In my opinion the CNC problems you have heard of are related to poor components and/or poor machine tool design and it shouldn't be assumed this is typical of CNC technology.
 
JerrySharrett said:
Think again Wally. I've been in one RCA plant in Indy.
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FWIW, I had an RCA flat screen to quit. Being a diy type of person, I decided to fix it myself. I was able to diagnose, oder the correct parts and repair the TV for something like $2. The diagnosis consisted of mostly continuity testing many, many capacitors and such inside the set. Nothing inside that RCA big screen had any other than "made in china" stamped on it, that I saw. I suspect that the plant in Indy may have been boxing them up at most.
What got me into this all was that their warranty didn't cover my part due to them no longer offering that part on a set that was only a couple of years old. Their solution was for me to ship them my old set, at my expense, and they would send me another for basically the same price as I could buy it for at wallyworld, PLUS shipping...AND my new set would only have a 90 day warranty. I fixed it for a couple of bucks and used it for a computer monitor for several years, till it finally died and went to tv heaven.
 
Joe Woosman said:
Nat,

I'll try to keep this simple but it won't be easy. CNC technology has come a long way, especially in the last few decades. The problems you are citing are from times long past. Ball screws are used on a linear axis. The idea behind a ball screw is to try to eliminate the backlash. Modern machine tool builders will even stretch the ball screw under tension and preload the bearings to eliminate any backlash. The leade screws/gears on a non-CNC type machine likely have much more backlash in them.

In my opinion the CNC problems you have heard of are related to poor components and/or poor machine tool design and it shouldn't be assumed this is typical of CNC technology.
Click to expand...

Some clarification about CNC technology. In the early NC (Numerical Control-1965-1974) days ball screws and rotary resolvers were used on machines that required high precision in accuracy and repeatability. On some larger machines linear feedback systems (glass or mylar/copper foil scales were used. On some really large machines a product called Accupins were used. These Accupins were in 10" blocks and had a precision 0.100" pin each 0.100" of distance. There was a reading devise called a double averaging head that read several pins at once and averaged the distance error. The Accupin system was a General Electric product and was used on both GE and Bendix controls.

We had large boring mills that had 18 feet of linear movement. Just a 18' ballscrew alone would cost tens of thousands of dollars and still contained some error.
With the advent of CNC (Computerized Numerical Control) a portable feedback system (master digitizers) is fastened to the axis being set up on a new machine. Then that axis was digitized and the error was memorized within the control for that axis. So if there was a 0.002" error in a certain spot that error was compensated for as the machine control passed the unit being controlled passed through that area. Later even the master digitizers were error compensated with lasers.

Getting back to stepping motors controlling axis of linear or rotary movement running them with DA (Digital from Analog) took most of the "jumping" out of the loop sometimes called a servo loop).

Today we think of CNC as the complete package of machining automation. The first features of "CNC" was simply the "control unit" running the program out of its memory as opposed to earlier NC where a punched tape was read once for each piece part. Now simple microprocessors (just like your PC) are used to control many more aspects like acceleration and deceleration, interpolation and scaling of irregular, non geometric, shapes like spirals and lofted curves.

My point with this over explained post is with modern and now much less expensive CNC technology there should be near ZERO error in the linear and rotary movements required for barrel making.
 
mwezell said:
FWIW, I had an RCA flat screen to quit. Being a diy type of person, I decided to fix it myself. I was able to diagnose, oder the correct parts and repair the TV for something like $2. The diagnosis consisted of mostly continuity testing many, many capacitors and such inside the set. Nothing inside that RCA big screen had any other than "made in china" stamped on it, that I saw. I suspect that the plant in Indy may have been boxing them up at most.
What got me into this all was that their warranty didn't cover my part due to them no longer offering that part on a set that was only a couple of years old. Their solution was for me to ship them my old set, at my expense, and they would send me another for basically the same price as I could buy it for at wallyworld, PLUS shipping...AND my new set would only have a 90 day warranty. I fixed it for a couple of bucks and used it for a computer monitor for several years, till it finally died and went to tv heaven.
Click to expand...

Mike, you must not be talking about flat screen LCD, PDP or DLP technology.

Today they are probably being made anywhere slave labor is available!! These modern CEO's have to trade their Grumman Gulfstreams ever couple of years. The ashtrays et full of cigar ashes you know.

It is/can still be WE THE PROPLE!!

www.house.gov

www.senate.gov
 
It was LCD, Jerry. This has been about 7-8 years ago. I know I bought it right before the price plummeted on them. Just my luck.:( That was part of me fixing it. I guess I didn't like the idea of paying something over $1000 for a tv, and then have the maker offer a $4-500 replacement with a 90 day warranty. Anyway...I agree with the principle of what you are saying.
 
JerrySharrett said:
Looks like this is the official site for RCA....it even says RCA, it doesn't say oncorpous!

http://www.rca.com/

So much for pi$$in'
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Of course it does. Linked right from RCA owners site at WWW.ONCORPUS.COM. Proudly made in South Korea. They know many Americans are easily convinced that there TV is still made in US. Maybe we won't become outraged at taxes, regulations and environmental wacko madness that's got us into this mess.

WallyW
 
Wally's gotcha' here Jerry ;)

Unions have ensured that until they're BUSTED anf gone you'll never see MADE IN USA again.


Except haircuts


and tanning salons.......



Ohhhh, and dog grooming. It isn't unionized yet.....


LOL
al
 
JerrySharrett said:
Ai, if WE THE PEOPLE are all like you, yes, we'll never see Made in US again.

Www.house.gov

Www.senate.gov

al, how many times. Have YOU used those web sites. I don't argue with non patriots!!! So, goodby!!!!!
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LOL!!!

You union apologists crack me up!....... you and WuhBAma gonna' "grow America from the middle class out" eh......

In my world ranting on government websites isn't "doing something." Our POTUS got elected fair and square.

Twice.

The argument is right here Jerry, the battle field is RIGHT HERE on the ground. RIGHT HERE on websites like this. Discussion amongst the voting populace. We The People still vote in our elected officials.....If you think supporting union corruption is "American" then you're squarely in Obama's camp, like it or not.

And no, running away and slamming the door isn't going to convince me that you're right. :)


BTW I've BEEN in those chambers, in those videos..... I've set in on those discussions, I've seen filibusters. I've seen guys screaming and shaking their fists....They're just a bunch of rednecks like you and I. Well, actually, NOT like you and I, most of them are pigs. Of the 15 or so senators and representatives I know personally I'd only allow one of them to date my daughter. And we'd have a serious sitdown first.

And we elected them :)

The real fight is right here on the ground...... neighbor to neighbor.

Talking.

al
 
alinwa said:
LOL!!!

You union apologists crack me up!....... you and WuhBAma gonna' "grow America from the middle class out" eh......


The argument is right here Jerry, the battle field is RIGHT HERE on the ground. RIGHT HERE on websites like this. Discussion amongst the voting populace. We The People still vote in our elected officials.....If you think supporting union corruption is "American" then you're squarely in Obama's camp, like it or not.


And we elected them :)


Talking.

al
Click to expand...

Al, before you go, I have never mentioned unions. My day job for 40 years was with Eastman Kodak and Eastman Chemical Division who were very very non-union. Besides, I was salary paid and not eligible to partake in unions even if one came by!!!

As to your comment :the fight is here in the streets". What are you going to do, riot like Kiev or Istanbul? Bad idea!!

The fight, as plainly stated by our Constitution, is in Washington, or should be. The US Congress has the SWORN duty to regulate trade and tariffs. In doing that, Congress needs to level the playing field, not by bringing US wages DOWN to third world wages, but to bring US originated jobs back home AND bring the US troops back home.

Protect our Southern borders with the US troops that are now in 180 different countries and 900 foreign military bases. Bring them home and away from the IED's the Bush/Cheney/Rumsfeld war machine created and let them enjoy a quiet respite in our Sunny South.

And NO I did not vote for Bommy Wommy!! I vote always but not for the Dems or GOP. In the last 22 years my votes have gone to two other Texicans, both initialed "RP"! The first RP made a fool of IBM, made a fool of GM, made a fool of Ayatollah Khomeini and netted $3.5 billion in the process!

About 3-4 years ago I had you on my IGNORE list. Reluctantly I took you off that list. Now I am obliged to IGNORE you again.

Goodby!!!

www.house.gov

www.senate.gov
 
Article 1 Section 8 of our Constitution does give Congress the power to regulate foreign commerce and to collect duties. Presumably they could use that power to stop imports. How would that improve anything.

The mess we are in is the result of the Executive, Legislative, and Judicial branches. They have destroyed our merchant marine. Stopped cold much of our ability to extract resources, refine them and make available to industry. The highest taxes of any industrial nation. Not a significant power generation site competed in over 30 year.

A vote for Ross Perot or Ron Paul was certainly not for higher taxes, tariffs or more regulation.

This fight is certainly one for the individual American. We can educate ourselves and those around us regarding the original intent of the founding fathers. How free citizens, with little interference from Washington, made this country the envy of the world.

Unshackle the most productive people on the planet.

WallyW
 
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