Milling Machines

[jegstad]

Dave K and anybody,

It looks like I will be getting a Rockwell 21-122 Horizontal/Verticle combo machine at my house soon (long story). Any opinions on this unit? It is at least 30 or more years old.

BTW it has been a 45 years since the last time I actually used a mill - in my EE undergrad machine shop course. Needless to say any mill is infinitely better than what I have had.

JimE

 

[tmanley]

Make sure you got a phase converter if the motor is 3 phase.

Prolly odvious, but sometimes overlooked.

 

[digger]

Jim E,
You might want to check this out.
http://www.lathes.co.uk/rockwellmillers/page2.html

 

[jegstad]

Charlie, Thanks, I have already copies of all the pages from that site (Why do the Brits have more/better info than the US sites?) The last picture on that page is the one I've got coming. First I need to get it running, then homebuilt DRO, and then homebuilt CNC. I can't wait to get it home.

Torin, Currently I don't plan on going the 3-phase converter route. I plan on replacing the motors since I already have one that should work for the horizontal drive. I may temporarly use the replaced motor as a phase converter for the vertical one since the vertical motor has a different frame style.

JimE

 

[kweaver]

Jim if you're planning on going the CNC route with that monster I hope you're going to put in ball screws and double row ball nuts. What are you planning on a home built DRO? I found a site back in the summer that has kits that seem to be pretty good. I've also seen how to convert a mouse for a DRO on your 'puter screen but I never could get the program to run because I couldn't get the computer to reconize a second mouse. Hope you're gonna use servo's with feed back and encoders. A little more trouble to build but 100% reliable compared to steppers. Anyway - HAVE FUN !
... oh and grease your hair real good , harder to pull out that way

 

[tmanley]

Thats the other alternative. It is cheaper for me to get the converter than to replace motors on 4 machines. And my Excello grinder is a 1 piece motor with integrated double spindle.. a real tough one to find in single phase, i'd reckon.

 

[jegstad]

KENTucky, I am just starting to look at what DRO & CNC involves. It will be a long term thing. Meanwhile I am going to try to find one of the optional table power-feed attachments that Rockwell made for these. That would go a long way towards doing both. If not I'll try to cobble something together, make mistakes, and learn a few new things. I have about 40 yrs of experience with computers but haven't really played with designing my own system so it should be fun - and I'll keep the grease handy.

Torin, I have no machines now except a 15 year old chinese table top drill press and HF bench grinder. There is nothing really special about the motors required except that they go around and around at the right speed and directions. I am starting out with less in this thing than what the typical unrestored plain-jane cub is going for so a motor or two doesn't seem too bad.

Thanks to all for the feedback. I hope to take some pics after we bring it home - all 1000# or so of it.

JimE

 

[kweaver]

Jim I didn't know they had computers in the stone age
Well then tell me how to get a second mouse to run in DOS then we can both use a mouse for a DRO !

I can send you some files to look over of mice being used if you want to try that instead of laying out the BIG money for dedicated DRO's. You'll need that money if you go to ball screws. The screws are cheap enough but you'd better have the smelling salts handy when you price the double row nuts !
1000 pounds ? That's a little feller. A friend of mine that I traded my new 14x30 lathe to bought a Cincinati that had to be hauled in on a 5 ton truck with a huge boom to unload it. He said it was close to 3 tons ... he got it in the shop , took it a part to replace the bearings ... 2 years later and it's still all over the shop , so's his Harley that he tore down to rebuild 3 years ago but the honey dos are getting done !!

Torin send me your schematic (if ya don't care) for running 3ph off a homemade rotary converter. I can get 3ph used motors for $5 per horse.

 

[dkamp]

Hey Everybody!

Haven't checked this forum much, but did today!

Kenny- Here's a picture of my Rotary Phase Converter project, about halfway in the assembly process... about two weeks ago...

Down on the bottom is a 10hp 3-phase motor.
Upper left box is the control box. It contains:
- 50A Line Circuit Breaker (3ph unit, but only using 2 legs)
- Line and Load contactors (3 phase)
- Starting Cap contactor
- Fault detection timer relay
- Run relay and Stop relay
- Terminal blocks for everything

To the right is the RUN capacitor bank- 140uf total @450v, and 50uF @ 450 for A and C legs, respectively yields final B (manufactured) phase voltage of 248, with A and C being 239... can't get much better phase shift than that.

For starting, there's a bank of 800uf, 400v starting caps in a box in the back, as well as a lamp-dimmer as part of the start-detection circuit (measures B-phase voltage to determine when to drop out start caps). ON the left side is a control-voltage transformer- 240v single phase in, 120v single-phase out. To the right are outlets for the Monarch and Bridgeport.

 

[dkamp]

Here's some more pictures... old Craftsman bandsaw (converted to low speed metal-cutting operation using surplus parts), Cheap Taiwan drill press, Monarch 10EE lathe (a '42 MG), Bridgeport Series 1 BRJ mill, a radial drill (with Bridgeport M-head), imported 20-ton press (I don't use it past 10), and my rolling welding workbench.

 

[dkamp]

Darnit... hate it when that happens.

 

[jegstad]

Dave, I thought I had a messy shop. "A clean shop is a sign of a warped mind". My drill press looks like a twin brother to your Taiwan one. Actually I've also got bandsaw and table saw and am trying to figure out how to keep the dusty stuff from the oily.

Ken, I knew a bit about computers long before they got up close and personal and never, ever went near a (gag) "mainframe" or "MIS". Sounds like you have a circuit to send pulses on a mouse line, interesting but how do you know if you missed one? I was thinking more along the line of position encoders.

JimE

 

[kweaver]

Jim you haven't seen my shop .. !
You have a paint program like Paint Shop Pro or also a CAD program ? ... The DRO / Mouse program will track the mouse movement just like the before mentioned programs , it just throws it up on a bigger screen. Some of the guys wrap a cable around the roller in the mouse to turn the encoder so there shouldn't be any slippage. I experimemted with printing lines on a transparency to use in place of the mouse encoder wheel but I guess the black ink wasn't black enough to trip it. It does work though with a fine tooth comb

I was going to make a scale instead of wrapping around the encoder wheel. So ... wouldn't that be a direct posistion encoder ??

 

[tmanley]

Here is a little bit of info I found on 3 phase converters.

http://www.metalwebnews.com/howto/phase-converter/phase-converter.html

 

[dkamp]

Well, Jim... I've been accused of many things worse than a 'warped mind'... but a sterile-clean shop is definately for someone who's more anal about cleanliness than dedicated to project success...

Anyway, it's in a shambles right now, after movin' stuff around, I yanked out a bunch of shelves, one workbench, etc. to get the 'big tools' in position.

Ken- there's a GREAT resource forum for DIY-RPC over at www.practicalmachinist.com... I recommend it!

 

[kweaver]

I was always told that if it was clean , you weren't working. I found that to be true too , when I first opened my welding shop I sat out there from 6am until around 5 - 6pm and had the cleanest floor , I think I wore out 2 pushbrooms just to be doing something. Now my walk path has turned into a trip path. The 2166 got nudged out when I needed floor space to pour the refractory into my heat treat oven.

Dave that linked worked when I took out the <font size="+2">...</font> after the com. Man I could spend some time there ! Wish they had a schematic section ... have'ta check out the gunsmithing section too }

 

[dkamp]

There's plenty of schematics out there, Ken... some are more complex than others.

Once I get the last few control bugs worked out of my unit, I'll revise my drawings and post 'em, and send you a PDF of 'em in higher-resolution.

The basic concept is pretty simple, really. The Rotary Phase Converter uses a 3-phase motor as a 'rotating transformer' (an "idler motor"), driven off a single-phase line. In order to make up for the 3-phase motor's 60 degree angular misalignment (single phase is two-on-180-degree, three phase is three-on-120) a pair of run capacitors are placed from the 'manufactured' phase to the single-phase legs. One leg will have approximately twice the capacitance of the other. To provide enough phase-shift to actually 'kick' the motor over, a very high capacitance is placed across the higher-capacitance phase... causes such an upset in one direction, that the motor starts turning, and picks up speed. Once the motor gets up above a certain speed, the 'start' capacitors can be switched out, and the motor will run all on it's own. At that point, 3-phase equipment can be connected in parallel to the idler-motor's leads. The idler motor's windings provide that 3rd phase, and the run capacitors provide phase-shift to correct for differences in voltage caused by the 20-degree phase diaspora.

Note that the conversion process isn't 100% efficient in terms of idler-motor usage- you can generally assume that since there's 20-degrees of phase difference, that the idler motor's rating needs to be 25% greater than the 3-phase device you're planning on powering. In my case, the Monarch's Ward-Leonard drive system uses a 6hp 3-ph motor, my 'idler' is a 10hp unit.

Capacitor sizing is a function of the idler-motor's size... kinda. The actual capacitance needed to create symmetry between line and the 'manufactured phase' has to be tweaked-to-perfection while the machine is in proto-test stage. I ordered more capacitors than I needed, and added and removed a few in order to get the right voltage balance. I came down to within 10 volts' difference between all three phases, which is darned good... some guys can't get 'em to dial down within 20v.

Once that's set, it all comes down to getting 'em to start automatically, starting caps to switch out, and the whole thing to shut down when something goes wrong.

 

[kweaver]

I know 2 things about 3ph for sure ! You can reverse 2 leads to change direction and that I don't want to get bit by it !
The friend of mine that got the monster mill has an old rotary converter just collecting dust , I ought to take it a part to check it out.
I've got a stepper controlled 3ph / 3 stacked variable step up transformer ... maybe I'll build a super bright street light Right now I gotta go find FOOD !

 

[jgeorg]

Theres a new posting on www.practicalmachinist.com under "phase converters and VFD" titled "new to forum but" and the whole concept is explained in detail. I finally have a clue. Thanks Dave.
John

 

[dkamp]

My Pleasure, John!

Stay tuned for a wiring diagram for my nifty fully protective, fault-detecting RPC controller...

...and the next variation- a microprocessor-controlled, load-detecting automatic-starting, self-protecting RPC controller KIT- just add contactors, breaker, idler motor, and capacitor stacks. Super-slick and easy, with sophisticated features, at a cost that a month of judicious can-collecting can cover, with enough left for a cup of coffee.