RPC, SPC or VFD

StrikerDown

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I'll give it a try, Thanks!

On another note I have been putting my 3 axis DRO from my mill drill on this machine and needed to make a spacer... Oh My God! The surface finish is so... so much better than the mill drill. It is so nice having a big heavy machine that runs smooth. When I put the DRO on the mill drill I used the supplied brackets to mount the readers and all was well until I turned it on. The vibration caused the reader to vibrate so much that on the display the 3rd and 4th digits after the decimal flickered like crazy on the Y and Z axis. I then built new brackets with some 5/8" aluminum plate I had, welded the angles instead of bolting like the original and it was then stiff enough to settle down the display! Of course the X axis was mounted almost directly to the saddle so it couldn't whip around like the longer brackets.
 
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StrikerDown

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I'm not having any luck finding a supplier for Syn Flush. Every place I've tried wants to sell a full case of quarts or gallons. Lubriplate's website shows 6 dealers within 25miles and none of them stock it... but one said they will order it for me $32.95 for a quart!

On the bright side I have pumped a bunch of Vactra 2 through it and all the ways seem to be getting a good supply of way oil. the wipes I've had in the base/catch pan have become quite oil soaked!

Loving the surface finish I'm getting. Here is a 5/8" plate pf aluminum I cleaned up to make brackets for mounting my 3 axis DRO from off of the mill/drill.



It is almost mirror like! :grin2:
 

NoNotAgain

Flashlight Enthusiast
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Jan 25, 2014
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By chance, do you own a fly cutter?

First off it will tell you how square you've got the head to the table, secondly you'd only have to make two passes, and third, the fly cutter uses cheap 3/8 " lathe tool cutters.
 

StrikerDown

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I have a fly cutter but I was playing around and kinda like this look! It didn't take too long at 4,500 rpm and a pretty fast feed rate!
 

precisionworks

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That's a beautiful mill, it looks brand new or used very little. It will last at least a few lifetimes in a one-person shop.

Good call on the rotary, static boxes suck & there's no need for a VFD when you already have a vari-speed head.

5 hp will draw 50 amps on 120 vac or 25 amps on 240 vac. A 30 amp double pole breaker will meet code requirements & allow the rotary motor to start without tripping the breaker.

You'll also need a three phase fused disconnect within sight of the mill, under $100 on ebay for a new one. Get the fuses on ebay at the same time. The disconnect protects the mill motor while the breaker protects wiring from the panel to the mill.
 

StrikerDown

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Thanks Barry.

It was delivered new in 2003 to the garage I picked it up from. The original owner is a retired machinist who bought it to do prototype work for a friend, he did this for 4-5 years until his friend retired, then used it occasionally for the occasional small home job until deciding to sell it. It is in beautiful condition, very smooth and tight. I watched it on Craigs list for a few weeks but he was asking what I thought was too much, then one day I looked and he had dropped the price a thousand dollars so I decided to look at it. the rest is history! There are a few chips in the paint here and there but it really does not look like it's 14 years old!

The RPC came with info stating 20A circuit is minimum required, 30A maximum, So I decided to try the existing 220V, 20A circuit already I had in the wall. It has not tripped the breaker yet so it must be adequate! The RPC spins up very quickly. I assume since it is a Baldor dedicated RPC generator (No Output Shaft on the motor) it has a very light weight rotating mass and does not require quite as much current to get it spinning as a full shaft motor would.

What do you think the full load amps would be on a 3 phase, 3HP motor? (around 9-10 Amps) Or should I ask, what size fuzes would you suggest?
 

precisionworks

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The calculation is 9.6 FLA so either 12A or 15A fuses meet Code requirements. You'll want a 30A fused disconnect with 300 volt rating (or 600V rated if you can find one for less money). EBay is funny but I find it to be the best place to purchase a fused disconnect as well as the fuses. Look for Bussman FRN-R fuses (or equal).


From April, 2010, Practical Machinist RPC Forum, see post #98:

http://http://www.practicalmachinist.com/vb/transformers-phase-converters-and-vfd/rotary-phase-converter-designs-plans-101231/index5.html

In my RPC there are no power factor correction capacitors, no balancing capacitors, and no starting capacitors. The 1 hp pony was a take off from my Burr King, while the 10 hp idler was purchased for $50 from Joe's Junk Jungle. The pony sits on a pair of strap hinges that allow tilting it back to tension the belt to the idler. Even though I have a number of VFD's in the shop, this RPC was built to power a gear head lathe without a clutch. The lathe motor is 3 hp, so the 10 hp idler is probably larger than necessary, but I won't have to build it twice :)

The pony drives an adjustable pitch sheave, so I was able to fine tune the idler rpm. The "ideal" (no load) idler rpm is 1793, and I ended up at 1812 rpm (according to my strobe tach). The frame is 1" square tube and 1.5" angle, butt welded.
 
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