# RPC, SPC or VFD



## StrikerDown (Dec 12, 2016)

I have had my round column Rong Fu Mill/Drill for about 6 years and finally got tired of it's limitations. Mostly the lack of rigidity. I recently got a little too aggressive milling a flat on the side of a 1" round bar with a 1" carbide end mill it started to chatter and before I could stop the feed it had shattered several flutes... an expensive boo boo!

The even more expensive solution:





It is a Sharp LMV50 (50" Table) It comes with a 6" Kurt, now I'll have two!, X and Y servo power feed, Cool Mist tank and coolant metering system and 2 axis Accurite DRO, which I will probably replace with the newer 3 axis DRO currently on the mill/drill, that has an integrated touch probe an LCD color display and Absolute magnetic scales. It not only has a ton more features but I already know how to use it! Plus It has a few of my favorite programs already in it!

Next I need to rent a trailer to go pick up this beast.

Question: What type phase converter should I use? RPC, Variable Frequency Drive or a Static Phase Converter. I believe the static loses 1/3 to 1/2 if the rated HP compared to hooking up to commercial 3 phase , not sure about the others
Any ideas, suggestions or recommendations would be much appreciated.


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## gadget_lover (Dec 15, 2016)

I went the VFD route when I wanted variable speed on my mill. I still have the belts and pulleys if I want to go real slow or real fast but mainly I use the VFD to determine spindle speed.

Of course, only the motor is being fed by the VFD in my case. Everything else is running from normal 120v circuits.

It looks like your Sharp already has variable speed, so there may be no benefit to using a VFD. If your Sharp is using 3ph for the auxiliary devices (the feeds) or DRO, then you may want to use the static phase converter. Please do more research before using my opinion for anything.

Daniel


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## brickbat (Dec 18, 2016)

I'd avoid a static phase converter on a vertical mill, because you can't 'plug' it into reverse and, as has already been mentioned, the loss of torque. An RPC makes a nice project to design and build.


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## NoNotAgain (Dec 18, 2016)

Get the rotary converter. Purchase one large enough to cover your future needs like a new to you lathe. 
A lathe will require a rotary converter due to having a flywheel. It needs that 120 degree pulse of power that a static converter doesn't create. 

IMO, the negative of the RPC, is the weight of the motor used. Mines got a 15 horse cast iron GE motor on it. It's close to 600 lbs, so it's a pain to move around.


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## StrikerDown (Dec 18, 2016)

Thank's for the ideas. 
I've decided to bite the RPC bullet. I found a 5 horse w/Baldor motor/generator for a decent price, should arrive next week. I really like the idea of speed changes on the fly, but that is built in already. It has a low and high range and and a hand wheel to dial in 60- 500 RPM(L), and 500-4,500 RPM(H).
Plus it followed me home yesterday:













The 50" table is like an air craft carrier compared to my outgoing RF31, Mill/Drill! 




All cleaned up, lubed and anxiously waiting for the RPC to arrive. 




I currently have a 20 amp 220V circuit in the wall behind the mill, but I'm thinking the 5HP RPC will need more amps. It's not a problem to update, when I put in the wiring I ran EMT conduit inside the walls so it should be simple to pull in larger wire back to the panel.


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## NoNotAgain (Dec 19, 2016)

While your waiting for the RPC, get yourself a 18" trammel and square the head to the table. Make sure to adjust the gibs first then lube and run the X and Y axis feeds. 

I usually do the Y axis first, then the X. Extend the quill, as this will be worst case.


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## StrikerDown (Dec 20, 2016)

Not sure what a trammel is but I do have the dial test indicator to tram the head... although I haven't trammed a mill with a tilt or nod feature before it should be much faster/easier than shimming a column! 
Thank you for the info!


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## NoNotAgain (Dec 20, 2016)

To get best results, extend your dial indicator as far away from the quill as possible. The larger the area sampled, the closer you'll get to square. 
Trammel. http://www.airgas.com/product/Tools...6750!&ef_id=WFnG1AAABGTceycZ:20161221000332:s

A knee mill will develop some sag with wear. The trammel holding an indicator will allow you to zero with Y against the base, and give you reach for Y extended full length away.


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## brickbat (Dec 21, 2016)

NoNotAgain said:


> ...Those that can, do. Those that can't, teach....



Kinda OT, but what's your sig line mean?


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## gadget_lover (Dec 22, 2016)

brickbat said:


> Quote Originally Posted by NoNotAgain View Post
> ...Those that can, do. Those that can't, teach....
> 
> Kinda OT, but what's your sig line mean?



In a positive light, it's an observation that education is not always all that's needed to do the job. Sometimes you need skills to go along with the education. If you don't have the skills to do the job, one alternative for using your education is to teach others. 

In a negative light, it's a slam against those who only have book learning and no practical experience. 

Daniel


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## brickbat (Dec 22, 2016)

...the question was really meant for NoNotAgain...


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## NoNotAgain (Dec 22, 2016)

brickbat said:


> ...the question was really meant for NoNotAgain...



Daniel pretty much summed it up. 

When I first started working in aerospace just about every engineer I worked with had a doctorate. They didn't know how to do anything, but wrote lots of white papers. 

When it came down to design, build, and fabrication they were no where in site.


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## brickbat (Dec 22, 2016)

Glad I asked - It's an unusual use of the phrase. Generally, I've seen it as a pissed-off student's insult on teachers, underestimating their skills and abilities, which seems a bit provocative as a sig line...

In fact, googling it now, I don't see it being used to convey your position. Weird...


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## StrikerDown (Dec 22, 2016)

If what you cite is correct and they were nowhere in sight than maybe they were off site!


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## StrikerDown (Dec 22, 2016)

This beast is really clean, all the little plaques, signs and dials still have their protective plastic film on them. I can appreciate this because I am that way and leave those on most of the time.





The RPC arrived a couple days ago and I got it mostly installed last night, except for clamping the flex to the wall and tying up a few loose cords...I can now make chips!








Looking at it It's hard to believe it is 14 years old!


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## NoNotAgain (Dec 22, 2016)

Lubriplate makes a cleaner for the oiler system called CFL, for clean, flush and lubricate. If the machine has sat for a period of time, the metering valves stick and don't meter the correct portion of oil when you pump the handle. The last time I purchased some from MSC is was close to $10 a quart. You've got way oil as well as spindle oil ports.

Did you adjust the gibs yet? Also, how much run-out are you seeing in the table both X and Y?


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## StrikerDown (Dec 23, 2016)

Original owner used Vactra #2 in the one shot pump, same way oil I use, need to order more and plan on getting mobile Velocite #10 for the spindle oil. 
I have not heard of the "Lubriplate CFL" and can't find it listed on MSC or Mcmaster, sounds like a good idea to clean it out, do you have a PN for MSC?

I have not had time to adjust the gibs yet maybe tomorrow or Saturday, probably not Sunday (Christmas!).

I assume you mean backlash in the X & Y and it looks like about .005 in the Y and .006 for the X. I will go through the Adjustment procedure in the manual hopefully when I have time to attack the Gibs. Both seem pretty tight compared to what I'm used to but I will work the procedure to learn it as well as get it right.

Thanks for the info.


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## NoNotAgain (Dec 23, 2016)

Lubriplate now calls it Synflush. 
I've got one last quart of what I purchased a few years back.


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## StrikerDown (Dec 24, 2016)

I found Synflush.
How do you use it. Empty and pump it through the system or just add it to the way oil?


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## NoNotAgain (Dec 24, 2016)

Empty the pump and use as you would use way oil. Give it about 6-8 good pumps and traverse the table and wipe the ways with a clean cloth. After around the 3-4th traverse, you'll notice a lot of dirty crap show up. Then top off using Vectrax oil.


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## StrikerDown (Dec 24, 2016)

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 (Jan 3, 2017)

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!


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## NoNotAgain (Jan 3, 2017)

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.


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## StrikerDown (Jan 4, 2017)

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!


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## precisionworks (Jan 6, 2017)

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.


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## StrikerDown (Jan 10, 2017)

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?


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## precisionworks (Jan 13, 2017)

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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