vfd on the big grizzly gun lathe?

S

skeetlee

Active member
I am in need of some info. I was hoping someone here had the big grizzly g0509 gun lathe with a vfd to convert the 3 phase. If someone does what vfd do you use and if you don't mind a phone call would be great. I need some info off the motor as well so I can see if a vfd will even work. Thanks a bunch lee
217 246 0787
 
Sounds like dad just traded the bridgeport mill for a newer one. Maybe a rotary converter is a better choice? Were can i learn about building a rotary phase converter? What size motor will i need for a 4HP lathe and a 3HP coolant pump? Lots to learn. Lee
 
From what I know, a VFD for a 4 hp motor should not be that much of a problem. I don't think my lathe has a 4 hp, maybe 3? Fed the VFD with two legs of 120 and a common and away it went! A 3hp pump? That's serious!
 
Varrible Frequency Drive

First, let me say I have used both a rotary converter and a Varrible Frequency Drive. No question I would pick the VFD. You might check a web site call dealersdirect.com They sell both new and used VFDs. You might also check your local commercial HVAC companies. They use them in chillers.
Nat Lambeth
 
I dont have any exp. with VFDs so I cant speak to them although I havent seen any negative remarks that I can recall. I will say that I have a half dozen 3 phase machines in my garage and I run them all from the same convertor. It is very simple to set up a rotary covertor, you can purchase one or make your own. I purchased a used convertor that suited my needs and got it very resonable. You want to try to size the convertor for the equipment you have bigger isnt really better. The downside with rotarys is that motor is running when your working with the machines and the motor noise can get annoying, plus its using juice. I saw a phase perfect like the one in the link at a surplus eq dealer the other day I can get you the particulars and pricing if your interested they also had a rotory unit there as well.
 
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I have 2 VFDs on my 2 Bridgeports. They are just great. Speed control and other features. You would need one for each machine. I have 2 phase converters also. Go to the Practical Machinest forum. They have a section on just this subject.
 
Skeet, one thing I failed to mention earlier, the Phase perfect unit will only deliver 3-phase power. It will not give you the variable speed control that a vfd will.
 
We wont need to run both machines at the same time. Were not that busy. LOL It would be nice to get both of these machines running for the fewest dollors without compromising performance.
I did talk to a motor shop here local and the fella said he could set me up with a VFD but it was going to take a little work, because of the two speed motor on the lathe. He also said it will cost a little more than 700 bucks. If we can do a home made rotary phase for about the same money then we could use that for both machines???? I dont know! Lee
 
Any idea how big of a motor i would need on a Rotary Phase converter for the new lathe 4HP main motor 3HP pump motor and the new Mill has a 3HP motor. Do i just go with the biggest motor X3? Lee
 
Guys im telling you wrong. The motor on the lathe say 3HP 4HP in the catalog. Not sure what that means. The pump is ony 1/8th HP Lee
 
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G'day Lee

I have VFD's on both my mill and my lathe.. Both are 1.5KW motors (2HP) and i run 2.2KW rated VFD's (3HP) . I chose to up rate the VFD because even though the motor is rated 2HP it can deliver quite a bit more than that for a short time without any problems.. The VFD has current limiting so you are then limited to what ever your VFD is rated for. Most modern VFD's are fully programmable so you will need to study the supplied manual and program and wire it your self or else get someone qualified in to set it up for you..
One KEY point i would make with any VFD for a lathe or mill is to ensure that is has dynamic braking. This is where a large suitably rated resistor is also connected to the VFD. When setting up the VFD you can choose how quickly the motor ramps up to full speed and then back down to a stop. Obviously the ramp up time is determined by the current limiting of the VFD ie faster ramp up the more current it will pull..
The reverse happens when you ramp back down to a stop. In this situation the motor and it's load(spindle,chuck etc) then act as a generator and the VFD has to dissipate this energy supplied from the motor. The shortest ramp down time is therefor determined by the current handling capacity of the VFD..
This is where dynamic braking and the large resistor comes in.. With the braking resistor connected, the VFD is able to "bleed off" the excess energy and dissipated it into the resistor.

All of this is is required in order to start and stop the machine as quickly as possible. Without the braking, lathes with their heavy chucks etc will take an age to come to rest.. If you try to push the ramp time too much without braking enabled, the unit will just fault out on an over current or over voltage fault,requiring a manual reset. With out braking, my small lathe would take around 10 seconds to come to rest from 1800 rpm. With Braking, it takes less than 1.5 seconds!

Being able to stop quickly is a good safety feature but it is also very useful when threading metric threads.. You can just withdraw the tool at the end of each pass and drop it straight into reverse.. The lathe will then safely and very quickly come to a rest and then accelerate up to speed in reverse.



Cheers
Leeroy
 
Skeet are you trying to run a 3 or 4 HP lathe? The convertor you linked is too big for that. I would look at one that will start a 3.5 or a 5 HP motor. On my convertor when the phase convertor idles ( no load from the lathe) the T3 generated leg will produce a higher voltage than the voltage on T1 or T2. When I put a load on the convertor(running the lathe motor) the generated leg will balance out and the voltage will be closer to the T1and T2 legs. When you get a covertor that is too large for the motor/ equipment youre trying to run the generated leg may be farther out of balance than is desirable, this will leave too much voltage on the T3 leg. I hope this helps a bit
 
I thought that the rotary phase converter motor had to be 3 times the size of the motor on the lathe? I catch on pretty quick to a lot of different things but electricity isnt one of them. Lee
 
The comercially manufactured one that I have is tagged with the largest motor it will start at one time and the total amount of HP that it can run combined. Check with the manufacturer of the convertor your looking at and describe the application they shoud be able to help you size it correctly. The one you linked looks big to me but I might be all wet
 
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Contact Ritten of Ritten Precision on either Snipershide, Accurateshooter, or Bayoushooter. He has the big grizzly lathe and runs it off a vfd. From what I remember when he told me about it, it was basically plug and play.
 
grizzly recomends a 15hp rfc but i have talked to a couple guys who are using smaller motors. one fella says he is using a 7.5hp motor with no problems yet another fella is using a 10hp but cant run his machine on the top two speeds. i dont understand that one bit??? not real sure what motor i need. lee
 
Lee,
Did you check this out on the Practical Machinest forum?

http://www.practicalmachinist.com/vb/transformers-phase-converters-vfd/type-phase-converter-264563/

I started with 2 Ronk RPC, one is a 3hp unit and the other is a 1hp unit. The 1hp unit ran both of my Jhead Bridgeports. The 3hp unit runs the lathe, Grob bandsaw, and Bridgeport surface grinder. I added 2 VFD, one ea. for the Bridgeports. They take the 3 phase from the 1hp rotary and to ea. of the mills. I have variable speed on my mills now. A cheap thing that a buddy did for me was adding stopping resistors. I can program the VFDs to instantly stop the mill spindle when they are switched off at the drum switch.
I have no troubles having multiple machines running at one time. I just start them one at a time. Normally not a problem unless you have Family or a Friend around and you have 2 or 3 machines going at one time.
 
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