Powering a Gorton 9J mill (4 motors)

[MattyP]

Recently picked up a big old Gorton 9J and I'm working through figuring how I'm going to get this thing making chips in my shop.

So far, here's what I know. This was previously running off a RPC. I don't have details around the size of the RPC or whether it was home built or a purchased model (like American Rotary, etc) or anything like that, but I hope to get that information this weekend.

The mill itself has 4 motors that are 220V 3-phase; 3HP main motor, 1/3HP motor on knee for power feeds, 1/8HP motor on the quill, and a 1/10HP motor on the coolant pump.

Honestly, right now, I'm leaning towards moving to VFD, even knowing this will require me to buy 4 VFDs to power this thing. My thinking around this is that VFDs feel like they are easy to manage and they feel like they are a more modern approach to the problem of going from single phase to 3 phase. I'm a computer programmer so perhaps that's why I'm leaning that way. Rather than having 1 big huge complex jumble of wires, it's 4 individual VFDs to manage. Makes more sense in my head. Also, I think even with having to buy 4 VFDs, the cost seems lower than going with a RPC vendor like American Rotary (VFDs seem to be around $250 for the big motor so I'm assuming less for the smaller motors and a RPC from American Rotary starts at $1k for sizing it up in the 7.5HP range). I could be way off on those estimates, so if I am, by all means let me know.
Also, I know I'm basically asking the same old VFD or RPC question that's been answered over and over, and I get a lot of it is completely preference, but I'm curious what others would say around this opinion since I'm completely new to this world.

Finally, if I do go VFD, I'm struggling to figure out what sort of VFD I would need for those really small motors. Scanning through Invertek's and Vevor's websites, all the VFDs listed are sized to 1HP at the smallest. I know you are supposed to properly size a VFD so I'm curious how that typically get's addressed with smaller motors. Maybe the 1HP rated ones can cover the super low HP motors. Any insights are appreciated.

 

[matthewsx]

Hi and welcome,

Former Gorton owner here so I'll give my take. When I got my 1-22 Mastermill for free it had a VFD powering the spindle motor and all the other drives were intact. The speed control for feeds was WWII technology with vacuum tubes and such, cool but not what I would consider reliable or something I wanted to spend much time troubleshooting.

I never did get around to installing the small VDF's I purchased for the conversion but I recall they were fairly cheap off eBay since sub 1hp drives are not in high demand.

What I would do is get yourself a good VFD for the spindle and start using the machine manually while building an overall modern control system. You can power the spindle directly without much hassle and start making chips while you design and install the rest which should be simple since they really don't need to be all connected together.

@mksj is probably the best resource on this forum for VFD systems so I would definitely recommend reading his posts or reaching out to get his take on what would be best for your application. You'll have lots of help on here, especially if you post pictures.

John

 

[benmychree]

I power all my machines with a home made RPC of 5 HP using a static phase converter to start it and a bunch of oil filled capacitors to balance the phases; it works fine with minimal investment; why further enrich China?

 

[Aukai]

Just thinking out loud, I do not even know what I'm thinking is possible or not. Could you not have a 5hp RPC powering a box with circuit breakers for each component rated for each ones amperage, and one plug in to the RPC?

 

[MattyP]

Just thinking out loud, I do not even know what I'm thinking is possible or not. Could you not have a 5hp RPC powering a box with circuit breakers for each component rated for each ones amperage, and one plug in to the RPC?

That's essentially what's on the mill currently. There are non-reversing motor starters to each motor (I think, I'm still confirming where all the wires actually go), with a singular plug out of the electrical box. The person I bought it off had many other machines in his garage so an RPC very much made sense for him. That said, I don't feel comfortable enough in my electrical skills to build my own RPC. Here's a diagram of the electrical on the mill currently. I still haven't tracked down what non-reversing starter goes to what motor, and given there are 5 of them and only 4 motors, I'm a little confused. Plus I haven't figured out what the step-down / up piece is for (the 170DE in the top middle).

I power all my machines with a home made RPC of 5 HP using a static phase converter to start it and a bunch of oil filled capacitors to balance the phases; it works fine with minimal investment; why further enrich China?

Mainly because I don't feel comfortable building my own RPC, and it doesn't seem like a cost savings or simplicity savings to stick with an RPC when I'm sourcing either from a company. But again, I know basically zero about any of this stuff.

 

[pontiac428]

First, congrats on the Gorton, those are neat mills.

Your mill is the perfect candidate for a ROTARY PHASE CONVERTER. Get it rated for the total draw, then it's plug and play. You're feeding the machine what it was intended to use: 3 phase power. The electrics are already there for that, nicely arranged for you in a ready-to-go package in your machine's panel box. Anything else would be an act of butchery. Four VFDs would be expensive and shows a strong tendency toward self-loathing for the owner taking that forsaken route. VFD is fine for simple electrics and single motors, like a drill press or a band saw. Multi-motor 3-phase native equipment really deserves a RPC if not beautiful utility-supplied 3-phase power.

 

[benmychree]

First, congrats on the Gorton, those are neat mills.

Your mill is the perfect candidate for a ROTARY PHASE CONVERTER. Get it rated for the total draw, then it's plug and play. You're feeding the machine what it was intended to use: 3 phase power. The electrics are already there for that, nicely arranged for you in a ready-to-go package in your machine's panel box. Anything else would be an act of butchery. Four VFDs would be expensive and shows a strong tendency toward self-loathing for the owner taking that forsaken route. VFD is fine for simple electrics and single motors, like a drill press or a band saw. Multi-motor 3-phase native equipment really deserves a RPC if not beautiful utility-supplied 3-phase power.

I quite agree on all points, and the 170 de is a control transformer for the control circuits to actuate the contactors, on machine tools that operate at high voltages, and in a sometimes wet enviornment, it is not good to have high voltages near fingers that push buttons. I was using a water based machine cleaner and sluiced down the stop/start/reverse panel on a Lucas HBM; the result was a boom and flash on 440 V; call the electrician! Lesson learned.

 

[markba633csi]

I agree with RPC approach also- it's really no big deal to put one together
Overall I would say the MTBF (mean time between failure) would be longer with a RPC than a bunch of electronics.
Also it seems a shame to tear out all those nice analog contactors and wiring

 

[mksj]

You can get an RPC control box complete for between $250-350 depends on the configuration and all you would need is a motor, or a complete RPC for $800-900 range, you also have shipping costs. The VFD's sure you can get cheap VFD's but anything halfway decent will be in the $200-400 range for the main motor, and figure another $150-200 for the additional ones, you also need switch gear. You will want to fuse/breaker each one differently, you may need braking resistors, and other ancillary items so you are quickly into the costs of a turn key RPC. RPC, hook up one end up to the breaker panel and the other too your machine and you are pretty much done. Press the ON button on the RPC and you are ready to run and the RPC should come pretty well balanced. Only caveat with the RPC is too not connected the generated/wild leg to the the transformer. Need to speak to the RPC manufacturer, you may get by with a 5 Hp RPC, as there is no significant load when starting a mill. Once the main mill motor is running it would add to the RPC motor, so the other drive motors would not really be a factor. Coolant pump takes almost no power and also could be replaced with a single phase, assuming you would even use it.

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[Aukai]

If you have, or can make the electronics EBay has new open box/NOS type 3ph motors. I found a Baldor with free shipping even to Hawaii.