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Thread: New Milll....VFD
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4th Oct 2018, 05:14 PM #1Golden Member
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New Milll....VFD
We did a bit more spending today at 600 machinery buying a new Clausing mill to compliment the 40 year old Bridgeport that we bought brand new so many years ago. The question that this raises is on the machine there is a plate specifying speeds at 50 or 60hz and it occurred to me that we could hook it up to a VFD for infinite speed control and braking which might be useful when running heavy cutting heads at the same time running it at 60hz. Has anyone done this and found it to be advantageous? I wouldn't know if it is an advantage as I don't use the machine only some of the stuff that comes off it and the operator has not got a clue what a VFD does apart from what I have described to him.
CHRIS
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4th Oct 2018, 06:23 PM #2Member: Blue and white apron brigade
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Not sure what your question is Chris. Are you asking about the issues involved with adding a VFD specifically to a Clausing Mill or to a mill in general?
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4th Oct 2018, 06:38 PM #3Golden Member
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4th Oct 2018, 06:52 PM #4Member: Blue and white apron brigade
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If the mill is multiple motor (main spindle, feeds and coolant pump) mill you can't usually drive the mill with one VFD as spindle and feed speeds really need to be independent so will need seperate VFDs.
If you already have 3 phase then it's far less likely to be worth the effort.
If you don't have 3 phase and are hoping to use a 240V 3P VFD to just drive the spindle motor then whether it's worth it depends on the motor - some mills have built in motors (ie cannot be replaced) and if these are delta then nothing short of motor rewires will get these back to full power.
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4th Oct 2018, 08:10 PM #5Golden Member
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4th Oct 2018, 08:18 PM #6Member: Blue and white apron brigade
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4th Oct 2018, 08:23 PM #7Golden Member
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Bob, they use this same mill at 60hz for the entire machine. If I put a VFD on it at 60hz what is the difference to plugging it into a 60hz power supply without a VFD.
PS....I see your point.CHRIS
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4th Oct 2018, 08:59 PM #8Member: Blue and white apron brigade
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A multiple motor mill typically has a contactor for each motor each with a built in safety switch. Lets say the table feed jams where by the load on the table motor goes up exponentially before it's own inbuilt safety switch kick in and cuts the power to the motor. Doing this to a VFD will blow chips and caps.
All the VFD manuals I read say the the safest way to use a VFD is to have them directly connected to a single motor and then setup the VFD up to suit and protect that motor. This means one VFD to one motor and use the VFD to switch the motor on/of. I know some guys have one VFD driving a bunch of motors - I just don't reckon its safe to do this. One member here is experimenting with using one 240V VFD then a step up transformer to convert to 415V to drive a mill with multiple motors and relying on the transformer to protect the VFD - I haven't commented on this but I still wouldn't do if for the reasons above.
On my small mill with just two motors I'm using two VFDs, a 2HP for the spindle and a 0.5HP for the coolant pump.
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4th Oct 2018, 09:07 PM #9Member
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7th Oct 2018, 09:09 AM #10
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7th Oct 2018, 09:18 AM #11Member: Blue and white apron brigade
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7th Oct 2018, 09:44 AM #12
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