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Vfd and motor change

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rimfire1903

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#1
need help, i would like to have a vfd on my clausing 8520 mill in very good condition, (but) it has a 3/4hp dc. with belt drive with pulley set up, i am a gunsmith and need to cut dovetails in slides and barrels, and run in a slow speed around 6-700 rpms,, herd i need a 3ph induction motor and a vfd, i dont have 3 ph. home shop 110/220
so what do i have to do to achieve this i wouldn't mind a 1 hp or even the 3/4hp is ok with me, can you explain exactly what i need to do including motor type and hp,vfd type for the motor i need,, wright i am running 110, i would like to avoid changing belts but if the cost is out of my ball park, i would like to modernize the older we get the lazier we get,,,, i get,,, please be specific thank you for your time
 

TonyRV2

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#2
You don't need 3 phase power in the shop. Part of the job of the VFD is to take your single phase power and convert it to 3 phase. You can run a 1hp 3 phase motor using your 110V shop power. You just plug your VFD into a 20A outlet and wire the VFD's 3 phase output to your 3 phase motor. Its that simple. You didn't mention what kind of VFD you were looking at, but I strongly recommend the KB Electronics KBAC-27D model. These are pricey, but come in a nema 4X/IP65 enclosure which is watertight with watertight knob and switches as well. This controller will drive up to a 1.5hp motor on a 110 volt line, and up to a 2hp motor if you wire it to a 220V line. Alternatively, you can go with a much less expensive Chinese import and build your own enclosure for it. There are plenty of folks that have done that with apparently decent results.
 

CluelessNewB

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#3
You might want to try and find a 900 or 1200 RPM 3 Phase motor if you are planning to run that slow most of the time. The problem with running the typical 1800 RPM motor that slow with a VFD is cooling. Another option may be to add an external fan. If your mill uses a 56 frame motor, finding a slower motor may be challenging.
 

rimfire1903

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#4
thank you both for all the help, i don't run slow most of the time just for dovetails thank you for your help, have a great day, does the motor have to be induction motor? or ac
 

markba633csi

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#5
You say you currently have a dc motor? With speed control or without? Or did you mean ac motor?
Mark
 

rimfire1903

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#6
dc motor, via belt and pulleys for speed control, not ac motor, dc motor thank
 

pacifica

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#7
You can get a open frame dc drive from automation direct for 136, need an enclosure and potentiometer, good for up to 1 hp at 90vdc.Probably even cheaper deals around.
Keep your present motor.Potential for dynamic braking, forward reverse , etc.
Others can tell you about the torque curve, ease of use and installation.
 

strantor

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#9
Post details of your existing DC motor. DC motor is variable speed, if you vary the voltage to it. Not sure why your machine would come with a DC motor and fixed DC voltage. DC was the old way to get variable speed, before the proliferation of cheap VFDs. DC is still a good way to go, and if you have a DC motor already then it probably makes more sense to get a cheap DC drive for it and leave the motor alone.

I'm half-ass suspecting you actually already have a DC drive buried in there somewhere, even if there's no exterior speed control knob, as I can't come up with a reason they would use a DC motor for fixed speed.
 

rimfire1903

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#10
This is a causing 8520 3/4 hp all there is a on and off switch. Only way to change speed is by changing v belt on several step pulleys.
 

strantor

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#11
So is that a hard "no" on the picture then?
 

rimfire1903

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#14
The name plate is covered by motor mount but it is a GE 3/4hp 1750 110 CW and CCW
 

markba633csi

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#15
You must have an ac motor there if you are just plugging it in- a dc motor would require, at the minimum, a bridge rectifier between the wall power and the motor, probably mounted in a little box somewhere on or near the forward/reverse switch (if there is one)
Mark
 

rimfire1903

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#16
No box. Just plug in and turn on
It does have a foreword and reverse and neutral barrel switch on the mill. Reverse dont work. The motor is not original thank you. What do I need to do
 

strantor

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#17
You must have an ac motor there if you are just plugging it in- a dc motor would require, at the minimum, a bridge rectifier between the wall power and the motor, probably mounted in a little box somewhere on or near the forward/reverse switch (if there is one)
Mark
Agreed. However a rectifier could be fitted inside the reversing barrel switch. That would be weird, but possible.

Seems to me more likely an A.C. motor. Without pictures to confirm it's DC, I will have to withdraw my (much cheaper and easier) suggestion of installing a DC drive.

So, you will need to go out and buy a 1hp 3ph motor, 1800rpm 230v, and a VFD 1hp 230V, rated for single phase input. For the motor I would check surpluscenter.com and for the drive, teco or automationdirect.com
 

rimfire1903

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#18
Thank you for all your help. I appreciate it thank you all . I will give a update soon I hope
 

Briney Eye

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#19
I did a video overview of the DRO installation on my 8520 but I also show the Fuji VFD that I installed. I set the VFD to vary the motor speed from 900 to 1800rpm, and it has plenty of low-speed torque, but I can always rearrange the belts if I want to go really slow (or fast). I added an external braking resistor so that the VFD can stop the spindle quickly and left it hanging in the video, but I cleaned everything up since then.
 

rimfire1903

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Thanks I will look at that. I liked the dro set up a lot that's next. Thank you
 

Bi11Hudson

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#22
It sounds like you need to use the back gearing to slow down the spindle speed. I don't think any sort of motor will reliablly operate at that slow a speed. Just a thought there. You might also consider my post of just a few minutes ago. On that very subject.
Bill Hudson​
 

rimfire1903

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#23
It sounds like you need to use the back gearing to slow down the spindle speed. I don't think any sort of motor will reliablly operate at that slow a speed. Just a thought there. You might also consider my post of just a few minutes ago. On that very subject.
Bill Hudson​
Yes sir. I dropped pulley size from 4in to a 1 3/4 carbide dovetail cutter's stated under 700 rpms small. 260 to. 500 thank you Mike
 

rimfire1903

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#24
up date, here is what i did, i found a treadmill they were giving away, the motor was a 2.25hp, i have seen many videos so, i ordered a 8000w s.c.r. with a pot installed, and a bridge rectifier, china of course, (good/bad) butt hooked it up and blew a fuse 10 amp, short fuse in the scr. tried a new fuse ran the mill in different speeds turned the mill off and then back on blew another fuse,??????, i'm stubborn and tried another and up and running again, i could adjust the speed no problem, this time i turned off the mill and turned the scr to the off position, powered up the mill then turned the scr on to ramp up speed needed and works like a charm i don't know for how long this will work, it will give me time to save and get a 3ph motor and a teco vfd, thank you every one for the help
 
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