Question about putting VFD on a step pulley mill.

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Georgia75

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I recently purchased a Jet JTM-1 (Bridgeport clone) step pulley mill. It is 3 phase and I don't have 3 phase at my house. I am going to purchase a VFD from Amazon to get 3 phase and take advantage of changing speeds with the twist of a knob. I do have experience with this as I have already done this with another 3 phase machine at my house and it works perfectly. My question is which pulley position would you use in my situation? Ideally, I would put the belt on one pulley and forget about it because I will be using the VFD for speed adjustments. Thanks for any feedback.
 

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Based on my experience with installing a VFD on a Hartford (another Bridgeport clone), you will still have to change pulleys and range. I didn't change the OEM motor so don't have the torque needed for lower speeds. Even a modern "gold plated" VFD specific motor would not likely cover the full range.
I look at it this way - at least I can run the mill in a home shop and the variable speeds are still nice albeit over a smaller range.
 
Based on my experience with installing a VFD on a Hartford (another Bridgeport clone), you will still have to change pulleys and range. I didn't change the OEM motor so don't have the torque needed for lower speeds. Even a modern "gold plated" VFD specific motor would not likely cover the full range.
I look at it this way - at least I can run the mill in a home shop and the variable speeds are still nice albeit over a smaller range.
I still change the belt on the drill press even though there is a knob. For tapping, countersinks and other high torque tasks it is nice to be able to slow it down below the usual slowest gear. Just slowed down the torque is not enough, so change pulley and slow down.
 
I would pick the belt setting(s) so that 20Hz-90Hz or 20Hz-120Hz on the VFD corresponds to maximum 3600 RPM on the spindle. That would put the minimum speed at that belt setting at 800 or 600 RPM. You could shift into low gear for lower speeds. If you need slower than than, you'll have to shift the belt down a notch or two.
 
I would pick the belt setting(s) so that 20Hz-90Hz or 20Hz-120Hz on the VFD corresponds to maximum 3600 RPM on the spindle. That would put the minimum speed at that belt setting at 800 or 600 RPM. You could shift into low gear for lower speeds. If you need slower than than, you'll have to shift the belt down a notch or two.
I've had a VFD wired into the low speed of the motor, on a step pulley turret mill and usually had the pulley on the low speed of the high range. If you have it there, you can usually do most of what you need but occasionally will have to go into the low range for large taps or large mills and in tougher stainless steels and exotic alloys, but not often. Some slitting saws will need to run less than 100 rpm in stainless and a few drills, faster than 3000-3500 rpm. Most regular motors will run quite happily at 3500 rpm, not forever, but then you won't likely be running at that speed for long anyway.
 
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BE CAREFUL ! That appears to be a 2 SPEED motor (1700 & 3400rpm?). You will NOT be able to change motor speeds without first stopping the motor with the VFD. Risky, as it is easy to forget... The motor will able to handle 120Hz ON LOW SPEED no problem, but I doubt it would handle it on the high speed setting ie 3400 x 2 = 6800rpm. I would wire the VFD into the motor's low speed terminals and use the 1750rpm pulley step and run the VFD as rklopp suggests ie 20-120Hz. That would be 2x and 0.33x the pulley speeds on the chart. A good 3500rpm down to about 220rpm in HIGH GEARBOX range and 420rpm down to a useful 26rpm in the LOW GEARBOX range. Unless you do a lot of tiny cutter work in aluminium, I doubt you will ever need to move the belt again.
Regards, Ross.
 
I recently purchased a Jet JTM-1 (Bridgeport clone) step pulley mill. It is 3 phase and I don't have 3 phase at my house. I am going to purchase a VFD from Amazon to get 3 phase and take advantage of changing speeds with the twist of a knob. I do have experience with this as I have already done this with another 3 phase machine at my house and it works perfectly. My question is which pulley position would you use in my situation? Ideally, I would put the belt on one pulley and forget about it because I will be using the VFD for speed adjustments. Thanks for any feedback.
I converted my lathe to VFD drive using (Clough42 on you tube) circuitry. After doing research on using VFD drives carefully consider the VFD drive horsepower range some recommend a size twice the motor horsepower. I powered the VFD drive with a high voltage (120 volt) Allen Bradley switch with a light indicator to remind me the power is on. I wired the low voltage emergency stop, directional control, and rpm box in a smaller box where the original control was located. Some three phase motors do not perform well at lower rpm and there are three phase motors designed to run with a vfd. Some of the issues is that can arise is at the lower rpm the winding and the VFD do not play well together. I found a motor designed for that application on EBAY and the name tag identifies it can be used for that purpose. I set the pulley belts to a range by trial and error to find the best band to operate in. If necessary I can change the pulleys to get lower speeds with more torque or higher rpm. The main challenge was interpreting the VFD Chinese instructions. The Vfd should be able to replace the function of the belts and I look at the belts as sort of a transmission between the vfd and the motor.
 
And more ..
Inverters using single phase power do not have a large power and ( And it may not have enough power as advertised ) when the speed is slow and the load is heavy it can overload the inverter. If need slower than , you'll have to shift the belt down


so-do-bien-tan.jpg
 
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BE CAREFUL ! That appears to be a 2 SPEED motor (1700 & 3400rpm?). You will NOT be able to change motor speeds without first stopping the motor with the VFD. Risky, as it is easy to forget... The motor will able to handle 120Hz ON LOW SPEED no problem, but I doubt it would handle it on the high speed setting ie 3400 x 2 = 6800rpm. I would wire the VFD into the motor's low speed terminals and use the 1750rpm pulley step and run the VFD as rklopp suggests ie 20-120Hz. That would be 2x and 0.33x the pulley speeds on the chart. A good 3500rpm down to about 220rpm in HIGH GEARBOX range and 420rpm down to a useful 26rpm in the LOW GEARBOX range. Unless you do a lot of tiny cutter work in aluminium, I doubt you will ever need to move the belt again.
Regards, Ross.
That is what I did on my TOS FNK25 with a two speed motor, though most turret mills, Bridgeport and their clones, don't have two speed motors. Even at 120Hz it was still running at only the high speed range speed.
 
Most of us have a cutter diameter that is our go to for most work. Pick the pulleys that you would use for that cutter with a normal 3 phase feed. Your motor will run at that speed at 60Hz on the VFD. Vary it up and down from there but as others have said, you're not married to that pulley. You still may have to change pulleys for large or small cutters or tapping. Bob
 
I have an older Bridgeport, 60's vintage, with the motor that specs at 1730rpm at 60hz only.
I usually leave my belt at between the second or third belt speed and run the variable thru the VFD. I never run faster than 60hz on the motor. I usually run 1/2" or 3/4" tooling max and I don't take too heavy a cut. Plenty of torque for that.
The back gear gives me plenty of torque for my face mill tool. My machine is fairly well used up so I don't push it hard.
Mine's been run like that for 5 years now and no issues running the motor windings with a VFD. All just my experience, your mileage may vary.
 
BE CAREFUL ! That appears to be a 2 SPEED motor (1700 & 3400rpm?). You will NOT be able to change motor speeds without first stopping the motor with the VFD. Risky, as it is easy to forget... The motor will able to handle 120Hz ON LOW SPEED no problem, but I doubt it would handle it on the high speed setting ie 3400 x 2 = 6800rpm. I would wire the VFD into the motor's low speed terminals and use the 1750rpm pulley step and run the VFD as rklopp suggests ie 20-120Hz. That would be 2x and 0.33x the pulley speeds on the chart. A good 3500rpm down to about 220rpm in HIGH GEARBOX range and 420rpm down to a useful 26rpm in the LOW GEARBOX range. Unless you do a lot of tiny cutter work in aluminium, I doubt you will ever need to move the belt again.
Regards, Ross.
Thanks a lot! You are right- it is a two speed motor. This is what I was thinking and probably what I will do based on your comments and others here. This is just a hobby for me and I rarely run faster than 2000rpm. I think my old round column tops out at 2500 and I am afraid to run it that fast.
 
Just my opinion, I've worked with & around VFD controlled motors for quite a while, but I think if it was mine I'd wire the VFD ahead of the 2 speed motor switch & primarily run on your second or third speed pulleys. That way you'll still have both speed ranges from the motor & backgear. You can probably drop to 45hz without dropping too much torque or developing too much heat in the motor & sneak up towards 90hz on low speed, I don't think I'd go much past 75hz on your high speed windings. That'll give to a pretty wide range with a combination of the flip of a switch & the twist of a knob.
I've been thinking about doing something similar with an old Bridgeport of my Dad's, we've been running it on an old Rotophase for years but I'm thinking the VFD could really spice it up. I'm curious to know how you go about yours & how it works for you.
 
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I'm late to this discussion.
First the VFD, if you want high torque at low Hz output, you want to make sure it is of the "sensorless vector drive" type of VFD, not the typical scalar type drive.
For both my mill and lathe, I leave the V-belts set to the mid range of the machine. The motors are all 4 pole so at 60hz operate at the 1725 nominal RPM. I program the VFD to run at 120Hz maximum, as this will not hurt the motor/rotor to operate at 3600RPM.
I would just leave your mill in the high speed motor setting. Most VFDs (not the low end ones I see on eBay and Amazon, typically the scalar type) will have program setting that will let the LED display show the output with a conversion constant, so I set that up to show spindle RPM. It's two different program parameters, one to insert the conversion constant of your gear train, and another to have it display that in place of Hz output.
 
I'm late to this discussion.
First the VFD, if you want high torque at low Hz output, you want to make sure it is of the "sensorless vector drive" type of VFD, not the typical scalar type drive.
For both my mill and lathe, I leave the V-belts set to the mid range of the machine. The motors are all 4 pole so at 60hz operate at the 1725 nominal RPM. I program the VFD to run at 120Hz maximum, as this will not hurt the motor/rotor to operate at 3600RPM.
I would just leave your mill in the high speed motor setting. Most VFDs (not the low end ones I see on eBay and Amazon, typically the scalar type) will have program setting that will let the LED display show the output with a conversion constant, so I set that up to show spindle RPM. It's two different program parameters, one to insert the conversion constant of your gear train, and another to have it display that in place of Hz output.

I have need of some vfds but have hesitating in buying.
A large part of the hesitation is due to the enormous difference in pricing that I can find.
I can buy from NA name brand distribution and its XX$.
Or dig around and find the non name brand NA distribution (there are a few) and its 65% (or so) of XX$.
Or mr jeff's emporium and its running 45 - 50% of XX$.
Digging around at Alie or Alib - - - 25 - 35% of XX$.
How does one ascertain the quality of the product?

(Verbiage seems quite the same in all the levels.
Brand names seem like a joke as most are built in China anyway.
So how does the non experienced find at least decent product (without buying stuff that will be junk pdq)?)

TIA
 
I have a '62 BP and keep the belt on the middle of the pulley. I've never needed to move it in 16 years. It's fine to overspeed these motors for short periods of time. For slower speeds needing torque I use back gear and reverse. I removed the power switch and control the start/stop/direction solely with the VFD controls.

My VFD is from Automation Direct. Never a problem
 
As to choose a name brand VFD or not - I've done a total of 3 so that is my level of experience.

Some considerations I've taken into account on converting my machines:

Name brand almost certainly has proper electrical / EMI certifications. ETL / CSA / UL / FCC / etc. These are important if the device is being hooked up to a permanent connection. Think worst case scenario where the fire is started by the VFD - if not certified - could insurance be denied?
Also, don't be fooled by a cheap device with CE marked on it - can very well mean absolutely nothing (not always but...) - you need to do your homework on it if that's all it has for cert markings!

Will the device ever be turned on and left unattended? If so I would look at a name brand with certifications.

If its a smaller device, and you can (and do) switch the power to it regularly and never leave it on unattended, then you could look at cheaper alternatives at your own risk.. They may be perfectly safe electrically but may not meet EMI regs, or may even be a fire risk but if used only under supervision then that may be a risk you are willing to make.

In my case - I have my mill and lathe both with name brand VFD's with and lots of certifications, connected by an electrician. I am comfortable leaving these VFD's powered (but still usually don't). I also have a cheap no name VFD for my surface grinder that is connected by a plug to a switched outlet, that I only switch on when using and switch the power off to the VFD when not. I really don't trust it and treat the grinder like a giant experiment - never to be left powered while unsupervised.

Lastly - getting back to EMI - if there are others in relatively close proximity to your VFD, the cheaper ones may make them unhappy as it could interfere with their electronics... no guarantees with the name brand ones either, as they are usually rated for an industrial environment, but the cheap ones aren't likely rated at all.
 
I have need of some vfds but have hesitating in buying.
A large part of the hesitation is due to the enormous difference in pricing that I can find.
I can buy from NA name brand distribution and its XX$.
Or dig around and find the non name brand NA distribution (there are a few) and its 65% (or so) of XX$.
Or mr jeff's emporium and its running 45 - 50% of XX$.
Digging around at Alie or Alib - - - 25 - 35% of XX$.
How does one ascertain the quality of the product?

(Verbiage seems quite the same in all the levels.
Brand names seem like a joke as most are built in China anyway.
So how does the non experienced find at least decent product (without buying stuff that will be junk pdq)?)

TIA
I'm not opposed to the noname VFDs I see on eBay. Just last week my neighbor purchased one to run his 10HP air compressor. It took a bit to get it to run the machine, as acceleration time and other parameters caused it to overcurrent. I got that to operate pretty well. They have been improving them, as they get more intellectual property from the name brand vendors that build their units in China or other offshore operations.
I've also had very good luck purchasing used VFDs from facebook/craigslist and eBay. The big thing, first find the manual online, if you can't, don't buy the VFD. About the only brand I've run into not finding the manual was Allen Bradley/Rockwell Automation, they seem to purge their older obsolete units from their web page.
Also make sure it is a 200v class electronics, as you can't use the 400v class in your home unless you have a 440VAC power source. And then make sure it can run the HP of your motor. They round the 746 watts per HP up to 750, so a .75KW drive is for 1HP motor. 2HP will use a 1.5KW model, 3HP will use a 2.2KW model. That information is in the instruction manual, first few pages.
If you can find the keywords "sensorless vector drive" or some buzz words like "magnetic flux vector control" in the eBay auction listing, that should be a good drive.
There are some Mitsubishi drives on seeing that are brand new and under $100USD for 1HP motors.
If the eBay seller of a new low cost VFD can't give you an english PDF manual for their VFD, don't buy it. You need to review the manual to see what program features it has, and if your stop/fwd/rev switch topology will work.
I've found that Mitsubishi, Hitachi, Teco brand VFD, that have 3 phase input terminals, will operate with single phase. I know there are some brands that will fault out as they monitor for missing phase inputs.
Typically above 3HP/2.2KW VFD, you derate them for single phase input, and purchase a VFD of 2x the KW/HP capability so the input diodes don't burn out. I have a 7.5HP lathe, that has been powered with a 10HP Mitsubishi drive since 2004, with zero issues. But I don't ever use the full 7.5HP of the machine. I have tripped it out on undervoltage faults when I set the acceleration too short. My 12x24 lathe has a 2HP motor on it, with the belt settings at mid range. I can dial the spindle RPM down to 10RPM, and run a 5/8" tap or die on it (cutting stainless/mild steel), and it does not stall. I have a remote with the stop fwd, and speed potentiometer, close by.
If you buy a cheap new VFD, install it right away, and test it. See if it fails. If you got it off eBay, then you can get a refund for a defective drive. There's a 30 day return period. Even if the seller say's they don't take returns, eBay's policy overrides that.

Do not mount the VFD on the milling machine, the vibrations during some cutting operations will shake the parts off the internal circuit cards.

Hope these comment help.
 
I'm not opposed to the noname VFDs I see on eBay. Just last week my neighbor purchased one to run his 10HP air compressor. It took a bit to get it to run the machine, as acceleration time and other parameters caused it to overcurrent. I got that to operate pretty well. They have been improving them, as they get more intellectual property from the name brand vendors that build their units in China or other offshore operations.
I've also had very good luck purchasing used VFDs from facebook/craigslist and eBay. The big thing, first find the manual online, if you can't, don't buy the VFD. About the only brand I've run into not finding the manual was Allen Bradley/Rockwell Automation, they seem to purge their older obsolete units from their web page.
Also make sure it is a 200v class electronics, as you can't use the 400v class in your home unless you have a 440VAC power source. And then make sure it can run the HP of your motor. They round the 746 watts per HP up to 750, so a .75KW drive is for 1HP motor. 2HP will use a 1.5KW model, 3HP will use a 2.2KW model. That information is in the instruction manual, first few pages.
If you can find the keywords "sensorless vector drive" or some buzz words like "magnetic flux vector control" in the eBay auction listing, that should be a good drive.
There are some Mitsubishi drives on seeing that are brand new and under $100USD for 1HP motors.
If the eBay seller of a new low cost VFD can't give you an english PDF manual for their VFD, don't buy it. You need to review the manual to see what program features it has, and if your stop/fwd/rev switch topology will work.
I've found that Mitsubishi, Hitachi, Teco brand VFD, that have 3 phase input terminals, will operate with single phase. I know there are some brands that will fault out as they monitor for missing phase inputs.
Typically above 3HP/2.2KW VFD, you derate them for single phase input, and purchase a VFD of 2x the KW/HP capability so the input diodes don't burn out. I have a 7.5HP lathe, that has been powered with a 10HP Mitsubishi drive since 2004, with zero issues. But I don't ever use the full 7.5HP of the machine. I have tripped it out on undervoltage faults when I set the acceleration too short. My 12x24 lathe has a 2HP motor on it, with the belt settings at mid range. I can dial the spindle RPM down to 10RPM, and run a 5/8" tap or die on it (cutting stainless/mild steel), and it does not stall. I have a remote with the stop fwd, and speed potentiometer, close by.
If you buy a cheap new VFD, install it right away, and test it. See if it fails. If you got it off eBay, then you can get a refund for a defective drive. There's a 30 day return period. Even if the seller say's they don't take returns, eBay's policy overrides that.

Do not mount the VFD on the milling machine, the vibrations during some cutting operations will shake the parts off the internal circuit cards.

Hope these comment help.
Interesting - - - thanks!
 

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