PM 1236 VFD Conversion

[Ray C]

All,

Now that the lathe has a new bench, it's getting converted to 3 phase VFD before final positioning and leveling. The VFD is the ever-popular Huanyang 1.5kW VFD shown here: http://www.ebay.com/itm/BRAND-NEW-2...272?pt=LH_DefaultDomain_0&hash=item2c69b9a1c0

Here's the correct motor for the lathe matched to the power of the VFD: http://www.globalindustrial.com/p/m...ors/iec-metric-motor-90l-ip55-3ph-c90t17fz2cc EDIT: BTW, the motor is wireable for 2 speed but that's ignored for our purposes.

Last night, I programmed the VFD and tested an external pot and signal lines on a bench setup. As soon as I double check registers and test thoroughly, I'll post the settings here.

Also, here's how I'll probably rewire the control aspect of the unit. View attachment 1236 VFD Control Wiring.pdf
I might tweak this a little so, hang-on until I'm done being the guinea pig. I'm not sure if the native switches are normally open or close and I'll try to reuse as many as possible. The FWD and REV switches on the lathe are mechanically mutually exclusive. The JOG button is not so I'll need to see how the VFD reacts if JOG is asserted while either FWD or REV is active. ... thus, I may need to tweak things a tiny bit. Here's a quick sketch -about as simple as it gets...


Ray

Edited to correct a broken sentence.

 

[GaryK]

Looking good Ray!

I'm kind of curious about how you plan on using it. Will you leave the gearbox speed settings at one speed and set the speed from the VFD.
If so do you have any idea what setting you'll use?

Or will you just use it to get the speeds between the standard speeds?

Or bypass the gearbox entirely?

What are your reasons for the VFD?

Yea, I know, a lot of questions!

Gary

 

[Ray C]

Some folks leave their lathe on the same gear and just clock the VFD up/down but that's got to be putting the gears through hell. That's the same reason crankshafts break when you go too slow in a high gear and why trans gears get shredded when you go too fast in low gear. My plan is to leave the VFD normally set for 60 HZ and use the lathe and gearbox the way it was intended. I may tweak the frequency down a tiny bit once in a while to avoid a weird vibration if one happens to pop-up. That kind of adjustment is usually just 3-10 Hz at most.

Other than that, the real reason is that I want "slow-start" capability with a 2-4 second (or so) ramp time. That goes a LONG way to making your gears last longer. And also near-and-dear to my desires is the smoothness of a 3 phase motor. You can feel the 60 Hz pulsing in a single-phase motor -you cannot feel it in a 3 phase motor. -This is more of a personal satisfacton thing for me... I happen to love 3 phase stuff and the mathematics behind it.


Ray

Looking good Ray!

I'm kind of curious about how you plan on using it. Will you leave the gearbox speed settings at one speed and set the speed from the VFD.
If so do you have any idea what setting you'll use?

Or will you just use it to get the speeds between the standard speeds?

Or bypass the gearbox entirely?

What are your reasons for the VFD?

Yea, I know, a lot of questions!

Gary

 

[darkzero]

Awesome Ray! The slow start has got to make a big difference in wear. Sometimes I hate the sound the gears make when starting the spindle. With a VFD, is dynamic braking a feature? I always wondered about lathes that have dynamic braking & I would love to have that. I figured it's only possible with 3-phase motors?

 

[Ray C]

Hi Will...


Yes, these VFDs support dynamic braking. I've never used it on any VFD because the need hasn't arisen. BTW, I just got this unit a while ago. My other VFD's are from Automation Direct. These are half the cost. Both have poor documentation. These unit itself can do some degree of magnetic braking with a controlled/expedited ramp-down but, true dynamic braking requires additional an additional external resistor that can handle a good bit of heat. ... Keep in mind though that letting things coast to a stop is the easiest on the gears, bearings and even the wound wires in the motor. Also, yes, it's pretty much a 3 phase-only capability. Theoretically, a single phase could do it but, nobody really supports that kind feature... -Too much complexity switching capacitors, centrifugal switches etc... It would be a nitemare. I only know of 1 manufacturer that makes a true single phase output VFD -and it only works with very specific types of single phase motors. -Don't bother with it.

Ray

Awesome Ray! The slow start has got to make a big difference in wear. Sometimes I hate the sound the gears make when starting the spindle. With a VFD, is dynamic braking a feature? I always wondered about lathes that have dynamic braking & I would love to have that. I figured it's only possible with 3-phase motors?

 

[darkzero]

Thanks Ray. I know very little about VFDs, never looked into them but maybe one day.

For the dynamic braking I was just thinking it might be good for threading metric. I remember seeing a video where a guy was threading without using the half nut. When he turned off the spindle to reverse it stopped pretty quick & I thought that was pretty nice. It was old American iron.

Many times I thread close to a shoulder or with no relief at all. When I turn the spindle off it coasts too much & is not consistent when i'm threading metric. I use the spindle brake in these cases but it seems like a lot of wear but luckily I don't thsingle point metric too often. Is there a better way?

Hi Will...


Yes, these VFDs support dynamic braking. I've never used it on any VFD because the need hasn't arisen. BTW, I just got this unit a while ago. My other VFD's are from Automation Direct. These are half the cost. Both have poor documentation. These unit itself can do some degree of magnetic braking with a controlled/expedited ramp-down but, true dynamic braking requires additional an additional external resistor that can handle a good bit of heat. ... Keep in mind though that letting things coast to a stop is the easiest on the gears, bearings and even the wound wires in the motor. Also, yes, it's pretty much a 3 phase-only capability. Theoretically, a single phase could do it but, nobody really supports that kind feature... -Too much complexity switching capacitors, centrifugal switches etc... It would be a nitemare. I only know of 1 manufacturer that makes a true single phase output VFD -and it only works with very specific types of single phase motors. -Don't bother with it.

Ray

 

[Ray C]

Metric threading certainly seems like a good use for dynamic braking. Still though, adding VFDs to manual lathes is (in certain respects) still in it's infancy. By my accounting, it wasn't that long ago that VFDs were becoming common-place and when they first came out, there was a wave of poeple burning up their old motors because they weren't designed for running at speeds other than 50 or 60 Hz. Now, let's extend that logic just a bit more and ask ourselves if our 1950's design lathes (yes, our modern lathes are pattern variations of mid-1950's technology) were really made to take the pounding of dynamic braking. Don't get me wrong... I don't have all the answers and am figuring this out as I go but, my intuition tells me to do some thinking before proceeding.

When big gears turn small gears and vise-versa, the torque applied and stress on the teeth must be considered. That's just one of the reasons why transmissions have stepped gears in the first place... -So you don't knock the teeth off all the small gears. If you were going down the road in your 6 speed manual transmission at 65 MPH, pressed-in the clutch, shifted to 1st gear and dumped the clutch... Good Bye Car! So what's the difference between that and dynamic braking? -Nothing.

Somone out there probably knows the answers to these things but, often times, people come back and say "I've been doing it that way for years so, it's OK"... -Sorry, that kind of answer doesn't cut it for me. It's a valuable data point but not a good answer.

Ray

Thanks Ray. I know very little about VFDs, never looked into them but maybe one day.

For the dynamic braking I was just thinking it might be good for threading metric. I remember seeing a video where a guy was threading without using the half nut. When he turned off the spindle to reverse it stopped pretty quick & I thought that was pretty nice. It was old American iron.

Many times I thread close to a shoulder or with no relief at all. When I turn the spindle off it coasts too much & is not consistent when i'm threading metric. I use the spindle brake in these cases but it seems like a lot of wear but luckily I don't thsingle point metric too often. Is there a better way?

 

[Pacer]

people come back and say "I've been doing it that way for years so, it's OK"...

Yep, thats me --- Got a SB lathe and a Bridgy clone both on VFD's for some 5-6 years and it just might be considered abusing the crap out of them? I run the lathe in every gear and from 0hhz to 75hz and all ranges between. When threading I select a lower gear and control the cut strictly off the pot, bringing the cut to a gradual stop at the end, back the tool out and can either run the lathe back under power for metric, or just use the carriage. I dont think in my home shop I could ever do enough wear to be a factor, even though I am a pretty active user of my machines.

On the mill I use the VFD and power tap on almost all threading, being able to advance the tap as slow as I want, even down to 3-5rpm. Now I do keep the mill in the mid range of belt settings for 95% of the time, using the VFD to control the speeds, here again from 0hz to max.

I have my units set to utilize the stop/start parameters in the unit and set both at 2 seconds, I find this to be a wonderful feature.
I have always used Hitachi VFD's, but recently on a rebuild of an old Sheldon lathe I was a bit short of funds and went with the Huangyang like you (they are MUCH cheaper!) Seems all the mfgs manuals are rather poor, but I had become familiar with the Hitachi and could program one quickly - the Huangyang gave me some probs, with parameter settings just enough different to give me some trouble. The Sheldon is already has variable speed drive, and I find I use the lathes drive and the VFD about equally.

Love my VFDS!!!!

 

[darkzero]

When big gears turn small gears and vise-versa, the torque applied and stress on the teeth must be considered. That's just one of the reasons why transmissions have stepped gears in the first place... -So you don't knock the teeth off all the small gears. If you were going down the road in your 6 speed manual transmission at 65 MPH, pressed-in the clutch, shifted to 1st gear and dumped the clutch... Good Bye Car! So what's the difference between that and dynamic braking? -Nothing.

Hey Ray,

Not quite the same at all but I see your point. Of course our lathes aren't designed for dynamic braking but I don't see much damage that can be done if set up properly. It could not be worse than using the spindle brake.

I was curious so I briefly searched on it. Many people do use dynamic braking & set up different delays for e-stop, regular stop, etc. In the case I was referring too, dynamic braking would be used at lower spindle speeds & the braking would not be instantaneous as with the lathes I have seen with dynamic braking. Higher speeds & large rotational mass (depending on what you're turning) would definitely not be good if you tried to stop the spindle quickly.

Just with some of the details I found while searching on VFDs, this thread, & Pacer's post above, I want VFDs too now!

Thanks Ray for adding more things to my long list of things to buy!

 

[Ray C]

Truth be known, I'm trying to be cautious about the "recommendations and modifications" that are being described because, it could cause someone grief. I could absolutely see someone ruining their lathe by hitting the dynamic brake at 2000 RPM. I think bad things would happen for the reasons I mentioned -and the analogies I use are an attempt to explain what's going on using examples people can relate to. -That's the real thinking in my mind. Yes, dynamic braking would be tolerated by our machines if used judiciously...

Stand by, I've got a little update on the switches on the machine. Just checked everything out and did some preliminary wiring and tests... Need a few moments to organize the pictures.

Hey Ray,

Not quite the same at all but I see your point. Of course our lathes aren't designed for dynamic braking but I don't see much damage that can be done if set up properly. It could not be worse than using the spindle brake.

I was curious so I briefly searched on it. Many people do use dynamic braking & set up different delays for e-stop, regular stop, etc. In the case I was referring too, dynamic braking would be used at lower spindle speeds & the braking would not be instantaneous as with the lathes I have seen with dynamic braking. Higher speeds & large rotational mass (depending on what you're turning) would definitely not be good if you tried to stop the spindle quickly.

Just with some of the details I found while searching on VFDs, this thread, & Pacer's post above, I want VFDs too now!

Thanks Ray for adding more things to my long list of things to buy!