Variable speed control for a small lathe

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nurd77777

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@nurd7777 Out of curiosity , what kind of motors are those ?
Souns like brushed or DC motors ?
Round here a washmachine will be brushless or the older ones single phase capacitor start .
Hi there
The motors I mentioned are universal brushed they are used on front loading washers. I can get loads I know a guy that scraps washers. They have a flat belt pulley and are designed to turn a big pulley which turns the drum. For machines its best to use the drum gear and cast another pulley where the internal drum was. On my lathe the total reduction is around 40 to 1 and this divides the 500-12000 rev range. With tacho feedback the speed is constant with load .
 

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almarghi

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Hi there
The motors I mentioned are universal brushed they are used on front loading washers. I can get loads I know a guy that scraps washers. They have a flat belt pulley and are designed to turn a big pulley which turns the drum. For machines its best to use the drum gear and cast another pulley where the internal drum was. On my lathe the total reduction is around 40 to 1 and this divides the 500-12000 rev range. With tacho feedback the speed is constant with load .
I have successfully used one of those on a BF20L for about 2 years, but upgraded to a 3-phase motor + VFD, due to noise :(
 
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nurd77777

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Hi Almarghi I only have small machines which are lashed together with bits I have accumulated. I would not have a lathe or a Gingery imitation mill if it was not for the versitility of motors. The type of controller I have/make feeds back speed info so the speed is constant at setting unless its overloaded in which case it limits at 20 amp. It does sound like a vacuum cleaner so I suppose it is noisy.
 

velocette

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Hi Shop Geezer " Prying the belts off to change speeds gets old real fast" Have you considered using an Eccentric or over centre belt tensioner on the motor to loosen the belts and just lift them between grooves. Loads of ideas posted that all require a considerable expense and modifications. Treadmill DC motors are fine but run at 4000 to 6000 RPM so require a sizable reduction ratio. A couple of Photos of the tensioner - clutch on my wood lathe may explain better.
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On my lathe the motor is firmly bolted to the frame. The belts are tightened by eccentric pulleys that are also bolted to the frame. They can slide in slots when loosened, so changing the belts requires digging out two different sized wrenches and loosening everything, prying off the belts and rearranging them (or swap them for longer or shorter ones) and using a bar to retension the pulleys while bolting them back down. Clever engineering insures that over centre levers would require some major re-design of the belt system. Just turning a knob on a VFD sounds sooo much better. But it would require bypassing all the safety relays that prevent the spindle from turning if the cover is up and I am guilty of leaving the key in the chuck and trying to turn the lathe on. So I leave it set at 520 rpm for everything. Too slow for aluminum and way too fast for reaming and tapping.
 

TonyM

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No need to worry about incorporating old safety features Shopgeezer. I changed my Warco 240 to three phase motor and VFD, kept all the original safety switches and even added another emergency stop near the VDF . bottom left of VDF in pic 2
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nurd77777

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Hi The problems of providing a wide speed ratio with VFD have all ready been out lined earlier in this thread. I am sticking with my triac controlled washing machine motor 500 to 12000 RPM since I also get a free drum pulley off the donor washing machine for 10 to 1 reduction.
Regards Keith
 

TonyM

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Hi The problems of providing a wide speed ratio with VFD have all ready been out lined earlier in this thread. I am sticking with my triac controlled washing machine motor 500 to 12000 RPM since I also get a free drum pulley off the donor washing machine for 10 to 1 reduction.
Regards Keith

My point was that all safety features are easily retained or even improved which was what shopgeezer was concerned about.

I can't compare my set up to a washing machine motor or treadmill motor so I have no idea if they are better or worse so I do not decry the use of scrap yard bits and pieces. .

I do know my lathe does a lot of work. It has better power and control than the original setup without the need for belt changing. It runs with more power than I need from 40 rpm to 1800 rpm. It rarely takes 8 amps even when starting and the cooling fan on the VFD rarely runs. I have retained all of the safety features plus one more. Work involved was minimal. However the cost was substantially more than a second hand washing machine motor and control from a scrappy.

We all do what we can with the resources we have.
 

velocette

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"Just turning a knob on a VFD sounds sooo much better". Variable spindle speed with independent variable speed power feed lets you find the "Sweet Spot" for machining all materials. The development of VFD drives has come a long way since I first experienced them used in industry in the early 1990's.
Eric
 
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The power feed is another question. My lathe has the two selector knobs at the bottom of the front panel that gives different speeds. Even on the slowest setting speed is still relatively fast. Since the gear train driving the lead screw is driven by the motor, slowing down the motor will also slow down the lead screw. Good unless you want high spindle speeds and slow speed rates as I would for aluminum. I have seen You Tube videos for electronic lead screw drives. That is really next generation but would be great to have.
 

velocette

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I had a similar setup and changing gears from roughing cuts to a fine finish cuts a pain. So fitted a 24 Volt DC gear head motor with a Poly Vee belt to drive the lead screw.
The motor speed is controlled with a PWM unit with a reverse switch. Ten years of use and so much easier to use the lathe would recommend it to anyone.
Eric
 

chrsbrbnk

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for a kinda cheapo variable voltage supply for dc motors I'v used light dimmers and a bridge rectifier they make some pretty good wattage ones for fairly cheap at the home supply stores
 

velocette

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for a kinda cheapo variable voltage supply for dc motors I'v used light dimmers and a bridge rectifier they make some pretty good wattage ones for fairly cheap at the home supply stores
A problem with this setup you get very little torque at low speed with a large diameter work piece in a lathe chuck.
 

EJay

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I converted my single-phase 13x40 lathe to a 3-phase motor with a VFD and made it so the existing controls all work.
Adding a VFD to my Enco 13x40 lathe
I'd be happy to give you personal advice if you'd like.

I added a VFD to my Bridgeport mill clone to replace a static phase converter. I elected to replace the existing control switch, and just use the VFD panel on that one. One could use the same approach on a lathe.

I'm happy with my lathe modification, and also happy with my mill modification.

Carl

I recently bought a 13X 40 Enco lathe with a 3-phase motor. I'm trying to hook up a Teco L510 VFD. I read thru your blog. But appears my factory lathe wiring is a little different than yours. I'm not an electrician. So I'm having a hard time following along. Do you have an e-mail address I can contact you with ?
 

cds4byu

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I recently bought a 13X 40 Enco lathe with a 3-phase motor. I'm trying to hook up a Teco L510 VFD. I read thru your blog. But appears my factory lathe wiring is a little different than yours. I'm not an electrician. So I'm having a hard time following along. Do you have an e-mail address I can contact you with ?
I've sent you a reply on my blog. It gets a little less traffic than HMEM.
 
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TorchHypnosis

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Good morning all, I just wanted to chime in to this convo and bring up a few talking points.

I'm actually in the same boat as the OP. I have a small parts lathe, which I use daily for my business. The controller dies religiously once every 12 months. At the moment, I'm looking at 12 days down time while waiting for a replacement controller to arrive, which is unacceptable. I have orders that need to go out yesterday.

I have a 480 3 phase motor and inverter that would be perfect for my application, a SEW Eurodrive...$4000 of motor for a $1000 lathe, but I cant use it until I get 480 3 phase into the shop. Would be great as the inverter is an explosion proof sealed unit that can provide excellent torque at 1RPM, but I cannot satisfy the power requirements at this time.

That being said, I am looking for alternatives to replacing my motor controller every year. Someone said use a treadmill motor/gearbox/controller. That seems like a very realistic alternative as you can still receive a decent amount of torque at low RPM's while not risking burning out the motor. I noticed a lot of folks here are recommending VFD's. I cant help but notice that not much attention has been drawn to the fact that you drop the RPM's too low(reduce the Hertz) you will burn out the windings in your motor. While the VFD solution may be fine and dandy for folks who keep their RPMs up, I typically run at 80 RPMs. Super slow. If I were to try and use a VFD to operate a motor that wants to run at, oh, I dunno, say 1000 RPMs, and dropped it down to what I need(80), I would burn out the windings in my motor. Not only that, but lose torque. So, anyone correct me if I am wrong, but a VFD is not going to be a permanent solution for me. I'm thinking something like a treadmill motor with a reducing gearbox would be best to maintain the motor torque and still provide the motor RPMs I need.

But the single phase motor that I have and am currently running at low RPMs does not seem to be experiencing any issues. This motor is 120VAC, controlled by a small PCB with a potentiometer. The motor isn't the part that is burning out...it seems to be the controller. There are 2 black wires and 2 white wires going to the motor, then 3 ground wires going from the motor controller to the lathe chassis. I have to wait 5 more days before my new controller gets here, but the symptoms I am experiencing are the exact same as those I experienced last time I had to replace my controller. I will update when I install the new board, but it seems to me that the motor is still fine and the controller is burning out. Always seems to go out in the winter time, and the lathe is in an un-heated shop so the electronic components of the PCB might be failing due to freezing temps. I would definitely be interested in hearing anything anyone else has to say on the topic.

Regardless, I just wanted to throw in my 2 cents, and would welcome any knowledge any of you might like to share. Still trying to find a cost effective solution that will not require me to replace parts every year. I have two conveyor belt motors with controllers but I am not sure what their power requirements are. I can do 230 3 phase, just not 480. I also have extra 120 single phase to 230 3 phase VFDs. It's just going to take me too much time to make the mounting, program the control, and wire up all the parts when I can just spend another $160 to get another controller and work for another year.

Thanks for reading!
 

dnalot

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I can just spend another $160 to get another controller and work for another year.

I would just replace the controller and go back to work. And order an extra controller to have on hand. If you use it so much $160 a year is not so bad. The treadmill motor should cost next to nothing. Just ask around, someone has a treadmill they would like to just get rid of.


Mark T
 

cds4byu

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What gearing do you have between the motor and the spindle? Is it direct drive?

If you have gearing that could get you to, say, 300 RPM at the spindle for a full speed motor, a VFD would reasonably get you to 80 RPM.

I would expect that your present motor is not an AC motor, but rather a Universal brushed motor.

I'm delighted with my VFD on my 13x40 lathe. It gives me plenty of "oomph" and works well at the speeds I need to run. But I don't use the VFD to control all the way from 30 RPM to 1500 RPM. I shift my gears, and use the VFD to give me a finer adjust. I actually only use about three of the gear ranges, and use the VFD to cover the rest.

But as Mark says, if you are using the lathe a lot, $3 a week to replace the controller annually is small change. Order a spare board so you can change it out in 30 minutes when it fails, and you avoid the 12 day down time.

Carl
 

TorchHypnosis

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Mark, good point. The first time it went out I thought it may have been a fluke so I just bought another. In retrospect I should have bought another one with the replacement to keep on hand, but hindsight is always 20/20.

Carl, it is not direct drive. The motor drives a belt which turns adjustable gears. I don't even know where to start to look for a motor and VFD...I have an extra 120V 1 phase to 230 3 phase VFD I am not using ATM...that kind of power seems a bit overkill...I will look to see what I can find as far as a low RPM 230 3 phase motor. Any suggestions would very much be entertained! But you both are right....just replace the da*# controllers as I need to. Still, there's always the desire to make your machine better...
 
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