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Spring meet up in Ontario, April 6/2024. NEW LOCATION See Post #31 Discussion AND THE
NEW LOCATION
I'm going to post a few do as I say not as I do pics, along with the caveat, DONT DO THIS with a hoist:
My brother and I used to live on the same street, 4 townhouses apart. Limited space in each ground level basement meant we split our shop between the two spaces.
We had to relocate our shop when my brother moved. In the Interim we had to stick the lathe and mill from his place in my cramped basement, twice the number of moves. Complicating matters was the fact a proper gantry crane would not fit in the space, and a engine hoist could not pick the lathe up at the balance point. Improvisation was in order.
Do build a rock solid platform that you can affix a lathe to that can handle whatever you put it thru. I screwed the wood into the steel frame below as well as putting blocks on the ends at the undersides to keep the wood from potentially sliding off the steel frames if all the screws snapped.
We rolled the lathe out the ground floor front door and down a 6" elevation change at the front entry and into an immediate left turn all facilitated by a 8 foot length of 1" thick plywood the width of the doorway. The plywood acted as a teeter totter the affect the level change. A winch controlled the cart from running away down the teeter totter once the balance point shifted.
Then just down the drive, into the road, where a flat bed tow truck winched it onto the bed and secured it for the trip.
A big improvement from when Busybee's recommended deliver guy showed up to deliver it in a truck that required a loading dock despite telling the idiot 4 times were needed a grade level delivery.
Sorry, I didn't get pics of the tow truck. That process was completed while I was moving the Mill.
That's a Craftex CT041 12" x 36" gap bed lathe getting the conversion. We installed a new 2 HP 3 phase motor from Hallmark Industries and an AT1-2200X 2.2KW variable frequency drive for more precise speed control and a little boost in low speed torque.
Not my first choice of lathes, but it is what it is. I especially hate the electrical cabinet and all the wiring on this lathe. Total garbage.
DISCLAIMER:
High voltage wiring is inherently dangerous and can kill you. If you are not qualified you should not engage in such activities and instead hire a qualified individual to engage in such work for you. I am not responsible for your stupidity if you proceed with any modifications to your lathe based on what you read here and get dead.
How I modified the wiring to send power to the new VFD circuit.
This lathe normally operated with 3 "power" wires (well really 4 but one is permanently disconnected, go figure) and a ground wire to the original single phase motor. Interlocking 220v contactors toggled between two inputs and a common line in order to reverse the direction of the motor. The switching to affect this is controlled by a low voltage control and safety circuit that goes thru two interlocked NO/NC spindle direction switches.
The variable frequency drive however is operated with only two non-switching 220 volt power wires and a ground wire. I wanted to use the existing wiring to the motor to go to the new VFD, but couldn't have the power toggling as the lathe was currently set up for. So, first up was deciding what is the best way to power the VFD.
I also needed to determine how I would control the motor direction. The first decision was easy. I'd control the motor direction from the VFD using the VFD's low voltage ports x4 and x5.
The next choice was whether or not to use the lathe's existing directional control switches, or a new forward, neutral and reverse 3 way switch I'd add to a new control box on the head stock. As I wanted to retain the existing directional levers I had developed muscle memory for I decided remove the existing control wiring from these switches and replace it with new wires to the VFD.
SO, what I did do to make this work was to leave all the lathe wiring intact EXCEPT FOR the two spindle direction switches. These two interlocked switches have 3 control outputs. The first are the two Normally Closed contacts that simply energize the low voltage circuit required to operate the lathe motor direction circuits. The two Normally Open contacts activate the interlocked 220 volt contactors that toggle the three 220 volt lines to engage the forward and reverse motor operation.
For the new operation I did not need to toggle between three 220 volt mains lines, BUT I needed one Normally Closed contactor to energize the lathe motor circuit, and I needed one Normally Open contact to activate just one of the two lathe direction contactors in order to energize two of the three 220 volt lines to serve the VFD circuit. The remaining third wire to the original single phase motor output becomes obsolete and was terminated with a wire nut.
So I transferred the wiring from the two spindle direction switches to a new single SPDT NC/NO latching switch labeled "VFD Power", except I left off the wire to the Normally Open contact for the reverse side of the two switches.
I was left with the choice of where to mount this switch. I was adding two new control boxes for the VFD, one on the wall for the power filtering circuits and another on the lathe for the speed control and display. The new VFD power switch was initially to be located on a new speed control box mounted on the lathe head stock. But we later decided to locate the VFD power switch in the original lathe control panel, in place of the JOG button. This put the VFD power right next to the main stop switch to keep everything together.
My brother wanted to have a jog function, so I added a forward and reverse jog button to the speed control box that mounts on the head stock.
New sequence of operation
When the original lathe power button is pushed the Normally Closed contact in the new "VFD Power" switch energizes the motor direction control circuit in the lathe. When the VFD Power button is actually pressed the Normally Open switch then energizes the contactor that starts the motor in the forward direction. The wire to engage the reverse motor direction is left unconnected and capped.
SIDE NOTE:
You can see from these images what a dog's breakfast the lathe's electrical box is as it comes from the manufacturer. It is too cramped, poorly laid out and uses a hodge podge of connector types. The ground terminals particularly suck, the manufacturer should have added proper DIN rail mounted ground terminals instead of installing a loose plate onto the rail. Grizzly made the manufacturer do this on the lathes they distributed.
I also don't like that the lathe's original (and current) 28 volt transformer actually puts out 34 volts which does not suit some of my new components which required the purchase of a new DIN rail mounted Meanwell 24 volt transformer I've mounted in a separate electrical box that serves the VFD.
Lessons Learned
IF I had to do this conversion all over again I'd gut the lathe's entire wiring scheme and rewire from scratch with all new components.
I'd run a single 24 volt circuit thru the chuck guard switch, the change gear safety switch, the power indicator light and then the emergency stop/main power switch.
I'd still eliminate the motor "jog" switch from that 24v safety circuit and instead convert that button to a VFD power switch. I'd also eliminate the interlocked spindle direction switches from the lathe's 24v circuit as I did. This would eliminate two superfluous contactors from the electrical box freeing up space.
When all the safety switches are in the closed position the 24v would then activate a simple 2 pole contactor with thermal overload to send 220VAC to the VFD electrical box with it's noise suppression circuit etc. A single new transformer would then power the tachometer and surface feet per minute calculator in the speed control box.
I'd then use the VFD ports to control the motor direction by wiring the two forward and reverse signals thru the two spindle direction switches. I'd still use the 10K potentiometer to control the motor speed in conjunction with the lathe gear box. I'd add the same two jog buttons to the control box as well
I have modified the controls I designed a few times now... but this is the last iteration.
A control box located on the lathe headstock as opposed to the VFD drive located on the wall behind the lathe meant that remote speed control would be convenient. This required the addition of a 10K potentiometer to control box. The final version of the box has two LED momentary jog switches and a potentiometer.
Of course I also need to know the spindle speed, which meant that I would either need to manually calculate the spindle speed based on the motor frequency (or rpm) and the selected lathe gearing, or I'd need to install a tachometer. Math in my head is unreliable and slow, so I went with a tachometer which is instantaneous.
In future I plan to swap an Arduino microcontroller for the tachometer and then also calculate the workpiece surface speed and feed rates. I will design yet another new front panel for Arduino.
The box is mounted on two legs that hold the box at a 10 degree upward angle for better viewing, but the box can be quickly detached for mounting elsewhere if desired.
See this link for the VFD's control box component details and files. I have three iterations of the front control panel if anyone wants a similar project done slightly differently than I've done mine.
A tachometer also requires mounting some sort of sensor to register the spindle speed. My tachometer comes with a 12 mm diameter hall effect sensor and a magnet to activate the sensor switch. Both need to be mounted within the head stock.
The best place for the sensor bracket, sensor and magnet where those components wont interfere with anything on my lathe is on the outboard end of the lathe spindle. This also happens to be where I wanted to install an indexing system.
This meant designing a multi-purpose mounting hub that could be used to mount various types of discs such as a balanced magnet disc, slotted optical sensor discs or various indexing discs.
It also meant designing a corresponding bracket to mount either the 12 mm diameter hall effect sensor or a 1/2" threaded indexing pin. For the indexing function I elected to go with a retractable spring plunger from McMaster Carr part #8507A12.
This sensor and indexing mounting system is covered in much greater detail on my multi-purpose lathe spindle mounting system thing page at the following link:
When I convert to an Arduino controller I will upgrade to a magnet disc array with many magnets instead of one for much finer speed resolution at very low rpm.
I also made two carriage end stop clamps to shut off the lathe motor instantly. I made one for forward travel and one for reverse travel. The end stop clamps have attached micro-switches whose NC terminals are wired in-line with the 12 volt forward and reverse inputs for the VFD. Upon contact the circuit opens and the motor stops. The two main bodies have mirrored holes to allow for left and right facing switches.
These same stops can be wired into the conventional lathe spindle direction control switches to interrupt the low voltage safety circuit of these lathes as well. With the single phase motor the lathe is just slower to stop and the carriage will travel a bit after hitting the switch as a result.
Good job! I am planning a VFD 3Ph conversion for my 220 1Ph lathe too. I have not really put my head to all the many challenges just yet, but I have reached and passed the it's a dumb idea milestone. Too many other priority jobs on my plate right now.
My lowest as speed is 70 and I'd prefer 50. Mine has rather simple wiring and a fair bit of room for a bigger motor. I want to go with a 3Hp motor instead of 2 to give the system some more margin.
As far as I know right now, the only switches are the power, emergency stop and an external fwd/rev handle/switch on the carriage. But ya, the e-box is full.
I will bookmark your post for future reference and if it's ok, I may call on you for questions. When I get to this project later this summer / fall / winter / 2023 / whenever...... LOL!
Good job! I am planning a VFD 3Ph conversion for my 220 1Ph lathe too. I have not really put my head to all the many challenges just yet, but I have reached and passed the it's a dumb idea milestone. Too many other priority jobs on my plate right now.
My lowest as speed is 70 and I'd prefer 50. Mine has rather simple wiring and a fair bit of room for a bigger motor. I want to go with a 3Hp motor instead of 2 to give the system some more margin.
As far as I know right now, the only switches are the power, emergency stop and an external fwd/rev handle/switch on the carriage. But ya, the e-box is full.
I will bookmark your post for future reference and if it's ok, I may call on you for questions. When I get to this project later this summer / fall / winter / 2023 / whenever...... LOL!
Let me know your lathe model and I'll look at the wiring schematic and see if anything will be complex. We replaced a 2HP with a 2HP because the old motor was ample for our needs, and frankly if we went any bigger we'd have had to redesign and manufacture a new back splash to leave the space required to mount a bigger motor.
As it was I could not bolt a fan onto the end as I'd wanted to and had to mount it to blow onto the side of the motor. I'm unsure as well if there is sufficient clearance to the headstock for a larger motor. I guess I should check that just in case we get the "more power" bug
I'm going to post a few do as I say not as I do pics, along with the caveat, DONT DO THIS with a hoist:
.... Complicating matters was the fact a proper gantry crane would not fit in the space, and a engine hoist could not pick the lathe up at the balance point. Improvisation was in order. View attachment 19600
I want to expound further on my first post in this thread.. The only part of my work that I meant "Do as I say, not as I do" was the hoisting method.
The reason is simple. I'm qualified to do what I did. Most people are not.
I'm qualified to perform structural calculations as well as to design environmental systems for residential, commercial and institutional buildings. Before I lifted the lathe as shown (wood gantry that was also fastened to the floor assembly above) I performed load calculations to assure that both the improvised gantry members would not snap but that the floor assembly would not be damaged or move in any way.
I wish to pose a theoretical question for those who may both have a 2x72 belt grinder, and a VFD controlled lathe, OR just have an opinion and dont own either.
I replaced a ~1800 rpm 2HP single phase motor with a 2HP three phase motor
I am building a 2x72 Belt grinder. I'd long heard that you really need a 3HP motor for such a project, but recently I've seen many builds that use a 2HP three phase and have plenty of power to eat metal at a fantastic clip.
So I have a ~3600 rpm 3HP motor that I could have put on the CT041 12x37 belt drive lathe and then put a 2HP motor on the belt grinder.
The 2HP motor has a lousy 2:1 constant torque speed ratio, but I added supplemental cooling and a temperature sensor to cut off the motor if it starts to over heat, so I can very likely use it all day long at the lower 5:1 variable torque ratio... 360 motor rpm.
The lathe gearing offers a 36:1 reduction so my low gear will give the lathe a speed of 10 RPM with this 2HP motor.
The 3HP motor is much better designed and aluminum so the constant torque speed ratio is higher at 15:1, but even with the higher rpm I can operate safely at the low speed of 239 rpm, with gear reduction I'd get 6.6 rpm with more HP and torque from the larger motor. On the speed side of the equation there is not a lot of difference.
Where I'd lose is on the high speed operation of the belt grinder if I used an 1800 rpm motor instead of 3600 rpm motor.... even if I overclocked the motor at 120 hz
In that case, I would take the hit on the belt grinder. It will work just fine at the lower rpm. It's also a lot easier to replace if/when that opportunity ever comes.
In that case, I would take the hit on the belt grinder. It will work just fine at the lower rpm. It's also a lot easier to replace if/when that opportunity ever comes.
I haven't used a 2x72 belt grinder yet so I dont have a basis for comparison, but some basic calculations for surface speeds with a 5" drive pulley and the 3600 rpm motor has a huge advantage if you want fast material removal.
Our old lathe motor had a reasonable amount of torque and power so I see not real disadvantage in keeping two HP on the lathe.
All of us here would like that. I'm just grateful to have enough to have fun with.
And as my daughter keeps reminding me: there are people all over the world who would gladly take my place on my very worst day. I am truly blessed. My 3hp lathe vfd upgrade can wait. If it never happens, it will be ok.
I haven't used a 2x72 belt grinder yet so I dont have a basis for comparison, but some basic calculations for surface speeds with a 5" drive pulley and the 3600 rpm motor has a huge advantage if you want fast material removal.
Our old lathe motor had a reasonable amount of torque and power so I see not real disadvantage in keeping two HP on the lathe.
I built a 2x72 belt grinder. Single speed AC motor. Was initially concerned about belt speed and stock removal. No issues. It takes of steel almost as fast as Aluminum.
