Jet GH-1340T lathe info

[Randoo]

I just picked up a 1993 Jet GH-1340T lathe but I can't find any real information about it. I'm hoping someone can point me towards a manual or electrical schematic. I'm going to power it up with a VFD but still want to use the foot brake most of the time. I thinking I can set the VFD to coast to stop when the brake is applied so I don't fight or harm the VFD. Not sure if I still want to use the forward and reverse contactors to break the motor leads or just use the contactors as inputs to the VFD. Anyone powering their lathe with a VFD and still use the foot brake? How did you set it up?

Thanks,
Randy

 

[Randoo]

I traced out the wiring and drew up a schematic. Thinking I will use one of the main contactors to power up the VFD when I turn on the control selector switch. Have a basic idea of controls for the drive but won't be sure until the drive arrives so I can check out the manual. I still am looking for a manual. Any 1340 lathes that are close to this that has a manual I can get?

Thanks,
Randy

 

[ignator]

You DO NOT want any contactor between the VFD and motor. It's the quickest way to blow up a VFD. So never put a switch contact between the VFD and motor. Let the VFD control it.
I have a similar lathe that has 3phase main motor and 3phase coolant pump motor. I did rewire the lathe to use the main power switch to power the VFD input. And a FWD and REV contact from each of the original motor contact switches to the VFD for digital input control using the +24VDC discrete power of the VFD.
And yes, you can set the VFD up to coast to stop.
This keeps the interlock parts of your lathe motor control, so if the FWD/REV control lever is left in the on position, it prevents the lathe from running on power up. So you don't touch any part of that interlock wiring. Just the output contacts of the FWD/REV contactors in the control box. And these are isolated from any input power of the AC mains during operation, as you've disconnected them to be reused to control the input discretes of the VFD.

 

[ignator]

As for the coolant pump, I bought a super cheap VFD from eBay, and power just that from the front panel switch, But maybe your coolant pump is not 3phase. Mine was, so a $40 VFD was the easy solution, as it's a less then 1/10thHP motor.

 

[Randoo]

As for the coolant pump, I bought a super cheap VFD from eBay, and power just that from the front panel switch, But maybe your coolant pump is not 3phase. Mine was, so a $40 VFD was the easy solution, as it's a less then 1/10thHP motor.

My lathe didn't come with a coolant pump. It's prewired for a 3 phase one though. I have a stand alone coolant pump that's 120V that I can wire in if I choose to use it.

 

[ignator]

My lathe didn't come with a coolant pump. It's prewired for a 3 phase one though. I have a stand alone coolant pump that's 120V that I can wire in if I choose to use it.

I got a deal back in 2004, Grizzly tools, had a super deal, never was in the catalog, online lathes for sale. I paid $7500 for a 18x40 (450x1000mm) lathe, 5600lbs, that has a 3-1/8" hole through the head stock (listed as 80mm outside of Grizzly's spec's. I wanted a large hole for shaft work, as part of my hobby is fix of broken stuff, and the 10x24 Jet lathe I got in 1976 was too small.
So what I found under the grizzly slapped on label was some other fake importer tool company, that had no searchable existence in the world. And from talking to Grizzly's customer support, as my #4MT tail stock had a manufacturing defect that prevented tool insertion past where they cross machined the taper push out hole in the quill. So they sent me one from their parts machine. The lathe was shipped out of MO, but parts was from their East coast store (now gone), and their customer support machinist (a real smart old retired guy that worked for them) indicated they had 6 of my size lathes and some others that were the 60 and 80 inch (1.5, 2 meter I'm trying to do this metric stuff) beds of the same import quality. They are good quality, except these are every incorrectly made part or spare excess parts put into assemblies at what was a big discount as scrap iron cost's to the importer. And I was seeing lathes from Grizzly of this same size in the $16K+, and Enco was $20K. I wanted it, and I'm happy with it.
So I did to through and kept the original safety interlock relays in place. I just pulled the old 3 phase power from the one contact I reused in each of the FWD/REV contactor motor switches, as there were no spare Aux contacts.
I did try to power it with my RPC of my build, and it caused some sort of high voltage arc to occur, and short out the FWD motor contactor to have a phase to phase short. I could not find where it was, but Grizzly sent me a new contactor from their spare parts machine. But to power 7.5HP main motor, I needed something to not deal with the locked rotor amps of startup, that would exist with 3phase line input, and my RPC could not deal with that.
So I got a 10HP Mitsubishi VFD (typical derating of the VFD for motor HP >3 is 2X VFD size to prevent input diode smoke release) that I integrated into the controls. I've never had an issue with the 30amp one phase input, it's never tripped the main breaker. More issues with tuning the deceleration so it does not overvoltage or trip some internal overcurrent brake resistor. It's of the same age 2004 (the VFD), and if it were not such a large size, I would get a replacement. I don't trust China low cost ones, but I may be wrong in them, as they've only learned how to make everything better and cheaper, especially since all US and EU name brand VFD's are made in China. Also I'm seeing them selling on eBay VFD for single phase input, to drive 40HP motors.
What they need is a VFD, that senses the motor load, and decelerates to stop as fast as possible. It would get the inertial data from monitoring the acceleration of the lathe chuck and part. It's just a hobby, not production, but safety is why I want fast deceleration. And if the VFD trips out, not helping.
The VFD on the lathe allows you to slow it down for die or tap threading to keep it under control (you're holding the wrench), and this as well slowing it down when there's harmonic noise in the cut.

I kept the main power switch of my big lathe. I know all these lathes with apron control FWD/REV levers, have similar contactor arrangements to interlock the motor from powering up, in the event of power loss, as well if there are door switches and such to lock out operation for the guy that wants to get his fingers crushed on purpose.
Since you have the diagram, the change is simple. Just keep the low DC signal stuff from any accidental AC mains power. The VFD manual has all the good install advise. The EMI is BS if you don't have long runs of motor wires. That's all industrial where motors are remote to the main VFD and contactor control room, that can be 1000s of feet away (as dumb as as this, but I worked on grain elevator in my youth as a apprentice, 300-500ft tall) and they had a remote lockout switch, that was two #14AWG copper runs per motor up in the head house, for electrical lockout safety of a maintenance guy that removed the covers to the motor belts and such) my point is that's when you need EMI/EMC filters and stuff. But on 10foot (3m) runs the switching noise has never gotten into the unshielded analog and discrete connections on any of my machines. My metal shop, all motors are 3 phase and for the drill press and old lathe, they got 3phase motor conversions a long time ago. I don't mess with belt changes unless I need some real torque, otherwise the mid range, and let the motor spin up to 120Hz input max to get the upper range of the spindle.

 

[ignator]

The problem with deceleration of the VFD or Acceleration, it's fixed in a program location, like 5 second, that's too slow for deceleration, but if you make it as fast as wanted, when I move to stop the spindle, the VFD does not care if the starting speed is 1100RPM or 30RPM, it just decelerates at that programmed rate. So they need a special Lathe mode and they don't have it. I also have problems with my vertical mill, that's 1.5HP, and same issue if you have a small collet with endmill or a huge face mill, randomly was always tripping, and sometimes on acceleration, being too short a time.
That's where I had my issues with VFDs
I should say that big lathe has a 12" chuck, lots of inertia.

 

[Randoo]

The problem with deceleration of the VFD or Acceleration, it's fixed in a program location, like 5 second, that's too slow for deceleration, but if you make it as fast as wanted, when I move to stop the spindle, the VFD does not care if the starting speed is 1100RPM or 30RPM, it just decelerates at that programmed rate. So they need a special Lathe mode and they don't have it. I also have problems with my vertical mill, that's 1.5HP, and same issue if you have a small collet with endmill or a huge face mill, randomly was always tripping, and sometimes on acceleration, being too short a time.
That's where I had my issues with VFDs
I should say that big lathe has a 12" chuck, lots of inertia.

Thanks for the info. The VFD I bought has an auto accell/decel setting that's supposed to sense the motor current and give the best times. We'll see how it works. My lathe has a brake so I'll be using that most of the time. The geared head makes speed range changes easy so I plan on getting it close that way and fine tune with the drive. I do have a plan now for wiring and I'm going through the many parameters to see which ones I have to change.

Randy

 

[djc]

The VFD I bought has an auto accell/decel setting that's supposed to sense the motor current and give the best times.

It would be good to investigate whether it has some hard limits that you can set because you know more about what is going on in a global sense than the VFD's computer.

Think very carefully about the "best times" you have written. Those times will be best for the VFD - assume it trips at 4 amps, it will adjust acceleration to pull no more than 3.8 amps.

What is best for the VFD might not be optimum for the rest of the (mechanical) system, the parts that the VFD can never know about. Just a simple example - if you have something imbalanced in the chuck, the acceleration ramp might not pull too many amps, but the vibration could be harmful/dangerous.

 

[ignator]

My lathe has a brake so I'll be using that most of the time.

Mine has a brake as well, and since there's a microswitch that senses the brake application to disengage the motor contactor, if a VFD is trying to decelerate the chuck, you are pressing the brake, and these Dang VFDs, want to control the deceleration at the timed rate, it fights the brake. So if that's your intent, coast to stop setting.
I never use the brake, and use the FWD/REV lever on the carriage. As odd as that seems, if you use the brake to stop, you'll have to reset the lever to off, so the safety interlock relay resets to ensure unwanted chuck operation.

 

[Randoo]

Mine has a brake as well, and since there's a microswitch that senses the brake application to disengage the motor contactor, if a VFD is trying to decelerate the chuck, you are pressing the brake, and these Dang VFDs, want to control the deceleration at the timed rate, it fights the brake. So if that's your intent, coast to stop setting.
I never use the brake, and use the FWD/REV lever on the carriage. As odd as that seems, if you use the brake to stop, you'll have to reset the lever to off, so the safety interlock relay resets to ensure unwanted chuck operation.

I'm wiring and setting parameters so that when the brake is used the drive enable is turned off which is coast to stop. Then I'll have to move the lever to off to reset the enable before I can restart the drive.

 

[Randoo]

It would be good to investigate whether it has some hard limits that you can set because you know more about what is going on in a global sense than the VFD's computer.

Think very carefully about the "best times" you have written. Those times will be best for the VFD - assume it trips at 4 amps, it will adjust acceleration to pull no more than 3.8 amps.

What is best for the VFD might not be optimum for the rest of the (mechanical) system, the parts that the VFD can never know about. Just a simple example - if you have something imbalanced in the chuck, the acceleration ramp might not pull too many amps, but the vibration could be harmful/dangerous.

I see what you're saying. I'll play around with the settings to see how it works. This is a setting I've not seen before so I'll have to learn about it.

Randy

 

[ignator]

I'm wiring and setting parameters so that when the brake is used the drive enable is turned off which is coast to stop. Then I'll have to move the lever to off to reset the enable before I can restart the drive.

They have made improvements to VFDs since my long ago purchases when I repowered everything.
Clearly you know what you are doing.
So what model of VFD did you find that has the autotune acceleration/deceleration feature?
I helped my neighbor power his 10HP industrial air compressor with a $120 VFD from eBay, and the only issue, I needed to convince him, he needed to have a much bigger copper wire size feeding from his panel. You don't see any brownout of the lights with it running. It was easy to take the pressure switch contacts, and wire it into the VFD. But for a >$10K compressor to run on single phase power (he does have 300amp service, and is very close to the overhead high voltage feed) it made him happy, and he didn't have to return a burned up fake not as described VFD back to them. I found it, and searched specific for a unit that was designed for that. And to see you can get them in 40HP sizes (last I looked those were $600).

 

[ignator]

So my Jet 1024 has a manufacture date of July 1974. Shows made in Taiwan. But I know that Jet was an importer, and not a manufacture. But lucky, I can still find information so I can recover the feeds/speed chart, which is scratched beyond use.
It has the fine threaded lathe spindle, of 8TPI on 50mm OD. What a bastard thing to do. But as the lathe has 8TPI threading feed, I was able to take a cast iron blank (many years ago, acquired from Enco) and make a new back plate for a Bison brand chuck. The down side, it's threaded, so I can't do power reverse. I wish this had a D1-3 or D1-4 spindle nose.
You'll be happy with this lathe. Check your 3 jaw chucks for runout, as the OEM ones that come with any import lathes from my experience, always have huge runout. Unless the owner has ground them using a tool post and jaw loading device. Even then the scrolls are not precision.
That said, I've had crazy luck when I wanted a cheap 3 jaw to mount on the rotary table, and found one that has a saturn planet drawing with the rings going around (and only Mandarin writing is seen on the label), and runout was less then 5thou. But the one that came with my Grizzly has 35thou, and I immediately got Bison backplates and chucks (wasted money on a 6jaw for thin tube work). That has a D1-8 spindle nose. At least I got them from Enco 20 years ago, when they were 1/5th the price of now. The Zero Set is nice too.

 

[Randoo]

They have made improvements to VFDs since my long ago purchases when I repowered everything.
Clearly you know what you are doing.
So what model of VFD did you find that has the autotune acceleration/deceleration feature?
I helped my neighbor power his 10HP industrial air compressor with a $120 VFD from eBay, and the only issue, I needed to convince him, he needed to have a much bigger copper wire size feeding from his panel. You don't see any brownout of the lights with it running. It was easy to take the pressure switch contacts, and wire it into the VFD. But for a >$10K compressor to run on single phase power (he does have 300amp service, and is very close to the overhead high voltage feed) it made him happy, and he didn't have to return a burned up fake not as described VFD back to them. I found it, and searched specific for a unit that was designed for that. And to see you can get them in 40HP sizes (last I looked those were $600).

I bought a DURApulse GS10 series drive from AutomationDirect. The 3HP drive is about $200 w/ free shipping. Found it mentioned on a couple different forums as being a good drive and having tech support that actually helps. I have no experience with them so I'll how it holds up. Not the cheapest drive out there but gave me a warm, fuzzy feeling that it'll be good. I hear you about chuck runout and I'll check it at some time. It came with a 4 jaw chuck if I need to be precise. Lathe has a D1-4 (I think) spindle so that's good. The Grizzly 10X22 that I'm replacing has a screw-on so I know what you're talking about.

Randy