PM-1236 motor issue

[mksj]

Hi Tino,

You need to set the VFD settings based on the motor nameplate, not the line in. So if you were sent a Leeson Metric 3 phase 60Hz motor at 230V, then that is the base frequency and motor voltage (also check the RPM and Amperage). You can also run an auto-tune to get additional motor parameters.

If you have a separate 24V power source for the power indicator light, then you need a separate switch or relay to connect it. You cannot use two power supplies in the same circuit if I understand your description. You can use the 24VAC transformer for the machine work light.

So you need to wire the relay in accordance with the socket base diagram, not the relay diagram, as the location of the connections are different.

 

[Blackhawk]

So the only option is to replace motor?

I've only used mine to turn about 10 barrels and it has the same symptoms. Of course I'm out of warranty.

Lanham

 

[mksj]

Go with a Leeson/Marathon metric motor and a VFD. World of difference. I have done systems for the PM1236, if you go with a Hitachi WJ200 I have all programming parameters, etc. I can send you. Otherwise, just replace the motor with a good quality single phase TEFC from Baldor. Marathon, Leeson, Lincoln, etc. and move on. The stock 3 phase motors on these machines, tend to be pretty crappy anyway. The problem with the single phase replacements is that they will be NEMA frames sizes, so you may have fitment issues, and need to check the motor dimensions with your machine.

 

[tmarks11]

Just so you are not shocked: expect your new Leeson motor to say "made in China" on it. Only a few types of Leeson motors are still made in the US.

 

[tino_ale]

Ok so I'm kinda waking this dead thread because I still haven't performed the VFD conversion. I do have the motor and Hitachi but have not had the time to take care of it. Shame on me !

As I want to move forward, and have used the lathe more, I have an idea of the jog button that I wonder if it makes any sense.

CHANGING GEARS. It can be a PITA to change gears on the 1236, you have to wiggle the spindle to get a shot at gears engagement. It is just not practical at all.

So I am thinking. What if, during forward or reverse operation, say I need to change gear, I press the jog button while still running, that action slows down the RPM to a very low value (only used for a short time and under no significant load so no danger for the motor), I change gears while running super slow, then release the jog button and the motor speeds up to the previous speed setting.

Jog speed would be a fixed parameter, very very low. Jog would run in forward or reverse depending on what was engaged. It would be a kind of temporary speed setting override.

If pressed while in neutral, it would run at the same slow rate in forward or reverse, based on a toggle switch.

Does that make sense and is that even doable ?

I am thinking maybe this need to be addressed by two separate switches :
- the "real" jog (only working when in neutral) as it is in the skematic
- the speed override that only works when running in either reverse or worward
If the two can be combined that would be nice but I don't see how that could be achieved in the skematic.

Any thoughts ?

Cheers

 

[tmarks11]

OCHANGING GEARS. It can be a PITA to change gears on the 1236, you have to wiggle the spindle to get a shot at gears engagement. It is just not practical at all.....say I need to change gear, I press the jog button while still running, that action slows down the RPM to a very low value...

Very typical to have the JOG button wired to tell the VFD to run the motor at 5 Hz (my VFD even has a connection labelled "JOG" in the manual). I don't think that is slow enough to prevent damaging your gears during engagement, depending on what gears you are talking about.

If you re talking about changing speeds, then the fastest gear in the gearbox at 5 Hz will be running at about 75 rpm... more than 1 revolution per second. That is very fast to be jamming against another gear. I don't think you would be happy with that.

If you are talking about the feed/threading gears, those are geared down quite a bit, so at 5Hz on the motor, they are probably only going 10 rpm or slower. Probably okay.

But lets backup....

First of all, with the VFD, you can (for the most part) leave the gearbox speed selection in one position (except for maybe the HI/LOW gear), and control the speed with the VFD.

Second, what you describe is typical of EVERY gear head lathe, not just yours. They all require rotating the spindle by hand to get them in gear. Chances are 70% that when you go to mesh two gears together, the teeth won't be aligned. Machinists for 70 years have been rotating the spindle to change gears. "Not practical at all"? I guess beauty is in the eye of the beholder.

You should try a belt driven lathe where you have to move belts around to change speeds....

 

[mksj]

Agree with Tmarks, you almost always have to turn the chuck to get the gears to engage.

The Jog speed is adjustable, the default is usually 6Hz, how fast it turns the gearbox gears is a function of the spindle speed gear selection, the gearbox speed will vary depending on the gearing. The difference in jog is that there is no braking applied so there is some momentum and the head will spin (free whweel) a bit to a stop. So that would be the time to shift gears, a bit like turning the chuck to get the gears to mesh. Changing the gearbox while pressing the jog may not be such a good idea no matter what the Hz/speed, as the VFD can apply full rated torque almost down to 0 RPM. So if something does not mesh well or binds, it may break. But I do sometimes bump the jog and when the chuck is almost stopped, I will engage one of the feeds if not fully engaged. Also when Ever I do change gears, either spindle or the gearbox, I always pump the jog to make sure it is fully engaged before running at regular speed. It verifies gear engagement.

I also recall more than one post where there where shifting issues with the PM1236, and it had to do with the key in one of the gear shafts being bent.

 

[tino_ale]

Very right about the spindle speed gears, for the most part VFD will make it a breeze to adjust speed without having to change gear.

What I had in mind was the feed/threading gear box. On the 1236, the carriage power feed is much faster than the compound feed, on any given gear selection. Meaning that when I'm for example finishing a part to what I'm trying to make a "perfect" finish, I have to finish the OD with one feed setting, then swap to another setting and do the facing.

That being said, I think I need to follow your advise here because as you said, if I change gear while under motor power, regardless of the speed at which it is set, any binding or stuck gear will end with something broken.

Thanks for you valuable inputs! Now I need to shop for all those electrical parts and wire up the system. I'm going to stick with the standard Jog function as described in the page 2, post #58.

Just so I get it right : I'm going to disconnect the physical brake and go with the two deceleration rates option :
- If the "forward" or "reverse" signal is simply lost but the BR signal is still here, it means there is no emergency => 5s slow stop.
- if the BR signal is lost, it means one of the security switch is opened (E-stop, cover...), the FW/RV signal is also lost => strong stop in 1s. And, the machine will not restart until back to neutral and ready (all security switches closed first).

If I understand the schematic correctly, I do not need the second foot brake switch, the one at the very bottom of the schematic.
All I need is to wire a "security" string of switches in series, and feed both the FW/RV switches and a custom analog entry (BR) with that signal.

Do I get this right ?

 

[mksj]

Yes, if the brake switch goes open and is serially connected, it acts like an E-Stop. If using 2 stage braking, it will revert to 1 stage when the E-stop or any of the safety switches go open. Its been a long time, and I no longer use the single relay design, so I need to review it. I would leave the physical brake connected and try it as is, since the VFD will stop it quicker than the physical brake. The physical brake is sometimes helpful when the you want to lock the chuck for manual tapping, etc.

An alternative if you just want it up an running with the VFD, is to just disconnect the high voltage power to KM1 and KM2, and use them to switch input 1 and Input 2 on the VFD. The motor is directly connected to the VFD. Yhe Jog will work at the speed pot setting, if you want the Jog at a Jog speed it needs to be reconfigured to activate input 3 and Input 1 for forward jog. There is also the issue that the once the contactors have been used for high voltage, the contacts get some resistance from arching and may not conduct low voltage signals.

 

[tino_ale]

Thanks for the confirmation. I like the way it works, it is exactly the behavior that I have now except that all security switches will have brake applied instead of just the foot brake. So it is pretty much an improvement in terms of behavior. I looks like I can do my shopping.

I'm not sure I understand your second paragraph. I just reached the point where I think I understand the schematic you provided, lol. I want to make the conversion with all the safety interlocks and brake abilities that we talked about so I'm sticking with your first schematic.

Thanks for your invaluable help