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Rotation problem with rotary phase converter

Mr.JAJA

Plastic
Joined
Jan 22, 2024
Location
Ramona CA
Hi, I have a Weiler LZ330 in the US and run it on a RPC. I never had this happen when the machine where used in Germany.
This is the first time I cut tread here in the US on this machine. (Cutting 1"-5 ACME)
Like I said, it runs on a RPC. When stopping or reversing the rotation the machine keeps going in the cutting direction. This only happens when I switch the lever and touch the reverse direction before the machine comes to a full stop.
I only have 1 1/2 turn to a full stop, and running with 28 RPM (Cutting 1"-5 ACME) the movement is still 6-13mm with not much time to correct or stop the chuck. No brake on the spindle.
I already broke 3 bits wile running into the lathe. (Not what I like to do).
It is like the 2 stroke engine, when turned in reverse direction, there run and you have 5 revers speeds.

Any Input on this?
My guess: I have to be very carefully to finish the shaft, not to over shift and run into the revers switch position.

Would a VFD with brake resistor solve this problem?
I would need a 1 ph 220 Volt input, 3ph 220 output and 5 HP $ 800.00

Thank you Mr.JAJA
 

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With a regular manual machine on real 3 phase you can switch into reverse at full speed and it will snap reverse. Doesn't happen with a converter. manufactured leg goes to zero. If I was rigid tapping in the milling machine on a converter, I would leave a whole bunch of space to reverse. Tap, switch off, let it glide a few revs, hit reverse, it slowly turns around.
You probably need a good VFD
 
With a regular manual machine on real 3 phase you can switch into reverse at full speed and it will snap reverse. Doesn't happen with a converter. manufactured leg goes to zero. If I was rigid tapping in the milling machine on a converter, I would leave a whole bunch of space to reverse. Tap, switch off, let it glide a few revs, hit reverse, it slowly turns around.
You probably need a good VFD
I have my manual machines on an RPC and they will reverse every time if switched. Feed motor or spindle motor, doesn’t matter. I prefer to let them spin down but they all will reverse instantly. Never ever had a failure to reverse.
 
Hi, I have a Weiler LZ330 in the US and run it on a RPC. I never had this happen when the machine where used in Germany.
This is the first time I cut tread here in the US on this machine. (Cutting 1"-5 ACME)
Like I said, it runs on a RPC. When stopping or reversing the rotation the machine keeps going in the cutting direction. This only happens when I switch the lever and touch the reverse direction before the machine comes to a full stop.
I only have 1 1/2 turn to a full stop, and running with 28 RPM (Cutting 1"-5 ACME) the movement is still 6-13mm with not much time to correct or stop the chuck. No brake on the spindle.
I already broke 3 bits wile running into the lathe. (Not what I like to do).
It is like the 2 stroke engine, when turned in reverse direction, there run and you have 5 revers speeds.

Any Input on this?
My guess: I have to be very carefully to finish the shaft, not to over shift and run into the revers switch position.

Would a VFD with brake resistor solve this problem?
I would need a 1 ph 220 Volt input, 3ph 220 output and 5 HP $ 800.00

Thank you Mr.JAJA
How big is the Weiler's motor, and the motor in the RPC? If the RPC isn't sufficiently larger than the Weiler, reversal is certainly possible. A VFD may be cheaper than getting a bigger RPC motor.
 
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How big is the Weiler's motor, and the motor in the RPC? If the RPC isn't sufficiently larger that the RPC, reversal is certainly possible. A VFD may be cheaper than getting a bigger RPC motor.
5 HP RPC and 5 HP Motor. I will look into the VFD solution. Its just a other $800. right? And this for a hobby shop where the machine is used 2 x3 time a year. But the last ride will not have a Bank account.
 
How are the forward/reverse functions in your lathe implemented? If there are control contactors used, it's vital that the control circuits be powered from the utility legs.
 
Get a bigger idler for your RPC (or add an additional 3hp motor). I used to have that happen with my LeBlond when running with a 5hp rpc (motor on the lathe was also 5hp). Works fine with a 7.5hp motor on the RPC.
 
It sounds like you just want to stop it at a specific point as in threading to a shoulder. But it does not stop because you have moved the switch lever from forward past stop and into reverse. I think you do not want it to go in reverse, just stop. If that is the situation, just turn it off sooner and finish the last few threads by hand turning, or thread away from the chuck. I don't see the need to have instant reverse on a lathe while cutting acme thread. Part of problem is language translation. My neighbor used to say stuff like " Throw the horse over the fence some hay." I don't think the braking resistor will solve your problem.
 
This is a bit complicated to implement absent a VFD, but the quickest way to stop a induction motor is to pass DC through the windings. Why? Well, we know that the rotation speed of an induction motor varies in direct proportion to the supply frequency. The "frequency" of DC is zero. Too much DC applied abruptly can damage things mechanically. I think that many modern VFDs can be programmed to do this.
 
+1

Easiest fix. Just plug in another machine and run it at idle for extra capacity.
So you say, if I run the mill during the lathe operation, it will help with the start-stop-reverse situation.
First I will check the created leg situation/condition.
Thanks for the advice.
 
yes, but take care you don't exceed the fuse/breakers of the small rpc. As others have said, your base problem is likely that the rpc is simply way undersized. Even at idle your lathe current will about 40% of the full rating (lousy power factor at low load.. before anyone tells me no :)).

A vfd is not going to give you instant stop/reverse. Unless you have a big braking unit and can program dc injection (take care) the reverse you desire is going to be limp at best, but you simply cannot "plug reverse" with a vfd.
 
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