Acorn and Emcoturn 120 with 8-tools-turret

[Spartan117]

I know, probably no one here really cares, but because it makes me so happy I wanted to let you know:

Buy Acorn CNC Kit:

[suntravel]

Good choice

Uwe

[cnckeith]

looking forward to seeing a photo album of the upgrade!

[Spartan117]

looking forward to seeing a photo album of the upgrade!

Well, I'll do my very best, Miss Sophie

[Spartan117]

Good things come to those who wait...
I finally got my hands on an affordable spindle-inverter for the motor in my emcoturn 120 (a 3~ 400V, 2,8kW 3000rpm asynchronuos motor).
I had to wait for that because i already have got a control-cabinet i want to use here (600x600x280mm) and so the layout was critical regarding the size of the inverter.
Fun fact: As murphy already told, i had to mount the inverter on the outside of the cabinet anyway meaning, i could have finished the control-cabinet weeks ago, and the layout is kind of weird now, too

I also replaced the original 5-phase-steppers with closed-loop-steppers. I think it's best to start another "Make-Thread" later with more pictures and less questions, and only link to this one. So no one has to read through lots of pages without the need to.


Another question, maybe @martyscncgarage is the right one to ask:
Is the "relais for forward-full-voltage, backwards-lower-voltage"-solution for the toolchanger still recommendable?
I often read about more complex current-sensing-hardware, that cuts off the motor-current after reaching the latch of the toolchanger (originally it was like that, too) and many people say, the relay-solution with two voltages will not work properly. e.g. here: https://emcocncretrofits.fandom.com/wik ... leComments
They say, the lower voltage/current for turning backwards is not sufficient for secure toolchange and/or much too slow.
As you (Marty) did go with the stepper-solution on the 140, too, i'd like to ask for the reason to do so?

I thought about using a LM2596 CC-CV-module for reverse, so i could limit the current instead of the voltage, maybe this could be a little bit better, if needed?

[Upnorth]

Is the latch for your turret a mechanical latch or does the reverse voltage just hold the turret against a stop? If it uses a mechanical lock you could set it up like I did.

My turret has a mechanical lock. I use 2 relays to control it. One relay (1) controls power to the turret and the other (2) sets the direction of the applied voltage. With relay (1) turned on and relay (2) off the turret rotates in reverse to lock. With relay (1) on and relay (2) on the turret rotates forward to the required tool position. The turret has full voltage in either direction.

I have a switch that sees if the turret locks after a tool change. If it does relay (1) turns off removing all power from the turret. If the turret fails to lock after 5 seconds, relay (1) turns off power to the turret and I get an error message. This prevents the motor from burning out in a turret not locked situation after a tool change.

I couldn't use the stock schematic and PLC to control my turret the way I wanted too. I contacted Centroid technical support and hired them to rewrite the part of the PLC to get it to work the way I wanted it too. First time it was close but not quite right. They did an edit and then all was good. The PLC can be edited to make your lathe turret work in any situation you can come up with. It was well worth the time they charged me to edit the PLC.

[Spartan117]

In detail, AFAIK, it is a pin, that runs on a helical ramp inside the turning disc of the toolchanger.
If the turret turns forward, the pin gets pushed down by that ramp and then snaps out/up in the next tool position.
Then it turns backwards, until the pin touches the wall of the helical ramp.

Originally, forward is full voltage and full current, backwards only at first, but after sensing the rising current of the blocked motor, it limits the current to a save non-motor-killing value. But it keeps holding the turning disc against that mechanical stop all the time.

[Upnorth]

Ok it sounds like yours is a mechanical stop and not a mechanical lock like mine. The turret I have does not require any power after the mechanical lock is activated. You could still use a two relay system. One relay is full voltage FWD/REV second one could be half voltage and activate or deactivate the first relay after the turret being against the pin depending on how you decide to set it up. You will need to do a little thinking on exactly how you want it to work.

My main point from my previous post is that no matter how you decide to make it function the acorn PLC can be modified to make it work.

[Spartan117]

Ah, now i got it. Yes, it is a mechanical stop, not a lock.

I phoned with a friend of mine today who will develop a little electronics circuit for managing that current-reduction via blocking-detection for me.
So i can go with the relay-solution.

Just to mention if someone else may need that: The motor current is rising from 100mA (free turning) to 2.2Amps when reaching the blocking pin.
Then it should be reduced, around 100mA is enough. Datasheet says, up to 700mA is safe for continuous-current, but referring to free-turning, not blocking. Should not make too much of a difference on a small, closed 24VDC-Motor.
It is a 24V Maxon DC Motor 2332 968-61.217-200

Good to know that i can "buy" that PLC-modification, if i can't get it to work

[martyscncgarage]

Good things come to those who wait...
I finally got my hands on an affordable spindle-inverter for the motor in my emcoturn 120 (a 3~ 400V, 2,8kW 3000rpm asynchronuos motor).
I had to wait for that because i already have got a control-cabinet i want to use here (600x600x280mm) and so the layout was critical regarding the size of the inverter.
Fun fact: As murphy already told, i had to mount the inverter on the outside of the cabinet anyway meaning, i could have finished the control-cabinet weeks ago, and the layout is kind of weird now, too

I also replaced the original 5-phase-steppers with closed-loop-steppers. I think it's best to start another "Make-Thread" later with more pictures and less questions, and only link to this one. So no one has to read through lots of pages without the need to.


Another question, maybe @martyscncgarage is the right one to ask:
Is the "relais for forward-full-voltage, backwards-lower-voltage"-solution for the toolchanger still recommendable?
I often read about more complex current-sensing-hardware, that cuts off the motor-current after reaching the latch of the toolchanger (originally it was like that, too) and many people say, the relay-solution with two voltages will not work properly. e.g. here: https://emcocncretrofits.fandom.com/wik ... leComments
They say, the lower voltage/current for turning backwards is not sufficient for secure toolchange and/or much too slow.
As you (Marty) did go with the stepper-solution on the 140, too, i'd like to ask for the reason to do so?

I thought about using a LM2596 CC-CV-module for reverse, so i could limit the current instead of the voltage, maybe this could be a little bit better, if needed?

The 140 used a 3 phase motor on the turret. In hindsight I should have kept it
The 120 turret works well, Emco engineered it, we have a schematic, why change it?

The turret is designed to roll forward slightly past the tool position and the roll back against the pawl.