Acorn and Emcoturn 120 with 8-tools-turret

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Spartan117
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Re: Acorn and Emcoturn 120 with 8-tools-turret

Post by Spartan117 »

martyscncgarage wrote: Sun May 29, 2022 4:39 pm 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.
This is exactly what i want to do. What did you understand i want to do?
As i said, i am german and maybe there are some communications problems with my wording^^


But (also Emco did that in original) the current of the turret-motor should be reduced after contacting the pawl to around 20% (PWM, 40kHz, 60%/40%)
And i found the datasheet for the Maxon-Motor, it says 700mA for continuous use. So 20% would be around 140mA.

Yes, I want to use the relais-solution from the schematics, but i also want to reduce the current after contacting the pawl/in "holding-state" to not overheat the motor. This motors are no longer available, afaik.
So a current-sensor in the reverse-direction-path that switches to a reduced-current after sensing the blocking-current should be the easiest way?
Upnorth
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Re: Acorn and Emcoturn 120 with 8-tools-turret

Post by Upnorth »

Like Marty says there is a pre existing circuit and software schematic that is known to work. If you go with the original circuit that reverses at half voltage your motor should be safe. If you find out it does not work for some reason you could then look at modifying the circuit and PLC software and using current sensors.
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Re: Acorn and Emcoturn 120 with 8-tools-turret

Post by Spartan117 »

Upnorth wrote: Wed Jun 01, 2022 11:46 am then look at modifying the circuit and PLC software and using current sensors.
This is what I've done now.
A friend of mine developed a current sensing circuit for me, that automatically switches a relay when reaching an (adjustable) current in backwards-direction.

So what I will get is:
Forward: full voltage, full current
Backwards: full voltage and full current, but with automatic switching to a PWM-Controlled source with only 20% of full current (approx 140mA) when overshooting the adjusted current because of running against the pawl.
This should be how Emco did it originally.

I did it that way because some LinuxCNC-guys often say, just reducing voltage (like in the centroid-schematic) in the complete backwards-period is not good for the motor and reliability.
Marty proved it works that way, but I have been afraid there could be some seldom constellations where it could not do so... So I went the safer way here.
Say Hello to my ODC :roll:


Next thing now is, I will have to find out if I can change the plc in a way, that I can use only one input for home and probe.
So CNC12 takes a high-signal on that input as Probe when I started a probe-cycle, and as Home when I am homing.
This would safe me one input, and I could really use that input for other things.
We'll see :D
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Re: Acorn and Emcoturn 120 with 8-tools-turret

Post by Muzzer »

The principle you are describing is widely used for solenoids and relays / contactors. Once the movement has been completed, the holding current required is small relative to the pull-in current. If you search for "relay economiser", you will see relevant information.

The simplest solution is a timer relay that switches a resistor in series with the coil after a short period (100ms perhaps). You can also use a spare set of auxiliary contacts on the main relay to control a small relay that does the same thing based on the actual closing of the main relay. Finally, there are "solenoid drivers" that deliver a controlled, 2-level current ie a high closing current, followed by a lower holding current. These actually regulate the current, rather the rely on a resistor but tend to be supplied as discrete components rather than standalone products.

To switch a resistor in series with the coil without losing continuity of drive current, you connect the main coil through the control relay contacts - with the resistor across those contacts. That way, when you open the control (timer) relay, there is no interruption but the drive current is reduced to a continuously sustainable level.

DIN rail timer relays are widely available with a range of drive voltages. Something like this: https://cpc.farnell.com/europa-componen ... ay%20relay The Finder ones will literally accept an input signal from 12V to 240V.
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Re: Acorn and Emcoturn 120 with 8-tools-turret

Post by Spartan117 »

Step by step...
First motor-movement today with the control mounted to the control-cabin :-)
Enable and Alarm/Drive-Fault working, step/dir from the DB25, only enable from the screw-terminals.
I am using the acorn-power-supply ONLY for the acorn-board itself, nothing else.
Sensors, contactors and so on are supplied by another 24V power-supply, both to the same common-ground, as well as the 48V-power-supply for the steppers.
I will take pictures tomorrow.

The current-sensing didn't work like i wanted it to, so i will go with the LM2596-circuit like in the schematics.
Can someone tell me how much reverse-holding-voltage should be used on a emcoturn 120?
I thought about measuring current and adjusting voltage to value where current reaches 150mA


And maybe someone can give me some search-words for looking up how i could use one input for home AND probe?
The wizard doesn't allow two signals to one input.
I want CNC12 to read a signal on that input as Probe when I started a probe-cycle, and as Home when I am homing.
This would safe me one input, and I could really use that input for other things.
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Re: Acorn and Emcoturn 120 with 8-tools-turret

Post by suntravel »

For me it looks less like biting in a lemon to get an Ether1616, than to rewrite a perfect working PLC, maybe because for my skills with programming I need to spend less time earning 299$ than to deeply change the PLC :lol:

Uwe
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Re: Acorn and Emcoturn 120 with 8-tools-turret

Post by Spartan117 »

After a first look at a "standard lathe plc" it seems quite easy to map the inputs... I hope it really is, too^^

This is in the "acorn_lathe_plc.src":

Code: Select all

;------------------------------------------------------------------------------
;                        INPUT DEFINITIONS
;               Closed = 1 (green)  Open = 0 (red)
;------------------------------------------------------------------------------
Unused1                       IS INP1 ;&*;
Unused2                       IS INP2 ;&*;
Unused3                       IS INP3 ;&*;
Unused4                       IS INP4 ;&*;
Unused5                       IS INP5 ;&*;
Unused6                       IS INP6 ;&*;
Unused7                       IS INP7 ;&*;
EStopOk                       IS INP8 ;&*;
; #endregion
If i am right, i will just have to change it to something like this:

Code: Select all

;------------------------------------------------------------------------------
;                        INPUT DEFINITIONS
;               Closed = 1 (green)  Open = 0 (red)
;------------------------------------------------------------------------------
HomeAll                       IS INP1 ;&*;
ProbeTripped                  IS INP1 ;&*;
Unused2                       IS INP2 ;&*;
Unused3                       IS INP3 ;&*;
Unused4                       IS INP4 ;&*;
Unused5                       IS INP5 ;&*;
Unused6                       IS INP6 ;&*;
Unused7                       IS INP7 ;&*;
EStopOk                       IS INP8 ;&*;
; #endregion
I will have to test if that still works when assigning two signals to one input.

But i will have to (wanted to anyway) install a second sensor in series on each axis (in case of the emco), because the emco's home-sensor sits on the wheel of the ball-screw. That means, with every revolution of the wheel a signal will occur. And so it would be possible to get a signal from that HOME-sensor when probing instead of the probe.
On my router that wouldn't be a problem because the HOME-Sensors are way out of the area where probing is done.

Also possible would be to change the position of the HOME-sensors of the emco to the axis instead of the ball-screw-wheel. I found inductive sensors that are precise to +/-1µm so the homing via wheel is not needed at all. But they are rare these days...

Or i will have to use an output to switch a relay when homing. So the HOME-sensors are electrically isolated/out of circuit when not homing and vice-versa with the probing-sensor.
I will have to see what is easier to set up, after clarifying if that double-assigning will work.
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Re: Acorn and Emcoturn 120 with 8-tools-turret

Post by suntravel »

You do not want to use probe detect?

Uwe
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Re: Acorn and Emcoturn 120 with 8-tools-turret

Post by Spartan117 »

suntravel wrote: Tue Jun 07, 2022 4:06 am You do not want to use probe detect?

Uwe
No, i don't need that. My probes don't have the choice if they want to work or not ;-)

https://www.baumer.com/ch/de/produktube ... 7/products
(physically opening in any case)

But even on my router (inductive sensor) i don't need that because i got the habit to always hit the sensor manually for testing before starting probing cycle
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Re: Acorn and Emcoturn 120 with 8-tools-turret

Post by suntravel »

Probe detect had saved me some probes, because you can not start spindle by error, or jog with speed in to the probe tip while positioning the tool in front of the probe on the lathe, or positioning the 3D probe on the mill ;)

I configure my probes so that probe detect is triggered with plugging in the connector of the probe.

Uwe
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