My first Plasma Rotary experiments

[msimpson99]

I purchased a harmonic rotary a little while back for the specific purpose of using it on my plasma CNC.

Image2.jpg

While I am happy with the results, I know I can make things even better, but first I have to solve a couple issues.

1. The plasma dust making its way into the chuck.
I am probably going to come up with some kind of plug that fits the can, as this only happens when the open end of the can is facing the chuck.

2. Easier way of setting up for various stock diameters.
There are a couple ways of solving this. One is to setup for a 1" diameter stock and just scale Mach3 to the actual diameter. I have done this in the past with success.

Everlast ARC OK Signal Failures.
In addition I have an issue with the Everlast 50S when cutting thin metals, IE 26 gauge. Very frequently the ARC OK signal does not get generated by the plasma cutter. I suspect the issue here is that the pilot arc just blows through before the arc can transfer to the stock. I do have a button setup so that I can generate the signal in a pinch, but it does mean standing there with my finger over the button when I cut thin stock.

If anyone has any comments or input, they would be appreciated.


https://youtu.be/OreTQE_-fUI

[ctgolfer1]

That is some really cool stuff, I don't have a need for a rotary plasma cutter but I wish I did , seems like it would be fun to play with.
Thanks for posting, video was cool.

[msimpson99]

My main reason for getting the rotary up and running on the plasma machine is not for doing round stock.

I have some components that I make for folks. These are cut out of steel angle. This means I cut the angle to size, mount it in a fixture, plasma cut the features on one side, mount the other side and plasma cut features.

With this fixture:

_MG_6727.jpg

I can plasma cut both sides and do a cut off from a larger piece of stock. Even mounted this way I can cut 6-8 parts at a time. The cool thing is that SheetCAM can do most of the work. All I have to do is create DXF profile for each side.

The down side to this fixture is that it can not be swapped out for one of the other axis. An additional driver must be added to the system to drive the rotary. This machine has a G540 with all four axis occupied. It uses a UC300ETH to drive the G540, but has several more ports available, so all I have to do is add a breakout board and tie it into a single driver.

I have all the parts, I just have to get them hooked up.

[Rodw]

b]Everlast ARC OK Signal Failures.[/b]
In addition I have an issue with the Everlast 50S when cutting thin metals, IE 26 gauge. Very frequently the ARC OK signal does not get generated by the plasma cutter.

A possible cause of this with (which caught me out with the same plasma cutter) is that your CNC controller input is a high impedance circuit so that the current passing through the Everlast's internal ArcOK relay is less than the minimum current mentioned on the spec sheet for that relay. What happens then is the relay contacts oxidize and eventually this builds up on the relay contacts resulting in intermittent ArcOK performance.

The solution is to add a pullup/pulldown resistor (depending on your logic circuit) to ensure the current exceeds the minimum threshold of the relay. This resistor needs to be able to handle the current in the circuit (determined by the impedance in the logic circuit. In my case, we used a 1k 1 W resistor. (Mesa 7i76e and 24 volt field power)

Be warned that it might take a few operations to burn off the oxidization and return to reliable operation.

[msimpson99]

Do you know what the minimum current is? Where is this called out?
Also does not make sense as the same relay contacts work perfectly when cutting anything thicker than 24 gauge.

[msimpson99]

On your circuit a 1K at 24V should pull about .024 Amps and .576 Watts.

For my 48V circuit, looks like I would add a 2K pullup. That will draw .024 Amps at about 1.152 Watts.

Now I just have to locate a 2K resistor thats larger than 2 Watts.

[Rodw]

Do you know what the minimum current is? Where is this called out?
Also does not make sense as the same relay contacts work perfectly when cutting anything thicker than 24 gauge.

Sorry I missed this. I think you need to consult your controller board docs and work off the impedance to ground. Thats what we worked off.