Plasma Pilot Hole Experiments

[msimpson99]

I decided to put some time in to some piercing experiments. I decided to see what kind of pilot holes I could create just using pierces. Discovered several things in the process.

First let me say, if you are going to be drilling out a hole for a #6 screw, you are better off doing a plasma cut just a little larger than what you need due to the steel hardening. It will quickly dull a colbolt or HSS bit. For larger drill bits, works very well, as the tiny divot or hole does not seem to effect them too much.


I also found adding the "Arc Transfer" (Arc OK) input to my CNC, I could alleviate the need to fire off the stock to fill the torch hose with air. However, when using the Arc Transfer signal I could not do dimples in thin stock.

Had a lot of fun playing with this. Here is a video of my tests:
https://youtu.be/PRiRAsFZph4

[acourtjester]

neat stuff could be handy to produce center punch divots for drilling holes in parts later

[rons]

great video thanks

[steel 35]

Very useful tool, looks like your's is touching off every time would be useful with uneven materials; mine touches once and dose the rest at set height.

[SeanP]

Nice work the video as well!

[tnbndr]

So, can you explain the process to do the first, just dimples?
Are you just putting nodes in the drawing? Why does it not penetrate?

[msimpson99]

@steel35
The actual cuts don't touch off. I can do that if I want to mix pilots with other larger cuts. I also have the ability to touch off manually, which is what I did for the second set of cuts. I actually did it in the first as well, I didn't get a vid of it. I could also play with the timing more to cut holes faster. I would also have to tweak the post processor I am using.

@tnbndr
The process is actually the same for both, The only difference is in the second set I am waiting for "Arc Transfer" on the second set of cuts. This actually takes few ms and in thin materials, it would be hard to make dimples this way. By the time the arc is transferred to the base metal and cut amperage actually starts, you already have a small pierce. For this reason, I added 100 more ms to the pierce. For the dimples, since I am not having to wait for the "Arc Transfer" signal, I can immediately (well almost) stop the torch.

Using the "Arc Transfer"/"Arc OK" signal requires a little more to get set up and working. I did a lot of research and in some places I have seen is stated that Mach3 automatically will wait for the signal if certain things are turned on. I have found this not to be the case, I suspect they have macros running that they don't know about.

First I had to rewrite my M03.m1s script to handle waiting for the signal. Then you have the wiring. Since the signal is simply a relay closure. You have to have to pull the signal low or high depending on the signal level you have set in your config. Note I am using a G540 and have to pull them up or down with a 1K resistor. Some breakout boards, (I have a couple) will pull them one way or another.

I plan on doing a web page on adding the "Arc Transfer" signal to my G540 setup"

I use Corel Draw to make drawing, then import into SheetCam. I then use the drill operation to move and fire the torch.

[exapprentice]

msimpson99

some very good work and experimentation, I second tnbndr above asking for an explanation on how you are doing this

What Post processor are you using, what changes to wiring, what settings etc, etc and so on and of course how is it all done

really interested in learning this potential feature for future use

[msimpson99]

Doing the dimples does not require any macros. However, you need to do two things:
1. Turn off THC and the machines ability to look for the "Arc Transfer" signal.
2. Prefire the torch before starting your dimples. If the hose is not already pressurized, The first dimple will most likely blow through. Note that on systems where the air solenoid is t the end of the torch can probably ignore this.

If you cant turn off your systems ability to look for the "Arc Transfer", you probably wont be able to do the dimples, as just waiting for the signal will most likely blow through 1/8" and below. When doing the dimples the arc never transfers anyway. Its the pilot arc that is creating the dimple.

[msimpson99]

I just did a write up on adding the Arc Transfer signal to a Plasma CNC. Please note this for use with a CNC without a THC.
http://www.kronosrobotics.com/wiring-cn ... fer-signal