CNC Interface and Torch Voltage Capture

[SeanMurphy265]

do you have the THC enabled in MACH3? I would think its similar MACH3 setup as the one I use http://www.ebay.com/itm/Proffessiona...item27ccdd2789

Although when I checked max cl mode, mine went nuts!!!!

[Rambozo]

You will need to give it room to work in, so the minimum height needs to be lower than the expected cutting height. Also be sure if you are using soft limits, that they will also allow the motion you need. I can understand not wanting the torch to slam into the work while you are debugging, but if the THC is going to work it has to have the room to do so. How flat is your test metal, and how well aligned to the X and Y axis? If you know the area you are cutting in is flat, and aligned, you can set your soft limit to around .010" off the plate and know that your torch won't hit it. If that passes then, you could shim up your plate to a slight angle and confirm that the torch can follow it. You could also run with the torch off, and feed your device with a variable power supply to confirm that it behaves as desired.

[EmptyNester]

You will need to give it room to work in, so the minimum height needs to be lower than the expected cutting height. Also be sure if you are using soft limits, that they will also allow the motion you need. I can understand not wanting the torch to slam into the work while you are debugging, but if the THC is going to work it has to have the room to do so. How flat is your test metal, and how well aligned to the X and Y axis? If you know the area you are cutting in is flat, and aligned, you can set your soft limit to around .010" off the plate and know that your torch won't hit it. If that passes then, you could shim up your plate to a slight angle and confirm that the torch can follow it. You could also run with the torch off, and feed your device with a variable power supply to confirm that it behaves as desired.

Ram - I still have a lot to learn about.... Am I right in assuming that the soft limits you refer to are in Mach? I didn't expressly set any.

Is it safe to assume that Mach will never allow the THC to drive the torch lower than programmed in G-code? (That seems to be what I'm seeing.) If that's the case, how do you deal with the time it takes the voltage to stabilize after the pierce? (It looks like it takes about 800 or 900 ms. for the torch voltage to "stabilize" after I get the "arc good" signal.) It seems like if you set the cut height too low, you could strike before the THC cuts in.

[Rambozo]

Sounds good. Mach will not let the torch go below the soft limits set in the machine setup. The g-code is not really checked for any other limitations and if you tell it to slam into the part and have no soft limits set, it will go ahead and do that. This is because there are a bunch of ways you can offset the positions, so even the DRO will not be telling you the real position. There are the machine coordinates, and the part coordinates and Mach allows a bunch of other offsets for doing multiple parts or fixture offsets. The soft limits look at the actual machine positions and will trigger an e-stop if you hit them. It is a good practice to set them up as a safety. You can also have hard limit switches, but they only tend to protect X and Y. Safe Z min height is too variable to set with a hardware switch, because it will be different for each thickness of material. At least with a plasma you don't usually have to worry about vices and fixtures. There is a macro in mach that will do the touch off from the plate to set the Z offset and you can have that set as a soft limit at the same time. It would be nice to see that voltage graph with the Z axis position on it as well. I don't understand the time scale, is the 0 at 73 really at 500ms? How long is the entire trace?

[EmptyNester]

It would be nice to see that voltage graph with the Z axis position on it as well. I don't understand the time scale, is the 0 at 73 really at 500ms? How long is the entire trace?

Since this isn't yet tied into the PC and Mach, I can't get the Z-axis.

The X axis is the sample number. I think that the 73rd sample was at 500 ms, so I just divided 500 by 73 to get an average 7 ms. sample time. (Now, I'm not sure if that is exactly right, but I have some newer, better captures to analyze.

[EmptyNester]

do you have the THC enabled in MACH3? I would think its similar MACH3 setup as the one I use http://www.ebay.com/itm/Proffessiona...item27ccdd2789

Although when I checked max cl mode, mine went nuts!!!!

I do have the THC enabled in Mach. I have the option to follow the torch moves without THC on. All the THC option does is stop the system if the arc is lost.

I looked at the setting link you gave, thanks. I'm good with all the settings. I don't have the MaxNC mode set, that appears to be for mills. I do want to jump on the sheet cam support boards to see what I can learn.