OH boy Hood are you in for an edumacation. With plasma you HOME z to find teh top of the material not to establish a real Z home. There are 3 main sensing methods ohmic tip, Remote offset switch, and floating Switch on Z. AND 2 possiblities of motion with each, G28.1 and G31

Now that is with the standard Mach3 methods. THere are actually many more but that is another story.

  TP

I will be homing to the surface or rather I will be touching off the surface, whether I use that as the Home or use  G31 (M31) and have a separate home switch for fully up I am not sure at this time.
I was thinking of having Index homing on full retract, or close to it, and then using the drives homing to touch off the material by using the M31 macro.

Hood

Oh... I use floating switch...

Have a look at this table, you can use bits of the idea too.

http://m.instructables.com/id/CNC-Plasma-Table/

Rob

Thanks Rob, will have a look in a bit
Hood

Whatever you use, i would not use motor current sensing for the IHS method, unless you cut 12mm plate all day it will buckle the sheet and give bad readings for z-zero. Since tweaking my system up with an offset switch probe and increased z motor tuning, the cuts have certainly improved and I am fairly confident it can follow pretty much any warp I will see.

The current sensing method can be set to any value so can be extremely sensitive, it can be that sensitive that it is set too low and the motor doesnt even move
As an example doing the testing last night I had it set to 0.5 amps and it just took a push against the end of the pulley for it to stop, I set it to 0.1amps and it wouldn't move, it just set home where it was. So next I tried 0.3 and it just needed the slightest touch to stop it. Obviously once there is the weight of the axis and the torch I will need to find the current required for the perfect touch off but it is as easy as changing a number on the computer screen and activating the home input to test.
 Mostly I will be doing 4mm upwards and the least I am likely to cut is 1.5mm so hopefully I can set the current value in the drive so as it only needs to tickle the material

I still have the floating z setup, connected to my limits chain, i would not build without  this as its a good safety feature in case of a dive, a mag-break torch holder would probably be a good replacement though, i will be wiring my z limit to the e-stop circuit soon as the limits are ignored when doing a g28.1 and if my probe switch fails it will plant the torch heavily into the sheet, there is enough torque in my stepper/screw drive that it will not stall the motor and just keeps on going! The failure point is that it rips the delrin nut out of the z-axis body which means stripping it down to replace it.

I was thinking about having the magnetic style break away torch holder, purchased a couple of 2mm sensing Prox's for this, intending to wire them into an E-Stop chain. If the torch hits something, as I am sure it will, especially at the start of my plasma escapades, then the machine will stop and hopefully nothing will be damaged

I admire your work on this though, I love R&D work, used to de plenty of it once in the day-job, only used servo's once though and that was step/direction to the servo drive and then closed-loop with encoder/resolver on the servo motor, this was a feed system for a stamping machine.

This will be a Step/Dir setup as although I think the CSMIO/IP-A is the best controller I have used so far with Mach, I have a CSMIO-IP-S pulled from the wee lathe, so will be using it

Proma did have an upgrade version of their THC and it took over direct control of the Z motor, switching back to Mach when stopped, I nearly tried it but splurged on the MP3000 instead. I managed to get the loop response times from Proma guy and it was certainly slow, ok for cutting thick stuff but I found it failed on thin sheet due to the speed needed.

From the info I got from Denis it seems the response time of the MiniTHC is fast, what it will be like in real life is another matter but I will soon find out. If I find I don't like it I can always try the software THC that the CSMIO has inbuilt.

Hood - Seems you have the following basic options:

1) MiniTHC driving CSMIO firmware THC functionality.

Arguably the easiest to set up and use because it *should* work out-of-the-box.

2) CSMIO Analog driving plugin THC functionality.

I don't really follow CS Labs description of how this ties together.

3) MiniTHC driving your "smart servo".

From your proposals, This looks like it *should* work. The "thing" about this method of course is that you're effectively converting your MiniTHC into a standalone. Not sure how you'd do anti-dive but (as you've indicated) with properly good accel it's less of an issue anyway.

My money would be 1,3 for a quick win and 3,1 for the fun of it.

may be of interest of someone:

http://www.metalwebnews.com/howto/plasma/presentation.pdf

Is this worth pursuing or am I better just letting Mach handle the whole thing?
 The advantage I see with the THC controlling the drive direct is it cuts out the middle man (Machs Up/Dn), so it should be more responsive, but would it make much difference?

Not sure if this is a slip of the tongue key, but of course Mach3 per se is going to have nothing to do with up/down. That's going to be done by your CSMIO. So the question would then become - does the "smart" servo react any faster or slower vs the CSMIO to any degree that makes a difference? remember it's not as simple as which one's faster. Fast is good but too fast is no good at all.

OK there are good things about a fast thc and bad things about a fast thc.

A fast THC makes it much more sensitive to things like corner dive, gap dive. With a fast thc you may find yourself having to set these features based on Plate thickness. What works well with thin sheetgoods may not work well with heavy plate.

DOes the CSMIO do anti corner dive based on Mach3 settings ?  Like Mach3 would do. Does the THC do anti gap dive ?? how adjustable is it ?? Does it have a spanvolt(deadband) setting ?  Can you adjust these from on screen ??

(;-) TP

From your proposals, This looks like it *should* work. The "thing" about this method of course is that you're effectively converting your MiniTHC into a standalone. Not sure how you'd do anti-dive but (as you've indicated) with properly good accel it's less of an issue anyway.

The THC has an inbuilt Antidive, I will post the info from the manual in another post.
I am sorely tempted to try the stand alone option but probably better just starting with the basic like TP says and have the option of easy swap wired into the panel so I can test the other options when time permits.

Quote from: Hood on February 03, 2016, 06:04:27 PM

Is this worth pursuing or am I better just letting Mach handle the whole thing?
 The advantage I see with the THC controlling the drive direct is it cuts out the middle man (Machs Up/Dn), so it should be more responsive, but would it make much difference?

Not sure if this is a slip of the tongue key, but of course Mach3 per se is going to have nothing to do with up/down. That's going to be done by your CSMIO. So the question would then become - does the "smart" servo react any faster or slower vs the CSMIO to any degree that makes a difference? remember it's not as simple as which one's faster. Fast is good but too fast is no good at all.

Well it wasn't really as I am not sure how things will work. The CSMIO has its own built in software THC which should be fast but if I use the MiniTHC via the CSMIO hardware to Mach, then it introduces another delay. I don't really know how that would behave. Rob said he uses the ESS and it seems to work ok, so I would imagine the delays would be similar with the CSMIO.

OK there are good things about a fast thc and bad things about a fast thc.

A fast THC makes it much more sensitive to things like corner dive, gap dive. With a fast thc you may find yourself having to set these features based on Plate thickness. What works well with thin sheetgoods may not work well with heavy plate.

DOes the CSMIO do anti corner dive based on Mach3 settings ?  Like Mach3 would do. Does the THC do anti gap dive ?? how adjustable is it ?? Does it have a spanvolt(deadband) setting ?  Can you adjust these from on screen ??

(;-) TP

I believe whether using the inbuilt software THC in the CSMIO or just using an external one via the CSMIO then it all goes via Mach and has the same functions. That is only what I understand though, it may not be the case as I do not personally know anyone using the CSMIO for Plasma.
The MiniTHC has inbuilt Antidive and it is adjustable on the THC itself, push the knob to select the AntiDive page and turn the knob to select the sensitivity you want. Again how well it works onl;y time will tell. Details from the MiniTHC manual will be posyted in the next post.
Hood

Ok I have just copied the relevant parts from the manual regarding the AnyiDive, it is attached below.

Hood

Well it wasn't really as I am not sure how things will work. The CSMIO has its own built in software THC which should be fast but if I use the MiniTHC via the CSMIO hardware to Mach, then it introduces another delay. I don't really know how that would behave. Rob said he uses the ESS and it seems to work ok, so I would imagine the delays would be similar with the CSMIO.

I think you're maybe getting the wrong end of the stick here. THC functionality is in the controller. i.e. it's in the Parallel Port Driver OR it has to be in the external controller - Mach "proper" only controls the interface.