Touch-off plate for CNC router?

[CanSir]

I've been playing with EMC2 while waiting for my CNC parts to arrive so I'm very new to EMC2, but from the sounds of it, it is very customizable. One of the cool add-ons I've come across for a CNC router is a touch off plate to accurately adjust the z height for the current tool bit.

I can find information on using a touch-off plate with Mach3 and how to add a custom screen for that application, but I haven't seen anything specific on how to accomplish the same thing using EMC2. The closest I've come across is adding probe functionality to EMC2.

Has anyone configured/customized EMC2 to use a touch-off plate? Care to share how it's done?

Regards,

Dean.

[samco]

The probe is what you want..

There is a sample g-code program showing how to set tool lengths.

http://cvs.linuxcnc.org/cvs/emc2/nc_...ngth-probe.ngc

I have used this for making circuit boards. Once the first tool length is known - the rest are referenced from that.

(I use a microswitch)

sam

[CanSir]

Thanks for the link! It's going to take me a little while to wrap my head around the g-codes and whatnot, but it does look like it'll do what I was asking.

[CanSir]

I've been looking over that code and I'm starting to understand it, but the implementation of it still leaves me puzzled. I use the AXIS interface and I can only see two ways to implement that touch-off gcode. One way would be to type in those gcodes line by line on the MDI interface and the other would be, even before launching EMC2, to do a search on the G-code file and insert that code snippet after every toolchange command. Is there a cleaner way?

I was envisioning the following:
I secure my workpiece to the table
I lay my touch-pad (the thickness of which is already known to EMC) on top of the material
I jog the router to be above the touch-pad
I hit a button in AXIS and it magically lowers the router until the bit touches the pad
Viola! EMC is configured to cut to the exact depth specified in my job

When prompted to do a tool change, it would be nice if I could repeat the above steps and afterwards have the router return to it's last XYZ position before signaling that the bit change is complete.

I see lots of examples on interfacing with hardware, but nothing showing how I can add a button onscreen that executes some G-Code commands. Does anybody have some examples of using python scripts within EMC?

[BillTodd]

Hi Cansir,

I found this thread after looking to do the exactly the same thing.

You might be able to get the G-code post processor of your CAM package to insert the measuring code automatically after each tool change (I'm using SheetCAM which has this type of option in the post processor).

All you'd have to do then is set the probe switch height to match the surface of your material at the start of the job. The machine could probe the tools after they're changed. (At least this is how I think it should work )

Bill

[CanSir]

I've made some progress by using bit's and pieces out of several how-to articles on the emc wiki site:
http://wiki.linuxcnc.org/cgi-bin/emc...cKnowledgeBase

I've managed to create a virtual control panel in AXIS and re-configure HAL to use my tool change code instead of the supplied manual tool change code. Unlike some other people, I discovered that I really do need to connect my cutter to ground in order to get a reliable "touch" signal. I believe I am 90% of the way there and just need to put it all together for a real test.

When I get it all working, I will create a knowledge base article on that linux wiki site to share what I've come up with.

I never considered looking into my CAM program to see how it could help. Probably just need to add code to the post-processor file for the Tx command?

- Dean

[Big John T]

As I understand it you have the tool probe in a certain spot and in your G code you move over and do a probe move to find the length of the tool. You can then do an offset from that. You have to hook up the probe to the probe input and define that. If you used stepconf to set up then in the parallel port page you can define which pin is Probe In.

If you need more help just holler.

John

[Zig]

I too am looking at tool changer for my gantry router.

I envisage a linar tool changer rack along an adge of the table.

The g code file ( job file) is to incorporate some code to controll the action of the spindle and to instruct it to go over to the rack and pick up tools from the rack.

The tools are 1/8" shank bits with distance rings held in cups.

I am yet to build up the tool rack and position it in its place, however the code seems to be working.

More as it becomes available.

[chazmtu]

I know this thread has been silent for a while, but I've been trying to do the same thing as cansir using this tutorial. I'm new to EMC and just starting to learn about the interactions between files.
Can someone help me figure out how to get a VCP button to run multiple lines of gcode? So far I have a button controlling a probe move for my touch off plate but can only run one line of code. I followed the tutorial then renamed the button and changed the gcode line. I'm pretty sure that I have to change my postgui.hal file line for that button. Right now it reads:

net remote-z-axis-touchoff halui.mdi-command-00 <= pyvcp.z-axis-touchoff

Here's what I know. z-axis-touchoff is my button variable. This "<= pyvcp.z-axis-touchoff" connects my button to the preceding command. and "mdi-command-00" lets me run one mdi command from my .ini file. What do the net and remote commands do? What do I replace "mdi-command-00" so that I can call a file or sub section in my .ini file with the code? Any help would be greatly appreciated.

Chuck

[chester88]

I was thinking about this. HAL-UI allows you to have MDI commands that are invoked by HAL pins. If you set up a few MDI commands on pins then had classicladder run these pins in order (you would have a button to start the process) , you may be able to do what you want. All theory of course I have not tried this. Food for thought.

[Big John T]

Originally Posted by chazmtu I know this thread has been silent for a while, but I've been trying to do the same thing as cansir using this tutorial. I'm new to EMC and just starting to learn about the interactions between files. Can someone help me figure out how to get a VCP button to run multiple lines of gcode? So far I have a button controlling a probe move for my touch off plate but can only run one line of code. I followed the tutorial then renamed the button and changed the gcode line. I'm pretty sure that I have to change my postgui.hal file line for that button. Right now it reads: net remote-z-axis-touchoff halui.mdi-command-00 <= pyvcp.z-axis-touchoff Here's what I know. z-axis-touchoff is my button variable. This "<= pyvcp.z-axis-touchoff" connects my button to the preceding command. and "mdi-command-00" lets me run one mdi command from my .ini file. What do the net and remote commands do? What do I replace "mdi-command-00" so that I can call a file or sub section in my .ini file with the code? Any help would be greatly appreciated. Chuck

Chuck the net part creates the connection, the signal name is remote-z-axis-touchoff, the <= are only to make it more readable. I'm not sure if you can call files from the mdi. Only valid mdi commands work. If your really wanting to call a subroutine look a the "O" codes.

John

[chazmtu]

Hi John,

Thanks for the clarification. I have looked into using the O codes for the mdi command but I got errors because they were not recognized as a valid command. Maybe because it doesn't know where to look for a subroutine? What I don't understand is, the integrator manual states that the mdi command function is for more "complicated tasks", but running one line of gcode doesn't seem all that complicated or terribly useful. Unfortunately, I only found the one example. Chester88 might be onto something though. I'll have to look into ladder commands. I'm not much of a programmer.