Touch-off plate for CNC router?


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    Question Touch-off plate for CNC router?

    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.

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    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



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    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.



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    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?



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    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



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    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



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    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



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    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.



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    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

    http://chuckscnc.blogspot.com/


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    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.



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    Quote Originally Posted by chazmtu View Post
    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



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    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.

    http://chuckscnc.blogspot.com/


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    If you need help with classicladder, I might be able to help.
    I would think something like:
    check for MDI mode, and start touch off button are true
    if true sent bit pin true for MDI comand - rapid to touch off position
    wait for emc idle pin true then set pin for MDI command probe
    I'm not sure how the probe command works, if it sets an offset or changes home or if it just triggers and you have to do the rest. But you get the idea.
    John programs ladder too and maintains the EMC docs so he may comment here.

    Chris



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    The O codes are for in your g code file. Are you sure the quote from the Integrators manual is correct? It should say for less complicated tasks....

    John



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    I'll have to install classic ladder to try it out. It sounds a little over my head though. I might save it for my last resort. All the probe move does is move til it hits something and record its position. What I want to do is, jog to where I want my x,y origin to be > set up my touch off plate > press a button > and whalla! my coordinates are set and all I have to do is start my program.

    I double checked the integrators manual and it says, "Sometimes the user wants to add more complicated tasks to be performed by the activation of a
    HAL pin. This is possible using the following MDI commands scheme"
    That's why I expected something more customizable like running a few lines of g code or logic functions.

    As for the O codes, I thought they were used on a line by themselves. So they're used in place of a value in a G code line instead? How do you think I could use that to squeeze two lines of g code from one MDI command? Calling a file seems like my best bet. I'll try running a simple o code statement tonight just to see if I can get one to work.

    As an alternative, would the hal file accept if then statements? I'm a little fuzzy on weather or not it flows like a regular programming language, or does it just keep track of pin connections? whew.. My laptop battery just died and this is still here. Thank you vista. On a second glance, is that what ladder logic is for, to add logic flow to a list of connections?

    Thanks for being patient with me, this is a lot to take in. And to think, all I want to do is get one button to run two lines of g code so I don't have to press two buttons.

    http://chuckscnc.blogspot.com/


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    your touch off plate is like a probe is it not? When the tool touches it it makes a connection/sends a signal? Then you could position manually X and Y and put Z just above your touch off plate. press the button to probe down in Z it records the trigger (and stops) then use that number to set Z (plus the plate thickness). Am I on the right track? You could try this manually in MDI right now to make sure it works id it does then we can make it work with a button for sure. It's the command to set Z by the recorded numbers that I am not sure of - I will have to look it up....



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    Yeah, you got it. I'm not using the recorded value (parameters 5061-5069 save the position)from the touch probe though because I want to set the Z height to .25in every time. It takes 2 lines of code to run. The first one is the probe move (G38.2) and the second should reset any coordinates I like using (G10). The probe move works just fine but the second one resets my Z coordinate different than my given value. I probably missed something simple like an offset on the second one. Here's my code:

    G38.2 Z-3 F16
    G10 L2 P1 Z0.25

    It would be nice to be able to run more in case I wanted to add on later.

    http://chuckscnc.blogspot.com/


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    When you jog to where you want the XY origin to be you do a touch off at that point. I'm not an expert but when you move over to your touch off plate you are setting the tool length offset based on the probe input... These sound like two different things to me.

    John



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    seems to me G92 z(plate thickness) would set the z cord. to zero for the bottom of the plate that the probe was stopped at. You would have to move the probe very slowly so it does not move much after triggering. If you use cutter compensation you could change the tool offset similarity. There is a sample for probing tool offsets under nc_file .
    Again food for thought I have not tried this...



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    Yes (if I understand this right) G10 sets an offset (the .25) on top of the existing offset of coordinate system(g54 in your case), Whatever that maybe.
    G92 sets the the physical position you in now, of the current coordinate system (g54? for you) to whatever you specify on the line.
    so G92 z .250 should do it.
    John he is using the probe command just to stop at the top of his plate not to measure anything.



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Touch-off plate for CNC router?

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Touch-off plate for CNC router?