Z Location - Where is the tool tip?

[brendanjerwin]

Hi all. I'm building a CNC conversion for a X2 but have no experience in CNC or machining in general. Learning a lot from the internet but I'm unable to wrap my mind around a couple of things.

Here is one of them:

How does the CNC software know where the end of the tool is? It seems to me that the length of the end mill would vary from tool to tool which would mean that the tip would vary every time I change tools.

[philbur]

Hi,

down load this manual and read section 7.3.

http://www.machsupport.com/documentation/Mach2-6-11.pdf

Basically you tell the software the length of each tool, either directly in a tool table or by "touching" each tool, when mounted, to a known refrerence point.

Phil

Originally Posted by brendanjerwin Hi all. I'm building a CNC conversion for a X2 but have no experience in CNC or machining in general. Learning a lot from the internet but I'm unable to wrap my mind around a couple of things. Here is one of them: How does the CNC software know where the end of the tool is? It seems to me that the length of the end mill would vary from tool to tool which would mean that the tip would vary every time I change tools.

[mikkojay]

I use mach3 for my mill, and it has a button that allows you to customize the auto tool zero function.
Here is a video I put on youtube that shows it working:

You Tube

You Tube

Hope that helps, Mike

[brendanjerwin]

Very cool. thx both of you. Documentation and Video to back it up. Now I need to make sure EMC2 can support that kind of magic.

[Rodm1954]

In the simplest form you can put a piece of thin paper (tobacco rolling paper is perfect) on the workpiece and move the Z axis down until your bit grips the paper but does not cut through. Moving the paper as you move the Z axis down helps you feel when it makes contact.
In the absence of other more sophisitaced measuring devices this will be your easiest choice.
A simple, cheap and accurate Z zeroing method is explained here.
Another Aussie Auto Tool Zero Setter

[bobkeyes]

Originally Posted by mikkojay I use mach3 for my mill, and it has a button that allows you to customize the auto tool zero function. Here is a video I put on youtube that shows it working: http://youtube.com/watch?v=jGey4aVXBm0 Hope that helps, Mike

I also use Mach3. I have the latest beta from the site. The auto tool function says, "Not Yet Implemented". How did you get it to work??

Thanks in advance.

Bob Keyes (new member)

[mikkojay]

Hey Bob,
You need to go in and edit the script that is associated with that particular button. If you go in and look at the script: from the menu --> operator/edit button script (sorry, from memory), then click on that button when it starts blinking, you will see that the default script is something to the effect of a message that says just what you are seeing. I can post a copy of the script that I am using when I get home tonight. Keep in mind that this should be used as a starting point, because my script is custom tailored to my machine. That's why they let you write a custom script that fires when the button is pressed- every one has a different machine & needs. You must be VERY careful messing with this script, because the machine will do exactly what you tell it to. Tell it something strange in the script, and the machine will be more than happy to oblige by crashing your tool into the table!
-Mike

[bobkeyes]

That would be great Mike. I WILL be careful. In fact, I'm running this without the motors attached to the machine. Kind of a simulation of sorts. That way if it doesn't work right-no harm.

Thanks again for your help.

[BrassBuilder]

Hey Mike,
What exactly is that auto tool zero sensor? Is it something that you built? I searched around and I cannot find anything on it.
Thanks
Mike

[mikkojay]

Attached is the script I am using.
If it looks foreign, try Googling some of the function names like SetDRO.
-Mike

[mikkojay]

My sensor is a piece of solid copper pcb.
I sandwiched it on some foam from a foam paint brush. I did this so that (while I experimented with the script), if I screwed up and sent the tool the wrong direction, it would smush the foam down instead of snapping my tool in half. This actually happened once, so I am glad I did- and had my hand on the e-stop button! Now that I have it working right, I might ditch the foam and just use a piece of solid copper pcb by itself.
The pcb has a single wire soldered to it, the end of which is attached to a parallel input pin. This pin is designated in the ports/pins config as the probe pin.
-Mike

[bobkeyes]

Gee, thanks Mike. I REALLY appreciate it a lot. This will give me an idea of what I can do and educate me on VB scripts as well.

Thanks again.