# Thread: Using machine coords to help speed up a tool change?

1. ## Using machine coords to help speed up a tool change?

Hiya,

One thing that's wearing me out with my self build CNC - certainly with is with intricate parts - is the time overhead for a tool change.

Basically, when prompted for a tool change, becuase I don't have sufficient Z clearance (temporarily, my Z 'reach' small!), I need to move the table suffiicently in the X & Y direction to clear the part - I can then lower the cutter out of the collet.

I'm doing this 'table move' manually at the moment & even though I'm using a contour shuttle, the constant jogging about makes me feel more like I'm playing some form of video game rather than operating a CNC machine!

If I understand it correctly, machine coords can be used to take the spindle to a set, repeatable location - this sounds perfect, for tool changes

However, when I click on the machine coords button - I can't seem to zero machine coords to zero (as seen on the the DROs)

I tried this yesterday, only to find out I'd zero the working coords - & I was half way through a cut, I don't have home switches yet, so my time was wasted!)

So...to the point - which bit am I missing to set the 0,0,0 location for machine coords?

2. Do you have home switches? You can't just arbitrarily zero the machine coordinates. You can set them in relation to your home switches using the home offset column on the homing/limits page.

3. Originally Posted by ger21
Do you have home switches? You can't just arbitrarily zero the machine coordinates. You can set them in relation to your home switches using the home offset column on the homing/limits page.
Aha...that would explain it!

I thought I could essentially have two sets of coordinates (one working & one machine) ...both independently controlled with their own zero points, but your suggesting that machine cordinates can only work with homing switches?

that's a shame - I envisaged the following wokflow.

Start up a new Mach3 work session - place the tool where I wanted (for best ease of access to the collet nut to remove the tool) set machine the machine coordinates at 0,0,0.

Load up my G-Code file, then set my working coords zero points.

Then, when a tool change is requested, flick to machine coords & goto zero - change tool, flick back to working coords...then off we go again.

I guess I'll have to fit those homing switches sloshing around in a box somewhere in my workshop!

4. Not exactly sure, but using the ref all button should zero the machine coordinates, unless you have an offset in the home offset boxes.

What you probably want to do is set up the work offsets and use those. (G54, G55, G56...)

You can also set a tool change location (settings page) and set up Mach3 to automatically go there when an M6 comes up.