Closer Centering

[zeeway]

I am not sure my latest mod is an original idea, but here it is…

When I lose center during a project, I must rehome my machine to reestablish center. This seems to take forever (maybe two minutes).
So to speed up things, I have embedded several ¾ inch copper pipe caps in my spoil board, wired back to the machine control (the probe input on the Gecko 540). I can now use a centering routing built into Mach 3, to locate center at any of those caps. One of these caps is located at the table center, and the others are at the bottom center, bottom left corner, and left center.

Much faster.

And yes, when skimming the spoilboard, my cutter can skim off the edges of the copper cap without a problem, also.

Angie

[dealguy11]

Interesting idea. Why are you losing center in the first place? I can't remember having that problem, except possibly in the case of lost steps from some dumb error on my part.

[zeeway]

Occasionally my machine runs into clamps...or somehow a wrong button is pushed...must be gremlins...

Angie

[Ms Wolffie]

Sounds VERY familiar

[rscrawford]

Why not just add some limit switches to your machine? One on each axis, and you can use them to set a permanent machine home that is repeatable. Every time I turn on my machine, I 'home' it by touching off on all 3 switches and then it knows exactly where it is.

[sawmiller]

would still be a good thing to incorporate into a jig board

[zeeway]

I do have limit switches on my machine...but moving all the way to machine home takes a while (see above), and I am impatient.

Angie

[rscrawford]

Ahh, I missed that part of your original post. Why does it take so long to return to your machine home? My 4x8 machine takes less than 5 seconds to return home from any position on the table, then I calibrate it (which takes about 10 seconds - I never start the calibration from anywhere but machine home or it takes forever!).

Your method would work VERY well for finding the centre of a jig, so you don't have to index the jigs as accurately.

I need to check if WinCNC has such a function. I've read the manual multiple times and don't remember seeing anything similar in there.

[zeeway]

I have used the centering cap on some of my jigs, and indeed that does work well.

As for the slow speed back to the homing switches, I always thought the slow speed was to improve accuracy. I thought the inertia from a faster speed may cause an overshoot on the switches - my switches are non-contact magnetic (Hall effect) switches. But, duh, I have never checked that. So, thanks, for that inspiration. I will play with the script that establishes that speed, and check accuracy.

Angie

Hey Russell,

I just reread your post...sounds like you home your machine, and then...recalibrate it. My machine does both functions simultaneously. Would you describe more about your process? Thanks.

[Adrian]

The homing on my machine goes at a reasonably fast speed until the switches (hall effect as well) activate at which point it backs off a couple of inches and then does it again at a much slower speed.

[rscrawford]

I have used the centering cap on some of my jigs, and indeed that does work well.

As for the slow speed back to the homing switches, I always thought the slow speed was to improve accuracy. I thought the inertia from a faster speed may cause an overshoot on the switches - my switches are non-contact magnetic (Hall effect) switches. But, duh, I have never checked that. So, thanks, for that inspiration. I will play with the script that establishes that speed, and check accuracy.

Angie

Hey Russell,

I just reread your post...sounds like you home your machine, and then...recalibrate it. My machine does both functions simultaneously. Would you describe more about your process? Thanks.

Just a little mix-up in terminology I think. When I calibrate my machine (some call it 'homing' or 'initialize') my speeds are set fairly slow, it touches off the switch and backs off an inch and then REALLY slows down. If I'm in the middle of the table and I decide to calibrate, it takes FOREVER. So I take my spindle to the machine home position (which it does at 1200ipm), THEN I calibrate off the switches. This way I'm only traveling an inch or so on each axis at the slower speed.

[zeeway]

Okay...now I understand.

Thanks,
Angie