A Cunning Plan For Accurate Homing With Mach 3?

[m_c]

It's been done.

Have a read of this thread - http://www.machsupport.com/forum/ind...c,18323.0.html

Just had a quick scan, and look at the exchanges between me and Dickeybird starting around page 3. He implemented it on his lathe.

[magicniner]

It's been done.
.

I hadn't seen it used before but given that I based this on the fact that closed loop servo systems do a similar thing it's not exactly a surprise.
What is a surprise is that it's not in a sticky on most home CNC sites and that there are so many homing switch queries where it doesn't get a mention.
But hey, the next time I have a thought that might help instead of posting it with a clear title I'll keep it to myself ;-)

[m_c]

The thing is, it's not really needed provided you pick good quality homing switches, and mount and actuate them sensibly.

If you have a read of the thread, those of us who fitted good quality optos, had excellent repeatability. Certainly in the couple years I had that lathe, homing accuracy was never a problem. I could re-home in the middle of a job, and accuracy was more than good enough, but it do show up how much flex there was. Even on my bigger lathe that uses the servo index pulse for homing, recutting something after homing will still remove more material, due to flex, not inaccurate homing.

[Boyan Silyavski]

I have done some experiments on homing and best real life repeatability was achieved when the switches were properly mounted so that they were perpendicular to metal that activates them.

From reading in forums it seems expensive vs cheap switch is not really important when properly done. Surprisingly cheap mechanical micro switches seem to give best results.
At least initially.

I don't see something better than an absolute encoder though, speaking for a diy machine. Or a hard stop