Saving position at close into memory

[vw_chuck]

Why is it that Acorn can't save it's position into memory at shutdown so that it knows where it is at on startup? Could this feature be added somehow? It is a real pain to have to zero the x axis on my lathe at startup every time.

[martyscncgarage]

Why is it that Acorn can't save it's position into memory at shutdown so that it knows where it is at on startup? Could this feature be added somehow? It is a real pain to have to zero the x axis on my lathe at startup every time.

No practical way that I know of to accomplish that.
If you had a method to precisely home the axis, that would be accomplished for you when you home the machine.
Index pulse on an encoder or something similar....

How do you home the machine now? What kind of switches do you have on each axis.
Proximity sensors and optical sensors are another way to home the machine more precisely than a mechanical switch.

[vw_chuck]

Marty. Homing is not a precise action. It is repeatable to maybe .005 in I am guessing. If the board had memory and you didn't move either axis it could start back up in the same position as when it stopped and you wouldn't have to do any steps for it to figure out where each axis is at. This would allow you to continue making the same part you where making yesterday with no setup time. It is strange that they didn't think some eeprom memory would be useful on this board??

[martyscncgarage]

Marty. Homing is not a precise action. It is repeatable to maybe .005 in I am guessing. If the board had memory and you didn't move either axis it could start back up in the same position as when it stopped and you wouldn't have to do any steps for it to figure out where each axis is at. This would allow you to continue making the same part you where making yesterday with no setup time. It is strange that they didn't think some eeprom memory would be useful on this board??

Like I said, if you can precisely home the machine, the previous part zeros are saved and the previous program can be loaded. (or optionally remembered)
Then your offsets should be accurate.

What you are saying is that YOUR particular homing routine is not accurate? Your switches your machine homes to is giving you .005" repeatability.
So you need to improve that with better switches or a drive like DMM DYN2 that will output its Z index pulse. That way, you home to mechanical switch to get in the ball park and then the control will hunt for the Index pulse, that is precise provided the rest of the machine mechanics are as precise.

[Muzzer]

My "other" machine which uses a different controller supports absolute encoders, so the machine knows where is when it wakes up. The encoders have a button cell to keep them alive when the power is off. I don't have them on my machine but it's not rocket science or particularly unusual. But clearly Centroid have chosen not to go this route.

[martyscncgarage]

My "other" machine which uses a different controller supports absolute encoders, so the machine knows where is when it wakes up. The encoders have a button cell to keep them alive when the power is off. I don't have them on my machine but it's not rocket science or particularly unusual. But clearly Centroid have chosen not to go this route.

You will not get this feature in an entry level motion controller like Acorn.
But it is attainable with a little work as I previously mentioned.

Marty

[martyscncgarage]

The way I do it, is I use a magnet embedded in the ballscrew pulley, and use a hall effect sensor. You can home to a mechanical switch and then have the control hunt for the magnet. Its NOT AS precise as a marker pulse but its pretty darn close for most hobby work.
Of course, the pulley must be shielded from swarf. A flag and optical sensor is another way to do it.

Marty

Example: