Using a photocell as a carriage stop

[The Landshark]

The storebro lathe i'm rebuilding isnt equipped with a carriage stop,
i was thinking of mounting a photocell on a movable bracket attached to some round stock running parallel to the ways and the associated reflector mounted to the rear of the saddle,
the photocell would be wired to declutch the motor drive when the beam makes contact with the reflector.
would swarf be enough of a problem to falsley trip the cell, obviously the reflector would be better at the right hand side of the saddle.
Has anyone else tried this and how did it work?

 

[toolman]

I don't know anyone who has anything like this, but I would love to hear how it works for you. Best of luck to you!

 

[Pmedic828]

Made a similar one by using micro switch and it worked great - updated to use hall effect sensor so your photocell should work also.

 

[DMS]

Rather than a photocell, I would recommend a slotted interrupter. Less chance of room light effecting it. If you arrange for the slot to be oriented down, then swarf should not be much of an issue. I have a similar setup on my CNC mill for the home and limit switches.

 

[Marco Bernardini]

A carriage stop must have at least a 0.01 mm precision and be repeatable.
I don't know if a photocell can do that (but you can try).

 

[DMS]

I was getting within 0.001" (0.025mm) repeatability on my machine. I didn't try to tweak it beyond that. Quite satisfied with it. With just a plain photocell I think you would be hard pressed to get that close without a bunch of additional complexity (both mechanical and electrical)

 

[The Landshark]

i'm not hugely worried about precision stopping, i'm more worried about running the tool into the chuck, maybe i could have phrased the question better,
i was also thinking about using a hall sensor, but i think swarf would be more of a problem here

 

[Marco Bernardini]

Then something with the same scope of a train station buffer:



(source)

At this point a passive mechanical stop would be safer, IMHO.

 

[John Hasler]

Then something with the same scope of a train station buffer:

At this point a passive mechanical stop would be safer, IMHO.

Not necessarily. If you stop the motor all motion stops. If you forcibly stop the carriage and the motor keeps running something may break.

 

[Marco Bernardini]

Not necessarily. If you stop the motor all motion stops. If you forcibly stop the carriage and the motor keeps running something may break.

Good point: I forgot on lathes there is a single motor moving everything.