Home location different every day - Lathe

Hey guys,

I have a home switch on the X axis of my lathe, it's currently a mechanical switch (But I'm hoping that's the problem here so I can change it and fix it)

But every day when I go to use my lathe, the home location will change, could be 0.05mm or 1mm difference every day.

This is a problem on the X axis because it means I need to basically set it up and tell it where the centre of the spindle is every time I want to use it, meaning a 2 minute part takes 15 minutes due to the setup. So I'll have to change the tool offsets every day. Is this a normal procedure, or should the home location stay the same every day?

I thought it could be due to inaccuracies within the mechanical switch, or if a slight (and annoying) variation in home distance is normal.

thanks

I should also add that I've checked this with a DTI. If I home it several times sometimes it'll go back to 0, sometimes it'll be 0.5mm out so this is why it leads me to believe the switch is the problem.

Would a hall effect sensor make a better switch, or something else?

Is this a stepper-based system?

I wonder if your final move to home is too fast, and you are stalling the motor (this would be a pretty random effect).

If you set the latch velocity _really_ slow you should be able to watch for the point at which the switch triggers on the DTI.

I use proximity switches for all my homes and limits and they work pretty well (but I also use resolvers / encoders so can use the index for 100% accurate home positions too).

One time when my lathe was acting random is turned out that the pulley was loose...

Yeah it's a stepper based system with a direct connection to the ball screws. I.e no pulleys of any kind.

I'll try slowing down the home search to see if that makes a difference