Limit / Homing switches and a software glitch

As I'm learning to use the lathe, but there's one thing I just can't understand. After powering on the machine, you can jog it all you want before referencing, but the limit switches are not utilized at all until you reference them. When jogging you can trigger the limit and nothing happens. So, it's possible to jog the machine against its mechanical limits. Why would you ever want this? Is it by design for some reason? In what scenario would you ever want to not read the switches and crash the machine into its mechanical limits?

On another note, I encountered an honest to goodness software glitch today. All of a sudden, the keyboard arrows would no longer jog the machine, but instead would increase or decrease the percentages on slider controls. A reboot did not fix it, but toggling the enable and disable check box on the settings tab did. Has anyone else encountered this?

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When you first turn on the lathe you are supposed to ref x and z so the machine can establish its home locations. If you jog without referencing you are hitting the mechanical stops and limit switches hard. Pathpilot has soft limits built in to keep it from hitting those hard stops. Ref x and z also will allow you to be more accurate with cutting and tool setup. You reference and take a test cut then you can enter the z and x values for the work and your tool settings with be on based on the tool offsets.

You keyboard jogging with the arrow keys can change based on the active window you are in. If you are in the MDI window it will not jog or if you used the slider window last with your mouse the keyboard jog will change the slider. If click your mouse in the program display window the keyboard will go back to jogging the carriage.

Good Luck !

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Originally Posted by cbyrd

When you first turn on the lathe you are supposed to ref x and z so the machine can establish its home locations. If you jog without referencing you are hitting the mechanical stops and limit switches hard.

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Exactly; I've learned this. My question is, in the software's internal programming, why not use these switches as real electromechanical limits all the time, whether they have been referenced or not? It seems like this would help prevent a crash in the positive X and Z directions if the operator forgot to reference the machine before jogging. Or, alternatively, the software could require referencing before jogging. With the current configuration, it seems entirely possible for the operator to inadvertently crash the machine into itself in the positive directions, which seems silly given that there are switches there which you would think could be used to prevent that.

Also, thanks for the tips on the mouse clicks. I didn't realize clicking in the program window activated jogging. I had been clicking on the slider, which worked for jogging previously. Strange.

My thought on this is there are no limit switches at the headstock end of the lathe. The switches do act as limit switches on what would be the tail stock side of the lathe. Given they are using a stepper servo to move the x and z axis and they do not have a closed loop system, The referencing of the x and z to the limit switches is required.

The pcnc 1100 is the same. You must reference the system so it knows where it is after an e-stop or power off.

I suppose they could add limit switches on the head stock end for the z but the limit is different depending on whether you are using a turret, gang tooling or qctp.

The limit switches are also mechanical so there is some variation on them. I have read on the forums that some are within .002" on reset and others as great as .015"

Glad the jog/mouse thing worked. I noticed it when I was using my touchscreen.

There are soft limits on the head stock side and at the bottom of carriage travel. Top side too. I don't think you will hit the physical switches before the soft limits stop you. That is after ref. Home. The head stock soft limits won't stop a crash if you have the chuck installed or if your tools stick out pretty far, like a boring bar might. Homing the machine initially and then setting G30 is the only way to start this machine.
I would also suggest that you invest in the Jog Shuttle thingy. Great little tool.
30616 - Jog Shuttle

http://www.tormach.com/uploads/image...troller_lg.jpg