Checking for lost steps.... homing switch verification?

[InspirationTool]

So, the mill homes, and finds out where it is in space.

Then you run a part.

If you then home again, Mach 3 should know where home SHOULD be. Is there a display view or program that will show you the difference of where home should be, and where Mach 3 finds it? It would be an easy way to find out if you are losing steps.

I've checked the manual, and googled around a bit, but didn't find anything.

-Jeff

[ger21]

The only way to check for lost steps is to use encoders to know your actual position. Like you said, mach knows where it should be, but has no way of knowing where the machine actually is. It just tells it where to go, but can't follow up and make sure it actually went there. There's an encoder board with a plugin to verify postion using encoders. It can actually pause your machine if it's not where it's supposed to be. www.rogersmachine.net

[InspirationTool]

Originally Posted by ger21 Like you said, mach knows where it should be, but has no way of knowing where the machine actually is. [/url]

It doesn't have any way of knowing where it is, EXCEPT for when it trips (actually, un-trips) the limit switch. I would like it to compare known to expected location (from the last home) when re-homing.

-Jeff

[ger21]

Like I said, the only way to get the "known" position is to use encoders.

You might want to use G28 to home, which will take it to a specified location before homing.

G28 X1 Y1 will move to X1 Y1 and then home. Check the manual, though, it may be G28.1. Don't remeber exactly.

[InspirationTool]

Ger, I think I'm not explaining myself clearly.

Home once using the switches. (aka Reference All)

Run a part.

Reference All again.

Mach 3 should be able to track how much it had to adjust it's known position by.

-Jeff

[ger21]

OK, now I understand. But I don't see how that would help you at all. Because if you're losing steps, then most likely you'll get different results every time. If you just want to know that you've lost steps, the fact that the parts will be wrong should tell you that.

[InspirationTool]

Originally Posted by ger21 If you just want to know that you've lost steps, the fact that the parts will be wrong should tell you that.

While that would work, when initially setting up and getting the speeds and accelerations correct, it would be a waste of time and parts.

The right solution is probably to test the speeds individually per axis with a dial indicator used to check repeat locations.

-Jeff

[Greolt]

Jeff sounds like what you are looking for is "Verify".

It is found on the MDI screen page in Mach3

What it does is do a homing sequence and return to position telling you
how much positional error you had acumulated since last homing.

Does that make sense?

Greg

[InspirationTool]

YES!



Thank you Greg!

-Jeff

[ger21]

I'll have to remember that.

[spoiledbrat]

Hate to hijack a thread, but I have a question about "verify".

When I push verify, all axis move toward the home position at a slow speed. Once they hit the switch, the respective axis moves off the switch. But the Z axis, after contacting the switch, moves even further into the switch, causing my servo drives to fault out. I hate crashing my machine. There must be another way...

Any one have any suggestions how to fix that?

[InspirationTool]

Do you get the same problem with "reference all" when you start up the machine?

If so, I had the same problem. My Z acceleration was so low that it couldn't stop fast enough after it hit the switch. Increasing the Z acceleration fixed that problem.

-Jeff