tool not clearing top

[Workinforwood]

I am having a problem where the tool goes crazy. It was working, but I've been playing a bit with the settings because I could not physically see the depth, the Z was not showing it even though it was there.  Now the Z is showing the depth and it is the correct depth on the first pass at least.  I have 4 passes to do.  The machine ran the entire first pass perfect. When it started over at the beginning, the first pocket went perfect. Then it jumped to second pocket and it went deeper than in the first pocket..that's where the trouble began. Then it came up but did not come up high enough, probably because it was extra deep in second pocket, it shot over to 3 pocket scoring across the top of the piece ruining it and tried to go triple deep, busting the bit.  I know for sure, the programming is good. I have had a successful cutting. I know for sure the a axis is tuned and the z axis is tuned and the x axis is tuned perfect.

My guesses of the problem might lay in one or both of these areas.

Safe Z setting perhaps.

Says allow safe z, no
safe z machine coordinates yes
safe z work coordinates no
safe z incremental rise no
safe z is zero
go safe z when stop button hit, no

Toolpath settings

Yes, 3d compass
Machine boundries yes
tool position yes  <<<since checking this box is when the z axis reading started to display I think
Axis rotation is checked X axis
A rotations enabled is yes
use radius feedrate is yes, and in settings page the radius of the rod is entered correctly.

[budman68]

Then it jumped to second pocket and it went deeper than in the first pocket..that's where the trouble began. Then it came up but did not come up high enough, probably because it was extra deep in second pocket, it shot over to 3 pocket scoring across the top of the piece ruining it and tried to go triple deep, busting the bit.

Hi, I like to try to look at the easy user mistakes first (how do you think I got this way?   ).

Did it show going deeper on the Z DRO ? I've had this happen where the DRO was correct but the cutter sucked/pulled out of the collet and therefore was lower in Z height. Had you checked the Z height of the cutter after this run?

Dave  

[ger21]

Sounds like your Z axis is losing position and getting progressively deeper. Try lowering your acceleration settings by 25-50% for the Z axis.

[Workinforwood]

Do my posted setting look correct?

The tool did not suck out at all. The machine said it was at .275 on the second pass the entire time. The Z axis certainly was getting progressively deeper even though it said on the screen it was constant, and only did this on layer 2 not layer 1.  I can certainly try lowering the acceleration setting on the Z. I will do that. I can change the toolpath and safe Z setting too if you guys think any of that is wrong.  I can't remember the setting exactly as to what it was on the successful one, I do not think "A rotations enabled" was checked as a yes.

I probably have to wait till tomorrow to reload, as all my bits are trashed but I do have more on order coming real soon. Last 5 attempts have ended pretty much like this. It's a little frustrating, seeing it go from failure to success and then back to failure.

[Tweakie.CNC]

Could it be something really simple like the tool is not properly locked into the collet and it is working it's way out during use ?

Tweakie.

[Workinforwood]

I sure wish it was as simple as the tool coming loose. I can repeat the error over and over again, happens at start of layer 2 every single time in the same place. The tool is secure, the workpiece is secure.

[RICH]

happens at start of layer 2 every single time

Nice if it's repeatable, since if you do as Gerry replied,you may see a change for the better.
At least you know where and when it is happening.
Post the gcode file and you xml.
RICH

[Workinforwood]

I'd be happy to do so, how do I upload the NC file?

[RICH]

Click the Preview button, when the screen refreshes click the Additional Options button, the click the Browse button to select the file you want to post.
RICH

[Workinforwood]

ok, sounds good.  The file is .5 mm flat mill bit, .3125 radius <.625 diameter rod>

I tried cutting again with z axis reduced by 50%.  I only made it 80% through layer one.  Then the machine stopped rotating. It was moving the numbers for rotations, but not actually rotating, when the rotation numbers would stop, then x would kick in and it would go across, then do the a rotation again but not physically moving, then x would move across again, over and over again.

I checked diagnostics, had yellow home light on.  I went to inputs and checked off A home output. Light went away.  I jogged bit up.  I jogged A, it won't move up.  I jogged a down, moves down fine.  I sped up jog rate.  I can jog down the a axis all the way around and keep going.  Then I can jog it all the way back up around until it gets to 315 degree mark, then it won't go more.  It will go all the way around one way but not the other. I checked homing limits, A is set at 9999, so that looks good to me, kinda says to me there is no limit on A. But A is acting like it's at the end.   If I jog Down the A all the way around and keep going, so lets say 500 degrees.  I can jog it back up 500 degrees until it gets to that 315 point and then it's stuck.  Makes me wonder, is there a limit as to how many rotations the A can go physically inside the unit?  Like it's got a worm gear inside that is at the end, and so I have to just jog it back a couple full revolutions to get that gear in the middle?  Makes sense but makes no sense to me at all, I would think the A could rotate in either direction indefinitely.