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Offline kolias

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Re: Strange Results
« Reply #30 on: November 18, 2009, 08:27:21 PM »
I have done a lot of work since my last post on this thread and never had a problem.

However today my luck run out. I was working on a piece, did the first trial pass with no problem and half way thru the final pass the bid went again thru the 1/2" stock and into my tabletop in the split of a second before I had a chance to hit the Estop.

Unfortunately again I did not recorded the Z DRO’s because I guess I panicked and forgot. I took a picture of my screen which shows the gcode and the DRO’s. The Z axis DRO shown is after I raised the bid to examine the damage.

Any ideas what creates this problem?

Thanks
Nicolas
Nicolas

Offline RICH

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Re: Strange Results
« Reply #31 on: November 18, 2009, 09:44:45 PM »
Nicolas,
I don't have a "specific" answer for why your machine all of sudden plunges down. It may happen for a number of reasons. I am not going to tell you to slow down / speed up/ retune ......... Instead just realize the following:

1.Not all material  ( wood  ) is the same so you need to adjust feeds and velocity based on what you are doing
and working with. No difference than if you were doing it by hand.

2. You can be missing a step. Normaly you would imediately hear it , but , because of the load router noise , you probably wouldn't hear the missed step.

3. My experience on missing steps is , two things happen, only a very small change in the axis location or it's  total loss of position and away she goes with nothing to control it except the estop.
During cutting air you can usualy just change velocity or acel leaving some headroom for cutting and thus not have a problem.  That may not be the case when cutting, as now you have introduced another parameter that can change the axis motion requirements as compared to air cutting / rapid move.
Nothing beats just cutting some scrap of different materials at different depths/ speeds / feeds  to get a good feel   of what to do in a program, AS IT RELATES TO YOUR MACHINE.

4.A router throws out all kinds of rf / noise / intreference / whatever you want to call it.......
You can be using it for a long time and then all of a sudden the noise will get ya !  Proper grounding, shielding , etc  will go along way to minimizing the chance that it can happen.

5.Now you also have the machine, suppose you jog the Z up and down or whatever 1000 times and all is well.
Now you cut something and at some time crap gets in your ways, or screw, etc ....and all of a sudden missed steps
because of mchanical influence.

6. I don't think it's the software, but one or a combination of some of the above.
    
FWIW,
RICH
« Last Edit: November 18, 2009, 09:47:48 PM by RICH »

Offline kolias

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Re: Strange Results
« Reply #32 on: November 18, 2009, 11:24:29 PM »
Thank you RICH for the info

I guess I just have to live with this problem, very annoying and dangerous but seems there is no solution

Nicolas
Nicolas

Offline kolias

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Re: Strange Results
« Reply #33 on: December 07, 2009, 08:22:05 AM »
My CNC keeps working well again but I’m always cautious about the out of control depth plunges.

Is it practical to install a limit switch on the Z axis to prevent unwanted depth plunges?

Has anyone installed a limit switch on the Z axis?

Nicolas
Nicolas

Offline RICH

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Re: Strange Results
« Reply #34 on: December 07, 2009, 08:33:54 AM »
You can add a switch that would protect from a loss in control and it can be movable / settable. But again you should not have the problem in the first place. As stated before, just don't exceed the capabilities of
"YOUR" machine.
RICH

Offline ger21

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Re: Strange Results
« Reply #35 on: December 07, 2009, 08:57:21 AM »
Your Out of Control plunges can only be the result of two things. Either the code is telling it to go too deep, or, the Z is stalling when coming back up, resulting in progressively deeper cuts.  If the g-code is causing it, you might consider investing in a simulator like CutViewer that will show you these problems before running the code.. http://www.cutviewer.com/

If the g-code is correct, then you need to either slow down your Z axis, or fix it so it stops causing problems. Try cutting the Z axis accel and velocity in half and see if you still experience problems.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html

Offline kolias

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Re: Strange Results
« Reply #36 on: December 07, 2009, 09:17:03 AM »
ok RICH I will install a limit switch to provide me with some extra security. And yes, it must be movable / settable for different cut depths.

Gerry thanks for the tip; it will be nice to get that CutViewer software but at that price it is out of my reach for now. I don’t think it is the gcode neither the Z axis accel / velocity. I tried to reduce the accel / velocity and the axis stalls and I believe right now she is set at the best combination.

My opinion is that I have rf interference and I will correct that by grounding all the control cables

Thank you both

Nicolas

Nicolas

Offline kolias

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Re: Strange Results
« Reply #37 on: December 11, 2009, 11:38:58 AM »
I think I found my problem.

I disconnected the Z axis cable and checked the cable with an ohms meter and all was ok. Since I use a 5 pin XLR connector to connect the CNC to the motor I pulled the heat shrink sleeve from each of the pins and voila one wire came off along with the heat shrink sleeve and noticed that there was no solder on the pin at all. An electrician friend of mine told me that although an ohms meter will show continuity on a bad connection, when current passes thru this bad connection it will create “hick-ups”. So I soldered this connection and now remain to try the CNC again.

I also installed a limit switch on the Z axis but I have problems getting mach configured for this switch. I used the auto configure button on the inputs screen and that triggers port 1 and pin 12 on the screen for the Z++ and Z-- which are the correct numbers but I still get the message on the status line “Limit Switch Triggered” and the reset button does nothing. My Estop works well but not the limit switch.

The switch is wired for NC and is good. Any help why I get this message on the status line?

Nicolas
Nicolas

Offline Hood

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Re: Strange Results
« Reply #38 on: December 11, 2009, 02:02:42 PM »
Change the active state and then see if the reset will , well I suppose, Reset LOL.
If it does then trigger the switch before you go any further to make sure it is working.

Hood

Offline kolias

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Re: Strange Results
« Reply #39 on: December 11, 2009, 03:43:52 PM »
Change the active state and then see if the reset will , well I suppose, Reset LOL.
If it does then trigger the switch before you go any further to make sure it is working.

Hood

If you mean the Active Low I did change it but still I get the same message “Limit Switch Triggered”.

If I press the switch with my finger it does nothing.

Does it matter if I switch the wiring? Right now the Black wire is connected to the Common of the switch and the Red wire is connected to NC.

Nicolas
Nicolas