Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: kolias on October 07, 2009, 05:47:30 PM
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After about 6 weeks that I did not work on my CNC I started again today but the results were very disappointing.
I tried to engrave the same piece like I had done before but for some reason the depth of cut was uneven and at one point it went thru the 1/2” stock.
I set the depth of cut in LC to 1/8” and all the other settings like I had done before but afterwards I noticed on the gcode the Z was 0.125 instead of -0.125
Anyone can tell me what I did wrong?
Nicolas
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Can someone tell me what is wrong with the attached files please?
I set my depth of cut to -0.125 in LC but that is not what I get on Mach3
In addition I noticed on Mach3 tool display window that the little arrow which indicates the depth of cut does not move up or down as the program runs and I remember that it used to go up and down
Nicolas
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Hi Kolias,
Did you use the exactly same .tap -file as 6 weeks ago? Or did you generate it again with LazyCam just before cutting?
If "generated again", would you still have the old file on your harddisk?
regards
Konrad
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Hi Kolias,
Did you use the exactly same .tap -file as 6 weeks ago? Or did you generate it again with LazyCam just before cutting?
If "generated again", would you still have the old file on your harddisk?
regards
Konrad
I did not use the old file, I thought that "I knew enough" to be able to generate a new tap file with LC.
I dont have this particular design old tap file. Normally I delete the old files since they are not important; they are only good enough for learning purposes. But I do have some other ones and they show the cutting depth to be -0.125
Thanks
Nicolas
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Hello again,
I just opened the Files with my local installation of LazyCam and Mach3. Everything looks normal for me.
Maximum cutting depth is -0.125 and also the tool position is displayed. :-/
;D Any other Person here with better ideas than I have? *g*
Konrad
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Hello again,
I just opened the Files with my local installation of LazyCam and Mach3. Everything looks normal for me.
Maximum cutting depth is -0.125 and also the tool position is displayed. :-/
;D Any other Person here with better ideas than I have? *g*
Konrad
That is strange because on my screen the tool position is always at 0 no matter which line of the code is running (I scroll down in the code with my mouse) and this happens even with other tap files I load.
I wonder if I have change something on Mack3 by mistake
Also in the tap file line N35 Z0.2000 and N40 G1 Z-0.0250 F60.00 my cutting depth should be -0.125 and not -0.0250
I dont know what I'm doing wrong
Nicolas
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Hmmmm, just scrolling through the code is not running it...
Only if you press "Cycle Start" there will something be moving in the toolpath.
(You can press the "offline" Button, if you don't want to move the machine. But then the machine must be referenced afterwards.)
Konrad
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Hmmmm, just scrolling through the code is not running it...
Only if you press "Cycle Start" there will something be moving in the toolpath.
(You can press the "offline" Button, if you don't want to move the machine. But then the machine must be referenced afterwards.)
Konrad
Thank you Konrad, one more item I didn't know
I will give it a try tomorrow again but I'm sure there is something wrong because I don't see the Z-0.125 anywhere in my code and I remember that before I used to see this parameter
Nicolas
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Z-0.125
on Line N150, N175, N200, N225 and so on.
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Z-0.125
on Line N150, N175, N200, N225 and so on.
Yes I can see that but why she starts with Z-0.0250?
Anyway I will give it a try tomorrow and see what happens
Thanks for the help
Nicolas
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Hello again,
just have a look to LazyCam:
1. You can turn the work object by pressing the center button (Wheel) of the mouse, to look to the drawing sidewise in 3D.
This is where you can already see how the toolpath will look like.
2. But now, lets look NUMBERS:
- have a look on the left side fo the screen: There you can see the tree of layers in your workpiece.
- activate Layer 0 by doing a click to it.
- Now, click "layers" in the menu at the bottom side of the LazyCam Window.
- Here, you can see:
Step per pass: 0.1250 units
Cut Start: 0.1000 units
Cut depth: -0.1250 units
- this will generate a G-code which does -0.0250 (=0.1 minus 0.125), and the the rest of 0.1 to get to -0.125.
Hopefully this helps.
best regards,
Konrad
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Nicolas,
Have you taken a look at the LC Manual?
RICH
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Yes RICH I did read the manual but as a beginner things are not always pretty clear.
I know that I’m doing something wrong and if I knew what it is I would have gone to the manual to get the fix. Unfortunately I don’t know what I’m doing wrong and reading thru the manual can get pretty confusing.
I understand what Konrad is saying but all I know is that before I used to follow the same steps and my code was everywhere Z-0.125. I don’t remember seen any -0.0250 in my code. Perhaps I was using for “Cut start” 0.0000 instead of 0.1000. I will try this and see what it will happen
On top of that, the “Boss” decided to do some remodelling in the house and she wants that done before X-mas otherwise I will loose my tools allowance. So this extra work does not give me enough time with my CNC to resolve the problem. Hopefully I will finish the remodelling job soon enough before I forget even how to turn ON the bloody CNC lol
Nicolas
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Hi Nicolas,
I would recommend to take much time for optimizing the mill, and the produce lots of nice (and useless) accessories for the remodelling of the house ::)
Konrad
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Yes, yes, Konrad has spoken words of great wisdom. Can make all knids of stuff for the remodel job. ;D
Brett
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Nicolas,
The best thing you can do is read through the first 30 pages of the manual as that basicaly defines all the tools , menus, etc.
More important is to go through each tutorial and follow them. The fisrt tutorial is key and then the others build on it. Make note of how the cut depths are done.
Don't hack your way through the program.
RICH
BTW, Work before play >:D
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Don't hack your way through the program.
Sounds like sound advise from someone with experience. ;)
Brett
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Nicely said and well understood, thank you all
BTW the remodelling job in nothing more than boring painting job
Nicolas
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I had the chance this morning to give another go on my CNC but again I have the same problem but its worst. Although my depth of cut is set at -0.0625” the bit eventually will go thru my stock
On file Tulip2.tap, by the time the code reached line N560, the bit went thru the ½” MDF
On file Tulip22.tap, by the time the code reached line N120, the bit went thru the ½” MDF
I can’t find in the manual anything to fix this problem. Any help?
Nicolas
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When it goes through the stock, what does the Z axis DRO show? The code only says to go down .0625, so it sounds like a mechanical problem.
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Thank you Gerry
Like a beginner, I never thought to check the DRO’s and so I don’t know, sorry.
I tend to agree that it may be a mechanical problem because I read the LC manual and as far as I know I do all the inputs correctly. I also looked at the code and never saw anything more than Z-0.0625”
I have checked all my mechanical connections and they all seem to be tight and nothing is missing. When the CNC is not working and I try to physically move by hand the Z axis it is solid like a rock
Are you able to point to something specific for me to check?
Nicolas
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Maybe the z axis is skipping steps when it trys to retract the z. Might tune the motor down on the z to 50% of present accel and vel and see if that helps for a quick test.
Brett
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Maybe the z axis is skipping steps when it trys to retract the z. Might tune the motor down on the z to 50% of present accel and vel and see if that helps for a quick test.
Brett
Sounds Good Brett, I will try that tomorrow.
Thinking again, I believe it's more of a software problem than mechanical. On the last file I was working (tulip22) the Z axis went down 1/2" in about a couple of seconds before I hit the Estop. I dont think a mechanical problem will have created that
Nicolas
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Can you post a pic of your machines Z axis.
I don't think it's a sofware problem.
DO you zero out the Z axis before running the program?
Take a look at section 8.3.4 and also Tutorial #6 section 1.0 Plunge Cearance in the manual to make sure
your not doing somehing wrong in LC.
RICH
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Can you post a pic of your machines Z axis.
I don't think it's a sofware problem.
DO you zero out the Z axis before running the program?
Take a look at section 8.3.4 and also Tutorial #6 section 1.0 Plunge Cearance in the manual to make sure
your not doing somehing wrong in LC.
RICH
Thank you RICH
Yes I always zero the DRO’s before running the program
Section 8.3.4 refers to the cuting parameters: I always set the Rapid height to 1.0000, Cut start 0.0000 and Cut depth to -0.0625 or -0.1250 and used to work before very good.
Tutorial #6 Plunge Clearence describes very well the cutting parameters and I always follow them. The proof is that the program starts well but after a few lines the cutting depth increases drastically and that is what I would like to find out why
Here are some pics of the Z axis
Nicolas
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When I say that I think it may be a software problem, I dont mean LC. I mean that I may be doing something wrong with my paramaters or I may have change some parameter(s) before which I now forget.
Nicolas
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Maybe the z axis is skipping steps when it trys to retract the z. Might tune the motor down on the z to 50% of present accel and vel and see if that helps for a quick test.
Brett
The Z axis was at 48 Vel and 8 Acc. I decreased the Vel to 24 and Acc to 4 but the motor got stalling after she went down for a couple of inches. I played with the numbers a bit but the motor was getting stalled and so I put the same values as before BUT the motor was stalling again now!!! what a mess.
When I move the Z axis with the right / left arrow keys the axis works fine with all the above numbers but when I try to run a gcode she stalls. X & Y are fine.
Is it possible that “noise” may create the problem I have with the Z axis?
Nicolas
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My CNC seems that is working fine now but when she goes to line N45 the feed rate drops to almost 0”.
From line N10 to line N40 she is fast but then when she hits line N45 she goes very slow and the motors sound like you have a musical instrument playing.
When I move all axes with the keyboard, all is working fine and fast. All DRO’s working well and the motors are calibrated fine as far as I know.
From the attached files, can someone tell me if there is anything wrong?
Nicolas
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Increase the feedrate. You have it set to 15ipm in line N45 (F15.0)
I think we went over this before, but when you lower the accel and velocity and it stalls, it's probably due to resonance.
Also, when it cuts too deep, be sure to check the Z DRO and see what it says.
Most likely, the Z axis is stalling when it should be moving up. The cumulative affect is that the Z goes too deep.
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Thanks Gerry, I will do that
The funny part is that with the same motor tuning and feed rate (F15) I did 6 pieces and all was fine. I dont know why now I have to increase the feed rate. Actually I had the feed rate before at F10 and the motors were never "singing" like the do now.
Anyway what you said sounds good
Nicolas
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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
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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
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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
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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
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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
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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.
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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
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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
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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
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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
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No, wiring polarity of a mechanical switch does not matter, sounds like your input pin is not working correctly, if you have another you can connect to try that.
Hood
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No, wiring polarity of a mechanical switch does not matter, sounds like your input pin is not working correctly, if you have another you can connect to try that.
Hood
I did try other pins, I switch the wires (Black & Red) and nothing worked, status line says (Limit switch Triggered). Switching the active low ON or OFF does not correct the situation and when I press the Reset on the screen it always has on the status line the same message (Limit switch Triggered).
I use the “Auto Set of Input Signals” on the inputs screen to set the limit switch and when I press with my finger the switch the message on the screen says “Select Next Signal” which means to me that the switch communicates with mack3.
Also I noticed that when the switch is connected the diagnostic screen has the light on Enable 1 OFF. When the switch is not connected the same light is ON.
Finally I decided to switch the connections on the limit switch from COM + NC to COM + NO. Now it works well and when I press the Reset it clears the status line message and when I move the Z axis down and trigger the switch the machine stops and by hitting the reset (after I move the trigger lever from the switch) it clears the status line.
With this setup, the Active Low for the Z axis limit switch is now ticked. My Estop is connected with COM + NC and the Active Low is not ticked. On the diagnostic screen the Enable 1 light is ON.
To me all seems to work fine now but I don’t understand why the limit switch must be connected with COM + NO and have the Active Low ticked and the Estop with COM + NC and have the Active Low not ticked.
I attach my xml file in case it is needed.
Nicolas
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The reason the Limits and E-Stop active state is different is because one is looking for an active Hi to signal a trigger and the other an active low and that is because you have one NC and the other NO.
All are best set up as NC as it means if a wire breaks or a contact comes loose Mach will not know if you have them set normally open and you will only know when you are needing the limit to be seen and it is not.
I will have a look at your xml and see if I can find a problem but have you tried setting manually instead of using the Auto Setting?
Hood
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Just had a look at the xml and dont see anything glaringly obvious wrong, if you try NC again change the active state on the limits and also try putting 2000 in the Debounce Interval on the General Config page.
Hood
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Thank you Hood
Originally I did try setting the limit switch manually and since I did not succeed I used the Auto Setting.
I will give another try tomorrow to set the switch manually and change the active state plus put 2000 in the Debounce Interval. I will also try another switch just in case although I did check the switch with an ohm meter and worked good.
I do know that is better to have a NC switch as you explained but I keep wondering why my switch only works as NO
Nicolas
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Thank you Hood
It worked! I installed a new limit switch, just in case, connected between COM + NC, set the Debounce Interval to 2000 as you said and now it works fine.
BUT after a couple of minutes and without touching anything on the machine including the limit switch, the warning came on that “Limit Switch Triggered”.
What the Debounce Interval do?
Why the “Limit Switch Triggered” message came on again without touching the switch?
If it has to do with RF noise interference would it help if I ground the jacket the limit switch cable to my DC grounding bar where I have grounded the motor cable jackets?
Nicolas
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Ok it is as I suspected, you do have noise on your wires to the switches. Yes grounding the shield should always be done on any 5v signal wires as they are very susceptible to noise. Make sure you just ground at the control end and try and ground all shield wires to a single point.
Hopefully once you have done that you can reduce the debounce interval to zero, although its not going to do much harm having it at 2000, just I prefer to not use it if possible. What it does is just filter the signal when it comes to Mach so that any signals less than the amount you have set are ignored, if you set 2000 that is only 2000 x 40 micro seconds, so its not a long time, only 0.08 seconds :)
Hood
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Ok it is as I suspected, you do have noise on your wires to the switches. Yes grounding the shield should always be done on any 5v signal wires as they are very susceptible to noise. Make sure you just ground at the control end and try and ground all shield wires to a single point.
Hopefully once you have done that you can reduce the debounce interval to zero, although its not going to do much harm having it at 2000, just I prefer to not use it if possible. What it does is just filter the signal when it comes to Mach so that any signals less than the amount you have set are ignored, if you set 2000 that is only 2000 x 40 micro seconds, so its not a long time, only 0.08 seconds :)
Hood
Sorry Hood, when you say at the control end do you mean at the end where the limit switch is?
Nicolas
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Well I did ground the cable shield from the limit switch and connect it on a screw in the ground bar where I also have the grounds from the 3 motor shield cables. I assumed that the control end is where all my motor drivers and power supply unit are.
But it seems that grounding the cable for this linit switch made it worst because now I get the same message again “Limit Switch Trigered”. I played around with the Debounce Interval from 0 to 2500 but the message comes back although not instantly, takes about 3 – 5 seconds and when I reset it comes back again.
I will not disconnect this ground until you tell me to do so
Nicolas
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You would be better disconnecting it if it makes things worse, seems that you are creating more noise in the wires by having it connected, why I dont know :(
Hood
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You would be better disconnecting it if it makes things worse, seems that you are creating more noise in the wires by having it connected, why I dont know :(
Hood
Thank you Hood
Much appreciate your help
Nicolas