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Author Topic: CNC router shudder and jerky / jitter doing 3D toolpaths  (Read 9966 times)

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Offline BR549

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Re: CNC router shudder and jerky / jitter doing 3D toolpaths
« Reply #30 on: February 06, 2016, 04:44:31 PM »
In this case teh User was using a Fanuc post cause Fanuc uses teh G8 P0 and P1 to turn off/on exact stop.

And someone is getting very Quick with Mach3 searches (;-) Old QuickSearch McGraw

NOW you know, (;-) TP
Re: CNC router shudder and jerky / jitter doing 3D toolpaths
« Reply #31 on: February 06, 2016, 04:50:42 PM »
Well, that dust is a workin'. You're reading my mind !
My next ? was regarding the "P*" I see in various searched examples.


From a search   ...    http://www.csun.edu/~hws86622/CNC_Mtrl/G_Code.html
G08 Ramping function at block transition / Look ahead "off"
G09 No ramping function at block transition / Look ahead "on"

Sometimes searching gets confusing.
Best to go directly to the Monkey Dust Man".

Thanks again Terry,
Russ

Offline BR549

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Re: CNC router shudder and jerky / jitter doing 3D toolpaths
« Reply #32 on: February 06, 2016, 04:50:52 PM »
In this case teh User was using a Fanuc post cause Fanuc uses teh G8 P0 and P1 to turn off/on exact stop.

And someone is getting very Quick with Mach3 searches (;-) Old QuickSearch McGraw

I also have a copy of ALL teh old Yahoo Messages even from teh Master5 days. There are MANYMANY thousands of pages of messages from that era of Mach3  Art did a LOT of explaining back then and it is ALL in teh archives.  Another late night best reader (;-).  Art is quite teh story teller (;-)

I would do the same for this site but don't have a clue as to how to get them all.

One day they are going to disappear and it would be a shame NOT to have a copy.  

NOW you know, (;-) TP

Offline stirling

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Re: CNC router shudder and jerky / jitter doing 3D toolpaths
« Reply #33 on: February 07, 2016, 05:18:01 AM »
Now this seems to have solved my issue but I am left with a couple questions:

1. What should I have turned on in relation to CV MODE (other than CV MODE)?
2. Do I need 4000 pulse/rev for microstepping or is there a better amount to use to optimize my system?
3. Is there any other things (settings, etc) you folks can think of to help make my system run smoother?
4. Why does my GCODE turn off CV MODE?
5. Should I always have CV MODE on?
6. How can I program Mastercam to always input a G64 into my GCODE?


1. Nothing if you can help it. All the CV settings cripple CV to one extent or another.
2. Unlikely - 2000 p/rev would be more normal. (caveat - I know zip about those fancy dandy servo type drives).
3. I'd be looking at why your CAM produces so many lines of code. It seems excessive to me. Are you for example converting arcs to lines unnecessarily? Also take another look at the pic I posted, why have the lines suddenly changed from around 3 hundredths to 7 thousandths for no apparant reason?
4. I think this one's been done...
5. Pretty much - unless you have good reason for turning it off - and then you'd want to look at 1. again first.
6. Looks like it does already - you need to stop it sticking the G8 in afterwards.

Offline ART

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Re: CNC router shudder and jerky / jitter doing 3D toolpaths
« Reply #34 on: February 07, 2016, 07:03:25 AM »
>>3. I'd be looking at why your CAM produces so many lines of code. It seems excessive to me. Are you for example converting arcs to lines unnecessarily? Also take another look at the pic I posted, why have the lines suddenly changed from around 3 hundredths to 7 thousandths for no apparant reason?

    This was the root of your trouble. CV was the cure in this case, but M3 ( and all controllers) have a problem with very small
segmented motion at times. Its a question of predictability. Even if in CV mode, a trajectory planner has to computer various
equations on accel, velocity and time on each segment as part of the process. Tell ArtCam (or what your using) to put out in
lower resolution and it gets much smoother.

        CV of course must be used in this type of file, but it works best with larger segments, it always has. Ignore the microstepping
stuff ( my advice), I use as high a micro-step as I can, balanced with speed, if I need more speed Ill lower the micro-stepping,
but in general , and in almost all cases, the higher the micro-stepping, the smoother the motion.. 
      Higher micro-stepping also allows using higher frequencies to control with , and the higher the kernal base frequency,
the smoother the motion as well. For steppers, micro-stepping is pretty much unavoidable for performance..

Nice to hear you've smoothed out. :)
Art


Art

Offline BR549

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Re: CNC router shudder and jerky / jitter doing 3D toolpaths
« Reply #35 on: February 07, 2016, 11:21:17 AM »
HIYA ART , You do know you just contradicted you r own advise to only run as high a kernal speed as you need to make the speed you are running (;-).

Now they are going to try as high as a kernal speed as they can get teh PC to run (;-)

Just a thought, (;-) TP
Re: CNC router shudder and jerky / jitter doing 3D toolpaths
« Reply #36 on: February 07, 2016, 12:21:49 PM »
The original poster is using a smooth stepper... Set the kernal speed at 25khz and leave well alone is the advice given on the warp9 forum.

Rob

Albert Einstein ― “If you can't explain it to a six year old, you don't understand it yourself.”
Re: CNC router shudder and jerky / jitter doing 3D toolpaths
« Reply #37 on: February 07, 2016, 12:42:26 PM »
3. I'd be looking at why your CAM produces so many lines of code. It seems excessive to me. Are you for example converting arcs to lines unnecessarily? Also take another look at the pic I posted, why have the lines suddenly changed from around 3 hundredths to 7 thousandths for no apparant reason?


I create all of my geometry in Mastercam X4 and it also writes the GCODE as well. It seems to put out BOTH the G64 and G8 codes. I don't understand why it is doing this. It is saying; use CV MODE, then turn off CV MODE.

I also have no clue why Mastercam is producing so many lines of code. Could it be that my geometry in Mastercam X4 is fine but my post processor in Mastercam is what is writing the excessive amount of code lines?

Offline ART

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Re: CNC router shudder and jerky / jitter doing 3D toolpaths
« Reply #38 on: February 07, 2016, 12:59:50 PM »
The reason Darwin was advised to be run as low as you can use is because Darwin and mach3 used CPU time and space in your system. At 25Khz, it used about
25% of your CPU speed, ( hidden from you, your true cpu speed was 0 - 75%), at 100Khz, you have 0% left.. so I always advised keeping it low,
to increase true CPU capability.
  In actual fact the best smothness is at 100khz, but no computers could really handle 100khz, but my system ran very happily
at 45Khz, so I rarely used less. However, take a hypothetcial system at 1000 steps per inch at 0 uSteps, at 25Khz he would get  25
inches per second at a set smoothness, increase microstep to 10 , he now has 10,000 steps per inch, but only 2.5inches per second. If he then bumps
to 250,000 as the core speed, he gets the same original 25IPS, but at a much smoother motion, and a higher resolution... one of the benefits
of an external controller.

Just saying...
:)

Art
.

Offline BR549

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Re: CNC router shudder and jerky / jitter doing 3D toolpaths
« Reply #39 on: February 07, 2016, 01:00:12 PM »
It is because it is using a Fanuc Post not a mach3 post ??  Micro segmented code IS normal for 3d machining it is the nature of the beast to be able to carve great detail and surface features. It is just some controllers handle it better than others. Being able to use very high accel rates in Z helps it run faster as well. A slow Z slows down the entire process.

(;-) TP

« Last Edit: February 07, 2016, 01:03:32 PM by BR549 »