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Author Topic: Tempest Planning - Preliminary information and testing  (Read 281612 times)

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Offline ART

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Re: Tempest Planning - Preliminary information and testing
« Reply #60 on: September 30, 2009, 10:18:04 AM »
Mike:

  Thanks, great report.

  The reason the time doesnt shave when you raise acceleration ( much anyway) is the Jerk Limit itself. No matter what acceleration you enter, the Jerk Limit will
stop the system from accelerating beyond a certain set point of Jerk. Raising Jerk to 100,000 would shave more time off.

 As a comparison, on such a file, Mach3 would have many points at which Jerk woudl be well over 1 million units/sec^3 ..

  So if you like, raise your accel, and raise the jerk limit a bit. The trouble is that the Jog is still linear, so you have to keep the accel down low enough your Jog works
well, and that will set the limit of the accel you can use. After that just experiment to find a good Jerk setting.

 Sounds like your system is working as well as mine. Thanks for the bugs AND this report. Im pretty pleased with Tempest's performance. It really makes Quantum look bad. :)

Art
Re: Tempest Planning - Preliminary information and testing
« Reply #61 on: September 30, 2009, 10:45:17 AM »
Quote
As a comparison, on such a file, Mach3 would have many points at which Jerk woudl be well over 1 million units/sec^3 ..

That's a staggering number - now I feel for those poor ballscrews and nuts as well as the servos  :o

As this is such an improvement over the standard Mach, is there no way we can put pressure on Brian to incorporate it? I know you said it is early days and that maybe it could be released as an upgrade, much later, but with such a significant improvement, in terms of machine longevity, it seems crazy not to do it sooner. Development can still continue on the planner but there would be hundreds of machines out there purring your name - brilliant!!

Thanks again for all your efforts,

Mike

Offline ger21

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Re: Tempest Planning - Preliminary information and testing
« Reply #62 on: September 30, 2009, 11:07:47 AM »
I ran a decorative 2D part the other day, and had to play with feedrates to get the detail I needed in a few places. Had to slow it down to 30ipm in a few spots, when the majority ran at 125ipm. Did a dry run with tempest at 150ipm and seems to do exactly what i want. Had a setting of .03. Basically get CV on tangent lines and arcs, and exact stop on corners. I'll do some more playing later with an even lower tolerance, but it looks really good.

I'm assuming the jog issue is just due to this being a test, correct? I can't really raise my accel on my stepper machine, as it'll stall when jogging.
Gerry

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Offline ART

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Re: Tempest Planning - Preliminary information and testing
« Reply #63 on: September 30, 2009, 01:52:30 PM »
Jogging is actually a hardware function of any of the devices.. In Printer port, the driver does it. In Smoothstepper or DspMC the devices do it.
All Mach3 does is send a jogon or jogoff command. SO I cant really attach Jog as it stands. Not tillmuch later if I attempt it at all.

   As to going in Mach3, theres still a long way to go and it wont attach properly in all aspects, so you wont see it as a release in Mach3.. at leats not in the near future.

 I will keep a tempest verison going though, so those that wish to use it can if they wish. Unfortunately, that means your stuck with this version of .028 until such time as testing is complete.


  Good results so far though, Im pretty pleased.

Thx
Art

Offline ART

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Re: Tempest Planning - Preliminary information and testing
« Reply #64 on: September 30, 2009, 01:55:25 PM »
>>get CV on tangent lines and arcs, and exact stop on corners.

  Thats a good point. If you set the CV blend down low.. .03 or so.. then the CV WILL only affect tangent lines and such. What happens is for each blend Tempest calculates how fast the system can progress though the blend, since .03 is too sharp at 90 degrees, it will slow way down..so very little cv, but in tangental motions, the small blend can be done at high speeds..so you get selective CV based on tengental nature of that connection. Tempest is pretty smart at doing that.

Thx

Art
Re: Tempest Planning - Preliminary information and testing
« Reply #65 on: September 30, 2009, 02:54:56 PM »
As major bugs seem to be recovered, I am about to test this TempestPlanner. Tomorrow I give it a shot. At least we will see how it works with SS.

Today I was playing with 2D code, having both long and short segment parts.
It is done as engraving, I need to engrave both sharp corners for rectangles, and smooth curves for curved shapes.

CV OFF: Nice sharp edges, but at some parts the machine was bouncing. Result: Engraved rectangles are nice, but the curved shapes have wavy edges.

CV ON: Curved shapes have nicely connected edges, but the rectangles are rounded way too much.

At this point I examined what I could do with CV settings, and I realized, that there is no good solution, and I wanted to ask if there is a setting that might set blending in the function of joining segment length, and I just realized that Art was describing this in this Tempest thread at reply #46...

So I am really waiting for the moment to see what the result will be with tempest.
I already made some photos of CV ON and CV OFF problems, so I attach pictures. Green arrow OK, Red arrow NOK... (Shall I see the same differences on the toolpath display, too?)

Offline ART

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Re: Tempest Planning - Preliminary information and testing
« Reply #66 on: September 30, 2009, 05:15:07 PM »
Hi:

  I assume the tests you were running were in normal Mach3?

>>Today I was playing with 2D code, having both long and short segment parts.
>>It is done as engraving, I need to engrave both sharp corners for rectangles, and smooth curves for curved shapes.
>>CV OFF: Nice sharp edges, but at some parts the machine was bouncing. Result: Engraved rectangles are nice, but the curved shapes have wavy edges.

    If CV is off, AND your machine is bouncing, this is a sign of too high an acceleration setting for your machine. Its not stiff enough to do that kind of acceleration using a linear planner.
In Tempest, you may leave the acceleration setting alone, but youll want to find a setting of JERK that allows you to do the code with CV off that doesnt jerk. Thats the whole point
of tempest. Once you know that your 2d code with CV off doesnt jerk your machine about, then turn on CV..

>>>CV ON: Curved shapes have nicely connected edges, but the rectangles are rounded way too much.

   Set a fairly low Blend radius. You say the rectangles are rounded too much, so set a blend radius your willing to live with.
If your table is set to cut without Jerking.. and Tempest will let you set that up.. then your CV will please you under all circumstances..or should.
Since the blends automatically shrink with the line length, you shouldnt see any blends that other you, certainly not in the micro code your running anyway.

 This is the benefit of being mathmatically pure.. and why Im trying to keep it that way.

thx
Art

Let us know how it works, Id love to see the same photos under tempest as a comparison.





Offline ART

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Re: Tempest Planning - Preliminary information and testing
« Reply #67 on: September 30, 2009, 05:19:01 PM »
Hi:

  On extra note.. You asked about toolpath display, Blending and CV changes to the output are never shown under the toolpath, they cannot be except as runtime information ( the green dots or line), this is because neither Mach3's traditional planner nor even Tempest really knows whats going to go out till it does. Its a very complex thing to calculate as it all depends on speeds,
blends and conditins at time of cut. Ive seen many errors reported as CV errors that aren't, they are a weak machine bending as it cuts due to acceleration forces , both motor acceleration
and tangental acceleration, Tempest however, knows abotu tangental acceleration and takes it into account, but a weak machien may bend more than you think.. setting low Jerk limit numbers
will stop the bending.. just a quetion of how much that slows you down really..

Thx
Art
Re: Tempest Planning - Preliminary information and testing
« Reply #68 on: October 01, 2009, 03:36:50 PM »
Hi,

Just done a number of test runs to satisfy myself how Tempest is working on my machine. I did an air cut of the full 'New Hub' file and noted the times. I did this six times with a few different settings. here are the results:

Standard Mach as the benchmark; Acceleration 400 (optimum for my machine) time to cut = 25 minutes
Tempest 1 Acceleration 1000; Blend 1; Jerk 10000 time to cut = 44 minutes
Tempest 2 Acceleration 1000; blend 1; Jerk 25000 time to cut = 39 minutes
Tempest 3 Acceleration 1000; Blend 1; Jerk 50000 time to cut = 35 minutes
Tempest 4 Acceleration 750 (Safe to use jog at this setting) Blend 0.1; Jerk 25000 time to cut = 39 minutes
Tempest 5 Acceleration 750; Blend 0.01; Jerk 25000 time to cut = 39 minutes

The conclusion seems to be that the jerk setting has far more influence on the time taken to cut than the blend setting. There was not a big change in time between 25000 and 50000 yet the machine did not run quite as smoothly at 50000. As Art said earlier, the higher the jerk setting, the closer it resembles standard Mach. I did try a cut at a jerk of 1000 but stopped the run after a few lines of code as it was apparent it would take a long time. On my machine, 25000 for jerk seems about right.

I haven't quite got the hang of 'Blend' just yet but from what I can gather, it has very little effect on small segment code. What I would like to know is whether a value of zero can be used and if so, does this represent a 'virtual' exact stop setting but with jerk still operative i.e. there is still effective 'S' curve acceleration? Very small values of blend seems to suggest this but can there be zero blend for maximum accuracy?

What was abundantly clear was that my machine sounded much happier, and although there is a 50% increase in time, it is time I am quite happy to sacrifice for the improvement in operation - I am lucky enough to not have to use the machine for income :)

Mike
« Last Edit: October 01, 2009, 03:38:55 PM by Mike_F »
Re: Tempest Planning - Preliminary information and testing
« Reply #69 on: October 01, 2009, 03:45:52 PM »
So as I tested, Tempest Runs well with SS, too :)

Attached pictures:
1. CV ON (Standard MACH planner, fast machining, smooth curve, but too much rounding at edges)
2. * CV ON With tempest (Tempest Planner curves are smooth, edges are nice, machining is somewhat slower of course due to Jerk limitation)
3. CV OFF with angles >45deg (Standard planner, just setting for CV angle is different,  same result as above, with faster run, and a bit more hickup at direction changes)

* this has the nicest cut IMHO

Unexpected event:
WHen I played with jerk settings I experienced no bugs, but one part was damaged during the following process:
I started to cut a part, but I forgot the feedrate override at 5%, so after 10 seconds, I pressed reset for the FRO, and suddenly one of the axes wanted to go crazily fast, and it lost all of its steps... I have don this without tepmest before many times, but had not seen this happening... whatever.

Acceleration:
Before tempest, I had acc. settings at 250 for all axes. I tested max acc. for X and Y axes, it started to be unstable at 2000. at 1500 I could not make the machine loose any steps. (max vel currently is 200mm/sec with 0,0005mm microstep increment)

Jerk values:
The standard 5000 Jerk value brings noticable results, I made 2 tests: running with max. speed a 4x4 rectangle, and a 40x40 rectangle.
without tempest, the machine is fast, but jumps, with tepmest, based on jerk value it goes smoot enough below 10000 (machine is more or less solid, but the desk it stays on is far from that, so with a better base, a 20000 jerk value would be OK for its mechanics I suppose.)
Setting a jerk value of 200 makes the movements tender even on the floppy legs, but for small distances it is way too slow, I suppose such low jerk is applicable on machines with larger workspaces than mine.

Some questions:
WHen I use CV together with tempest, will tempest blend setting override CV settings? or how it is going to work?

Comment:
For the moment I decided to cut parts without tempest, but in the end it would be nice to have it always active, to protect the spindles. (I have another machine, solid as a rock, it can run at high accel. rates with 2kW servos, but that bang-bang is not good for the ballscrews)
Jerk on the small machine means it jumps, the large one "only" knocks... but I am more afraid of those knocks, if you know physics, you can guess why...
So the more Tempest is adopted to MACH, the happier I will be :)

About toolpath display:
I understand it has to calculate first to know the exact blends, accelerations, etc... but theoretically it should be possible that MACH "preprocesses" the Gcode file, and then it can draw what actually will be output for step pulses...
Of course if it is not written that way, it might be hard to reconfigure for this "simulation" mode...
I would see an advantage of it to know how much my real feed speed would deviate from my commanded feed... Benefit would be better chip load control.
e.g. I command F600 and I calculate that spindle should run at 10000 for proper chip load, but if there is a section where MACH can run at F100 only, then it will run at that low speed, but it won't touch spindle speed. with some materials it would lead to no chip formation, but friction only...
But this is another story I suppose, however, I would like to have some opinions about it :)
Or what I described above could be handled with software as MasterCam for instance? I have not that deep knowledge, but CAM software is aware of physical limitations of the machine tool, then it should be able to correct for those values...
« Last Edit: October 01, 2009, 04:00:51 PM by hunserv »