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Author Topic: LazyTurn  (Read 1058071 times)

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Offline ART

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Re: LazyTurn
« Reply #1170 on: January 26, 2010, 12:07:16 PM »
Well, a few algorithms later..

   As some of you may or may not know, what LTurn is attempting is very very hard. SO much so thats its really a subbranch of math code you can call "physics similations on concave polynomial motion. ". I might add that it, like so much I attempt is very much above my pay grade. Its why very few good lathe programs exist that are easy. Most are difficult due to the collision detections required, so they pass much of that to the user to use his ituitive abilkities to overcome the difficulty in the math. Its much easier for a person to tell how much a tool will collide and which direction one woudl have to go to correct it than a computer can. Attempting this has
given me high appreciation for the math wizards that do this well. ( Few of them as there are..).

   LazyCam is meant to be easy, I dont want all kinds of user interfaces and things or it fails its purpose and is best left to the Wizards. No, this isnt a "I quit" message,
I just want to explain with this release some of the inherant rules that will now start to apply in order to get a good toolpath. I found many bugs anf inefficiencies while attempting fine pathing, and have corrected and changed much of the code in roughing as a result.

  Roughing works ona scan line pricinple, scan horizontal lines though the profile, clipping them when they enter and leave the profile, and correcting their lengths for
things liek polygon( tool) hitting the profile. And tool non-flank areas hitting the remaining stock. The only way to do this in the time that is feasably given the code, is
to check the start and end of lines for these complex collisions and adjust the lines accordingly. This means a tool may hit in the center of a line IF the tool radius is not the outter most point of the tool. For example if you rotate a diamond more than 27 degree's or so. Youll find problems in your cuts if the tool does exceed as the scanline calculations only see the tool at the start and end of the lines. It assumes a cut across the lines of tool radius size. ( You may not understand all that, but it boils down to this rule: )



  LazyTurn Roughing Rule #1: If any part of a tool is further out in the X than the radial tip, then the roughing may fail and cut into the profile. USers shoudl always check their profile onthe screen to ensure the leftover material is not cut into the profile..

  I may , soon, force that rule into effect codewise if you testers dont see any reason not to. You may find however that in certain instances your fine with the cutoff as long as you KNOW it will happen. If so, Ill leave it alone.


 Issue #2.

   Finepathing is more difficult than rough by orders of magnitude. This is because the true difficulty mathmatically, of calculating
oriented polygon intersections over the profiles length comes to the forefront. After experimenting with a great many methods using very complex modelling and logical analysis , I came to the conclusion that the only real way to do it was to simulate the fumbling of a
user as he would try to follow a mental image of what he's trying to cut. Even attempting to follow the intuitive nature of a person
as he cuts is more diffcult than youd imagine. However, by simply limiting the capability of a polygon to hit in the X direction
we come very close to what one woudl think of as the "best pass" type of finish pass.

  Few problems with this of course. First, a human sees distance as infinitely variable. As you move a tool from Z0 to Z-10, you see
at each point along the way if youll cross into the profile. A computer has no sense of the infinity of distance, it must granulate
the distance to check it, meanign it cant check every .000000001 inch to see if its a hit or not, since the profile is not moving in straight
lines necessarily, you cant simply vector check the collision, ( you could if the profiles were convex, but most are concave in nature).
SO we have a setitng in the fine path called "Tolerance" . This is how often along the profile we progress from step to step. In Inch mode I use .01 inches. Seems a fair constraint, but your feee to override it with the cost being time of caluclation. In Metric I use .05mm's. These
limits get me a finish pas sin a few seconds, if you desire high precision your time penalty for that is decided by how small "Tolerance" is set to in the finish pass dialog.

   Undercuts are not yet dealt with. Soem program simply dont allow them, I will , but I have to come up with a few filtering tricks in the logic to take them into account, another complex situation thats easy for a human.


  So with all that being said, Here is release 1.02 . You cannot yet cut any finish pass. You WILL see one though, and it will reflect
how far laong we are to getting a final output. This release is to hopefully make the roughing better and more accurate, and to allow you to send me pictures of problem area's in finsih pass generation. As it gets better and more usable, Ill set the post processor to allow its output. What youll see is only the final finsh pass, other passes will be generated form the final pass profile.

  Let me kwno what you find generally. I suspect we'll come up with rules as to what works and what doesnt, what can be done, and what will have to be passes to human intervention.

  There is a new button called ToolTest that allows you to put the screen tool on any spot to ensure the toolpath actually works. Ive seen many instances where I thought he tool will definitely hit, and when I plce the tool there it is indeed a fine place for it. :)

  To use that button, hit it, the cursor will become an arrow, click on th screen at any spot and the tool will appear there..


Good luck
Art
   

Offline ART

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Re: LazyTurn
« Reply #1171 on: January 26, 2010, 12:25:18 PM »

Heres is an example of a finish and rough cut on a test file.
The red line is the proposed finihs pass, youll note I dont remove the material so
you can see how much the finish tool woudl in theory cut off.

Art

Offline ART

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Re: LazyTurn
« Reply #1172 on: January 26, 2010, 12:28:16 PM »
By the way, youll notice on the left side of the output, the red line seems to follow the end points of the roughing
operation. This is a good intuitive check of the output, they are computer in different ways, so if the red seems to follow the
roughing endpoints, thats a good sign that if there is a collision error, it was duplicate dby both sections, which shoudl be very rare.

  IF the red line DOESNT follow the roughing constraints, thats a good reason to double check your output..

Art
 

Offline RICH

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Re: LazyTurn
« Reply #1173 on: January 26, 2010, 12:58:37 PM »
Hi ART,
Making it easy ain't easy.....glad you stuck with it.
I am sure i will have questions and comments.
I'll  get into it in the next day or so and see how it works. Been away from LT for some time, and that is good
since i can start off with an open mind so to speak. Probably will do a quick fix to the manual......

Till then,
RICH

Offline budman68

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Re: LazyTurn
« Reply #1174 on: January 26, 2010, 05:08:07 PM »
Hi Art,

I don't really have a lot of time here lately but wanted to ask a quick question about the latest "test".

So far this finish pass looks nice with 3 of my files at this point. Not very elaborate parts but....

I have a screenshot with some picture inserts showing the tool parameters I used and also showing a blow up area of my question. Notice how the finish pass line in red hooks around the end? It does it at "Z" zero as well, is this an issue or just something that's unimportant at this point?



Thanks for keeping on this, I appreciate it very much -
Dave
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Offline RICH

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Re: LazyTurn
« Reply #1175 on: January 26, 2010, 05:25:14 PM »
ART,
Looking pretty good but there are a few things I am finding. One of them is what Bud commented on above, but, depending on the tool used the finish pass will continue on to X =0 actualy cutting the part off. I'll post pictures, just want to first try a bunch of different profiles and see how LT is behaving. Will say that "out of the box" so to speak, it is doing better than before.
RICH

Offline ART

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Re: LazyTurn
« Reply #1176 on: January 26, 2010, 06:24:18 PM »
Hi Guys:

   In the "hook" case, I notice the tool is quite narrow at the top, and I suspect if you use the tool placement test button youll find there is no problem and the tool actually fits
there so it goes there. It shoudlnt in the end make any difference as the line will have to be processed before being turned into a toolpath. Processing will mean clipping its front
and back to the size of the profile, and then progressively extending it outward suntil no more stock mterial is found.

  If you see such a "hook" try placing the tool on the tip of the cut by zooming in and usign the tool begig button, ("forgot that didnt you :-) ")

Since the finish pass if offset fromt he profile by the "CLearance" distance, its quite possible the tool will fit those hooks..

Art


Offline budman68

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Re: LazyTurn
« Reply #1177 on: January 26, 2010, 06:41:49 PM »
Art, thanks for the reply, I actually did play with the new tool but not sure what I'm doing, so I am guilty of that.

Here's another blowup super close with the tool tip, and remember, the tool tip is .002" of an inch.

See how the pass does a graceful angle and then makes a sharp right angle (hook) towards  X.000? (Note, image is a bmp for clarity as a JPG got too fuzzy, sorry.) Not sure I completely understand your explanation but I think when you said: "Processing will mean clipping its front and back to the size of the profile, and then progressively extending it outward suntil no more stock mterial is found." I believe that clears it up for me.



Thanks,
Dave
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Offline RICH

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Re: LazyTurn
« Reply #1178 on: January 26, 2010, 07:02:11 PM »
ART,
Pics were done so forget about the cut off comments in them.
I must say looking pretty good .....only 98 more files to try..... ;)
I will say that the three balls were handled very well and there are other programs out there that fail bitterly with it.  ;D
RICH

BTW folks don't try the simulation!

Offline RICH

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Re: LazyTurn
« Reply #1179 on: January 26, 2010, 07:10:59 PM »
 ART,
Quote
LazyTurn Roughing Rule #1: If any part of a tool is further out in the X than the radial tip, then the roughing may fail and cut into the profile. 

So basicaly your saying your cutting on the back side of the tool and that dosen't work to well.


Quote
I may , soon, force that rule into effect codewise if you testers dont see any reason not to.

I have no comments at this time and need to play some.

RICH