[Cartierusm]

OK so i've been working with Rhino for about 6 months and machining things will good results. Now I'm at the critical stage and I've machined some holes that came out very hexagon looking. Well I realized that the tolerance settings in Options and when I create the tool path were at .01. SO i did a test with a new circle at the old settings and one with settings at tolerance in options and toolpath at .0001. THe circle came out perfect. So HERE'S the question...

If I change the tolerance levels in the OPTIONS and on each toolpath to .0001 and regenerate the toolpath the models I've already made will be fine???? I don't have to redraw everything??? Thanks.

[RandK]

Changing the absolute tolerance settings applies forward from that point. It doesn't go back and change geometry, surfaces etc that have already been made. Not sure where your hexagons are coming from. A circle at low tolerance is still a circle. If it was an extracted edge of a surface made at low tolerance perhaps. Maybe your cam is using the Rhino tolerance for what it does so maybe just changing that will help. Be suspicous of trims; check intersections with the analyze>curve>geometric continuity tool. Recreate any really critical surfaces.

[chmillman]

Hi,

What CAM are you using? If you make circles in Rhino, they are mathematically perfect NURBS circles no matter what your absolute tolerances are set at. The "hexagon" stuff has to be coming from either your CAM program, or how you are exporting the geometry to your CAM. If you give us more info we can probably help you further... --ch

[pointcloud]

The circle is perfect but the toolpath will not be... The machine information is in steps... Now if you use a g02 g03 then the machine path will not have any steps... But the toolpaths that are g01 xyz threw 100s, 1000s, 100000s or even 1000000s of lines and they are all move here, then here, then here, then here, and so on... Setting the tolerance in the rhinocam or any other cam will cause a smoother or more jagged path. Most times you want them to be a CLOSE as you can get them but some machines have backlash or can not hold a .0001 tolerance with out an error...

What control software are you using? You can also set tolerance there? Further more if you use Camsoft try a G08 which will look ahead and smooth things, use a G09 before any G00 or F changes... If you are using Mach try G64 I think... Which turns on the look ahead and you can set the look ahead in Mach to as high as you want... I use 50 lines.. Some go 200.

[Cartierusm]

Thanks for the help, but it was the tolerance settings. I'm not sure if it was the global settings in Rhino, which I changed Units and Tolerance > Absolute Tolerance : .0001, and changed Page Units > Absolute Tolerance : .0001, or if it the tolerance setting in RhinoCAM. When you make a tool path it says Tol. and it was usually set to .01, when I changed it to .0001 all the circle came out smooth.

One thing I wish I could do it setting all those options in Rhino once, it seems everytime I start a new file I have to change it, can I change it permanently as the default?

Also are there any settings in Rhino or RhinoCAM that i'm missing, like the tolerance discussed here, that should be set?

[pointcloud]

Well on all the ones you have modeled you'll have to change... On all new ones use a template... Make Rhino/cam/art how you want them to open and save as template, every time you open rhino use the same template....

[COMMAND JOHN]

And your cam needs to output G02 and G03 that will also help keep code size down.

John

[Cartierusm]

What is G02 and G03 and why does it matter how big my code is? Thanks.

[pointcloud]

G02 is clock wise circular motion and G03 is counter... Your computer will run out of memory

[Cartierusm]

I'm using RhinoCAM how do I get to those options? When will my computer run out of memory? Meaning is it file size in comparison to RAM?

[awerby]

go to the Machining Preferences (in the Browser, in the Setup tab - the icon looks like a yellow gear) and uncheck "output arcs as linear segments".

Conceivably, if you've got your tolerances set too coarse, and you're outputting arcs as segments, you could get circles that looked like hexagons. I'd also check to see if you aren't having an issue with inches and millimeters. If your parts are really in mm but you're treating them like inches, this is the sort of problem you're likely to experience. (In Rhino, go to Dimension/Dimension Properties/Units). The default tolerance for mm is .01, but you'd want .001 or .0001 if you're working in inches.

As to running out of memory, that shouldn't happen on a simple linear toolpath like yours, even if your computer is somewhat old.

Andrew Werby
www.computersculpture.com

[pointcloud]

In your post processer generater... Go there and pick the one you use... Remember what you change if you change anything!!! Look and circluar motion..

Also your drawing will be a huge file too and that is on the normal screen...or just type mesh in the rhino command line and follow those directions..

if you need I can get some screen shots tomorrow...

[pointcloud]

Oh... When??? Well I recomend you save your work automatically every 5 or 10 minutes... You never know.. How big are your items? I can handle some items that are 36" diameter and 48" long on a 4th axis, but I warn you to save.. I learned some really good methods of haveing large files without a crash... One of them is mesh, another is layers.. Use only the layer your working on or as few as possiable... Color and label them correctly as you go.. Booleens are HOGS, try to model with out using that function to often.... Sometimes I have 5 or 6 different files that make one part... Do not run anything other than rhino/cam... Your video card is most likly the weakest link, so if you are rendering you might want to turn down the quality... I run 2 512 79??s that run togather... Ram is an issue and reccomend all you can stuff undder the hood... I use patriot, its great quality...

[Cartierusm]

Awerby, you're located in Oakland, I'm in Burlingame. What kind of stuff do you do over there besides the probing? Any cnc machines? It's a pretty good computer so I don't think I'll run out of memory. What will unchecking output arc thing do to the rest of the shapes, nothing?

P.S. I'm using Mach3 should I uncheck all 3 in machining prefences? Arcs to linear, spiral and helix? How will this affect the machining, I suspect it will stay the same but make the file smaller?

[pointcloud]

Changing anything in RHINOCAM will not affect RHINOSOROUS Lines, surfaces, nurbs, meshes.. Only the output of RHINOCAM... You want arcs / Spirals / helix.....

Machineing? well in a circle you would have s bunch of gcode lines where thesee selections will make much fewer lines.... pluse a more fluid motion...

Use a G64 (check to be sure) It is a look ahead feature in mach, it will anticipate a move and make nessacery adjustments to your feed rates to make smooth transitions...

[Cartierusm]

Thanks, Yes I do G64. Whenever I post a code I always go into it and manually change the G61 to G64 and then change all my Plunge and Feedrates. The only post files I have found for Rhino are Mach2 files and that limits the feedrate to 20ipm. When I've tried to alter the Post File and change the maximim feedrate to 60 IPM it makes the lines off in the gcode. SO even though I'm only changing the "2" to a "6" in the feedrate it make some of the lines run together in a file. So if I post a file in Rhino and then open it up in notepad some of the lines run togeter. I figure better safe than sorry and just open in up in Word and have it change all of the feedrates, works for me.

[pointcloud]

When you get back to your computer, change that? You know where to go now.... The magic yellow gear, then remember what you change.... That g61/64 is there too...

[RandK]

There's a Mach3 post on the Mecsoft site

http://www.mecsoft.com/Mec/Downloads/Posts/Mach3.spm

You should be able to make your own version of this tweaked dejour. The Rhinocom/Mecsoft support forum was pretty good too.

[Cartierusm]

Thanks, now I have to redo everything...lol, no problem as I've done it a million times already. I do have to redraw some stuff. Originally my neck pocket was drawn at .01 resolution set in Rhino and I then set it to .0001 and re-did my code and tested it. The size came out the same, even though it measured correctly in Rhino it came out at 2.158 instead of 2.1661. Then I redrew over it and reposted the file and cut it with the Rhino and RhinoCAM resolution set to .0001 and now it comes out correct. So most stuff doesn't have to be perfect but I will redraw some of the stuff. Thanks for all the help.