Pixelation ???

[Angus_Hines]

SO why is it when I enlarge one of the 3D files that comes with Aspire do I get these weird pixelations?

How do I fix them? Do I have to grab the Smoothing tool and work on them that way?

I'm guessing they arn't true vector art?

[james mcgrew]

are you speaking of the round nose bit trying to climb up a flat at an angle?

we either have to sand it, reduce stepover (time) or use a smaller bit that disturbs us less

jim

[Angus_Hines]

I dont know if I can reduce stepover....This was a1/16th ball nose @ 3% running 50 ipm

But yea all those tool marks along the edges is what I'm talking about.

Can they be fixed with the smoothing tool?

[james mcgrew]

that photo is much closer than i imagined, i thought itwas a 1/8 or 1/4 just how big is the circle (bowl) oh and the answer is we use a flogging sander

[Angus_Hines]

I took the dish from the 4.5" it came as, and enlarged it to 11.5".

Flogging sander, that was my thought too.

[james mcgrew]

check this
jim

http://www.vectric.com/forum/viewtopic.php?f=12&t=5010

[GJMATHEWS]

SO why is it when I enlarge one of the 3D files that comes with Aspire do I get these weird pixelations?

How do I fix them? Do I have to grab the Smoothing tool and work on them that way?

I'm guessing they arn't true vector art?

Angus, without seeing the actual file that you used to create the tool path, one can only offer speculation. Since you stated that you used a 1/16th inch ball mill at a 3% stepover and assuming a parallel cut strategy, it is safe to say that pixelation is the correct term. When you resize a small stl, obj, lwo, or whatever that has been created using puff volume, inflate, sweep, or whatever command you want to call it to generate a solid object, the original shape is going to enlarge proportionatly to the scaling operation used.

Layman terms. Create a 5 circle using lines that look like a staircase and those lines are each an 1/16 inch long. When you create a puff volume of that circle, (Relief Object for half a sphere or 3D object for a complete sphere) the staircase effect transfers to the finished file. When you enlarge this, the steps get larger. This happens alot when people use Corel and create an outline of an image and save it as a DWG file. The outline is made up a little squares called pixels. When the bitmap is converted to a trace outline and scaled, stepping occurs. To eliminate this problem, smoothing of the DWG file or converting lines to arcs will eliminate the stairsteps, however, the accuracy of the original image can suffer.

This is where arcs and lines come into play in CAD software. If your circle is made using lines, choppiness occurs. When it is made using an arc command, the circle is smooth based on the tolerance selected in the original CAD program.

When you create a 50 inch circle using the lines that are 1/16 long and make the object smaller, the steps get smaller. If you create both circles using an arc instead of lines and a tight tolerance, you can pretty much scale the object and have a smooth surface.

Long story short, in my opinion, your model is to blame.

I will post some screenshots of what I am talking about later today.

I am working on the chess pieces for Jim. Unless I create a mesh file for him that has a very small decimation, (the amount of space between points) the effect will be exactly the same when he scales it up.

This all seems quite complex and there are other ways to do this same procedure so save the emails, I am aware of about 95% of them. As complex as it seems, after you create and run a few files it will become childs play.

I hope this clears things up for you. The file of the dog can probably be cleaned up. I do not use Aspire, but if the file is an stl, obj, lwo, dxf, or any of a number of extensions, chances are I can open it, smooth the detail and allow you to scale it to eliminate the problem.


By the way, the dog is super cool looking. Nice job!


Guy

[GJMATHEWS]

The two photos illustrate what I am talking about.

This is an extreme scenario but it cuts to the point. (Pun intended! :D)

The first photo shows the model as you would get it from the person who made it. For argument sake, I am comparing this to the dog file that Angus used.

The pixel edges form a sharp edge every .04 inches, this is not a problem when milling with say a 1/4 inch ball mill and a milling tolerance of .01. The object would finish somewhat textured, however, since the bit will not fit between the points, you really won't notice it.

The second photo shows what happens when the same object is scaled to produce a larger object.

Since the gap is almost 3/8's of an inch, a 1/4 inch ball mill has no problem defining the edges.

I hope this helps folks understand a little better as to what happens when you resize a file.

[Angus_Hines]

Thanks for the excellent explanation Guy !!![fantastic]

So the trick to modeling an enlarged model is to use a larger bit than the distance between the pixels? and this effect will be lessened?

I pulled "pixelation" out of the same place I pull a lot of things occasionally.[lol]

Now off to dictionary.com to see.

[Angus_Hines]

According to Dictionary.com

Main Entry: pixelation
Part of Speech: n
Definition: the process of digitizing a printed image; also, the display of such an image as a pattern of pixels which are obvious to the eye; also written pixellation

My definition:

[spam] that shows up that makes life hard ! cause now I gotta work

[GJMATHEWS]

Thanks for the excellent explanation Guy !!![fantastic]

So the trick to modeling an enlarged model is to use a larger bit than the distance between the pixels? and this effect will be lessened?

I pulled "pixelation" out of the same place I pull a lot of things occasionally.[lol]

Now off to dictionary.com to see.

You can use a larger bit but the you loose detail even at a smaller stepover. Whenever I am trying to achieve fine detail I will use a 15 degree veining bit and use pencil trace command. My CAM software generates a tool path that picks up everything that the other bit leaves behind. Your bits have to be zeroed at the same location and height or the difference is very noticeable.

After you cut a few thousand different parts and projects, the tips and tricks will come a lot easier!

[Angus_Hines]

Thanks Guy....I'm getting the hang of it slowly I think...

IF I disassemble enough trees I might even get good at it [lol]