Vector unwrapper - Model to small for material diameter

Topics related to wrapped rotary machining in Aspire or VCarve Pro
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kaartman
Vectric Apprentice
Posts: 80
Joined: Sun Sep 21, 2008 6:41 pm

Vector unwrapper - Model to small for material diameter

Post by kaartman »

I am playing with the Unwrap Vector gadget, with the normal unwrap process do I have success, with the spiral feature can I not get the model to Close completely, it is almost if the model is to small for the material diameter, the opening is visible in the tool-path preview window, (this is the Unwrap tutorial PDF that I am using for the dimensions and setup)
1)I notice the bounding box is the exact size as the model all center aligned
2)Polygon vectors slightly smaller than the material diameter
Attached is the .crv file for review
Questions:
1)Please advise how I go about preventing this and ensure neat joint,
2)Should I go ahead and cut this model will the tool ‘’fall down the edge’’ and create a gorge in the material with this opening

Advice appreciated as always
Attachments
Spiral Wrapped Output.crv3d
(2.47 MiB) Downloaded 269 times

spinningwood
Vectric Wizard
Posts: 338
Joined: Wed Aug 12, 2009 2:09 am
Model of CNC Machine: Taig Mill and Self Built Routers
Location: Space Coast, Florida

Re: Vector unwrapper - Model to small for material diameter

Post by spinningwood »

Hi K - In my experience, the "opening" I am seeing in the model you attached should not be an issue for machining (notice I said "should", not "will". If you are worried, do an air cut for a test). If you look at the end of the wrapped model in the preview and you see the model extending into the interior (not the case in the file you attached) you have a potential problem. Generating your toolpaths and looking at them in the preview will reveal if the tool is going to bury itself in your work (I find it easier to see this in the unwrapped view, but it shows in the wrapped preview as well). It is not in the file you posted.

As near as I can figure, these gaps show up as a result of "rounding" when you specify a size that doesn't evenly round to the precision of aspire. I deal with this by setting up my wrapped project to 2 or three decimal points. For example, if my wrapped creation will be a maximum of 6" diameter, the radius of the (and the size of the wrapped dimension) would theoreticaly be 18.8495559215388 inches. Aspire will round that (too many decimals) and you get the teeny gap you are seeing. I would set the project up with a size of 18.85 on the wrapped dimension. This would mean a project diameter of 6.000142 inches. Nobody will notice the extra width (unless you need a ultra precision fit) and it eliminates the worrisome preview gap as well as some other issues that you will eventually encounter on more complex designs.

Don't try and visually size your components to the bounding box by dragging the handles. Always use the "Set Selected Objects Size Tool". It will save you a lot of headaches.

Ed

kaartman
Vectric Apprentice
Posts: 80
Joined: Sun Sep 21, 2008 6:41 pm

Re: Vector unwrapper - Model to small for material diameter

Post by kaartman »

Hi Ed
Thank you for your well explained answer and tips, with normal unwrapping I did not notice tiny holes in the components but only with the “rotational “ components, at first the tiny holes appear at the location of the bottom drive rail that separate the main component and the additional component created by the offset drive rail, after baking the two components those tiny holes disappear, I guess trial and error and to follow the many mentors advice.
Thank you once again

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