3D cutting depth?

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13brv3
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Joined: Fri Sep 05, 2008 12:16 am

3D cutting depth?

Post by 13brv3 »

Greetings,

It's been a half dozen versions of Aspire since I actually tried to cut a 3D shape. I must be doing something fundamentally wrong, because I can't make the tool cut to the bottom of my model in V11. This is just a half cylinder that was created as a test. It's flat on the bottom, so the tool will need to go to the bottom of the material to finish the shape. For some reason, the rough and fine toolpaths stop well short of the bottom, and no setting I can find changes this behavior. It's got to be something simple I'm overlooking, and it's driving me crazy :-)

I'll attach the test file, and imagine it will take about 30 seconds for someone to see what I'm doing wrong.

Thanks,
Rusty
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half cyl test.crv3d
(979 KiB) Downloaded 25 times

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adze_cnc
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Re: 3D cutting depth?

Post by adze_cnc »

Remember that finish paths (with no other adjustment) stop when the centre of the bit is at the edge of the model / limiting vector. So, for a half-cylinder that would be "up in the air”.

The “Boundary Offset” is your friend. You can start at the bit tip radius and work around from there.
If you are machining a raised object, often the tool will not fully machine down the edge. This field is used to specify an offset to the selected machining boundary to increase its size to allow the tool to go past the actual edge if needed.

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13brv3
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Re: 3D cutting depth?

Post by 13brv3 »

Boundary offset is one of the many things I tried. If you make it a negative number, it makes the situation worse as expected, but no positive number allows the center of the bit to go past the edge of the model.. It's clearly tied to the center of the bit though, and if I use a smaller diameter bit it gets better, but still won't go all the way. There has to be something simple I'm missing, because this really has to work I think.

Thanks,
Rusty

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SteveNelson46
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Re: 3D cutting depth?

Post by SteveNelson46 »

First of all, your "half dome" isn't really a half dome. It's flat on top and looks as though it was made with 2 seperate models? I recreated the shape using a 2-rail sweep, added a zero plane, and set the position of model in the material to the bottom. Also, I wouldn't use a ball nose for a roughing toolpath. An end mill with a 40% stepover works better and faster. Steven's suggestion of using a boundary offset is absolutely correct. I used .25" for both roughing and 3d finish.
Attachments
half dome.png
half dome 2-rail sweep.png
Steve

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SteveNelson46
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Re: 3D cutting depth?

Post by SteveNelson46 »

You can also do this with a moulding toolpath
Attachments
Half dome moulsing toolpath.png
Half dome moulsing toolpath preview.png
Steve

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13brv3
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Re: 3D cutting depth?

Post by 13brv3 »

Thanks for the comments. There's nothing wrong with the half cylinder I used as a model. I'll be trying to help my brother cut some guitar parts, and one is the neck. None of this will be created in Aspire, only imported as stl files from a CAD program. The half cylinder, created in CAD and imported as an stl approximates the neck shape of a guitar, so I was using that as a test.

I just figured out what I was doing wrong. As expected, it's simple, and not so bright... When importing the model, you have to set the position relative to the modeling plane. Since zero for me is the top of the material, I figured the model needed to be entirely below the modeling plane. Now I see that it needs to be completely above the plane. Everything is working normally now.

Thanks,
Rusty

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