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Author Topic: 3D Questions  (Read 3698 times)
ajayre
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« on: October 18, 2009, 06:43:52 am »

I think I must be misunderstanding some major aspects of 3D operations, so any hints or pointers are appreciated.

Attached is a 3DS file, created in Google Sketchup and converted to 3DS using MeshLab. When I load it into CamBam it shows in black. How can I get a wireframe view? I also tried STL with the same result.

When creating a 3D operation, why is the holding tabs option missing? Is that because holding tabs are somehow not used for this type of work? If I want to create an object from a block of wood what stops it ripping off when the last few cuts are made?

Thanks! Andy

* TestPart.3ds (101.68 KB - downloaded 236 times.)
« Last Edit: October 18, 2009, 06:48:29 am by ajayre » Logged
Bertram
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« Reply #1 on: October 18, 2009, 17:02:09 pm »

When I load it into CamBam it shows in black.

The part is black because it has the normals for the polys facing the wrong direction. Open it again in Meshlab then select Filters > Normals, Curvatures and Orientation > Invert Faces Orientation.
Open it again in CamBam and you should see the model.

For the holding tabs, see the the Cambam help file. If you have the latest version of CamBam, you should have this.
C:/Program Files/CamBamPlus/help/tutorials/3DProfile.htm

3D Holding Tabs.

There is currently no automatic 3D holding tabs funcionality, but this is planned for a future release.

Here is a method to manually create 3D holding tabs or sprues using cylinder meshes.

Extrude a circle

Hide the drawing layer containing the 3D mesh and create a new layer to hold the holding 'tabs'.

Draw a 2D circle with a diameter of the holding tabs to be used. Place the center of the cirlce at the drawing origin (0,0).

With the circle selected, select Draw - Surface -Extrude. Enter an extrusion height large enough to span the largest width of the model plus an extra margin to allow for tool diameters. Enter the number of extrusion steps or facets around the extruded mesh to create.

Rotating the drawing view should show a 3D cylinder extending in the positive Z direction.

Position the cylinder

First, center the cylinder (Transform - Center (Extents))

Use a combination of cut and paste and transformation rotations to position the cylinders at required positions around the model.

Adjust the machining boundary

The holding tab shapes need to be added to the 3D profiles list of surfaces to machine. To do this, right click on the machining operation in the drawing tree and select Select Drawing Objects. Ctrl+click to select the extruded cylinders.

To prevent the machining operation machining around the ends of the cylinders, we need to reduce the bounday shape. This is acheived by specifying SelectedShapes in the BoundaryMethod property and selecting only the main surface object, exluding any holding tab cylinders.
Property                   Value                              Notes
BoundaryMethod       SelectedShapes         Will create a trimming boundary just from selected shapes.
BoundaryShapeIds    1                              Enter the ID of the main 3D surface to machine, excluding  any holding cylinders.
 
The [...] button to the right of the property can be used to select the shapes.


« Last Edit: October 18, 2009, 17:17:50 pm by Bertram » Logged

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ajayre
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« Reply #2 on: October 18, 2009, 18:54:33 pm »

Thanks Bertram, that helps a lot.

This raises another question. In the example it appears the front face operation goes to half the height of the object - i.e. where the holding tabs are. I would assume that the back face operation does the other half.

However, if you look at the way my object curves I need to cut the entire outside profile from one direction, then the entire inside profile from the other direction. I would place the holding tabs either in the middle of the outside or at the widest part of the outside.

Can this be done with CamBam? I guess I just need to modify the VolumeMax setting.

Thanks, Andy
« Last Edit: October 18, 2009, 19:31:52 pm by ajayre » Logged
Bertram
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« Reply #3 on: October 18, 2009, 23:13:26 pm »

I would be inclined to add the tabs to the outside of the widest part and cut out the inside first. Then flip over to cut the outside. The tabs will then be at the bottom of the cut against the spoil-board (or table top). This way you won't have to alter the volume settings as you will be cutting full depth from both sides.

If you have the tabs in the middle of the outside, you won't be able to cut the area between the tab and the widest dimension of the part. With the wide side up, there will be a small overhang to cut between the top edge and the tab. With the wide side down, the bottom of the cut will be shadowed by the tabs. 
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ajayre
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« Reply #4 on: October 18, 2009, 23:15:50 pm »

Thanks! I'll give it a try.

Andy
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