Author Topic: STL machining primer?  (Read 214 times)

Offline pthien

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STL machining primer?
« on: August 01, 2020, 04:33:36 am »
My goal is to be able to draw something in SketchUp, export that as an STL file, open the STL file in Cambam, and then create a 3D Profile to cut that shape.

But when I do that, Cambam only generates toothpaths that seem to represent an outside bounding box of my part.

Are there any primers on doing this, any tips or ideas?

Offline dh42

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Re: STL machining primer?
« Reply #1 on: August 01, 2020, 07:18:27 am »
Hello

The CamBam file is needed to see what is the problem ... but the workflow is right ;)

attache your .cb file to get more help ;)

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David

Offline pthien

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Re: STL machining primer?
« Reply #2 on: August 01, 2020, 15:18:10 pm »
I went back and re-did it in its most simple form, and I have attached it.

Note that the part is below the z-axis because that was the only way I could get anything to cut when I zeroed off the top of the material.

I've tried playing with a bunch of the settings Boundary Method, etc., without the hoped for result, so I just did this again with everything set back to defaults.

Thanks in advance.

Offline pixelmaker

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Re: STL machining primer?
« Reply #3 on: August 01, 2020, 17:08:24 pm »
1.) The faces are in wrong direction, it points to the inside.
Edit -> Surface -> Invert Faces
2.) This is not a 3D part. It is to be milled in 2.5D, so it should be done that way. The bevel is to be made with a side profile, not even that one has to be milled in 3D.
3.) In 3D milling, the tool paths are always parallel in one axis. You are using X-axis parallel toolpaths, so it is not possible to mill the cutout to the correct dimension. A bit better will be you use vertical toolpath and a very small value for resolution an stepover.
4.) There are many boundary methods in CamBam, they are all described in the manual. So I won't go into them, because I expect you to read the manual first, such basics as 1.) and 2.) should be considered.

ralf

Offline pthien

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Re: STL machining primer?
« Reply #4 on: August 01, 2020, 19:10:43 pm »
Thanks Ralf, I'll work through your notes here, I appreciate the help!

Offline dh42

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Re: STL machining primer?
« Reply #5 on: August 02, 2020, 04:46:11 am »
Hello

Yes, as said Ralf, this is essentially a 2D part ; even the ramp can be cut with 2D mop (but it is not very intuitive for a beginners)

for the ramp, you've 4 way to cut it.

- 1) using 3D mop (horizontal scanline) with bundaries to restrict the machining to only the ramp.

- 2) using 2D profile on a simple line with a "side profile" option (not easy to set)
http://www.cambam.info/doc/dw/1.0.0/cam/side-profile.html

- 3) using the Curved surface plugin with the "flat surfaces" option

- 4) after that the contour as been cut, mount the part in a vise with a tilt = to the angle to cut, so you are able to machine the ramp as a flat surfaces ; in this case you can machine straights angles between the slope and the walls with an endmill. This is certainly the best way for this part.

I attach the "side profile" and "3D mop" versions.

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David

Offline kvom

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Re: STL machining primer?
« Reply #6 on: August 02, 2020, 13:23:55 pm »
I'd cut the ramp as a 2nd op with the work angled in the vise.

Online lloydsp

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Re: STL machining primer?
« Reply #7 on: August 02, 2020, 15:32:01 pm »
Yeah -- That's the simplest way to get a nice, clean cut.

Lloyd
"Pyro for Fun and Profit for More Than Fifty Years"

Offline pthien

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Re: STL machining primer?
« Reply #8 on: August 02, 2020, 15:40:29 pm »
1.) The faces are in wrong direction, it points to the inside.
Edit -> Surface -> Invert Faces


Did I do something wrong when creating my drawing in SkethUp which would have led to the faces being inverted?

Just kinda curious.

I don't think I'd have found that in a million years.

Offline pixelmaker

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Re: STL machining primer?
« Reply #9 on: August 02, 2020, 22:14:21 pm »
Faces and Surfaces in SketchUp have a Front side and a Back side.
SketchUp’s default face materials are:
Front = White
Back = Bluish Gray

Best practice is to keep all visible faces of a model oriented such that the Front Side (white) faces outward.
Face orientation is important as certain export formats and renderers only support single-sided polygons.
You can check face orientation anytime by viewing the model in Monochrome Face Style.
View > Face Style > Monochrome

Change face orientation by using the Context Menu commands.
Right context click on a face and select … Reverse Faces or Orient Faces.

• Reverse Faces
The Reverse Faces menu item is used to flip the front and back sides of the currently selected face.

• Orient Faces
The Orient Faces menu item is used to automatically orient all the connected faces of your
model to the orientation of the currently selected face. This option could lead to unexpected
results when an edge of a face bounds three or more other faces.

Faces and Surfaces retain their Front / Back property regardless of what other materials you might apply.
And each side of a Face or Surface has its own individual material attribute.

Notice when a Face or Surface is selected the Entity Info Box displays two material swatches.
The left swatch is the Front side material; the right swatch is the Back side material.
You can change/edit the front or back face material by clicking on the respective swatch.

When creating 3D objects it is important to pay attention to the correct orientation of the faces always and from the beginning. The more complex a model is, the more difficult it is to repair.

ralf
« Last Edit: August 02, 2020, 22:17:20 pm by pixelmaker »