[mikemaat]

Im a complete mastercam newbie. I have a 3d part. Ive setup my rectangular stock. I want to cut the 3d part's 2d perimeter (looking down). How do I go about this? I think im supposed to use contour, but what chain do i select if the part is 3d? Do I need to manually draw a perimeter around the part and use that for my chain?

[SF Giants Fan]

Use a 2d countour tool path.

You'll need some geometry to chain which may or may not be available in your file.

Create > curve on all edges

[Superman]

Simplest is to use a C-hook, it creates a flat wireframe from your selected surfaces or solid faces

Alt-C to open the available DLL's, scroll down to find CREATE_BOUNDARY.DLL
-set the Z-level that you want the new geometry to be on ( suggest it be placed above the part ie Z+0.1")( default is usually at the Z origin )
-set the level (layer) ( use a new one, so you can turn it ON/OFF individually)
-set a different color ( so it stands out from the other wireframe features )

- select the model's surfaces &/or solid faces, & accept
follow the prompts to get what you need

then you can use this new geometry in your toolpath op

[goalcreas]

Do you actuallyl want to cut the 3d part, or do you want to cut the 3d profile

If you want to cut the profile, create the profile by the menu drop down
"Create - Sillouite Boundry"

Same Principal as what Superman said, but it is within the software, don't have to go to a chook.

you will probably want to be in 2d (toggle switch at the bottom of the screen) and have z set to zero (window right next to the 2d / 3d toggle switch)
It doesn't have to be that way, but it will make more sense to you when you create the profille toolpath, assuming your Machine "Z" origon is from that same place on the model.

you can just do
"Toolpath - mill - profile" if you just want to drive the tool around the stock and cut the profile. Chain the created part geo.
If have a lot of stock to remove around the part and it is uniform, you will set the option "Multi Pass" on and select the amount of passes you want and the distance between passes so you don't just slot mill thru a bunch of stock (unless that is your desired result)
You can select to leave stock for a finish pass as well.

If you have alot of material that is not uniform to the profile shape and you don't want to cut alot of air with multiple passes, you can use the toolpath

"Mill - 2d highspeed" and select "core mill".
You will chain the outer chain representing your stock, and the inner chain representing your part.

alot more settings with this one, but play with it and you may come to like it.

ON THE OTHER HAND

If you want to cut the part 3d (roughing I assume) don't have to create the part profile (but it could still be helpful later) and you can do
"Toolpaths - Mill - HighSpeed - Core"
This will cut like the 2d version, but you can set z level depths, say every .1 or every .25, the tool will automatically stay away from the part (the stock to leave distance you select) and continue down the 3d part so you have a near net representation of the 3d model you are starting with.
Then you will need assistance with fininshing stratigies.

One last thing if you wanna get trickey.
You can do the last toolpath I said, the 3D core mill.
if you give it a depth of cut that is as great as the material, you will get the same results as the 2d version, but you will be able to skip creating the profile boundry all together.

There are also options for chaining off the model, which is very easy, but there are times when it is not possible to get the desired result. For instnace, you want to cut a 1" square and you have a 1" cube to start with, you want a full depth cut with zero stock. your 1" cube has .1 radius on all edges.
Now what part of the solid do you chain, you can't do the bottom surface (unless you offset your toolpath .1) and it's not as easy to so one chain around a solid on a series of surfaces. But if your bottom edge was flat to zero, you wouldn't have any trouble using the model for chaining.

Bottom line, lots to learn, buts it all attainable.