Precut using offset or bigger mill?

[adryan]

Hello,

I'm trying to generate some program in Bobcad demo.
I have a question:
If I want to do a precut first should I draw the part first bigger, generate the program and afterwards create the part to size and generate the program?

or

should I generate the program entering a bigger mill size in the input then actualy used?

I'm not sure how to do this, perhaps someone can give me advice

thanxs in advance,
Adryan

[The One]

Are you profiling, pocketing or surfacing?

Regards

[adryan]

Hi,

I want to profile and pocket.
The surfacing I did generating different depth

regards,
Adryan

[The One]

OK.

When you are doing the pocket use the spiral/tapered(if needed) and input a stock distance. This is the amount of material you are going to leave on the walls of the pocket and islands for finishing.

Then you can just use the Profile function from the NC-CAM window to generate your finish around those contours.

Regards

[adryan]

Thank you!

I didn't know this was possible. The "stock distance" is also the distance between the outside of the tool and the inner side of the "final" pocket, right?
Can you also tell me something about profiling? I mean cutting the outside of a product? I know you can enter the different depths but how do you leave a small amount around the outside for a final cut around?

[tjones]

I do mostly 3D solids but I use an easy trick that just helps keep things like this easy. Tell the software you have a larger diameter tool than you will actually be using. This may get a few arguments in that it isn't the correct way but it really does work and it is easy.

[Cammotion]

Originally Posted by tjones I do mostly 3D solids but I use an easy trick that just helps keep things like this easy. Tell the software you have a larger diameter tool than you will actually be using. This may get a few arguments in that it isn't the correct way but it really does work and it is easy.

Does the software have the ability to leave either a plus or minus amount of stock on the part without "lying" about the cutter size?

Edit: I re-read the thread, and someone's already suggested that!

[The One]

Bill,

That option is not available in any of the current versions. However, I am not quite sure I understand why you would want to use a negative stock value. Wouldn't this result in over cutting the contour?

Regards

[Cammotion]

Originally Posted by The One Bill, That option is not available in any of the current versions. However, I am not quite sure I understand why you would want to use a negative stock value. Wouldn't this result in over cutting the contour? Regards

Yes, the negative stock would have that result, but once in a while it can be used as a way to get the cutter to go where you want: let's say you have a rectangular part with a pocket in it resulting in a 3/8 wall all around. You want to drive a 3/4 cutter around the top of the wall to clean it up. You could select the top outer profile and tell the software to leave -.1875 on the profile, then the centerline of the cutter would go around the centerline of the wall. Just one way to do it, different CAM packages have different ways to accomplish the same thing

[tjones]

Well if a negative will not work then why not change the cutter comp direction and give it the comp amount you want?