3D Milling With Ballmill/Feed and Speed help

[Matthewkral]

Hey guys,

I get to try my hand at 3D milling for the first time. Parts are Inconel. Essentially just milling three ears clocked 120 degrees onto a tube. Going to be doing these on a live tooled lathe with a 5/16 ball mill for roughing and a 1/8 ball mill for finishing (largest radius allowed).

I was curious what kind of stepovers you guys use to achieve a nice finish along the 3d milled surfaces.

I was also curious if there is any rule of thumb you guys use for calculating speeds and feeds of a ballmill as opposed to a standard square end mill. I want to make sure I nail these speeds and feeds.

Any help appreciated. Thanks!

 

[empower]

what are you programming with? i'd go with scallop height instead of stepover, let the CAM system figure out the stepovers. with a small tool like that you'll likely be rpm limited anyway so i wouldnt be too worried about rpm. i'd keep the chip load in the .0003-.0005" range. leave no more than .002-.003" for finish

 

[Mtndew]

First time milling and you're cutting Inconel?

 

[Matthewkral]

First time milling and you're cutting Inconel?

Ive been machining for 10 or so years but this is my first time milling 3d features.

 

[Matthewkral]

what are you programming with? i'd go with scallop height instead of stepover, let the CAM system figure out the stepovers. with a small tool like that you'll likely be rpm limited anyway so i wouldnt be too worried about rpm. i'd keep the chip load in the .0003-.0005" range. leave no more than .002-.003" for finish

gibbscam, my idea was milling about the C axis and having my ball mill dip and dive in x as I move along the Z axis. That was the tool pathing I came up with. I posted a picture of the part in another reply.

 

[empower]

gibbscam, my idea was milling about the C axis and having my ball mill dip and dive in x as I move along the Z axis. That was the tool pathing I came up with. I posted a picture of the part in another reply.

which part were you planning on doing that way, blue or silver?
blue, looks like that can be done with normal lathe tools.
silver - yeah that could work, but still, see if gibbs has an option to go by scallop height instead of stepover.

 

[mhajicek]

which part were you planning on doing that way, blue or silver?
blue, looks like that can be done with normal lathe tools.
silver - yeah that could work, but still, see if gibbs has an option to go by scallop height instead of stepover.

Looks like they're going to turn it to the blue model, then mill it to the silver model.

I'd make the primary motion of the tool along the Z axis.

 

[empower]

Looks like they're going to turn it to the blue model, then mill it to the silver model.

I'd make the primary motion of the tool along the Z axis.

good catch, makes sense!

i'd also finish most of that with a larger diameter tool, then finish the small fillet separately with the 1/8" endmill.

 

[Houdini]

Depends on how you like it to look.
I would rough it will a corner radius end mill, pre rough corner steps with ball if needed, and finish with ball.
make sure the ball radius is smaller than the radius on the part. if .125" use like a .109" , .118" (3mm) end mill.

I would program milling in the Z also, top of lug to center, top of opposing lug to center.
that would leave the linear grain in Z though.

you could just do a lace cut in X as you mentioned. grain would be aligned to radial also.

In Gibbs if you cant get the edges of the top of the lugs to extend up in the program, you can extract a surface extend it say.010" and add it to the silhouette.
this will keep the tool from gouging the top if it tries to.

 

[mhajicek]

Yeah, depends on the cost / time / tolerance / esthetics balance.

 

[13engines]

You might ask about purposely leaving either a few thou recess or a few thou land to match the length of the remaining tabs. It will be tough, especially milling on a lathe, to nail the X depth to match the turned tube exactly. Doing it without witness marks would be a stroke of magic. Better luck doing something that looks like it was done on purpose.