Problem- bosses are milling askew egg shape

[chaz6966]

i have a simple boss, .396 at top, .365 at bottom, and 1.008 deep.
for some reason it is milling an eggshaped boss like i had the solid tilted on a 2 degree angle or something.
theres a .312 pin hole there and down in the bottom of the 1.008 deepth the boss has a ledge like it should but only on 2/3rds of the diameter . the rest feathers out to nothing. and the top diameter is like .020 eggshaped.
im using a .188 endmill with .030r
v23

i made a surface cone instead of the solid and it milled the exact same shape.

anyone have any ideas.

[Allen123]

When you say a boss you are talking about a pocket that is circular with taper?





How are you cutting this? Because of the taper, are you using a 3D tool path like the Z level?


What about

Drilling a hole first so your end mill can enter.





Then using Z level finish to profile that tapered wall/ Under the link tab I used spiral so the tool doesn't plunge for each of it steps down in a helix. Good for the type of tool you are using.




Tool Path




Does the simulation show the egg shape or is it how the part cuts on your machine?

Are you sure the part is draw flat in the XY plane? BobCAD needs the part to be located on the drawing board the same way your machine is setup. The spindle looking down on the part in Z.

[chaz6966]

yes the tapered boss in a tapered pocket down into the steel, top diameter is .400 botttom .365 and it is 1.008 deep.
there is a .312 ejector pin hole in the center so it is not milling much stock.
i can circular interpolate on the mill just fine......
the tapered pocket worked fine a few days ago on a different cavity.
the part is flat as on the machine instead of using my detailes core i just made a separete solid and extracted these bosses from it. but everything still in proper location.
i used z level finish, it starts the tool path on some funky quadrant and mills half of circle to next quadrant then back to start point...
when its done i have a .020 egg shaoed boss, and at the 1.008 deep i can only see a ledge at the .312 hole- 2/3rds of the way around it.

[Allen123]

There is something wrong with the geometry that is causing this problem. As you can see in the screen shots I have above, you can cut this type of part.

Can you post your file here to I can play with it. I think some of the geometry needs to be redrawn.

[Allen123]

What is your linking on the z level finish?

[moldmker]

Originally Posted by Allen123 What is your linking on the z level finish?

I think you got it.
Either Spiral link radius is too big or a Circular Lead In/Out is too big.

moldmker

[Allen123]

There is no gauge protection in the BobCAD software on the lead in and outs or the links.

So Burr is right, that must be where the problem is coming from.

[BurrMan]

Originally Posted by Allen123 So Burr is right, that must be where the problem is coming from.

oops Allen,
Burr hasnt posted on this topic yet! That was Mo.

[chaz6966]

i dont know what you mean by my- linking on z level finish-
i used a solid block and extracted a cone shape solid from it. so i think geometry is right.
i also made two circles top and bottom sizes and created a surface just from the diameters of the top and bottom and the machine still milled the same canted oval shape.
i circle milled a circle 1" deep manual programing and it was fine...

i deleted v23 and reinstalled it from the cd. now it machines the bosses fine...
thanks for your help though....
i want to see if in 5days the software starts screwing things up again...

can you tell me what changing linking your refering too.
thanks

[moldmker]

If you're down inside a hole, the Spiral and/or lead in radii can't be too large or it will cut into your geometry. You can use the hole radius minus the tool radius minus .010" for safe lead in and spiral radii.
With your geometry and cutter specified in the the original post, .078" radius would be safe.

If you look at your toolpath in a top view it will show if your lead-ins violate the contour.

The reference to linking and leads is in the Z-level setup boxes.

Here's the leads tab:
Attachment 76807

Here's the links tab:
Attachment 76808