Bull nose or Ball nose

[jcnewbie]

Are these tools use for specific toolpaths or depending on the application ?

i.e. How would one know when to use a bull nose tool or a ball nose tool ?

[Superman]

It's a programmer thing, and it really depends on the part features

You have a pocket 2" x 3", 17/32" corner rads with a fillet of 1/8" running aroung the base that is 1" deep

your choice of 1" bullnose with 1/8" corner rads
or 1/4" ballnose

Whch one would get the material out faster. and have a good chance of not breaking.

now, same shape but 1/8" corner rads,
I'd still use the big tool to get the material out, and then bring in a smaller tool to just concentrate on the corners, finishing with a 1/4" ballnose

now have 2 or more deeper pockets side by side with a wall thickness of 0.050" and the whole ball-game changes

[fizzissist]

More than just a programmer thing.

You can get the surface feet per minute needed for maintaining proper cutting conditions for carbide tools with a bull nose that you can't for a ball nose. No SFM at the center of the tool with a ball nose.

Granted, there are times where you're limited by the diameter of the tool by the geometry of the part and so you're stuck with a ball nose, but where you can use a bull nose, you're got the advantage of lower RPMs, the ability to face, and often a cheaper tool. Especially with radiused inserts.

I generally don't use a ball nose unless I have to anymore. But I'm not doing molds or intricate 3D stuff much. In Mastercam it's easy to justify ball nose mills though with rest mill abilities.

[ViperTX]

The tools are totally different....a bull nose if meant to produce a rounded profile on an edge and a ball nose is meant to produce a rounded groove on the surface of some material.

Paul

[thebowman]

Originally Posted by jcnewbie Are these tools use for specific toolpaths or depending on the application ? i.e. How would one know when to use a bull nose tool or a ball nose tool ?

A bull nose will hold up better and allow you to take off much more material than a ball nose for roughing where you don't care about surface finish.

[Superman]

Originally Posted by ViperTX The tools are totally different....a bull nose if meant to produce a rounded profile on an edge and a ball nose is meant to produce a rounded groove on the surface of some material.

Yes, their forms are completely different,
But I can get stacks more volume out of the part by hogging with a bullnose than by using a ballnose, the larger bullnose is stiffer, chip evacuation is better, lower RPMs used, quieter
Plus the added feature that the base ( if flat ) is almost complete

[fizzissist]

Originally Posted by thebowman A bull nose will hold up better and allow you to take off much more material than a ball nose for roughing where you don't care about surface finish.

Uh, I just ran an aluminum part with a .25 radius around the top of a hole, and a 5/8 bullnose cutter with a .030 rad. The surface finish came out an easy 16 rms.

[jcnewbie]

I'm using a 1/4 diameter ball nose tool and roughing out grooves with cutter compensation set to OFF
(programming center of a line)

-Top of Stock = 0abs
- Clearance = 1abs
- Retract = .25 abs
- Tip Comp = Center
Stock depth = 1 inch
- Feed Plane = 0.1inc


1. Now my question is if I enter in a depth of -0.035 the tool moves from Z 1.0(clearance) then feeds to 0.1 above the stock and goes to Z0(Top of Stock) and then to depth of -0.035. Verify the part and everything looks good. If I post it out I get a Zdepth of -0.035 ( What I expect)

2. Now if I enter in a depth of 0.035 ( not negative), the tool moves from Z1.0 (clearance) then feeds to 0.1 above the stock and goes to Z0.035 (positive). Verify the part and everything looks good. If I post out I get a Zepth of 0.035

Are both correct ? I personally don't think so because the depths are different, so why does verify show both as correct.

Your help is greatly appreciated

[ObrienDave]

One of the features of Verify is to automatically scan the toolpath and create a stock block based on the axis limits of the path.
That is probably why your verified toolpath looks the same.
Try using the same to examples with the Z max (or min, can't remember which) set to zero.
I can guarantee the second toolpath you describe will NOT show up.

[jcnewbie]

Hi Dave,

Thanks for the response back. I'm just doing a 2D contour toolpath, no surfaces, therefore there is no setting for max or min z.

The geometry I created is at Z0. My stock size is 4" in X, 4" in Y and my stock size is 1".

Any other ideas ?

[ObrienDave]

What I mean is, when you turn on Verify, press the configure button shown in screen snippet capture008.png.
You will see the pop-up window shown in capture009.png.
The "Initial stock size source" is probably set to "Scan toolpath(s)".
Set it to "Use last size" and make the Z Maximum value Zero.
This is where you will see a difference in your toolpath verification.

[jcnewbie]

I've taken a look at the backplot of both operations and verify and now I see what is going on, but need to know if both are correct.

1. With depth set to 0.035 and tip comp set to Center.

Tool starts at clearance, then feeds down to Z0.1 (I'm using a 0.25Ball with a 0.125Corner Rad). Then the tool goes to depth of 0.035. At this point as seen in backlplot the center of the tool is above the stock, however the tip of the tool is already engaging in to the material and that is why verify is showing the part being cut.


2. With depth set to -0.035 and tip comp set to Center. T

Tool starts at clearance, then feeds down to Z0.1. Then the tool goes to depth of -0.035. At this point as seen in backplot the center of the tool is already into the stock at z-0.035

So now, which one is correct ? My head is spinning