Roughing Pass

[Aussie]

Hi All,

Does it make a difference if you use an end mill or ball nose tool for this tool path. I normally use a 1/4 inch EM.
Machine allowance ? I normally set this to 1 mm for the finishing pass... how does changing this value effect the detail of the final result

Regards,
Ron

[dealguy11]

1. You can use either an end mill or ballnose for roughing. If you're doing 3d raster roughing a ballnose might get closer to the final model in some areas. Or not. Depends on the model. Sometimes I've had less problems with material chipping away with a ballnose.
2. Final detail is not affected by machine allowance. Machine allowance is just how much material the roughing pass leaves for the finishing path to clear away. Generally make it smaller for smaller finishing bits to reduce stress on the bit.

[loopacrylics]

I had a similar question regarding roughing pass. I’m going to be making a fairly large 3D model out of 2 inch cast acrylic. I have a half inch ball nose, or a half inch end mill for roughing. Would I want to use the ball nose for this? Or is it the same answer as above?

[TReischl]

I had a similar question regarding roughing pass. I’m going to be making a fairly large 3D model out of 2 inch cast acrylic. I have a half inch ball nose, or a half inch end mill for roughing. Would I want to use the ball nose for this? Or is it the same answer as above?

On some materials it may make a difference.

When an end mill is roughing it is cutting on the circumference of the tool.

The same is true of a ball nose, the only difference is that the "circumference" becomes smaller closer to the tip. Essentially the machine cannot go fast enough at the tip to produce a decent chip load. That may cause heat near the tip.

Of course, the same is true when doing the finishing with a ball nose mill.

As my old machinist boss told me all those years ago: "Tools do not want to cut on the point, instead they push."