Scallop height stepover

[Smit]

I'm just wondering what everybody prefers to use when 3D milling with ball mills. My dealer tells me that old school people use step over by distance while new school programmers use the scallop height.

 

Well, I guess I'm old school. I've always used step over by distance.

 

I'm finishing a race track shape with a 1/8" ball. I'll typically use a step over by distance to get the finish I want, probably .006 in this case.

 

What scallop height would you new school programmers use to achieve a polish free finish? And do you leave it the same regards of the size of the ball mill you're using?

 

TIA for any replies!

[Thee Rickster ™]

i USE .004 to .005" ON GRAPHITE USING THAT CUTTER. stupid caps....

 

but I have a high speed CNC's

[John @ High Tech Machine]

I'm just wondering what everybody prefers to use when 3D milling with ball mills. My dealer tells me that old school people use step over by distance while new school programmers use the scallop height.

 

Well, I guess I'm old school. I've always used step over by distance.

 

I'm finishing a race track shape with a 1/8" ball. I'll typically use a step over by distance to get the finish I want, probably .006 in this case.

 

What scallop height would you new school programmers use to achieve a polish free finish? And do you leave it the same regards of the size of the ball mill you're using?

 

TIA for any replies!

 

I have used both methods, which one I use for a job mostly depends on the surface shapes and blend areas that I am trying to cut.

[Buddy J]

I'm in the step over group because I know what works for the finish I'm looking for, but I do wish that when you entered a value in the

scallop field, the corresponding step over distance would pop up in the step over field, and vise-a-versa

Would be interesting to see

[90rsgnuguy42]

I use scallop height because that's the most telling as far as what my de-burr people are going to have to finish. I don't have to guess what the finish is going to be and a scallop height stays the same even if I have to change over to a different size ball mill.

[Smit]

i USE .004 to .005" ON GRAPHITE USING THAT CUTTER. stupid caps....

 

That's a stepover distance, Rickster?

 

I'm in the step over group because I know what works for the finish I'm looking for, but I do wish that when you entered a value in the

scallop field, the corresponding step over distance would pop up in the step over field, and vise-a-versa

Would be interesting to see

 

That would be sweet, but if I understand how it works the stepover (distance) will vary as the angle of the wall changes. It would sure be nice for helping to get a grip on their relationship.

 

I use scallop height because that's the most telling as far as what my de-burr people are going to have to finish.

 

90rsgnuguy42 , what kind of scallop height do you choose if you want a 64 or a 32 finish?

[YoDoug®]

Depends on the shape of the surface and what CAM program I'm using. If the shape is relatively consistent then a stepover usually does fine. If the shape varies a lot I use a scallop to have a more consistent finish. If the software I'm using has the ability to apply the step over relative the the surface being cut rather than the cutting plane then I have found the stepover usually gets a good enough finish and calculates faster than than scallop height.

[90rsgnuguy42]

.0001/.0002" I thought at one time I found a chart somewhere that gave a surface finish that corresponded to scallop height. I don't have that anymore though.

[Guest CNC Apps Guy 1]

I prefer scallop because I generally am looking for a uniform finish and often I am dealing with non prismatic stuff.

[MotorCityMinion]

Go here and grab the Surface Finish (Step Over) Calculator.

 

http://www.1helical....ol-calculations

 

EX: .125 ball at .004 Step over across a horizontal face will produce roughly a 32 micro. Of course as the slope changes, the finish will as well. (Yup, I'm looking for a calculator that can factor in slope.)

 

 

"That would be sweet, but if I understand how it works the stepover (distance) will vary as the angle of the wall changes. It would sure be nice for helping to get a grip on their relationship."

 

This is correct and a good rule of thumb for most tool paths. Exception is SF Blend with 3d enabled. This will make some very nice surfaces. A few draw backs with this tool path is calculation time is longer, and geometry with radical changes in wall angles or shapes in general will cause the tool path to dip (spike) sharply.

 

IMO, getting a grip on their relationships boils down to deciding on. ..I 'm going to program as many surfaces as I can with one tool path, or I'm going to make the most accurate and/or sweetest looking part I can using as many tool paths as it takes. There's always trade offs.

 

On occasion, when things get fussy, I'll program a parallel tool path at both 0 and 90 degrees (or tilt it to flow with the surfaces) just to cover all the bases, from a accuracy and finish stand point.

[90rsgnuguy42]

If you have a calculator that will tell you the surface finish based on a step over then just use step over on a flat surface and look at what the scallop height is then use that and you will get the surface finish the calculator said regardless of the angle you're cutting. When you fill in the step over amount the scallop height field fills in.

[Thee Rickster ™]

That's a stepover distance, Rickster?

 

Yes, for scallop or hybrid

[LaszloK]

I prefer scallop since it is directly related to surface finish reguardless of cutter size. One value works for all ball mill sizes. You will need a different stepover value for each size ball mill.

[Smit]

Good stuff, thanks for the input gentlemen!