Scallop Toolpath

[jcnewbie]

I'm trying to understand when to use the scallop toolpath. The definition through the mastercam help to me does not explain it clearly enough for me.

What does it mean by scallop heights ? and when can I use this toolpath ?

Thanks for your help in advance.

[Matt Berube]

Scallop heights...

Lets say you use "scallop" to cut a flat surface with a 3/4 inch ball end mill and your stepover is .100 (very coarse) you will be able to measure the crests and roots of the resulting surface with an indicator. The difference between the crest and root would be the "scallop height". In reality if we were trying to put a fine finish on a part we'd use a much smaller stepover which would result in a much smaller scallop height. I think on most of the electrodes I toolpath my scallop height ends up around .00002

For my work scallop is rarely useful. It can be helpful when trying to cut numerous faces with angles ranging from very steep to very shallow and provides a consistent stepover at all angles.

Personally I strongly prefer to use 2 separate operations. SF Contour with shallow paths suppressed (cutting 40° - 90°) and then a SF Shallow to hit the remaining areas (0° - 45°). Probably over 90% of my surfacing jobs get toolpathed this way.

[BobWarfield]

A lot of machinist's calculators and other software will tell you the scallop height given the other parameters.

In Matt's example, with a few other assumptions, I see a scallop height of 3.4 thousandths. If you wanted that to be a tenth, you'd need a stepover of 0.0173" or 2.3% of the tool's diameter.

So the calculation is a way to trade sort of a surface finish or accuracy versus stepover and hence the speed. Less stepover will mean more passes to create the surface.

Cheers,

BW

PS I used G-Wizard to do those calcs: http://www.cnccookbook.com/CCGWizard.html

[jcnewbie]

Sorry still do not understand.

Is it possible to give a pictorial explanation of what scallop heights are ?

[jcnewbie]

I guess my exact question is what does one mean by "scallop" in CNC machining terms..

[BobWarfield]

A scallop is the trench like path cut by a ballnosed cutter.

[jcnewbie]

sorry for my ignorance.. my vocabulary is not that advance.

I am thinking that using a ballnose cutter for a roughing pass, leaves a trench ( steep mark along the path) and hence a scallop is produced...

Am I correct ?

[ObrienDave]

Picture Attached