Contour and pockets

[jcnewbie]

I have created a 4 by 4 rectangle and creates a 5 by 5 rectangle.

Using a contour operation I only chain the 4 by 4 rectangle and use the 5 by 5 rectangle as stock with a z depth of 1 inch. Top of stock is 0
Now I only want to machine the 4 by 4 rectangle as a boss therefore only go to a depth of -0.5. Now when I verify the toolpath it looks like one block on top of another.. Thats good

Using a pocketing operation with the same parameters as contour I have chain both the rectangles (4*4, 5*5) and get the same result. Thats good.

Now my question is how to do I explain myself the difference between the 2 toolpaths ? I am thinking that for this case both are suitable answers, am I correct ?

[cob]

i just drew it up in mastercam and did both operation and yes it gives you the same result

[kvom]

Seems you'd only get the same result with a tool diameter of 1/2" or more.

[Superman]

If using a 1/2" cutter, then you will get the same result

try using a 1/4" cutter for both ops, and a 3/4" for both

the 1/4" cutter
on the contour path will need extra passes on the outside to clear the shape, but extra passes will be calculated on the pocketing op.
the 3/4" cutter
on the contour path, the tool will overhang the stock contour leaving the shape ( this is a better machining option ), but M/C will error on the pocketing as the tool will not fit into the gaps between the contours.

lesson,
bigger cutters = quicker and more efficient metal removal
smaller cutter = extra cuts generated, tighter corners possible, less power required by the machine