Need help with confusion about "Clean-up" pass

[buildswithbrian]

Please let me know if I have this correct
so if you are doing multiple passes profiling out a thick part and you want to clean-up any small ridges
left by the individual passes...

1) if you select the allowance shown in red, it will just cut out the profile set-back that you
    specify and then you need to run an entirely separate toolpath with no offset allowance
    for your clean-up pass (I am guessing full depth of part in one pass) 

2) if you select the "do separate last pass" option shown in blue, it will cut all the passes
    except the last one ? using the offset allowance entered, and with do the final pass
    with NO offset allowance ?

I am a bit confused, can anyone shed some light on this

[stevem]

I have the same question!
I have so far simply made an offset of something like .002 and just create another profile, set it for the full depth to eliminate the watermark you get with multiple passes.
I guess if you do a separate last pass you could do the same thing.
I really don't know if one is better than another.
Hope someone else chimes in, before I go to the Vectric forum and ask there.

[traindriver]

I sometimes use this feature. For the one shown in red, I always have"Conventional" set for the direction. In case you are unaware of what this is, it is a machining term. If you have used a router table, you know that when you feed the board against the direction of the cutter, the cutter pushes back against you, but you can take a fairly aggressive cut, but if you feed the board the other way, it wants to take off. In conventional cutting, the spindle moves so the cutting edge of the tool is going in the opposite direction of the feed. This is what you typically do when using a hand held router or router table. "Climb" cutting moves the spindle so the cutting edge is moving in the same direction of feed. It's called climb cutting because the tool wants to "climb" on the edge you are cutting. If you run a toolpath, and there is a lot of tool chatter (tool cuts, but makes a real loud noise), chances are you are climb cutting. Climb cutting typically leaves a better finish and is used to clean up a cut by taking a very small amount off while climb cutting.



SO, I always do a conventional cut, and sometimes on a profile cut, where I'm cutting the part out of the wood, I check the "Do separate last pass" box and also check the "Reverse direction" box.  I put about .005 or .010 for the allowance so the tool will skim the part, making it just a wee bit smaller than designed while climb cutting for a better finish when I'm cutting something out.  Ideally, a climb cut should be done at a different feed/speed than a conventional cut, but I just let it ride. 

If memory serves me correctly, if I were to add .010 to the Allowance offset in the red part if will make the part .010" bigger if I'm cutting on the outside.  Then, if I do a separate last pass with a .010 allowance, they should cancel out.

I would recommend making a test cut with about 1/4 of the way through your material, then make the same cut with a .100 Allowance offset at full depth so you can see the difference and see if I'm telling you right.