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kb9ydn
in reply to: Anonymous


@Anonymous wrote:

Here is a great example of junk time estimates.  Look at the "Slot Finishing" op in the attached model.  If 0 roughing stepover passes is specified, it estimates 2:15 machining time.  If 20 passes is specified (doing 20X as much work!) the time estimate increases to only 9:48 (or 10:26 in simulation)!  I've set all feedrates to the same 40 IPM so we don't get tricked by lead-in/out, plunge, finish rates, etc.  This makes no sense at all....

 

Regards,

Ray L.


 

 

Except it's not 20x the work, it's only 8.5x, if you're talking about only the number of passes.  If you specify 0 roughing stepovers you get a total of 8 passes.  With 20 stepovers you get a total of 68 passes.

 

How does this make sense?  Well with 0 roughing passes you have 2 finishing passes and 4 depths, for a total of 8 passes.  With 20 roughing passes you have 20 + 2 = 22 passes per depth.  Now you don't have "Rough Final" checked under multiple depth passes, so the final depth doesn't do any roughing passes, only finishing.  So that only adds another 2 passes.

So in total you have:  22+22+22+2 = 68 total passes.  68 / 8 = 8.5.

 

 

It also looks like the early passes are shorter than the later passes, so the actual time/distance for your 20 roughing passes will be even less than 8.5x.  Comparing the distances I get 323 in. and about 60 in..  That's about 5.4x, which seems plausible.

 

 

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