I have an issue when performing shallow pocketing (vectric pro, offset strategy, whiteside 3 cutter surfacing bit, 250+ipm and 1/64 doc) to flatten panels too large for my planer. With the offeset strategy, the router travels from center outward by the stepover with each “lap” around the board, and I find that I get scortching in 3 of the 4 corners of each lap (the corner where the bit “kicks out” for the next lap does not scortch), because the router actually pauses very slightly before changing directions EXCEPT for the last lap around the board, where the router slows down but never stops during that final circuit. I brought this up in the vectric forum, and users there say this is an acceleration/deceleration issue that is a controller config, not a vectric issue. Any thoughts?
I see the same thing when I use carbide create to do surfacing. It’s a surface speed thing. When it turns the corner, the router is traveling much closer to 0 ipm than the 250ipm setting. The 1” bit is spinning 10k+ rpm (depending on your dial setting) and sitting stationary. It’s gonna burn.
When I am not lazy, I use fusion 360 for surfacing paths with lead in and lead out space to give the machine time to get up to speed after doing a 180° turn. I also prefer a back and forth pattern over the spiral you describe.
Tl;dr: ipm in the corners slows so much large bits will almost certainly leave burn marks.
Thanks. After some experimentation I found several different ways to avoid the scortching including those you suggest. However, the question of why the router comes to a noticeable halt in each corner save for the very last lap around the board remains. Since during that last lap the router slows but does not stop in the corners, I get no scortch on that final lap. On a large panel the number of laps at a 40% stepover represents a significant time savings if the router just slowed down without completely stopping during all those intermediate laps.