CNC Shark Forum

Excellent advice, sharkcutup, regarding going with the grain.

There are also "adjustments" (modification?) you can make to the machine that will get rid of them.

Essentially, what you're seeing is the leading or trailing edge of the bit being just slightly above/below because the spindle isn't exactly perpendicular to the wood surface. And, because the system has some flex in it, even when perfectly aligned (aka "trammed"), movement of the system can cause the bit to "dive" when it changes direction. The system responds differently depending on which direction the bit is being moved, which shows up in marks like that. Fixing it IS possible, but, the overall value of making those adjustments is to be weighed: On these machines, even near-perfect tramming isn't just a matter of turning adjustment screws.

A couple other things that can help:

* Using a radiused end-mill instead of a sharp-tipped one will not only give you a stronger bit (wears more slowly, doesn't break or chip, etc.), but also minimize those lines, due to the more-gradual transition between lines.

* Using a larger diameter bit can at least lessen their number (and speed up that pocketing). Your system will determine whether that's feasible for you.

* Using a smaller (or larger) step-over. Sometimes those lines can be "masked" by adjusting the stepover so that the nice clean part goes back over the lined part.

* Have a distinct "finish" pass. When you do the cutting with that bit, leave 0.010" or so, and then run a finishing pass to take that last 0.010". The much gentler cut will be a lot smoother and less prone to those kinds of issues, but will increase the machining time by that added finishing toolpath. The good news is that finishing passes can usually be run at significantly faster feedrates because they're taking off so little material. If you're planning to sand aggressively anyway, then the finishing pass might end up merely consuming time. But, if you want it as smooth as feasible, try adding a finish pass. Ideally, use a "new" bit, or one that you only use for finishing passes.

I'm sure there are more, but I'm suspect I'm late for something, somewhere....

Regards,

Thom

What bit did you use and what was your stepover? Thank you

Sharkcutup....if you don't mind me asking, what's the size of this sign. What bits were used. And how long did it take? I have been to craft shows were people are selling hundreds per month. How are they about to cnc that many? . I tried one that was 11"x6 and took about 1 hour 10 minutes. What am I doing wrong. Thank you for your help.

Thom...thank you for the great advise!

Sharkcutup....if you don't mind me asking, what's the size of this sign. What bits were used. And how long did it take?

The Sign I posted earlier on this thread was 11" x 6" x 3/4" thick premium pine

Bits used:
.25 dia x 1.0" cut length down cut spiral end-mill (for Pockets to a max depth of .375" .1875" for top layered text & another .1875" for the bottom layered text) Could not go any deeper because of the next clean up bit used only has a 5/16" max cutting depth.
.0625 dia. x 5/16" cut length carving straight bit (for cleanup in & around all lettering and the small gaps like between the dot of the i)

I do not have an answer as to how long it took because I was not in any hurry to get the sign completed and I took several days in planning each of the tool paths. I will say this though the process does speed up considerably when you merge (create merge toolpath tool) toolpaths that use the same router bit rather than doing each toolpath individually (but of course this can only be achieved through thorough and decisive planning).

Have a GREAT DAY!!!

Be Safe around those AWESOME machines!!!

Sharkcutup