I have read that slotting is bad for the bit and that I should use the pocketing tool. I am 3 weeks into C&Cing so very new. My first question is, if slotting is bad why does all C&C software include a cutout tool path? Second how exactly would you create a pocket tool pact to cut out a 3/4" project and have tabs for holding? Is using the Ramp feature on a cutout path of a 3/4" cutout enough to alleviate the slotting issue?
Thank you for your support!
Itās a necessary thing, and itās fine within the limits of the tool and machine and material.
Ramping will help, but canāt overcome a really deep slot many times deeper than the diameter of the tool.
One discussion on this:
Slotting can not be avoided all the time. Itās a necessary move.
You just need to be aware. Balance is the key.
Slow the feed rate if you can.
Thanks Will for the response.
I figured that was one way to do it, I had hoped that it would have been easy like checking a box to create cutout with tabs which acted like a pocket adding 10% or whatever is need for relief based on the selected bit.
Cheers!
Iāve found it to be dependent on material, tooling, how well chips are cleared, and a ton of factors. Cutting baltic birch Iāve found I just run it fast and hard with stock to leave. Then run a finishing pass. In aluminum, I avoid it whenever I can, but air blast/coolant, single flute endmills, and fast shallow depths of cutā¦help a ton.
The issue with slotting is that you get 50% tool engagement at all times (the entire front arc of the tool) which generates more heat in the tool and requires more force and rigidity to push through it. Heat is the enemy of tool life. Pocketing is generally 50% or less stepover so only about 25% or so of the tool is in contact with the material most of the time, even if you are cutting out more material by pocketing the tool will generally ride it out better. It also requires less machine rigidity. That being said, slotting is sometimes the best way to go depending on what you are doing, really depends on what you are milling and what the stock is like and how itās workheld.
As far as āhow exactly would you create a pocket tool pact to cut out a 3/4ā project and have tabs for holding?ā, I wouldnāt but if you think in terms of mutliple paths you could create a 1/2ā inch outline around the whole project, mill it out as a pocket down to about .1inch from the bottom and leaving a few thou on the part for a finishing pass, then have a contour path run as a finishing path that would bring the part to dimension as well as cut the contour path slot to the bed leaving tabs. The .1inch interrupted slot cut wouldnāt be too hard on the tool. This would be one way to accomplish it (there are as many ways as their cnc programmers) but I personally would just slot it out using subdued doc, feeds and speeds to not overwork the tool, the workholding or the steppers. Runtime is more valuable in projects for me than tool costs and slotting is faster. Your calculus may be different depending on what your focus is.
As a side note, Iām not a grammar cop but just as a heads up, itās CNCāing which stands for Computer Numerical Control, not C and C ing.
You may also consider a chip breaker style roughing bit for the slot slightly offset and leave .1 at the bottom as stated above and then come back for the final cut with a finish bit.
Guess I should have just said CAD software not CAD and CAMāing software (C&C) sorry to confuse you. Military, we make abbreviations for abbreviations.
Thatās my plan from now on. I think it would leave a better edge anyways.
Cheers!
I never use a pocket cut to do a contour cut. I use a rough cutting bit instead.
They are pretty much bulletproof. However, it does leave very small lines on the cutting surface, which sand off much faster than I could run a cleanup toolpath.
Hereās my favorite rough-cutting bit.
Note that in our new line of āEl Ochoā tooling:
we have:
which dials this up by at least a sixteenth.
Thanks Will, Iāll probably pick one of those up. That should also leave a small gap when I finish with a 1/4ā DC.
Cheers!
Willās suggestion of using the #213 is a good one, it does a great job of fast material removal!