I’ve been mostly cutting aluminum with my very new Pro and I’m getting ready to cut a project out of ash which has a lot of corners. Rather than pocket it, I want to run an adaptive clearing but I really don’t have any idea what to use a starting point for feeds/speeds/optimal load/DOC. As a test, I ran the same settings I use for aluminum in a piece of 2x4 and it worked perfectly but I feel like I should be able to go faster.
Does anyone have a recipe that they use for adaptive clearing with a 1/4" endmill? Even if it’s not a #201, I’d be interested to know what settings you use (and the # of flutes)!
I’m leaving this here in case it’s useful to you as a starting point:
For aluminium, feeds and speeds are typically tuned to get a 0.001" chipload (a.k.a. the golden value), and as you found out it works quite fine in wood too, but you’re leaving (a lot) or MRR on the table. In hardwood with a 1/4" you should be able to at least double that chipload to 0.002", likely more but then it depends on a number of things, so 0.002" sounds like a good next step in the optimization for you.
From that chipload target, the optimal load you will be using (I tend to stick to 1mm for adaptive in hardwood), the RPM and the number of flutes, you can derive the feedrate value (see spreadsheet near the bottom of that page)
And then…there is the debate about DOC, especially for adaptive clearing. The rational thing to do on a Shapeoko is to limit DOC and push feedrate instead, me I just like watching deep adaptive toolpaths running so against all advice I’ll cut up to 200% endmill diameter because I crave those long chips
In wood the number of flutes is less of a dilemna than in other material. For metal and plastics single flutes are great, in wood not so much as chip evacuation/recutting is less of a problem and a lower number of flutes also means slower feedrates. Even in wood slotting is still bad, but with an adaptive clearing toolpath and helical entry, chip evacuation and tool engagement is not a problem so a 3 flute like the 201 will work great. For some reason my favorite tool for wood these days is a sturdy 2-flute 6mm endmill, that I know I can push to agressive feeds and speeds.
I do realize you were asking for specific feeds and speeds values, but I feel it’s more useful to let you determine what they should be (learning how to fish etc…) as…it depends.
That Feeds & Speeds chapter is something I spent several hours really working to understand one day. It really opened my eyes on how to approach feeds and speeds!
I ran 18,000 RPM, 80 ipm feed, 3mm DOC, 2.5mm optimal load with an effective chipload of 0.0014" and a MRR of 0.93in^3 / 0.1 HP.
It sounds like you might be saying 16,000 RPM, 140 ipm, 0.5" DOC, 1mm optimal load for an effective chipload of 0.0021" and a MRR of 2.8in^3 / 0.28 HP? Is that somewhere around the ballpark of what you’d be using?
I would recommend going more gradually in experimenting how far you can push things.
Doubling the chipload to 0.002" should be just fine, but also adding a x4 factor on DOC at the same time is probably a too aggressive (even with the reduced optimal load) and as I mentioned not even desirable on a Shapeoko (even though I think those feeds and speeds you mentioned would work on a Pro).
Also, the higher the RPM the better as far as cutting forces are concerned, so if your goal is to increase MRR, there is no real drawback in maxing out RPM (well, there is the noise…)
So I would probably experiment in steps, starting from the recipe you have that works fine:
pick a higher RPM, say 20k, and scale up feedrate accordingly (x20/18). Easy, no risk, but a 20/18th improvement in MRR without thinking twice
then increase chipload to 0.002" but using the original DOC
then gradually increase DOC until the machine tells you you’ve gone a bit too far.
you will likely be able to push chipload and optimal load further than you can push DOC.
Even with the great spreadsheet from @gmack’s to predict MRR/cutting forces vs machine limits, experimentation will be key.
Thanks for the recommendations. I guess I’ll try 20,000 RPM, 120ipm, 3mm DOC, 2.5mm optimal load which gives me a 1.4in^3 mrr. That sounds like it should be reasonable compromise between my original recipe feeling overly conservative and avoiding pushing the bounds of the machine.
