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Hello! I am a high school technology teacher and was able to purchase an elite Axiom CNC this year for my classes. I know the math of calculating speeds and feeds and incorporating chip loads, etc., but also know all machines need to be dialed in to fine tune what setting should be used for each type of material. Before I re-create the wheel, does anyone have something I could use as a starting point for this machine, or any Axiom CNC's? Thank you in advance!
Mackenzie,
It's not so much "dialed" as it is knowing if your machine can handle the feedrate calculated for a given chipload. Ignore the YouTubers that say "listen" because that's hogwash and you should be wearing ear protection anyway. :)
I looked up the specs of that machine with a spindle and it appears to be pretty good with 320 IPM max. So I would calculate a chip-load based on the type of material. Start with MDF. Then, I would target the low range chipload, maybe -15% from nominal and I would try to keep my IPM at 180-200'ish and adjust spindle speed as needed. That's about all you need to do. Then try the same thing with a piece of plywood and a few species of hardwood.
For my CNC I actually did get a bunch of different materials I use, for example, MDF, 13 ply baltic birch, vanilla ply from Home Depot, walnut, maple, hickory, paduk, red oak, rift sawn white oak. I then created 3 toolpaths that were 6" in the X and then 6" in Y (kind of like an L so I could test with and cross grain) with chiploads of nominal, and +15 and -15%. I then ran them on the machine using a brand new bit and looked for anything like tearing, burning and I actually measured the chips. Then I just wrote down what looked the best and those are my targets I now use. I really only have 3 main targets (MDF/ply/hardwood with a few notes on smaller bits where I have slight variations for softer "hardwoods).
This is a good source for starting points: https://gdptooling.com/chipload-calc/
Jim is very knowledable as well and I'm sure he will provide some invaluable insight. Gary is also a venerable guru, who frequents the forums, so anything he says you should take under advisement as well.
Chers,
"Ignore the YouTubers that say "listen" because that's hogwash and you should be wearing ear protection anyway. :)"
I agree with Michael's advice with this one exception. You can and should listen to the tool while it's cutting. You can pick up the sound of chatter (even with hearing protection on), which indicates the feedrate being too fast or the rpm too slow. Whining or screeching tells you just the opposite - rpm is too high or the feedrate too low.
@micksimon @michaelburnside
Thank you both for the valuable help - this is great to get me started.
Cheers!
You can listen all you want but if you did your homework it’s irrelevant. My point was that you should pick chiploads based on actual numbers provided, not something mysterious like listening. I’m not saying that if something is waaay off you can’t hear it, but that’s an entirely different topic and I didn't want to confuse the OP. The point is not to listen for proper chiploads.Quote:
Originally Posted by Mick Simon
Sometimes harder material makes a higher pitch sound (e.g. bloodwood), but the cuts look good and chips are properly sized to remove heat, so it doesn’t matter.
I was told by a onsrud rep to also look at the waste piece it the cut looks better then the piece you are cutting then reverse directionQuote:
Originally Posted by Michael Burnside
"You can listen all you want but if you did your homework it's irrelevant."
After 30 years in the industrial CNC business, selling, installing, training and supporting CNC routers, and 7 years teaching it at the college level, I'm well versed in chip loads and how to determine proper feeds and speeds. I started my comment by agreeing with all of that. My only point was that it's not uncommon to hear a problem arise due to unforeseen circumstances that requires an adjustment. Recognizing it while it's happening can give you the opportunity to make corrections on the fly. It's the reason most all controllers have real-time adjustments available.
Mick, I don’t disagree with your comments nor did I question your experience. Apologies if I came off that way.
I was just trying to separate listening to the machine and calculating chip loads. I see the former as fine adjustments and detecting major problems, like a loose collet or a very dull but. That’s all.
I appreciate the apology.Quote:
Originally Posted by Michael Burnside