Looking forward to hearing about it ! (and back to the OP’s questions)
Great overview!
One thing I’d add would be the diameter considerations:
- spindle / trim router — able to use the overhang cutting area
- milling motor — narrower, reduces lever effects, but also loses some (~11mm) of the overhang cutting area
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@Vince.Fab, and several others on this forum, are magicians - I’m merely a mortal. Haven’t seen any posts with spindles running higher than 24k.
Thanks. I’ve added your and other’s inputs as well.
Id get the Makita cause its a proven little work horse
Eventually you may venture towards bigger/better spindles, but theres nothing like a drop in unit and making parts.
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The (insane) thread thread that @Vince.Fab started has multiple references to his 60K spindle
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Here’s another thread about this. Did @Vince.Fab ever get his 60,000 RPM spindle working properly? Can someone please explain why software control of speed is so important - especially if it disables important spindle current display from the HY VFD’s?
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It’s not important, it’s just very convenient (to not have to care about setting the RPM manually, and to not have to turn the router on and off between jobs). It’s one of those things that once you get a taste of them, it’s hard to go back, even though it’s just a little thing.
I could imagine other possibilities like having the CAM software generate varying RPMs for different parts of a cut, but that does not exist as far as I know (nor would it be useful in 99% of cases)
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ER collets should be added to this list, for their wide variety and low price compared to router collets.
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Wouldn’t it be more useful to have the software adjust the feed rate (to control cutting power/force), and have the operator adjust the spindle speed based on how things sound (i.e. avoid resonances and such)?
When I first heard of G-Wizard, that was my assumption — that it imported a G-Code file, parsed the physics of it, and dynamically adjusted the feeds and speeds for the best possible cut.
Yes, and you should have electronic speed control for this, either in the communication/control program (are there plans to add a spindle speed rate override to match the feed rate override in Grbl?) or in an external unit — no one should reach into the machine’s working envelope while it is running to adjust a dial.
Power down (and unplug if you have that option — I place the plug for my trim router on top of the holder for the collet wrenches so that I never forget to plug it back in, and so that I have a habit of unplugging it before an endmill change) and be absolutely safe about reaching into the machine’s working area.
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CNCjs does implement RPM override
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Assuming that the spindle isn’t exciting some kind of machine resonance, I think that the last thing to do to optimize the cut would be to adjust spindle speed.
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Dynamically was the wrong word to use there — my erroneous assumption would be that the spindle speed would be adjusted as necessary during the cut to adjust for different aspects:
- climb vs. conventional — when climb milling, adding the current feed rate to the SFM speed to adjust for the spindle movement/cutting, but conventional would subtract it
- when accelerating / decelerating — apparently the machines adjust speed quickly enough that this isn’t an issue, but doing this might eliminate the need for a dwell command as is used by some processes
At some point I’ll get back to experimenting with TPL, or some other tool for making G-Code directly, and will have to experiment with these ideas.
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Feed rate (IPM) and direction do not affect cutting speed (SFM) unless the spindle bogs down.
In normal usage, no.
But, consider the extreme case — if feed rate == SFM, then when climb milling the endmill edges wouldn’t move relative to the surface, and when conventional milling it would be twice the effective movement — I’m willing to accept that the speed difference is negligible and inconsequential, but I’m curious if one could reap a slight improvement in feeds and speeds.
I also wonder if varying the spindle speeds would better distribute wear on the motor and so forth.
In my experience, having gcode controlled spindle rpm has proven very useful and allows you to achieve consistent chip load from one job to the next. Combined with the bitsetter(which I don’t have yet) it would make for a really seamless job.
It also means you need to remember less… If your tools are configured correctly in the cam software then you never need to set spindle speed, at all.
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How about a speed controller with feeback loop from tachometer for the router? The power would be adjusted to maintain proper RPM or feed speed adjusted if the router cannot maintain set RPM.
This is what SuperPID does, you install an optical sensor that can see if the router is beginning to bog and increase power. I’m sure there are others that work this way as well, I’m only familiar with the SuperPID.
Dan
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I think, getting back to the original question, a Makita is the best bet. Even a converted brushless cuts aluminum quite nicely.
All sorts of trade offs, side benefits, personal preferences that only experience will mold.
Go with a Makita. Move on from there if you like.
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