Roughing Endmills

I’ve been using a single flute carbide endmill and have been quite pleased with the results using adaptive tool paths. What I’ve struggled with is 2-D Contours and chip evacuation with single flutes in general. I ordered a 1/4 4-Flute roughing endmill cheapo (SpeedTiger) from Amazon and couldn’t be more pleased with the surface finish (Yes, the surface finish is decent), but more importantly the chip evacuation is awesome.

Running the 2-D contour at 1000mm/minute with a DOC of 17.5 in what is approx. 18mm plywood. Minimal chatter on the spring pass. (Not sure why that is.) Dewalt 611 is set at approximately 4.5 - 4.75. No fires yet, not even charred wood or hot bits

Has anyone else tried roughing endmills with their LowRider? Is there something I’m not thinking of or seeing as a downside?

Those are some impressive numbers. How big is your LR, and do you have any links to the endmills you are referring to?

~17mm/s at 17.5mm DOC…wow!!!

Am I missing some detail? What’s a spring pass? Are you cleaning up a full depth edge like a finishing pass? This would make sense at those feed rates, my mind would be pretty blown if you are actually full depth cutting though?

I’ve full-slotted at that speed in mdf at about a half inch doc(12.7mm)on my lowrider. Much deeper and I worry about losing steps because I start to get vibrations from my crappy build quality (never lost any on mdf, but I HAVE lost them). But deeper, and on plywood? That’s pretty great!
Can you show us this endmill? And I’d really love to see some video if you have any. I imagine the chips rooster-tailing out of the cut like watching somebody take off on a dirt bike, lol.

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Endmill is this, only 1/4" shank with 1/4" cut.

My LowRider is a full sheet capable machine. Just used all that awesomeness to work on this:

Not finished with the desk just yet. A few details to finish out. But, without the LowRider - I wouldn’t have been able to make the pieces accurately enough to glue up.

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I’m too new to this to know this is crazy, I guess. The 6mm single flute didn’t come close to these feed rates. more like 5-600mm/minute max. I threw in the roughing endmill just to see what would happen and kept bumping up the feed rate until I landed with a happy 1000mm/minute. 17.5 DOC was dialed into because of undulations in my spoilboard making 18mm DOC too deep at times.

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I’ll get some cuts lined up and some (shaky hand) video posted this weekend. And yes, the material just flies out of the slot… but that could also be in part do to my vacuum too.

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Very cool, thanks for the info and neat work on the glue up too. I bet that was a little tricky for clamping with that many thin pieces.

It’s not crazy at all, as far as I can tell. It’s unusual to run 4 flutes, but it’s come up before and and there isn’t much reason not to use them. My guess is that you could probably turn the router down a little. Unless my calcs are wrong, you’re sitting at 0.011mm per tooth (0.0005"). I calculate my starting point at double that.

Very impressive. Higher flute count requires higher feed rates and not everyone is able (or comfortable) running that fast, so this is above and beyond in that way. Another aspect of a 1/4" bit instead of 1/8" is that for many thin pieces it uses more material to have a wider kerf, but time is also a consideration, so with that plus chip evacuation I can see it being worth it overall.

Well done.

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Great find… this encouraged me to order one to play around with, there is a 3 flute version available on amazon.

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Not sure if this works or not. This should be a link to a simple 2-D contour 18mm DOC at 1000mm/min with a spring pass at the same DOC and feed rate. The router is at 4.5, though it is true I can dial it down to about 3.5 or so. The issue with the slower speed is that the rails/tubes begin to experience torsion when cutting near the middle on the x-axis. However, if factoring in some slop in the cut with the settings, it is easy to run a clean up pass to make it all look nice.

https://youtu.be/yQIieHT-M1I

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I implemented your vacuum duct modification. Works great!

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Duuuuuuuude that’s so deep! Video is super awesome, absolutely LOVE IT!
For real, you’re my hero of the week!

Holy crap man, get after it!

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WOW!

That is solid cutting.

Something to be aware of. Overheating of stepper motors is far more likely when running faster. A “duh” moment.

6.35 (1/4") Roughing endmill with 14mm DOC this time. Pushing the LowRider up to 1500mm/minute with a 6mm step over on a 2-D Pocket tool path. Worked great until the end of the two hour program (of course), the steppers overheated and I lost 5mm on the X and 5mm on the Y. The project wasn’t ruined, but from now on I’ll be running smaller program segments to avoid overheating. Ambient temperature was approx. 80F

Actually the current through the motors is the same if they are moving fast or slow or even stationary, as long as they are energized. The duration of the job will primarily affect how hot they get. Faster would decrease the chance of overheating if it means a shorter job.

And it’s really the motor drivers, not the motors, where the heat causes lost steps. The drivers have a thermal shutdown feature when they get too hot. The motors will happily melt the plastic before they lose torque (which is its own problem).

If you can get nearly a 2 hour job, then it sounds like the cooling of your motor drivers is almost enough to keep up with the heat generated. A more aggressive fan and you are probably good to run indefinitely.

Of course if the motors begin to soften the plastic then that’s a problem too, so keep an eye on that.

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I think losing torque is likely the real problem in this case. As @jamiek noted, the current through the steppers (and drivers) is constant, so there isn’t a significant difference in the heat generated.

Stepper motors generate their maximum torque when stationary. As they move faster, they generate less torque. This is primarily due to an effect called “back EMF”. Basically, as the motor turns it starts to generate electricity and this happens to be in opposition to the electricity being supplied to drive the motor, so it reduces the torque produced. Stepper manufacturers provide torque curves for their motors to help us choose the best model for our application.

You’ve probably found a combination of feed, speed, and DOC that exceeds the steppers torque output.

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I’ll hook up a fan and try it out.

If that doesn’t allow for extended run times… I’ll try cutting the red wire.

Thanks