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Re:Show HN: I built a CNC-machine from scratch, using 40x 3D... by giantg2 on Wednesday November 03, 2021 @04:00PM (#29099551)
"I can't see any situations where adding more torque to the X or Y axes using a smaller gearer stepper makes sense."

Generally agree. Torque is only needed to a specific threshold. If it requires a lot of torque, then that's probably a good sign to slow the movement down (for the sake of the machine's longevity).

Re:Show HN: I built a CNC-machine from scratch, using 40x 3D... by jacquesm on Wednesday November 03, 2021 @08:19PM (#29102264)
On the contrary, plenty of tools need to move and chip otherwise they'll get dull, cutting speed is a function that increases a machines' longevity. But cutting speed does require a solid mechanical setup, drivers that can source some current and a drive train that does not suffer from over or undershoot ('slop').
Re:Show HN: I built a CNC-machine from scratch, using 40x 3D... by giantg2 on Wednesday November 03, 2021 @10:45PM (#29103151)
"plenty of tools need to move and chip"

Not sure what you mean by that. I dont know all the tools in the world, but generally a chipped tool gets less sharp. Even something like obsidian would get less sharp in regards to the intended use with a random chip as compared to a well knapped tool.

"cutting speed is a function that increases a machines' longevity."

I'm not sure you are using cutting speed the same way I'm talking about movement. Applying too much lateral torque to a router bit is how bits break, bearings wear prematurely, etc. You don't need much torque to move the router.

If you want faster cutting speed, then the RPM of the bit can be increased, or using a different bit design. You can cut faster and it still shouldn't require much torque for the movement.

Re:Show HN: I built a CNC-machine from scratch, using 40x 3D... by craftinator on Wednesday November 03, 2021 @11:43PM (#29103495)
They possibly meant "plenty of tools need to move chips".

A common problem that causes chatter and poor tool life is not taking a large enough chip. Large chips stabilize the tool (the rotation of the tool pulls it into the part) as well as allowing for a more continuous, uninterrupted cut (whereas too small of chips cause the flutes to have to re-engage the cut over and over, and the number of engagements and tool life have an inverse relationship).

Re:Show HN: I built a CNC-machine from scratch, using 40x 3D... by giantg2 on Thursday November 04, 2021 @12:13AM (#29103629)
True. My point was that it shouldn't take very much torque to match the cutting speed with the movement speed. Even if you increase cutting speed you can keep the same torque (for movement) by increasing movement speed. It should be a balancing act with torque (for movement) being fairly constant in the range to provide continuous engagement, with the cutting and movement speeds changing.
Re:Show HN: I built a CNC-machine from scratch, using 40x 3D... by dekhn on Wednesday November 03, 2021 @11:23PM (#29103379)
I suspect he means that you want to move quickly through aluminum, especially if you don't have active cooling. If you move slowly you can get problems like chip welding and everything goes south.

I actually didn't have enough torque to move the router through lots of material until I moved to some fairly serious stepper drivers and configured them to use max current and voltage (IE, I got a 48V, max 20A power supply). Even then, if if accidentally move the router bit while it's not spinning into the work, the motors stall well before the bit breaks (1/4" carbide end mill).

Re:Show HN: I built a CNC-machine from scratch, using 40x 3D... by giantg2 on Wednesday November 03, 2021 @11:56PM (#29103552)
I guess if they're getting welding there's no sprayer set up. Some emulsified oil (10% Ballistol) usually works great for lube and cooling, even in small quantities.

Yeah, that makes sense. That sounds like it's really not that much torque the way you describe - just above functional minimum and no where near too much (eg people forcing it through and breaking bits).