Spindle Speeds, Just trying to understand

[aycompay (Ernesto)]

Hello, I"m a new Shapeoko Pro owner, so forgive me if you are disturbed by my question. I’m trying to understand the spindle speeds. The Carbide3 website saya that the spindle runs 12,000 - 30,000 RPM. If I understand this correctly, when my spindle is set at “1” is running at 12,000 rpm. If I set it to “6” it runs at 30,000 rpm. In fact, I ran a spread sheet to figure out all other speed seting based on the number on the spindle:
1 - 12000
1.5 -16500
2 - 18000
2.5 - 19500
3 - 21000
3.5 - 22500
4 - 24000
4.5 - 25500
5 - 27000
5.5 - 28500
6 - 30000

So today I was running a Nomad End Mill (0.125 inch) #102 and Vcarve Pro set the spindle speed at 6200 rpm. But I can’t get to 6200 rpm the slowest it goes is 12000, almost twice the speed. So what do I do? Do I run it until it fails? Do I increase the feed rate? Suggestions?

[LiamN (Liam Newcombe)]

So that’s the standard 1/8th Inch mill, what material are you cutting?

And what depth & width of cut were recommended?

[aycompay (Ernesto)]

I was cutting 1/2” MDF, 1/8” wide

[LiamN (Liam Newcombe)]

In woods higher cutter RPMs definitely work and the Pro is rigid enough to not have a problem, especially on such a small cutter.

You can use @gmack 's calculator sheet to work out sensible values

Speeds, Feeds, Power, and Force (SFPF) Calculator

Here’s a free Microsoft Excel workbook that facilitates the estimation and logging of CNC machining parameters and performance. The three tabs at the bottom left of the workbook access worksheets showing estimated parameters for a 60,000 RPM HF Spindle, the Makita 0701 Router, and Dewalt DWP611 Router in Shapeoko 3s. The maximum spindle/router speeds were used on each sheet to minimize cutting forces. The same 1/8" 3 flute endmill with 0.25" DOC and 0.005" WOC in 6061-T6 aluminum with ~0.001 …

For slotting in wood I would run that 1/8" at (minimum) 20,000RPM in my spindle, 1,000mm / min feed rate, that’s 0.03mm/tooth, 3mm deep. I’d push it more normally but a full engagement slotting is hard on the cutter and it’s only small.

You can go faster, for MDF no reason not to go to full RPM, just don’t let the feed per tooth go much smaller, you’re just wasting cutter life and making dust then.

You can also probably cut the slot deeper than the 3mm, but I’ve never pushed the 1/8" cutter, I only use it for detail finishing after roughing out with something larger. A 1/4" in the pro should slot at least 10mm deep and be quite happy.

[Julien]

@aycompay

But I can’t get to 6200 rpm the slowest it goes is 12000, almost twice the speed.

Double the feedrate to match the doubled RPM, to maintain the same chipload. But mostly, ignore Vcarve default settings and start from CC database values instead?
Or if you feel like it learn about how to determine feeds and speeds yourself?

[gmack (Gerald Mackelburg)]

@aycompay

Vcarve Pro set the spindle speed at 6200 rpm. But I can’t get to 6200 rpm

IFAIK Vcarve Pro doesn’t provide any meaningful speeds and feeds guidance, even for the tool databases from Amana and Whiteside. 6200 rpm is really crazy. You can get more out of your machine by running the spindle at the highest speed (30.000 RPM) as long as you keep the feed rate above 0.001" per tooth (IPT).