Wood Router - typical accelerations?

[pjkumpon]

I'm designing a 3 axis wood router. I would like to get feedback on two design aspects:

1. typical acceleration profiles: I could guesstimate this - but I'd like get some feedback on what other's use on their DIY CNCs (for all three axes).

2. loading: on the tooling: I'm not sure what a typical design load would be... how much force does it take to route through wood at 'typical' accelerations and speeds.

I'm looking at a 20" x 30" x 5" table, wood structure with ball screw drives on all three axes (Two on the X, one on the Y, one on the Z). I'm targeting NEMA 23 motors, but wondering if I can get away with less than 350 oz-in.

Any input would be appreciated.

Thanks!

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[ger21]

1) I think most DIY machines use settings between 20-50 inches/s^2. Generally, the higher the better, but with most hobby level controls using trapezoidal (linear) acceleration, many people run into issues with the machine shaking at higher accelerations.

2) It depends, but I doubt that you'd ever see more than 20 lbs of force, 30 max. That would be taking deep cuts, with 1/2" diameter tooling, at a pretty good rate.
Spindle power, machine rigidity, holddown, all play a role here.

I'm targeting NEMA 23 motors, but wondering if I can get away with less than 350 oz-in.

Why would you want to go lighter on motors? What pitch ballscrews? What kind of speeds do you want?

[pjkumpon]

Thanks for the quick feedback. Was thinking of going lighter on motors to save on the cost of the drivers associated with the larger torque motors. Honestly I haven't done much research into the cost deltas so maybe it's not that big of a deal. That said, I do have a few follow ups:

3. What are typical linear speeds for a wood router?

4. When selecting a stepper, should I consider other features (aside from NEMA size and torque)? Ie. low impedance, etc. ?

Thanks again!

[ger21]

What size is the machine, and how much are you looking to spend?

3. What are typical linear speeds for a wood router?

Depending on how much the machine costs, "typical" could be 50ipm for a lightweight hobby machine to 3000ipm for a high end industrial machine

4) Inductance is the most important factor, with lower being better. 1.5mH-2mH would be best.