[mike_Kilroy]

no pupetxls, you got it totally WRONG! Just cuz I had the pleasure and experience working with Rick is absolutely no reason to say that. Besides, you already showed imperically that I am wrong about the inertia on stepper system and it is not so important like it is on servos. I stand corrected and appreciate knowing that! Guess I shouldn't have assumed inertia was so important to steppers too.

[harryn]

Hi, Thanks for that reply. I should spend some time on that site myself.

You are right that I completely forgot some items that are very important.

- approx 25 Kg to move up and down
- Counterweight - also about 25 Kg
- Z motion - will then of course by horizontal

For cutting forces, It is a pretty classic 3 hp bosch variable speed router, running 1/2 in shaft, 3/4 in cutters.

Rather than calculate the forces exerted by the router cutting, I attempted to estimate this with a simple experiment. I ran the router along a 2x4 at my goal speed of 360 ipm manually, and played with how much force I needed to maintain the router in position and at this speed.

My first order measurement was around 80 lbs force on the handles, so that is the number I have been using in the design. That is slightly misleading of course, as the router was also getting supported by the board, but it is as close I as could get.

It also matches some numbers that I have seen on some commercial routers that are sold around here, so it might not be horribly off.

My plan is to use either a pair (2 belts x 4 in wide x AT 10) or a single belt 6 in wide. This number came from stretch calculations and a check of tooth strength, although the stretch calculation is what really drove the belt width.

Over the next few weeks, I will spend some time on that site. I gues what isn't so clear to me, is where the motor inertia number comes from, as most of them don't list this, at least on the motor.

It seems like the motor inertia would be increased by the addition of a heavy gear on the shaft, but that seems to show up in the load side. I keep thinking of this like an engine + flywheel equaling the motor inertia, but perhaps that is an incorrect analogy.