1. Originally Posted by Sven
I'm building a 1250mm sq router planned to run at 10m a minute, using 2 nm steppers....
Calculations suggested 8 nm would get me 12m a minute or so.

Direct drive, 1610 screws, 2 motor/screws for the gantry.
Don't need 8Nm for machine that size if slaved motors 3 or 4nm nema 23 will be more than enough provided the gantry is less than 80-90Kg and your using ballscrews. If used with good motion control card you'll get 12nm or more.

I wouldn't use 2Nm because while they spin faster there will be very little torque left at the Mid/higher end of speed curve which is were you want it while cutting.

8nm would mean Nema 34 which would actually run slower with the same amount of volts. So you'd need more voltage which means larger drives and PSU. Really Large steppers need high power drives that run at mains voltage for best performance.
Last edited by JAZZCNC; 25-09-2016 at 02:33 PM.

2. Originally Posted by JAZZCNC
Don't need 8Nm for machine that size if slaved motors 3 or 4nm nema 23 will be more than enough provided the gantry is less than 80-90Kg and your using ballscrews. If used with good motion control card you'll get 12nm or more.

I wouldn't use 2Nm because while they spin faster there will be very little torque left at the Mid/higher end of speed curve which is were you want it while cutting.

8nm would mean Nema 34 which would actually run slower with the same amount of volts. So you'd need more voltage which means larger drives and PSU. Really Large steppers need high power drives that run at mains voltage for best performance.
At 10800 mm/minute (is 10.8 m/minute with 10 mm pitch) the 2 Nm had 0,8 nm of torque left, which is enough for my machine.
The cutting force was set at 100N in these calculations.

I cant run higher speeds on a ball screw of the length I am using.
Steppers with higher torque had a torque curve that plummeted as soon as they start rotating, the 2 and 3 nm motors were comparatively flat.

3. Originally Posted by Sven
At 10800 mm/minute (is 10.8 m/minute with 10 mm pitch) the 2 Nm had 0,8 nm of torque left, which is enough for my machine.
The cutting force was set at 100N in these calculations.

I cant run higher speeds on a ball screw of the length I am using.
Steppers with higher torque had a torque curve that plummeted as soon as they start rotating, the 2 and 3 nm motors were comparatively flat.
Ok if you don't want to listen to experience and would rather go with calculations then who am I to argue.

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5. I thought I'd post a video of the machine during it's acceleration tests today.

Now I'm unsure of what Jazz means but here is the machine running at 0,4 G with two 2 Nm steppers and 1610 ballscrews:

Topspeed is 10200 m/min
Last edited by Sven; 05-02-2017 at 01:21 PM.

6. Originally Posted by Sven
I thought I'd post a video of the machine during it's acceleration tests today.

Now I'm unsure of what Jazz means but here is the machine running at 0,4 G with two 2 Nm steppers and 1610 ballscrews:

Topspeed is 10200 m/min
What I said was Don't require 8Nm motors which is still true. Also that 2Nm will struggle while cutting at higher feeds. Cutting air is very different to cutting the hard stuff so suggest you stick cutter in and see how well it handles cutting with decent DOC at 8000mm/min.! (Which is MDF like feeds)

7. Ah, I thought it might be in that direction.
I'll test and let you know!

8. Originally Posted by Sven
Topspeed is 10200 m/min
Blimey, that is 380mph

9. Whoops, well spotted!
10200mm/minute.

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