[davemorl]

Hi all,

I currently am running a uc300 usb with mach3 and I have open loop steppers. This was fine for a homemade small router I had built as a prototype but I am now building a new heavy duty frame to migrate all my hardware onto. As I'm upgrading the lightweight frame I am also going to upgrade the positional motors as the weight of the table being moved is now steel and considerably heavier. Prob around 120kg so it is going to be pretty rigid*

What my choices are is a closed loop stepper system or a servo system. But I am thinking of using UCCNC instead of mach3 as I've seen it gives better results. I've been looking at these drives and motors;

3HSS2208h-100 with 20Nm nema 42 motor
https://rover.ebay.com/rover/0/0/0?mpre ... 2187432593

Also this servo configuration
https://rover.ebay.com/rover/0/0/0?mpre ... 2411229621

My question is basically this, has anyone got any experience with these options and how do they perform. Also how would I go about if it's possible to have a fully closed loop system to uccnc. Is it possible with the uc300 usb?*

Or if anyone else has any options of better motors and drives to get? My budget is max around £1000.

Thanks,
Dave.

[ger21]

My budget is max around £1000.

That pretty much takes the AC servos out of the equation, as 3 of them will put you over your budget.

I don't have any experience with the closed loop steppers, but I can tell you that I've never seen a DIY router with Nema 42 steppers. You definitely don't need motors that big.

I don't know anything about your machine, but some mid sized Nema 34's, and good digital drives (standard open loop) should be more than adequate, and a bit cheaper.

UCCNC is an open loop control. If you want full closed loop, you need to go to LinuxCNC.

If you stay with UCCNC, get the UC300ETH, not the USB version.

[davemorl]

Hi Gerry, thanks for your reply.

Sorry I don't think the link to the servos worked properly. I can see a servo 4Nm with a nema 34 frame for £325 and has step dir inputs.

https://rover.ebay.com/rover/0/0/0?m...2F112411229621

I wouldn't really say it' going to be a router to be honest. It' a steel frame all filled with concrete with a steel bed. It' going to be something along the lines of a tormach pcnc 1100 hopefully apart from its concrete filled steel instead of cast iron.

I know the rotor inertia is a problem with larger motors but I think with a 1100mm x 320mm x 25mm table with 25 hiwin linear rails, vice, work weight, also the lower 400 x 250mm steel plate will be very conservatively close to 120kg.

I have only nema 23 4Nm open loop steppers at the moment so I know this will not suffice. My ball screws are 10mm/rev pitch and I'm trying to stay away from any pulley systems if I can. I think I'd rather change the ball crews to 5mm/rev or even 2mm/rev of necessary rather than a pulley system as I know servos don't loose torshe like steppers at higher speeds so you get more bang for your buck.

I'll attach a couple of pics of my progress so far.

Dave.

[ger21]

You need to determine the maximum rapid speed you want, how fast you want to accelerate, and how much weight you are moving. You can use that info To calculate the required motor size.

[Jim Dawson]

Looks like a nice heavy machine you are building there.

Maybe this will help you with your calculations and give you some ideas. I also have a moving table machine.

Specs:
1200 x 2400 mm table
Table mass = ~ 350 Kg
40mm/rev leadscrew
NEMA 34, 9.12Nm stepper motor, driven at 80 volts.
Maximum motor RPM in operation = ~560
1.5:1 timing belt drive
Maximum lead screw RPM in operation = ~375
15,000 mm/min maximum speed
12,000 mm/min normal rapids
1 motor micro step = ~1 micron table movement
Am using 1 micron linear magnetic scales to close the loop, a very accurate machine.

I'm posting this to point out that using a finer pitch lead screw is not always the best answer. Since you want to use direct drive, a 25mm/rev leadscrew would be my choice for your project.