[Ringo51]

Hi all

My first post

I was wondering if someone could give me some advice on Nema 34's.

I'm building my cnc machine at the moment.

It is approx 1.2mtrs in length and approx 1mtr wide.

I am thinking of running the Nema 34 motors on it but was wondering if they would be good enough for the length part of the machine.

Would it be better to run 2 motors to work the length or one straight up the center.

Can anyone advise me on this?

The machine will be based on JGRO type of design and made from metal.

Cheers

[Eddymeister]

Hey chief...
I've bought the same slze motors for my machine build... Which will be 1200x1800x125 in size... I'm running dual balls screws for the x axis using 1 motor for each ballscrew...
I'm no expert but there seems to be a lot about underestimating steppers... Generally speaking, there's a lot of people using 425 or 387 ozinch for your size machine...
Considering my gantry will probably weigh around 30kg I've opted for 640's... This was just an educated guess but I'm fairly sure they'll be alright... The hardest thing is that anything extra in torque is usually wasted and converted to heat...
I'm starting small then will up grade if I need to... I'm using gecko 203s which feature a simple LEDindicator to tell you if the motors are working fast and hard enough...
I know this probably answer your question but if you convert ounce inch to kg cm... Its somewhere around 35 kgs 10mm out from the shaft of the motor... That's a hell of a weight... And transmitting that power through a screw which increases torque hugely, it wouldn't surprise me if you only need 1 of those puppies to drive your gantry...
But then again... I'm no expert..

[yancho]

Do not confuse length of the screws with the forces of cutting.The two are different things.In the long screws, they begin to droop.A traction power is the sum of the weight of the mass of detail and cutting power.It is given by the manufacturer of screws as static and dynamic loading.

[Manicalistical]

Might I suggest you do a google search for a pdf title CNCMechanics v1.2. It was written by one of the more knowlegable guys here and gives a skeleton outline of what you need to consider.

Personally I am going for a single direct drive up the centre, this is far cheaper with ballscrews and in either scenario it would be a very bad idea to continue operation if a motor dies or runs at a different rate. In the end the most powerful axis will most likely be your z one.