First build

[ack1]

Hey, So im planning my first cnc router and aiming for steel framed 5'x10' based on Cncrouterparts new kit. I have most things decided yet not all.

I'll be cutting mostly 3/4" plywood. But probably all kinds of materials.

I just cant decide wether to save some $ and go with the Nema 23 380oz kit or go for the Nema 34 960/640oz kit.
Im thinking i'd need the 34s for this size machine, but wherever I look ppl are praising their G540+380kit saying it can handle anything.

I really like that the 23 kits seem quite "plug and pray" since its my first machine too but it wont hold me back should it come to the 34's.

What's YOUR opinion ? Is the Nema 34 kit worth the extra money over the Nema 23s on this kind of machine ?

Please give me some input.

[ssutton]

The size of your table makes little difference when it comes to the size of your motors/drives. All that really matters is you targeted speeds and materials that you plan to cut. I have a 4' X 4' table and when I build again I will go with nema 23 motors and a G540 again. For what the average home shop is doing this is all that you will ever need.

As I said the size of your table makes little difference, but keep in mind that a large table with a heavy gantry will be hard to accelerate fast which may dictate the need for larger motors/drives. Having said that, my gantry has a cut path of 49.5 inches wide so when I build again I already know that with the weight of my gantry (75 pounds) nema 23 works very well with the acceleration that I am using.

Scott

[DonFrambach]

If it fit in my budget, I'd go with the NEMA 34 motors. It just seems to me that with a machine that big you'll want to cut big things, move large cutters, and want to do it fast. Having said that, if the bigger motors didn't fit with my budget I'd go ahead with the NEMA 23 because any router with any motors is ever so much better than none at all!

[Balcomwoodworks]

I certainly can't help in this arena....But I have the same question as the original poster in my head. I know calculations can vary wildly based on many things, but it would be nice if someone can post some specific examples such as:

With a Nema 34 960oz/in motor, and a 100lb gantry, you should be able to accelerate @ x , rapid at x, and cut @ x, with a force of x.


Another thing I'd like is a solid comparison to a machine that I can find on youtube cutting, such as a Shopbot Alpha.....

The Alpha lists these specs on their website

150lbs of linear cutting force
600"/minute cutting speed (with full force)
1800"/minute rapids in x and y

Is it possible to get anywhere near this with the Nema 34 motors from CNCRouterparts.com?

[ack1]

Thanks for the replies, im still having trouble deciding but it'll come to me.

Looking to buy a 1.5kw spindle+VFD,probably 2.2 if I end up going with the Nema 34s. Any recommendations ? Been peeking at those cheap ebay ones, but ebay feels like a minefield.

[hemsworthlad]

First go with the ER20 2.2kw from china but buy the VFD local or in EU, the cheap chinese vfd's are very poor quality. ER20 makes a more flexable range of cutters available.
I can fully recommend chai @ linear motion bearings for the spindles he sells, I've bought several from him now for personal use and also supplied several with machines I've sold. Also recommended him to folks i've helped all who have been highly satisfied.

RE: 23's or 34's Well it's not really that simple and like what has been pointed out table size doesn't really matter. To put it in very simplified terms its the mass you need to move and ultimatly slow down and the force required to overcome the friction from the linear system used which all this mass is fastened that will ultimately determine motors/drives required.

Now IMO lots of folks take the wrong route and try to make the Gantry as light as possible so they can use a particular motor or drive.! . . Mass can be your friend that will show in a suprior cut and can enable deeper cuts if the spindles upto the job lessening cycle times. And all thou it does come with a slight cost in both terms of rapid speeds and overall extra expense it's worth every penny IMO.
My rule of thumb is for machines under 4ft-sq with a moderate gantry weight with either lead/ballscrews or R&P then 23's and the G540 are perfect.
Over 4ft and using R&P which most machines over this size use then 34's and 203v's are the best combination, thou 201x's are still nice drives if on a budget, just 203's are the daddy IMO.!!

One thing I'd like to point out is how much the overall attention to detail and build quality of the machine will play in the friction factor.! . . It doesn't matter if you use the best profiled linear rails and highest quality ballscrews combined with the best motors and drives in the world if they are fitted incorrectly or connected to an inferior built frame work they will perform badly.! . Infact they are even less tolerant of poor workman ship than cheap components due to fine tolerances they work in.!! . . Again worth every penny if fitted correctly because they will last for ever.

I say this to every one who ask's (or even those who don't) Dont try to save penny's at the begining because it will cost you far more pounds or dollars down the road. . . Thats fact.!!

Dean.

[louieatienza]

Originally Posted by Balcomwoodworks I certainly can't help in this arena....But I have the same question as the original poster in my head. I know calculations can vary wildly based on many things, but it would be nice if someone can post some specific examples such as: With a Nema 34 960oz/in motor, and a 100lb gantry, you should be able to accelerate @ x , rapid at x, and cut @ x, with a force of x. Another thing I'd like is a solid comparison to a machine that I can find on youtube cutting, such as a Shopbot Alpha..... The Alpha lists these specs on their website 150lbs of linear cutting force 600"/minute cutting speed (with full force) 1800"/minute rapids in x and y Is it possible to get anywhere near this with the Nema 34 motors from CNCRouterparts.com?

Check out the documentation at geckodrive.com; there are a lot of useful formulae there....

[ack1]

Thanks hemsforthlad for taking the time, I really appritiate it. I'll take your advice and do just that, ill start looking for another VFD.

Any further advice on wich model to get ? I feel pretty clueless but a couple of days of research will take care of that.

[hemsworthlad]

Originally Posted by ack1 Thanks hemsforthlad for taking the time, I really appritiate it. I'll take your advice and do just that, ill start looking for another VFD. Any further advice on wich model to get ? I feel pretty clueless but a couple of days of research will take care of that.

Most decent brand manufacters like ABB, mitsubishi, hitachi etc will be fine so long as you get the correct model to match spindle spec. IE Amps KW, frequency range.
The only advice I would give is go for a sensorless torque vector drive over the cheaper flux drives because they dont cost much more and give better performance when the going gets tuff by doing some magic to maintain the torque.
My VFD model is ABB355 and is a nice bit of kit.

Some thing I forgot to suggest last post was that some times it can be worth while waiting to buy motors and drives untill your further into the build and have a better idea of friction and Mass you need to move/overcome.

[ack1]

Thank you yet again. Been looking at the ABB350 and 355 and It just so happens ABBs dep that sells these are less than 30 minutes away.

Just hope it doesnt break the bank.

[ger21]

What's YOUR opinion ? Is the Nema 34 kit worth the extra money over the Nema 23s on this kind of machine ?

MY opinion is that the 34 kit doesn't have enough resolution, and doesn't provide much of an advantage, as it's only geared 2:1.

380*3 = 1140 oz holding torque for the 23 system. Which equals 142 lbs of force (when not moving) (divide torque by 16 for lbs, and divide by .5 for pinion radius)

640*2 - 1280 oz holding torque for the 34 system. Which equals 160 lbs of force

Without seeing accurate torque curves, it's difficult to know which will have higher more torque at higher rpm.
But it doesn't look like there's much advantage to me.
Again, MY opinion.

[hemsworthlad]

Originally Posted by ack1 Thank you yet again. Been looking at the ABB350 and 355 and It just so happens ABBs dep that sells these are less than 30 minutes away. Just hope it doesnt break the bank.

Your welcome,
Wished they where that close to me because I actually have the 350 as well which needs repairing. The main cable on the spindle dead shorted and fryed the motor and also damaged some thing inside the vfd, now it just shows an error code and cant be reset.
I didnt have time to wait for repair so bought another, the 355 supercedes 350. . . Basicly the same just with a few more bells and whistle, I actually use the same front panel of the 350 so didnt need to buy another.
The best upgrade of the 355 to me is now the noisy cooling fan only runs when actually operating spindle, 350 run constant the minute you applied power.