Advice on stepper slection please?

[sco]

I am making a 3 axis router.

The x axis screw I am thinking of getting will be 16mm diameter 10mm pitch steel, the screw is 1.5 meters long (5 feet).

The gantry not including the x screw but including the y screw will weigh about 30 kilograms (70 lbs)



The y axis

I am thinking of getting a 16mm 10..pitch screw.By itself not including its screw is about 10 kilograms (22 lbs)


I will be routing dense foam and wood for wing and fuse moulds. I have aspirations of being able to route aluminum, but that is not the most important.

I was going to buy a nema34 960 oz for the x and a 720oz for the y

Can you suggest a stepper motor size that may be better sized for my X,Y?

Thankyou,
cheers
sco

[sco]

I thought that I would post a couple of pics to show that I am not a "time waster"
Does anyone have any advice on stepper sizes from the first post?

cheers
sco

[TOTALLYRC]

With those unsupported rails for the Y aluminum and possibly even hardword is going to be problematic just because of the flex.

The thing with cutting foam and wood is proper speeds and feeds. If you are going to use a router/dremel/rotozip then you will need to move pretty quickly or you will just melt the foam instead of getting a nice cut.
A 10mm pitch is 10mm of travel per revolution???

a speed of 5000mm/min (200IPM)is a good starting place. This will take ~15 seconds to travel the long axis.

5000mm/min divided by 10mm/rev =500rpm well within the range of a nema 34 motor. If you need to go faster, say 10kmm/min, this would be 1000rpm and it would be difficult to get the nema34 to go that fast, at least in direct drive.

Of course it all depends on your budget. can you afford drivers that will handle the power to run the nema 34s at max volts. Which would be 3 gecko g203v or similar. I have a 1m x 1.2m router in the same weight range and run it with 425 nema 23's so the power is not so much an issue but matching the power output to the pitch of the screws and speed needed.

So what it took me so long to say is that decide how fast you need to be able to cut, and how fast you want to be able to rapid. Then figure out how many rpms that is. See what motor has the torque curve to match it and what voltage it needs to operate at that speed.

Mike

[ger21]

The bigger the motor, the slower they spin. I'd stay in the 400-600 oz nema 34 range, with the highest current rating you can find. 400oz, 6-7amps Nema 34's should have enough power, and will give you the most speed.

Here's a simialr size machine and that's what he used.

http://cnczone.com/forums/showthread.php?t=2249

[TOTALLYRC]

GER21,

Just to clarify, driven by as close to their max voltage as possible.
Say g203v at or near 80v which would give the best possible torque at max speed.


Mike

[ger21]

Actually, those motors I mentioned are usually rated at ~1.5V, so 80V is way to high. The Keling KL34H260-42-8A Should be run at about 40V for best performance. Voltage should be 32 times the square root of inductance (according to gecko).

http://kelinginc.net/KL34H260-42-8A.pdf

The Oriental Vexta of the same size is similarly rated. (But double the price)

[sco]

Thankyou for your input gents. I really appreciate it.
I've been told by a sales person that I will need up to 1200 (I will say though that speed was not part of our conversation) so I appreciate your input, as it has sent me off to look for more info that supports your own.
I think I will go for 600's...(I just can't help myself, not having any prior experience.)

I need a nema23 for the 'z'...should I maybe go for a 400oz (because they are supposedly faster) for that since its screw is around half of the pitch of the x and y?
Any other input out there.
Thanks
cheers
sco

[TOTALLYRC]

Bigger is not better, so try and help your self.

Getting it right the first time will make your entire cnc experience better.
Search for Taig and see all the users, myself included, that used nema 23 425s and had a slow machine, when they should have been using 270 or even 185's depending on the driver. When it takes 1 minute to go the length of the table, you will cry infrustration after a while, especially if you are trying to make money with your machine.

I have a nema 23 425 from keling on my router z axis. It hauls 2 rotozips and a large aluminum plate with no trouble at all, except that it is running under volted so I have a speed limit. 82 v motor on a 50v power supply.
Make sure that your z axis motor will run well on the voltage needed for the other 2 or you will end up running 2 power supplies.

In my case, a single sheet of material can have several hundred holes, and anything that you can do to make it rapid faster, within reason, should be done.

In your case of doing 3d foam, all three axis should have the ability to run at the same speed or pretty close, if one axis is a lot slower than the rest of the machine, when you do 3d moves, the machine will be limited by the slowest axis. As I said before, foam needs to be cut at a pretty good speed, and so does wood.

[ger21]

Originally Posted by sco I need a nema23 for the 'z'...should I maybe go for a 400oz (because they are supposedly faster)

Remember, the bigger the motor the slower they are. Since a 400oz Nema 23 is at the top end of Nema 23 size, it'll be one of the slowest nema 23's you'll find.

The 400 oz motors I mentioned above are Nema 34's.