I’ve reached a bit of a dilemma, and I could use some sound advice:
Now that I’ve just about got my big machine up and running where I want it, some ppl in another forum are suggesting it may be underpowered for its size. Right now, I have two 425 oz-in Steppers driving my table, which are 2 2010 Ballscrews. Admittedly, the drivers aren’t what they should be. I would like to reliably cut aluminum. I saw an ad that is selling 3 Nema 34s (1700 oz-in) Steppers with 3 201 Gecko Drivers for $475. Do you think it would be wise & necessary to purchase those to run my table and gantry axes?
Yes. That is what I’m learning. I posted one type of Stepper and was informed I would need about 100+ volts to get the full power of the motor and their torque really falls off with speed.
Definitely test it out and use it. Try some light passes in aluminum scrap- start very slow and increase speed to find a sweet spot. You will quickly learn your limitations, and may be surprised how strong it really is.
I have found it’s most important to have a “tight” machine for aluminum, not necessarily power. Try to do everything and adjust everything you can to decrease deflection all the way to the tool tip, that will greatly increase your success.
425 oz/in sounds plenty powerful to me. Get some aluminum and do test cuts in it. Just write a program that cuts progressively faster and deeper. See what your machine can do. I would not put much stock into what people say. Seeing is believing. Set the drives up you have right and you’ll get plenty of power out of them. More current does not always equate to more power.
If you’re going to have any issues cutting it is going to be rigidity not feed force. Aluminum extrusions are not exactly heavy iron castings. Not even close. Torque comes into play with CNC machines on acceleration. So if your machine moves good then it is good. “Fast” CNC machines get going fast.
The vast majority of what people are going to tell you about CNC on the Internet is bunk. They’re idiots.
I should finish by saying that holding torque is not the whole story when it comes to stepper motors. In fact it is very little of the pertinent part of the story. If I wanted my machine to sit still I’d weld it solid. I am far more interested in how it moves than how it sits. When you’re choosing a stepper motor for what we’re doing you want a low inductance high current motor. These typically are low voltage rated too. They’re going to perform the best running, not sitting or holding. But they’ll hold just fine too.
@Mark_Leino someone here sounds like they know what they’re talking about. Indeed rigidity is everything in the machine world. When a machine is solid you don’t need much in the way of anything else at all in order for it to perform well. When I am cranking through steel on my mill I am not straining on the hand wheel. I might be using something like 10 or 20 oz/in. A half a ton of cast iron does the rest.
Same as my machine 2x425 on the y, I can bury a 1/4 end mill in aluminium and snap it off. The problem I have is chip welding with only air for coolant.
It’s easy to say go buy a clearpath servo, but when you are fitting the bill out of pocket, you have to think twice. It would be nice, but it’s a luxury I cannot afford right now.
I think you have a great machine @George_Allen you just need to put some time in on it before making big changes. Find out what it’s max is, and it’s not enough, Build it better!