Aluminium FEA optimalized CNC router

[magicniner]

I have heard open loop steppers is not good for point to point 3D toolpaths. They loose step easy and you cant push them very well.

Closed loop steppers are a solution looking for a problem, correctly designed open loop systems don't lose steps, if that can happen on a machine then it's badly configured or broken.
Closing the loop doesn't make a bad machine good, using the correct motors & screws and running it within it's limits does.

[Boyan Silyavski]

Closed loop steppers are a solution looking for a problem, correctly designed open loop systems don't lose steps, if that can happen on a machine then it's badly configured or broken.
Closing the loop doesn't make a bad machine good, using the correct motors & screws and running it within it's limits does.

While this is true generally, closing the loop with servos definitely makes machine faster. I also am not fan of the closed loop steppers price wise.

But if the machine will be machining Metal i dont see why at all there is a discussion for sth else than servos and closed loop. Given the price of aluminum material that will be machined and eventually a mistake made.

[magicniner]

closing the loop with servos definitely makes machine faster.

But is this a function of the closed loop or is it the fact that the drivers are part of the package and this stops cheapskates buying inadequate hardware and then blaming low speeds and step loss on open the loop?
;-)

- Nick

[PotatoMill]

I thought selecting a stepper or servo should bee easy, but it seems like nothings easy here. So for each person I ask I get a different recommendation. Steppers, open loop, closed loop, no only servos is good enough. The common thing is that everyone recommends servos if I want to use the money. But they are waaaaaaaaaaay more expensive than normal steppers. And all the cheap servos and closed loop steppers is a pain to get information on, since the datasheets and torque curves is not easily available and I have to ask the sellers for it for every motor. But my logic is as follows, if open loop steppers is good enough for Tormach it's good enough for me. First to comment on how this is not a mill. Then I can use some higher quality steppers instead.

By the way can someone remember the good reason to not use overkill steppers like 8nm nema 34? It's not like they are a lot much more expensive. I read it somewhere but I can't find it.

[Clive S]

With nema 34 you will need mains voltage drives to get any decent results You won't go far wrong with decent 23,s from Zapp or CNC4you

With AM882 or similar drives and 68V power supply non linear

[Fenza]

By the way can someone remember the good reason to not use overkill steppers like 8nm nema 34? It's not like they are a lot much more expensive. I read it somewhere but I can't find it.

I think Nema 34 steppers would be too large for your machine. The Load/Motor Inertia Ratio would probably be below 1:1 and therefore you're using more energy accelerating the motor shaft than you are accelerating the 40kg load!

I'm not sure about Steppers but for Servos a 5:1 Load to Motor Inertia Ratio is pretty normal, with 2-3:1 being higher performance and even 1:1 is used for super speedy machines.

A belt reduction gives you flexibility in the gear ratio. If you happen to under size the motors you can lower the gearing and get more torque with less speed, but if you over size the motors you can get some free speed!

I'm sure you can see how this becomes a hobby for many people... Haha!

Cheers,

Fenza

[magicniner]

How about fixed screws and rotating ballnuts?
No problems with whip from the screws and reduced rotating mass ;-)

[PotatoMill]

How about fixed screws and rotating ballnuts?
No problems with whip from the screws and reduced rotating mass ;-)

I'll just need CNC router to make it first

[Boyan Silyavski]

...or is it the fact that the drivers are part of the package and this stops cheapskates buying inadequate hardware and then blaming low speeds and step loss on open the loop?
;-)

- Nick

I couldn't have said it better.

[Jonathan]

Closed loop steppers are a solution looking for a problem, correctly designed open loop systems don't lose steps, if that can happen on a machine then it's badly configured or broken.
Closing the loop doesn't make a bad machine good, using the correct motors & screws and running it within it's limits does.

Well said.