[chrisw765]

So I'm setting up my mill and figuring out the steps per inch I'm swapping out the old dos base system on my servo impact mill to mach 3 i bought the g540 but didn't realize its stuck in 10x micro stepping??

my setup

387 nema 23 from keli

so 280 deg
x10 micro stepping =2800
5 to 1 belt drive = 14000 steps
5 turn to one inch ball screw= 70,000 steps per inch !!!!!!

that's a lot I'm not sure what mach 3 can even do I'm running a due core 2.4g

[chrisw765]

200 steps per rev not 280 i miss read 2.8deg==brain fart
so that brings it down to 50,000 steps per inch thats still a lot?? tho
or is that normal ??

[jalessi]

Chris,

Why are you using 5 to 1 belt reduction with the ball screw?

Jeff...

[chrisw765]

im just using what came on the mill, it has nema 23 ac brushless servos on it now,im just swaping the old servos with new steppers so i can run mach3 .. its how the factory has it set up..

[Crevice Reamer]

Servos are HIGH RPM motors and are usually geared down to trade speed for torque.

Steppers are LOW RPM motors and are usually mounted direct drive or 1:1.

Running steppers at 5:1 gearing will effectively neuter them. Change the pulleys to one to one ratio.

CR.

[jalessi]

Chris,

Crevice Reamer is 100% correct, either change the pulley to 1-1 ratio or remove it and attach the stepper directly to the ball screw.

Jeff...

[Mariss Freimanis]

Chris,

Go 1:1. With 5:1 you are putting 1,935 in-oz (13.7 Nm) of torque on your screw. It in turn is producing 3,800 Lbs (1,730 kg) of thrust. That's almost 2 tons.

You'll go 5 times faster and still generate 760 Lbs of thrust. Mach3 set to a 45kHz kernel speed will get you 1,350 RPM on the motor or a decent 270 IPM.

Mariss

[vintageracer]

My Dyna Myte 4400 has the same set up. 200 step 160oz/in steppers, 5:1 pulley ratio and 5mm ball screws. That works out to 50800 steps per inch. I've installed a Gecko G540 and Mach3. At 45kHz kernel speed rapids are 53ipm and at 60kHz kernel speed it can go 70ipm but it tends to fault once in a while so I set it down to 45kHz again.
I have to run some sort of pulley system because the stepper housing is also the ball screw support, so it has to stay. I just wanted to get the mill up and running so I decided to stay with the 5:1 rather than try to search for replacement pulleys.

The G540 runs flawlessly. What an awesome product.

I must admit though, I can cut 0.750" deep with a 0.750" two flute cutter at 12ipm and the machine doesn't even flinch.

Timothy

[Jeff-Birt]

Steppers are LOW RPM motors and are usually mounted direct drive or 1:1.

Most steppers are mounted direct drive because people don't know any better or they are just lazy. There are even a few direct drive servo systems out there!

Small machines like the Taig and Sherline use a 20 pitch lead screw so there is enough reduction built in to use a direct drive. With a lower pitch screw like you will find in most other machines you really need some sort of reduction. Now depending on the power band of your motor/driver combination 5:1 may be a bit high. The goal, IMHO, is to have the motor have the most power available in the speed range you will be cutting at. For the most part 100 IPM rapids on small machines are pointless and only serve to wear things out faster.

Servos produce their power at higher RPMs and need more reduction than a similar stepper driven system.

[HRW-MASTER]

Most steppers are mounted direct drive because people don't know any better or they are just lazy.

Poppycock.

They are mounted that way because they do not need any more reduction.

Hank

[Jeff-Birt]

They are mounted that way because they do not need any more reduction.

Sorry, not to argue and get way off topic, but that is just not the case. It is like trying to start out in the 3rd gear of a five speed transmission. It is why folks have tendency to mount huge 1000 oz-in motors on a little X3, they are trying to drive a 5 pitch screw with no reduction.

[HRW-MASTER]

Jeff-Birt,

If the ball screw is the correct TPI or pitch then mounting a stepper directly to ballscrew is perfectly acceptable and the prefered choice.

Are you implying THK, NSK, and many other state of the art manufacturer's are lazy?

You must be joking right?

Hank

[Jeff-Birt]

We are actually agreeing on one point, here is the first few sentences of what I said:

Small machines like the Taig and Sherline use a 20 pitch lead screw so there is enough reduction built in to use a direct drive. With a lower pitch screw like you will find in most other machines you really need some sort of reduction.

So, yes if you have the correct pitch screws for the application at hand then your OK. A lot of folks convert manual machines, or build them from scratch from bits and pieces that they scrounge up, therefore you can't be assured that the lead screws would be suitable for direct drive. What I was saying is that direct drive is not inherently best for steppers, you have to have the correct reduction ratio be that through the lead screw only or through a combination of screw pitch and some other belt/gear reduction.

To play devil's advocate let me pose another question. If no further gear reduction is needed on stepper systems why do major manufacturers make all sorts of gear/belt/bearing reduction systems for them?

Don't get me wrong I'm OK with what ever someone chooses to do. I just want them to have all the facts and make an informed decision.

[chrisw765]

OK so i changed the belt setup to a 1.5:1 form the 5:1 but i read a article buy Maris saying anything slower then 3 rotations a sec will have vibration issues i calculated that if i cut at 20ipm the stepper will be turning at 2.5 rps so now am i going to have issues with resonance and vibration??

[chrisw765]

if im cutting alu at 5inpm thats only .6 revs per sec so i know im going to have mad tork at the slow speed but am i going to have vibration issues? and if so i have a set of 201's laying around would they be better then the g540 to handle the the slow speed?