[DaStompa]

So I'm looking at converting my Benchmaster mill to a CNC machine, its similar to an X2 or X3 machine in size, but is a tankish ~600lb unfortunately this is about the maximum size I'm going to be "allowed" to have for now. Ive found a gentleman that did the same conversion, who used a gecko drive.

Now I myself am eying Xylotek, cost is lower, power seems adequate, but mainly they sell prewired kits, my biggest fear here is I'm going to end up smoking something expensive or buying something incompatible (I'm not a complete bonehead, but electronics are not my forte and troubleshooting a circuit board isn't happening on this planet)

questions!:
-is xylotek junk or what, it sure seems like everyone goes gecko, gecko looks to use one driver per motor so they are more modular if one burns out.
-how do I decide on motor power? for the xylo, 600 oz/in sounds like plenty, but I'm assuming that is torque at stall not actual usable torque
-I have no idea what 1/16th step is in the description of this drive, is it 1/16th of a revolution (terrible?) the motors themselves are nondescript too.
-are my fears of weird difficult to identify compatibility issues unfounded?
-it also looks like xylotek has ceased selling boards by themselves (?)

[ger21]

I'm not even sure if the Xylotex drive box even uses Xyltoex drives.
Xylotex drives were 1/8 microstepping, not 1/16. This leads me to believe that he's using a different drive for the boxes, which might explain why he no longer sells individual Xylotex drive boards.

Xylotex drives were designed over 10 years ago. Gecko G540 is a much newer design, capable of providing almost twice as much power to the motors. The G540 also has many features that the Xylotex did not have, which resulted in much smoother running motors and potentially much higher rpm capabilities.

Personally, I'd go with the G540, or a Leadshine MX3660.

[109jb]

Can't comment on the Xylotex drives themselves, but I can answer a few questions for you.

1/16 step - What this means is that each "native" step of a stepper motor can be subdivided into 16 microsteps. So, a typical stepper is built to have 200 native steps per rev, and with 1/16 microstepping that is transformed into 200 * 16 = 3200 microsteps per rev.However, the actual positioning of the motor is only truly accurate up to 1/2 stepping.anything beyond this is really for smoothness of movement.

Stepper torque - The torque rating of a stepper is usually the holding torque. What this means is if the motor is at zero RPM with power applied, it would take XXX in-oz of torque to force the shaft to rotate. the running torque is lower and decreases with RPM.

As for what size motor you need, that is dependent on a few things.
1. The machine size. obviously bigger machine need bigger motors
2. Direct drive to screws or belt drive - a belt drive cal multiply torque at the cost of complexity and lower maximum speed, thereby allowing a smaller motor
3. Ball screws or acme screws - If you are going to convert to ball screws, you can get by with a smaller motor due to the reduced friction (ie: better efficiency)
4. Desired performance - A lot depends on what you want. If you want a machine that does 300 IPM rapids and can cut with a high material removal rate, the motor requirement will be much different compared to a 100 IPM rapid, light duty cutting machine.

For a first conversion it is probably a good idea to check out successful setups by others and duplicate them.

Good luck.

John B.

[DaStompa]

Thanks for the reply,

Leadshine was not on my radar, i'm looking into them now, it looks "better" than the gecko from what I understand of the statistics, I'm poking at the manual now, looks good and the manual is pretty verbose about setup, major plusses!

[DaStompa]

As for what size motor you need, that is dependent on a few things.
1. The machine size. obviously bigger machine need bigger motors
2. Direct drive to screws or belt drive - a belt drive cal multiply torque at the cost of complexity and lower maximum speed, thereby allowing a smaller motor
3. Ball screws or acme screws - If you are going to convert to ball screws, you can get by with a smaller motor due to the reduced friction (ie: better efficiency)
4. Desired performance - A lot depends on what you want. If you want a machine that does 300 IPM rapids and can cut with a high material removal rate, the motor requirement will be much different compared to a 100 IPM rapid, light duty cutting machine.

Well yeah
I can grab a torque wrench and estimate how much torque i'll need, but these motors have no power curves (stated at least) like standard electric motors, Ideally I'd know the stall torque of a motor at a given voltage and could roughly get from that what my speed would be at a given load, there's not even rpm stats given for these motors, so I'm having difficulty sizing to what I have. I've been googling around for similar projects, there's one guy that did a benchmaster whom hasn't replied to his email in a while, so here I am. Its sort of a middle of the road mill, MUCH bigger than the chinese guys but much smaller than a bridgeport.

[ger21]

A Xylotex is typically better suited for a Sherline mill. It's at the low end of the power range. It sounds like you might want something more powerful than a G540 or MX3660, which would get you into individual drives.

[ger21]

I can grab a torque wrench and estimate how much torque i'll need, but these motors have no power curves (stated at least) like standard electric motors, Ideally I'd know the stall torque of a motor at a given voltage and could roughly get from that what my speed would be at a given load, there's not even rpm stats given for these motors, so I'm having difficulty sizing to what I have. I've been googling around for similar projects

Sizing stepper motors is much more complicated. It's not uncommon to change to a larger motor and get poorer performance. You need to figure out what RPM you need your motors to spin at, and what torque they need at that rpm. Then find a motor that will give you the performance that you need, and get a drive that will work with that motor.

Getting a lot of torque out of a stepper at high rpm can require a drive capable of 6-7 amps and maybe 60V-70V.

[DaStompa]

A Xylotex is typically better suited for a Sherline mill. It's at the low end of the power range. It sounds like you might want something more powerful than a G540 or MX3660, which would get you into individual drives.

Yeah that sounds like where I am heading, the X and Y axis aren't too bad (especially when I ballscrew them) but the Z axis is probably 200+lbs with the knee and table

I don't really mind having low speeds very much in the Z, I'm thinking of ~500-600oz/in motors and then gearing down the Z axis 2:1 or so

[ger21]

Be careful when using gear reduction with steppers. As the rpm increases, the steppers torque decreases. It's possible that when you double the rpm, that you'll only have 1/2 the torque, which means that the gear reduction adds nothing.

[DaStompa]

Be careful when using gear reduction with steppers. As the rpm increases, the steppers torque decreases. It's possible that when you double the rpm, that you'll only have 1/2 the torque, which means that the gear reduction adds nothing.

Yep! gearing and mechanical stuff is my wheelhouse, I'm sure I could figure out exact choices to get exactly what I want... if these motors stated their actual performance information not just the holding torque!

[109jb]

Some do have torque curves. Automation Tech has several motors with torque curve plots. Here is an example for the popular 570 oz-in Nema 23 motor.

http://www.automationtechnologiesinc...flat-570-oz-in

http://www.automationtechnologiesinc...oad.php?id=284

[DaStompa]

I appreciate the help folks, I had some additional questions as I figure this thing out

I am probably going with the leadshine 3360, the documentation is excellent and it looks to have everything I could want.
Particularly today: inputs: home/limit switches:

Now from the manual, this controller only has 4 inputs, but I have 6 switches I need to install: (home and limit for X Y and Z)
Obviously the home switches need their own input so that the machine knows which one it is pressing, so that is out

Since these switches are normally closed, I /could/ wire multiple limit switches in parallel to the 4th output, or I could wire the emergency stop (normally closed) in series to 3 of the limit switches. The manual doesn't state behavior once the a limit switch is pressed, I assume that it just stops and doesn't attempt to return to home or it might pass through the part or do any number of other terrible things.

so my question is what is the "proper" way of doing this?

[ger21]

Are you talking about the leadshine manual? The software controls what happens when a limit is tripped, unless you have the limits wired to kill power to the machine.

Depending on your control software, you may be able to have all the home switches on a single input.
It's common to have all the limits share one input.

[DaStompa]

Are you talking about the leadshine manual? The software controls what happens when a limit is tripped, unless you have the limits wired to kill power to the machine.

Depending on your control software, you may be able to have all the home switches on a single input.
It's common to have all the limits share one input.

Ah, I was planning on mach3, I thought that the driver controlled limit faults not the software, thanks

The driver itself looked like all of its inputs were just standard open/closed so it wouldn't be able to differentiate between, say, the X and Y home switches being tripped if they were wired to the same one.

[ger21]

By default, mach3 homes one axis at a time. If all the home switch share one input, mach3 looks at that one input for each axis.
If you use a separate input for each home switch, then you canmodify the homing to home all axis simultaneously.

[DaStompa]

Ah thats logical, got it

Pretty much just need to size up the steppers at this point and the project will begin, thanks for all the help

[CNC-Joe]

I've used and have both Xylotex and Gecko (Gecko 212's -w hich are now discontinued).
The Xylotex is driving my Sherline Lathe
My Gecko's are driving everytrhing else: CNC Router (ala Joe 2006 but with a lot of improvement mods, South Bend 9" lathe, South Bend 10" Lathe
The Xylotex is fine for driving the Sherline. I'm running it with 24 volts dc.
The Gecko's I am driving with 70 Volt DC, for stepper speed (and power)

I would only recommend going with the Gecko's. Great customer support there, too. I actually mucked up a drive by blowing air in the control cabinet...and somehow a small wire shorted one out - and it was replaced for free, in like a week and a half.

Go Gecko and you won't regret it.