MOTOR ADVICE NEEDED

[Imacman]

I Have started my build, with parts arriving each week, I am looking ahead to the Electronics, I have decided On the Gecko (540? 520? ) the one with the 4 built in drivers ( I think most are familar with it ) My question is what motors are recommended based on my build. I hope to carve Wood, Plastics and Aluminum... here are my specs so far.

Foot Print = 60" X 30"
Cutting Area = 45" X 24" with 5" of travel on the Z axis.

The machine is Fully supported on the X & Y Axis
The machine frame is 1/2" Aluminum ( Gantries & end plates )
Side Bracing Top Bracing ( For cutting bed ) is 8020 Aluminum

X and Y-AXIS both use a 5/8" 8 tpi Single Start ACME lead screw with bearing support on both ends into a Helical Coupler for the drive end.

Z-AXIS uses a 1/2" 10 tpi Single Start ACME lead Screw with Bearing support on both ends into a helical Coupler for the drive end.


The overal machine is very rigid ( My Gantries and Endplates are From George In Toronto XZERO Automation )

So... Based on this information what size motors should I be installing on this machine?... I do plan to upgrade to Ball Screws down the road. Any and all thoughts and suggestions are greatly appreciated.

Imacman

[mactec54]

Imacman

You should take a look at DMM ac servo package the 400W would do you with a 2.1 to drive your screws you will get around 400ipm

This is a great package & easy to set up

[Imacman]

Thanks.... I'm not familar with that item... do you have a link to it / more information on it?... what do you reccommend it?

Thanks

Imacman

[mactec54]

Imacman
Here is the link they are in Canada

There boards drives & encoders are all designed in Canada & some of the parts
are made there,They have the best package price & quality that you could get
not to forget the service is great to


http://www.dmm-tech.com/

[rowbare]

When selecting motors for the G540, or any stepper drive in fact, it is important to keep the drive parameters in mind. For instance, the G540 voltage and current limits are 50V and 3.5A per channel.

The rule of thumb formula for determining stepper voltage is 32 * sqrt(inductance). So to keep things simple, if you have a stepper motor with 4mh inductance, you get 64 volts as a result. While this motor will work with the G540, it would only put out about 75%.

The other trap we often fall into is that we confuse holding torque with actual cutting power. This post gives a good explanation: g251's w/SS BoB or g540

One of the motors best suited to getting the most from the G540 is the 381 oz-in KL23H2100-35-4B from Keling. It draws 3.5A and has an inductance of 2.8mh. Its voltage rating works out to 53.5 volts which is pretty close to optimal.

Is this the right combination for you? I don't know. A lot depends on what you are using for screws. If you are using a 10tpi ball screw, it might be. If you are using a 5 tpi acme, probably not. (Screw selection is a whole other subject. You have to look at things like the efficiency of the screws, critical speed etc...).

Another factor is that the torque curve for smaller motors tends to be a bit flatter, i.e. as you spin them faster, they lose a smaller percentage of their torque. This makes them better for use with high pitch screws. For instance, I have a Taig mill. It has 20TPI screws. This means that to get any real speed from it, those screws have to turn pretty fast. Another user here (Jeff Birt from cnczone.com) is using 166 oz/in motors on his and is getting great results. Yet a lot of these are sold with much larger motors.

I have probably confused things even more but the thing to take away from this is to make sure your motors specs fall within the drive's parameters whatever drive you choose to use. And that a router is a system, no one part makes it. A seemingly lesser set of well matched components will often outperform poorly matched great components.


bob