X3 conversion using big servos - direct or belt drive??

[messar]

Hi,

I'm in the process of designing a conversion for my X3. I will be using ball screws on all axis (probably 5mm lead), driven by 1000W servos (the surplus sanyo ones).

Can I get away with direct drive, or would it be better to go with a belt drive?

Thanks,

Matt

[pstockley]

What count encoders do those servos have? Torque wise I think they would do the job direct drive with no problems.

[messar]

Thanks for the reply.

I believe these are 2000 line encoders. I'll be using Emerson EN204 drives (haven't actually tested these yet together - next week's project...)

Matt

[pstockley]

Are you going to use Mach? With that encoder count you would be better off without a gear reduction. Otherwise you could have problems generating enough pulses to get an acceptable rapid rate. On the other hand, I think those sanyos are 4 pole motors and you may experience some cogging at slow speed. This would result in poor surface finishes/accuracy. You will need to get them running to see if this is really a problem. If it is then you will have to go with a reduction to increase the minimum speed.

[JFettig]

Those motors are nearly enough to rip that machine apart

Definately go direct drive, you'll have enough torque to go around and more speed than the machine can likely handle.
With mach3 you'll be able to get that moving 270ipm with 2000ppr, but you got 2000cpr encoders which will put out 8000ppr. If you have step dividers it could help, or mach4 would fit the bill.

I got some 400w servos I intend on putting on a similar sized machine in the near future and I think that'll be great fun

Jon

[messar]

thanks again for the replies.

Yes, I'll be using Mach. I'd not though of the pulse limitation. I think the drives allow pulse multiplication though, so I might be OK.

Another option is to go with a faster screw, and hope the torque is enough (I'm guessing it will be...).

[JFettig]

Another thing you have to keep in mind is that there are rpm limitations on some screws I believe. I am not completly sure at what speeds thos are or if they an issue. I was reading something about some other kind of screw that was bragging about its ability for high rpm and how ballscrews cant handle all that speed. Its something to check into.


Jon

[messar]

hmm, again, good point. I don't think I'll be going anywhere near those speeds in any case.

I've looked for info on Mach4, but haven't been able to find anything about availability - is there a link you can point me to? (I'm assuming this goes with the gecko G101?)

Thanks,

matt

[JFettig]

Mach4 should be available sometime in the spring.

I took a look at rotons documents, they state 3000*nominal diameter should be your maximum diameter.
http://www.roton.com/index.php?section=59#12
although their example is wrong....

Jon

[JFettig]

I was wrong about the rpm, I had sent them an e-mail,
the equation is more like this:

rpm*in=3000 so solving for rpm is 3000/in=rpm so a 3/4" diameter ballscrew can take up to 4000rpm.


Jon

[tintruder]

Messar,

Maybe I missed it somewhere, but what drivers were you intending to use with the Sanyo Denki servos?
I got 3 of the 400W ones and I am at a loss what to drive them with. I have a Unidex U12 4-axis CNC controller, but 3 axes are set for DC Servo and one for Stepper. I'm stuck.

I guess I jumped the gun on the motors...they are very nice, but I seem to have missed the electrical difference between AC Servos and DC servos...plus I can't seem to find a wiring diagram for the motors...lots of wires, no info!

Tom

[messar]

Hi,

I'm planning to use Emerson EN204 servo drives. They are commercial drives that can be driven by step/direction signals. (I haven't actually tried this yet - waiting for my breakout board, and some spare time..). These drives are off ebay, and I think I paid between 70-150$ per drive.

There have been some threads about this - check for surplus motors on the rutex forum. I believe that the motors have been made to work with rutex drives. Also, buried in one of the threads is a list of what the wires are.

Matt