Servo Dynamics or Rutex

[Tig]

Hi, I hope this is in the right forum. I am collecting the parts for a large router with the X-axis driven by two rather large SEM servo motors with rack and pinion for the drive. I was wondering if anyone has had any experience with the Servo Dynamics brushed drivers such as the MB2-16B, they seem to be reasonably priced.
The other way I am thinking of going is with Rutex, R2000 series???
My question is: Will the MB2's give me better performance/resolution on an X-axis driven by the two SEM servo motors, or should I go with a couple of the R2000's and Mach3 for control. I am looking at OneCNC for the CAM software ether way.
Any thoughts? Thanks

[ViperTX]

I believe the Servo Dynamics are "closed loop" controls?? If so, then they would be the better choice.

[Al_The_Man]

Are you hoping to control the amps with step & direction as the Servo Dynamic amps look like analogue input.
Al.

[Tig]

Hi,
Thank you for your replies. I think the Amps are the closed type, the motors have tachs on them. I imagine that the tach functions much the same as an encoder only analog, wave versus pulse?
From the Servo Dynamics web site under: Products/Brush Amplifiers/ MB2: Quote "The velocity feedback functions are tachometer, or sensor less. The power stage is fully isolated, and the inputs are either TTL/CMOS compatible or optically isolated."
The X-axis on the router is 6m long and I am wondering if I wouldn't be better of using a closed system with some feed back to keep the two motors from fighting each other. I am going to invest in some precision rack and pinion with precision gear boxes, and use split pinions to help reduce positioning error and backlash.
The other issue is speed I wonder if the software controller (mach3) and a Rutex driver can deliver the same speed and precision as a dedicated hardware driver.
I think the MB2's have a dedicated processor for each axis and I believe a built in power supply. Hard to beat for the price.
Is anything else needed between the amplifiers and the CAM software, I haven't checked with OneCNC to find out if the have a post for the MB2's yet.
Thanks again

[Al_The_Man]

I think you will find that they only need closed (velocity) loop when used in the velocity mode, the prefered way is in the torque mode with encoder feedback to the controller, you will need encoder FB anyway, The tach is not needed and in this mode and should not be hooked up, again they look like +-10v analog input only.
Al.

[ger21]

Originally Posted by Tig Hard to beat for the price. Is anything else needed between the amplifiers and the CAM software, I haven't checked with OneCNC to find out if the have a post for the MB2's yet. Thanks again

If I'm not mistaken, I'm pretty sure you're going to need some type of motion control card and some machine control software. Plan on a couple thousand $$.

[Tig]

Hi Al,
you asked:

Are you hoping to control the amps with step & direction as the Servo Dynamic amps look like analogue input.

I am looking at both options. This group of forums seems to deal mainly with step and direction, I am interested to know what the pros and cons of an analogue system are. Can one get the same resolution as an encoder system?

Gerry,
I looked for controller hardware and or software on the Servo Dynamics web site, but couldn't see any. I think I will dig a little deeper.
Thanks

[Al_The_Man]

Like Gerry said, you will probabally need to use a motion card like Galil, Delta-Tau, Acroloop etc to run these drives, there is limited software however, Camsoft and MotionMax and Delt-Tau's own, encoder feedback is required on all these systems unless they are hooked up to stepper motors with step/dir signal. An encoder feedback system allows as fine a resolution as the encoder is capable of, you also have the advantage of confirmation of actual position.
Al

[ViperTX]

Simply:
Closed Loop System - Will have greater accuracy, more expensive!

Open Loop System - Will have less accuracy and it's cheaper!

Tach will give you velocity and depending on the controller it may be used when ramping up in speed or ramping down.

As Al mentioned you'll need some Axis control board. The control board does all the interpolation, and control for each axis and they are generally a minimum of $3K for a 3 axis card.

Open Loop Systems - Like Rutex, Gecko, and most everything mentioned on this site are $80 to $150 per axis.

[Tig]

Hi,
I contacted Servo Dynamics this morning and talked to a technician regarding the MB2-16's it cleared up some questions regarding what the drives could and couldn't do. They do have built in control of velocity and current, but do not accept encoder input for position feed back..
It was suggested I use the MB2's in current mode, disconnect the tacho on the servos, and install an encoder, and use a controller such as Galil for position feed back.

Its starting to look like the Rutex drivers will deliver the best bang for the buck. my only concern now is speed. What other options are available for control of the Rutex boards. I only see reference to Mach 2-3, or EMC.
Thanks again.

[ger21]

Originally Posted by Tig What other options are available for control of the Rutex boards. I only see reference to Mach 2-3, or EMC. Thanks again.

Any step and direction controller software. Flashcut, DeskCNC, TurboCNC, Mach3...

Sometime in the next year (maybe a lot sooner, but noone can tell for sure) will be a version of Mach3 (Mach4?) to control Gecko's soon to be released G100 motion controller, which can control 6 axis' at 4 million steps per second.

[unterhaus]

Pico Systems sells a board that will control these drives with EMC. I believe this hardware costs about the same as the Rutex option. EMC is free and you can download a CD off of the internet to install Linux and EMC at one shot. There are other EMC compatible control hardware options costing under $1000.

Mach probably will support these drives eventually with a new Gecko driver board.