Are thinking of going with Rutex drivers but what servos?

[kayakman]

Hi I'm currently buildign a CNC router as can be seen in this thread:

My first CNC mill on the way : )))))

The working area of the router is 1100x900 mm and I was first thinking of going with Xylotex stepperdriver and stppermotors. I have now started to glance at servos and are interested in the Rutex R990H servo drive but I don't know what servomotors to use. WHat size are apropriate for this kind of router and where do I buy them to a affordable price?

Please help / Anders Molin

[Bubba]

kayakman,
I got my servo motors from:
http://www.surpluscenter.com/
They usualy have some that are pretty hefty. The ones I used on my mill/drill are 48V 1000 rpm units about 11lbs each! Prices aren't to bad, but they do NOT have encoders on them. I put my encoders on the lead screws so I could play around with the pulley ratios and not effect the settings in my TCNC program.

Of course, YMMV, and usual disclaimer.

Bubba

http://bellsouthpwp.net/A/r/Arts_home_page/cnc/

[ynneb]

I use Rutex with these servos. http://cgi.ebay.com/ws/eBayISAPI.dll...tem=3844568448 I know the auction is finished but if you email him, I know he has more. He will fit the encoder of your choice ( Included in the price)

Mine have been very good, and get a 4 hour daily work out.


EDIT: Those ones that Bubba posted look very similar to the link I posted. They also seem a lot cheaper. I guess If you can fit and source your own encoder then Bubbas ones are the go.

[Bubba]

I used encoders from

http://www.usdigital.com/

and they were the "cheap" 500 line E2 units.

I have some 1000 line left from my DRO project, but the computer ran out of steam in order to use them to the maximum advantage.

Mariss of Gecko fame has published some guidelines of what you can expect preformance wise out of any given circumstances. Based on his recommendations, I found the 500 line encoders (attached to the lead screw) to be the best for ME:})

I can't break the elusive 100 IPM rapid, but then again; I only have about a 16" max travel on the X axis and 5" on the Y so it can still seem scary when I go stop to stop

My recommendation is to go for a servo with as high a Kt as affordable, and then fit the drive train and power supply to fit. Do the math first, and then build to suit. Paper is cheap compared to changing power supplies etc.

Bubb

[ynneb]

I have some 1000 line left from my DRO project, but the computer ran out of steam in order to use them to the maximum advantage.

The good thing about using Rutex is that they have step multiplier switches on them.
This means if you did use 1000 line encoders on them, and your computer did run out of steam, you could use the step multiplier to reduce the steps per revolution to suit your computer. If one day you got a better computer you can just turn the step multiplier off.

[Bubba]

Ynneb
I have Gecko 340s on 3 of 4 axis and can do the same!

Matter of fact, before I put ball screws on, I was using the 1000 line encoders, but they only have a 5mm shaft (press fit) and I decided to go with somthing that was easier to install. That is why I got new ones and the method of installtion. I don't really need 0.00005" resolution! After all, this is a mill drill and not a production machine in a controlled environment. Right now, I am having problems on the X axis trying to hold .2" for some reason.
The repeatiblility sucks. I tried to mill a part today and the axis would not hold a repeatibilty of .200"! I think I may have a noise problem and will work on that this week.

[ynneb]

Bubba, I have heard, (Not personal experience) That by not having the encoders on the actual servo and by placing them on the drive section further down the line can cause search problems for the servo. I think this is due to backlash.
Have you considered this, or is that not the casue of your problem?
I am just guessing and answer for you, and dont know for sure.

[kayakman]

Do you have the mailaddress to the seller of the Servos at ebay? I don't want to register my visa card number at ebay and then I cant get the mailaddress : (

His servos looks nice. And if the work great with Rutex then it looks promesing.

Best regards / Anders

[Bubba]

yennb,
Refering to the location of the encoders, YES this can be a problem. When I first cncd my machine, I tried to leave the original encoders in place (on the axis itself); and what a disaster due to the backlash in the acme screw. I relocated the encoders to the end of the screw, and there is basically zero backlash in the toothed belt drive between the servo motor and the screw so it works very well.

Bubba

[ynneb]

Kayakman, he is also a member of this forum, you can get hold of him via this link http://cnczone.com/forums/member.php?u=2870

Just make sure you mention that I gave you his name. He may then look after me if I order from him again.

[kayakman]

Hi
I´m going to order the rutex R990H cards to use with my woodrouter. I have a question about one thing. Do I realy need the limitswitchcards or can I connect my mechanical limitswitches directly if i have limitswitches that can take the voltage and amps that will be used on the servos?

I will drive my servos on around 34 V.

As I understand it the limitswitche cards is to be used when the motorvoltaga is so high that large enough limitswitches will be to big or to expensive. Is this right or have I missunderstood the whole thing?

Pleas help me fast so that I can order the servodrivers '

Best regards / Anders Molin

[ynneb]

I think you are refering to the Rutex relays for the limit switches?

Because the amperage of your servos is high, it is too much to route through a tiny micro switch. It will melt it. You still use micro swithes but they activate the relays which inturn do the switching of the servos.

There are two ways to wire your limit switches, one way is to make the limit switches activate a stop in your computer software program. The only problem with this method is that you are relying on the software to stop the servos. This is not the proper method for a limit switch and is not the safest method. The other method is to use the relays and cut all power to the servos themselves. This is the most reliable method. If for some instance the encoder on your servo has a fault, you can get runaway of the servo and it will drive your machine to an axis end. This happens regardless of any of your computer controls. That is why you should use the relays.

That been said, you can always buy your own relays from a local electronics supplier and maybe save some bucks.