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Messages - fdos

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281
General Mach Discussion / Re: machine conversion starting all over,
« on: May 17, 2006, 02:46:20 PM »
NO.... dont take the motors apart!    Do they have brushholders or none?

Take a digital photo of the motors and post in here.

You say six wires?  Possibly steppers...

Wayne...

282
General Mach Discussion / Re: machine conversion starting all over,
« on: May 17, 2006, 02:00:42 PM »
Come to think of it...   I've worked on a few old Bandit controls many years ago and they were all Stepper based.   Are you sure you have servo's?

Do the motors have name plates with specs on them?  If so let us know what they say..

Wayne....

283
General Mach Discussion / Re: machine conversion starting all over,
« on: May 17, 2006, 01:58:00 PM »
I'd bet your original servo drives only take 0-10v analogue velocity commands.  Do they have tacho's and encoders?

There are several step/dir > analogue converters out there, by far the best value for money is the skyko ones at http://www.skyko.com/

Never used them thoug, but I have heard good reports.

Whatever, you MUST get as much information about your machines original circuits as possible.   It's not fun having several hundred wires to buzz out and work out what they do!  Been there and done it!

You can make it work, it just takes some research..

Wayne....

284
Dave... Don't forget you got an open enquiry from me somewhere ;)

Wayne....

285
General Mach Discussion / Re: motor tuning
« on: May 15, 2006, 09:03:27 AM »
There is no play, some "give" maybe, but nothing that affects my work.   I work to very close tolerances too.

There is probably more slop in a toothed belt setup than these, but I'd never run a stepper rigid coupled.

The link I gave you was just one of the 1st ones that showed up in a google search.  I just normally buy these from my local bearing suppliers here in the UK.

Usually I have to bore them to fit the shafts in use, and sometimes broach keyways in where needed.

286
General Mach Discussion / Re: motor tuning
« on: May 15, 2006, 05:02:38 AM »
can you provide me with a link to the fenner type coupling are they simmular to a lovejoy coupling like these
http://www.lovejoy-inc.com/jawtypecouplings.htm

Very similar...  I use this type...

http://www.fptgroup.com/products/hrcjaw.asp

Wayne...

287
General Mach Discussion / Re: motor tuning
« on: May 15, 2006, 05:01:01 AM »
Your problem maybe a signal jitter or length problem.   Not sure what drives the Dynas has originally.   I know a few people who have retrofitted these, but htye have always dumped the original drives and fitted Gecko's

288
General Mach Discussion / Re: motor tuning
« on: May 14, 2006, 07:05:58 PM »
Yes It does seem strange but Steppers do not like being unloaded.  Try it on the bench...  They will stall at high speed and will actually stop turning and scream at you!

Note the speed at which this happened, Load them up, and you will get a higher speed before they stall.

Re the couplings, Not it's not like backlash, unless they are sloppy!   The type I use are fenner type, with a nitrile rubber insert between two hubs.   This nitrile has quite a high Shore rating and you can hardly deflect it by hand when it's assembled.   Probably as stiff as a toothed belt on a servo system.

In fact sometime ago it used to be recommened steppers were driven through a viscous coupling, this is not really required with microstepping drives, but something in between that and a rigid coupling does help a lot.   

Rigid couplings add more problems as it's very difficult to get both angular and radial allignment perfect.

I've done a lot of retrofitting, and ony passing on what I've learnt the "hard way"!

289
General Mach Discussion / Re: motor tuning
« on: May 14, 2006, 03:41:21 PM »
testing on the bench, the motors normally will stall at a lower speed than they would under normal machine load.  SERIOUSLY.

Steppers need some load to work correctly.   You can test them on the bench, but in my experience you can normally up the max velocity a fair bit after fitting to the machine.

Do yuo have some form of flexible coupling between your motor shafts and the screws?   They also work better that way rather than rigid coupling.

290
What are you using for a sensor?

To convert I've jut used opto couplers witht the correct current limiting resistor for 24v..   All my limits,homes, etc are 24v already.

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