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Author Topic: Step losses in specific displacement  (Read 9201 times)

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Re: Step losses in specific displacement
« Reply #20 on: August 15, 2007, 01:45:39 PM »
What I have found while battling that damn monster.  Was that at certain speeds.  Resonance would kill the system.  So with the dampener installed I am able to reliably run at ALL speeds.

They are a very wise decision and very easy to make.

When you changed out your motors  you moved your Resonance level to another speed for the most part.  A good test I found is to run a g code that moves a certain axis back and forth for a long period of time  and use the feed over ride and slowly step up for speed.   Around 22 IPM was my "DEAD" spot.   Installed the dampener  and it was all good!!!

Re: Step losses in specific displacement
« Reply #21 on: August 15, 2007, 02:19:43 PM »
Thank's a lot for this very interesting thread !
I can't say that the sound I witness is the same as the machine is mechanically different but I'm quite sure that the phenomenon is identical.
The difference with and without the damper is amazing ! I actually thought about a kind of fly wheel but I wasn't sure if it would really be efficient.
I think I will study this solution as, as mentioned, what I've done may have just moved the resonance frequency to an other rotating speed.

Nb : I also use Xylotex control board and the motors I have are the reference 23LC100-025-8W (details here : http://www.stappenmotor.nl/Stappenmotor/Stappenmotoren/Stappenmotoren_globaal_overzicht.htm)



Re: Step losses in specific displacement
« Reply #22 on: August 15, 2007, 04:40:34 PM »
Dr Stein, did you say you are running nema 34s on the same drivers? What  is the  amp draw of the 34 motors compared to the 23 motors?? Is the driver rated for a 34s?  (;-) TP

When testing don't try to do it in what may look like the easy way. There "is" a method to the madness.


Re: Step losses in specific displacement
« Reply #23 on: August 15, 2007, 07:36:09 PM »
So I take it this machine used to have 23s on it?

 Did you have the problem then?

If the Amp rating is say 5 amps and you are only driving it at 3 amps the 34 motor may be a little whimpy on the accellaration curve.

Don't know if that driver has current limiting capability or not, but that high of a amp load from the 34s could also drag the performance of the driver down.

If it did not do it with the 23s then I would start digging into the motor/drive specs a little deeper.

That is of course if it is not a mechanical issue.

Just a Thought (;-) TP


Re: Step losses in specific displacement
« Reply #24 on: August 15, 2007, 08:53:40 PM »
Does the driver have heat sinks. You may want to increase the size of the sinks and install fans to help cool them, could be the culpret. (;-) TP
Re: Step losses in specific displacement
« Reply #25 on: August 21, 2007, 12:51:36 AM »
You said your having problems when the machine changes directions, right?  Check the backlash settings, disable them if they are turned on.  I had a problem when I started my machine up.  I'm running servo's, so they won't stall, if they go out of position by 128 encoder counts, they go into fault, or shut down.  Initially, my backlash settings were set to 20% of set speed.  This gave me problems in the same place every time in the same programs.  At certain points, not many, but the same place every time, the servo's would fault where they were supposed to make a direction change.  I now have the backlash speed set to 1% of set speed and have no problems, and I don't notice any problems as far as machining quality either, my initial worry is that the endmill would dwell.  BTW, I rapid at 96ipm and cut with a ballmill at 90ipm using constant velocity, no problems since.


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Re: Step losses in specific displacement
« Reply #26 on: August 22, 2007, 12:12:31 PM »
I can dial-indicate and inch back and fourth, and it appears to accurately locate back to zero each time.

This is not checking the backlash, only repeatability. You will only see backlash when it changes directions. Put the indicator on something solid. Jog your axis until you move the indicator to a reading of about half of its travel. Write down the reading on the indicator. Jog the axis in the other direction by a set amount, say .010" and see how much difference the indicator shows. If the indicator says you moved .005 and Mach says it has moved .010 then you have .005" backlash.

;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!
Re: Step losses in specific displacement
« Reply #27 on: August 22, 2007, 02:37:24 PM »
I used the Logitrol "Low Cost CNC" system.  And I don't reccomend them to anyone.  Basically, it's a 50V DC power supply, Gecko 320 drivers, US Digital encoders, and Pacific Scientific motors, supposed to be 1800oz/in.

  When I recieved the system, the Pacific Scientific motors had encoders pre-installed that were drawing too much current, 150 mA, which is 3 times what the Gecko driver reccomends since the encoder get's it's power right from a onboard regulator in the G320's.  I blew 2 of the Gecko drivers immediatly.

   I emailed back and forth with Steven Kennef from Logitrol to try to get the system working.  He claimed that the Gecko drivers were under warranty and that it must be a problem with the G320's as they were having some issues with "mosfet suppliers", or some other bogus crap like that.  So I took the system apart and sent the drivers back to Gecko for evaluation.

   After recieving and evaluating the Gecko 320's, I talked to thier engineer on the phone to discuss the problem.  He asked a lot of questions and informed me that the encoders that were installed at the time, "remco's", were drawing too much current causing the servo drivers to fail.  He also told me that if the drives were repairable, they would repair them for free of charge, even with Gecko paying return shipping!  But all 3 drivers were beyond repair......  Gecko did replace 1 servo drive for free under thier "one time stuff happens policy", which they didn't have to do and I was very greatfull for!  The other 2 I had to pay for, as well as 3 new encoders that the Gecko engineer reccomended from US Digital Encoder.

   Steven Kennef refuses to admit fault to this day.  He did send a $140 refund towards my costs of repairing the system that was supposed to be plug and play that his company built.  He claims that he can't afford to refund me at this time because his wife is sick in the hospital and he's having financial issues.  I apologize, I hope the best for everyone is health and happyness, but not being able to seperate business from personal issues and affairs is poor business.  I'm not even going to discuss that further, we'll just say my life isn't perfect at the moment but I don't use that as an excuse, and definatly no to customers.

   Sorry for the long story, just pissy about the Logitrol deal and I want to warn others of my dealings with them.  Basically, it's a 50V power supply, Gecko 320 drivers, an isolated break out board, sevo's and encoders that are wired up in neat looking boxes.  My personal opinion is if your at all capable or atleast willing to learn, just do it yourself....  I will if I do it again.  Plus the knowlege gained will be worth 10 fold of what you save as far as money when you can diagnose and repair your own system.  Logitrol didn't design or wire anything special and all of the components are available from diffrent suppliers and I'm sure that there's people here in the Mach forum that would be more then happy to help you locate and source.  Plus you can probably save a lot of money, I paid Logitrol $2600, plus $600 for replacing damaged drivers and new encoders, and a $400 phone bill for calling Steven in Australia....  Lesson learned.

   And I highly reccomend Gecko drivers.  Thier customer service is amazing!  And this is also why I love the Mach controller!  This is an amazing support group and I'm very impressed with the knowlege and helpfulness of some of the members!