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Author Topic: Bridgeport Romi lathe retrofit with csmio ipa  (Read 953 times)
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Johnny Bravo
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« Reply #10 on: March 12, 2017, 06:37:48 AM »

Not sold on that Gecko drive idea ,seeing as the SEM servo motors are rated at 140v and the Gecko drive can only handle 80v. Would need to sort out another power supply and then the servos are still running  roughly 40% down on power,so speed and torque would be down too.🙁
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Johnny Bravo
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« Reply #11 on: March 12, 2017, 02:38:23 PM »

Not sold on that Gecko drive idea ,seeing as the SEM servo motors are rated at 140v and the Gecko drive can only handle 80v. Would need to sort out another power supply and then the servos are still running  roughly 40% down on power,so speed and torque would be down too.🙁

Or would they? Not sure on that.😊
Did check what power is coming out the supply, 110v.
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mikecole
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« Reply #12 on: March 12, 2017, 11:22:54 PM »

Hey Johnny,

Perhaps Gecko are not the best choice... Did not notice they maxed out at 80vdc. I'm using Servo Dynamics amps... They are much more expensive however... Here's the link: http://www.servodynamics.com/product/1525-br-servo-amplifier/
American made so can't compete with the stuff from China on price. Great quality however... You still need to verify servos are good.

Here's the procedure I used to verify my servos and amps were good:

1.) I disconnected the belt from each axis. (not sure if this is possible for you?)
2.) I bypassed all the relays that implement safety and ready status logic so I could enable the amps. Remember once you enable the amps you could have an axis go wild so be careful!
3.) I used a 9vdc battery and a 1k pot to create a 0 to +9vdc input to the servo amp. This allowed me to verify that the servos would turn at an rpm proportional to 0-9vdc.
4.) Lastly, I reattached each belt to verify that the servos would move the table and Z axis. This too needs to be done with great care lest you run an axis past it's limit and damage your machine!

Hope this helps!
Mike



 

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Johnny Bravo
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« Reply #13 on: March 12, 2017, 11:47:48 PM »

Hi Mike
Thanks for your reply 😊
I had remembered reading about testing servos with your mthod awhile back,but for the life of me I couldn't find where I had read it 😂
So that can get that side tested. Not a problem with pulling the belts off,the one on the x axis has a nick in it,so was going to be replaced anyway.  Had the top cover off the gearbox yesterday.Absolutely pristine inside. Looks like the gears have hardly turned.Was so excited that I forgot to take photos,😂😂😂.

Measured voltage coming out the psu that drives the servo drivers,110v.  Have found a Uk manufacturer of Analog triggered servo drives. Very reasonable price. Designed to run 100v.  Going to ping them an email and ask if their drives would cope with 110v.  Otherwise I don't think it would be that difficult to lose 10v. It's a pretty crude set up,unregulated with a huge 2kv transformer,a couple of diodes,resistor and the mother of all capacitors..
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mikecole
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« Reply #14 on: March 13, 2017, 09:05:18 PM »

Hey Johnny,

Great to hear the gearbox looks pristine. Sounds like you've got a great lathe which will be worth the headache of upgrading the control system. The power supplies in these machine do seem crude but they work. Simple 60hz transformer, rectifier, huge caps... Curious about your servo amps. Do you have a web link for them?

Mike
 
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Johnny Bravo
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« Reply #15 on: March 13, 2017, 11:12:51 PM »

Hi Mike. Emailed the company about the servo drives.  http://www.trminternational.com/
Not sure if that will work as a link,so you might need to google the name.  Very helpful. Plan on using two of their 20A drivers coupled to a csmio ipa.Long and the short of it is,that 99v is the maximum you can run as the overvoltage protection will shut the drive down at 101v. Being a local manufacturer does help.  Also had a chat to one of the old boys at work. He explained one of the quirks of our power supply grid. Here in the Uk we run 240v ,50hz. Most houses are single phase,the street lights are normally on a different phase,and industrial is three phase. I am pretty rural,down in the South East of England,not far from Rye and Hastings. Two of the phases when measured are over 240v and the third phase is quite along way down. At home it measures out at 248v. At the shop two phases measure out at 248v, with the third being down at 231v.  Because of this,the psu outputs about 104v which isn't any good for my needs.  Everyday a school day!

So,the plan is to get a 2kva toroidal transformer with two windings of 70v. Run the two windings in parallel to double up the amperage,use a 50A bridge rectifier ,a bleed resistor and a smoothing capacitor. This should result in a voltage between 94-98v, dependant on the capacitor used.  Psu will be able to supply 28A which will be more than enough.Not sure about re using the old capacitor,have been told to be wary of big electrolitic capacitors that have stood unused for many years.  Apparently they should be reformed with a lower voltage before reuse? So, I might go down the route of using a bank of new,smaller capacitors connected in parallel for the smoothing part of it.

Well, I haven't gotten very far. Still haven't decided whether or not to convert this lathe,but it is looking more likely as I work my way through some of the issues I already know about. Learning a lot,and I haven't even started 😂


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