Centroid CNC4

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16 Jul 2011 20:06 #11570 by PCW
Replied by PCW on topic Re:Centroid CNC4
I would suggest a 7I52S daughtercard as the 7I47 only works with differential encoders
The 7I52S encoder inputs can be set for TTL or differential mode. Only disadvantage of 7I52S is that it requires EMC2 version 2.5 or > (you can download this from the buildbot)

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16 Jul 2011 23:52 #11574 by andypugh
Replied by andypugh on topic Re:Centroid CNC4
tpwjayson wrote:

I was wondering why you recommend to keep the old power supply?

Because a good, reliable, linear power supply suitable for running three motors is expensive. You need a nice big rectifier and nice big capacitors, and the latter simply aren't cheap.
Depending on the voltage your motors run at, the capacitors quickly become very expensive, for example the ones that I need for my machine are:
uk.rs-online.com/web/p/aluminium/3111254/
(Luckily I found some on eBay).
Replacing the old, industrial supply with a cheap, modern, switchmode probably won't give you a better or more reliable PSU.

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18 Jul 2011 16:55 #11606 by forhire
Replied by forhire on topic Re:Centroid CNC4
tpwjayson, I looked at your photo of the back of your control. I don't see the secondary BCD board (Page 131). If you look at page 35 item 3 you'll note that the speed is done via the secondary board using BCD values. I suspect the the gcode generator inserted speed values and the control simply ignores them. I really doubt you have a BCD interface as the BOSS originally was manual change.

Does the machine have a VFD that controls the motor? Your speed control board should output either a 0v to 10v value or a resistance value. On most VFD controls you can do both. Spindle directions will likely be controlled by a relay. How are you controlling the spindle at present? A rheostat maybe?

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18 Jul 2011 17:41 #11612 by tpwjayson
Replied by tpwjayson on topic Re:Centroid CNC4
I have no control of the spindle speed right now. Here are some better pics of inside the electrical box on the back of my machine

picasaweb.google.com/1083975133402373892...er=0&feat=directlink

Not sure what is in there, it looks like kind of a mess to me. I am considering buying a VFD and re-wiring all of this, at least the spindle portion.

Any recommendations on VFDs?

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18 Jul 2011 18:22 - 18 Jul 2011 18:22 #11616 by forhire
Replied by forhire on topic Re:Centroid CNC4
tpwjayson wrote:

I have no control of the spindle speed right now. Here are some better pics of inside the electrical box on the back of my machine

picasaweb.google.com/1083975133402373892...er=0&feat=directlink

Not sure what is in there, it looks like kind of a mess to me. I am considering buying a VFD and re-wiring all of this, at least the spindle portion.

Any recommendations on VFDs?


It looks like the two upper relays control the spindle direction, forward or reverse. You should see one or the other of these click when issued an M3 or M4 command.

I have a Square D brand VFD. It came with the machine when I bought it.

Found this link doing a quick google search:
www.driveswarehouse.com/?prop_3=2&prop_6...49&filter=1&x=28&y=8

Looking at above there appears to be three types... not sure which is preferred on a mill.
Volts per Hertz (V/F) Variable Torque
Sensorless Vector Constant Torque
Flux Vector Constant Torque

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Last edit: 18 Jul 2011 18:22 by forhire.

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18 Jul 2011 18:54 #11617 by andypugh
Replied by andypugh on topic Re:Centroid CNC4
Flux-vector drives are great. Especially if you think there is ever any chance you might want to accurately position the spindle for a tool changer.

Keep an eye out on eBay for second-hand known-brand. I would be wary of the very cheap no-brand ones from China.

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