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rmerrick



Posts : 3
Join date : 2011-10-19

PostSubject: CNCDIY controller   Sat Dec 10, 2011 8:12 pm

I had a problem with my CNC6040. one of the stepper wires broke for the 3rd time. caused the cutter to destroy over 8 hours of machining and blew the fuse in the controller.
Now I dont have smooth control.
I put an oscilloscope on the motor & I see only one phase of the mains being controlled.
I need to know what are the SCR's used. I am sure one is open circuit.

Someone sanded the part numbers off the components.
please email me.

Also the 240VAC phase controlled is far too much voltage for the motor brushes. After one month the commutator is burned and one set of brushes is gone..

where can i get new brushes? (Not refurbished as supplied with the machine).
thanks
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c.bourgoin



Posts : 11
Join date : 2011-11-22

PostSubject: Re: CNCDIY controller   Sun Dec 11, 2011 2:32 am

how can the wires broke ?
it's not a moving part so how can you break it ?
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rmerrick



Posts : 3
Join date : 2011-10-19

PostSubject: wires broke   Sun Dec 11, 2011 4:10 pm

ok. the wires are in the cable ducting.
The wires are twisted 4 x 16/0.1mm (1.5A) in a pvc coating.
When the wire is flexed in the ducting due to the moving gantry, the outside strands are under tension and the inside strands are under compression. The very fine wires just break after a few thousand movements. Result is +x, +x and crash..
The wires should be 4 core flat cable with at least 32/0.1 or 50/0.1 or 128/0.1 or 32/0.2. And rated at 3 - 5A. I made my own carefully taped flat..

Spindle motor.
I used a set of brushes in one month. I tried the replacement brushes as supplied. they dont reach the commutator. The braids are too short but i had to open the motor to see the problem.

This saturday the spindle motor stopped completely. So I gave up the warrenty and dismantled the motor. I remachined the badly burned commutator. Then I modified ALL the brushes to lengthen the braid so that the brushes would actually reach the commutator after they were 1/4 used..
I see the replacement brushes supplied are refurbished.. now they are more refurbished. :-)

Because the motor controller is phase control on 240VAC the motor is getting pulses about 200V peak (at about 0.2A). This voltage is excessive for the brushes & commutator and burns them if used under load.

I am going to add a series iron inductor (secondary 6V 5A winding of a 30VA toriod transformer).
It measures about 47mH and 2-3 ohms. then I will add a 450V 220uF capacitor so that the motor sees smooth DC.
Until I repair the controller I am running the motor from an 80V 5A variable DC power supply and it is "sweet" on DC.
Ray
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