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spindle drive questions
« on: March 08, 2011, 12:28:19 AM »
i am converting an older Anilam Eagle cnc km-750..
during the course i have gotten most everything working once again with a new drive package..
i am using  LeadShine M860 stepper driver in 1600 microstepping mode and Leadshine  4.5 NM NEMA34 motors ( 1/2" shafts) in parallel coil configuration and a cnc4pc c-10 breakout board ( one more on order  for i/o)  the axis tests are perfect ( almost better than original.. .0002 resolution) ..  someone had the brains to have a ball screw cover..

the problem..
the spindle once had a vfd and had an air controlled variable spindle speed setup...
i am converting the air system  with a stepper .. and the vfd is toast..  i have spent so much money in fancy controls and doo dads..  i am holding off on a replacement vfd for a few months.

 i am replacing it with a set of 3phase contactors.. one for cw the other for ccw  and one for e-stop that kills power to the whole motor circuit. ( for redundant protection)

the problem i am wondering is  when i issue a m3 or m4  command  is there an xor designed into the software to prevent the simultaneous  output on both the pins assigned to m3 and m4?

or should i design a safety circuit that xor's the output and ands them back into the relays controlling the 3phase contactors?

another question is the output of the signal of the m3/4  is it a pulse or is it a sustained signal high or low until i issue a m0  or e-stop.

way too many questions .. but i have not seen the topics  asked or answered yet..









 

Offline Tweakie.CNC

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Re: spindle drive questions
« Reply #1 on: March 08, 2011, 02:35:52 AM »
The M3 and M4 will toggle one or the other and when assigned different outputs will not both be on at the same time.
The output signal from the M3 / M4 command is a steady state high or low.

I never leave anything to chance with 3 phase so, if it is possible, it would not hurt to incorporate an interlock into your contactors just to be sure to be sure  ;)

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: spindle drive questions
« Reply #2 on: March 08, 2011, 02:41:54 AM »
thanks..  i thought it would be that case.. but wanted to be sure.. i will still build the xor safety circuit  just to be certain that it is not possible to  cross phases during a crash or catastrophic software failure..
 

Offline Hood

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Re: spindle drive questions
« Reply #3 on: March 08, 2011, 03:06:08 AM »
The software should only activate one or the other but personally I would not rely totally on software. Depending on your contactor type you may be able to get a mechanical link between them which will prevent one being operated if the other is already operated, my lathes contactors were like that.
Regards output, it is a steady signal and also M5 will also stop it.
Hood

Offline Hood

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Re: spindle drive questions
« Reply #4 on: March 08, 2011, 03:06:33 AM »
ah too slow in typing I see ;D
Re: spindle drive questions
« Reply #5 on: March 08, 2011, 03:11:08 AM »
exactly..


 i want to idiot proof the design.. JIK someone else decides to bypass the contactor interlocks..  ( stranger things have happened) ..
 how is Scotland tonight?

Offline Hood

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Re: spindle drive questions
« Reply #6 on: March 08, 2011, 03:14:07 AM »
Afraid I dont know how Scotland is tonight as its only morning ;D

Safety is always a good thing, especially when talking mains voltages.

Hood