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Member postings for Mark Czarnecki

Here is a list of all the postings Mark Czarnecki has made in our forums. Click on a thread name to jump to the thread.

Thread: Stepper
05/12/2009 06:17:41
Hi, Alan:
        Right on, my sensing circuit is just as you describe, it even uses an LM339.
I'm aware of the importance of an "unwobbly" tool slide; I'm making two 3/8"
columns some 70mm apart, with a central lead screw moving the tool holder.
 If I can get it not to jam, it will be a straight liner.
 Spark power is:  70v (supplied by two Sony Betamax Xformers in series;
luckily I was able to use all the secondary windings, so all the copper is in use!)
smoothed by 2000uF, through 15 Ohms 200W to the head, with a switchable C
up to 850 uF. Also there is a mosfet that shuts off charging when the tool shorts.
     Fluid will be circulated by a small pump, so my tools will have to be hollow. I'm
planning to use kerosene ( with an extinguisher handy!)
Will post pics when build is complete.
OT Gloat:  Just received a solid state Oscope: two channels,15 screens storage,
60Mhz, DMM function, all the digital bells and whistles,battery powered. Me
mucho happy.
Best Regards, Mark
 
03/12/2009 05:15:00
Hi, Alan:
 
 The motor plate says 14v,  27.5 ohms/coil. It was bought some ten years ago, and it
probably was surplus anyway, so who knows how obsolete the thing is!!.
  You're quite right, the 176 rpm will be used solely for manual fast up/down; as is it
will give me some 45mm/min. Not supersonic, but I can live with it.
The stepper is driven by a 555, through an up/down counter to a TIP41; this is full 18v during the whole step (unipolar).  As planned, I'll have a demultiplication giving me a 0.0065 mm/step. If this is too fast at the actual slowest motor speed of 40 rpm, I can always slow down the 555 further.
   Are the 0.1 uF caps across the motor coils necessary?
   Having no experience with EDM, my plan for operation would be to have the head
lower at the slowest rate, and then increase speed until it starts backing out often.
Is this the correct way?
   Re modern PWM drives and motors, I'm in Venezuela and getting material here
can be quite a hassle, so I tend to make do with whats available ( read scrap box )
Eg, I found a small (MXL) belt in my recycled collection, the locals had no pulleys
that size, so I had to make them. And so on...
 Thanks for your ideas and the link.
   Regards, Mark
26/11/2009 20:27:04
I have this stepper to go in an EDM head:
Dia. 2 3/4" Long 1 3/4" 48 steps 18v.
Its maximum unloaded speed is 176 rpm; above this it stops and shudders.
Is this normal or do I have an error someplace?

Thanks & Regards,Mark
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