RE: [CAD_CAM_EDM_DRO] upgrade strategy

Check item 2, he is using DeskNC for windows which is the one with the
external pulse generator so the computer should not be the problem unless it
can't send commands through the serial port in a timely manor. I would
think it has more to do with software configuration, or wiring from the
pulse generator to the drivers. It may also have something to do with the
wiring from the drivers to the motors.

I have a problem with my Sherline running reliably at anything over 13.5
IPM, I think it is power or wiring but I have not been able to track it
down. I tried replacing my motor wiring with 4 x 18 gauge shielded cable,
microphone connectors at the driver box and soldered connections at the
motors with no joy. For 14 IPM on a Sherline your need a pulse train of
1867 pulses per second to get the job done. If you want to run at 20 IPM
you need 2667 pps to run at that speed and for 25 IPM you need 3334 pps
assuming you are running in 1/2 step mode. In my case I am micro stepping
at 2000 steps per rev so for I need 8000 pps to run at 12 IPM. I am running
on a 266 MHz Pentium with 64MB ram. Mine is definitely problems other than
the pulse train, most likely motor torque. I am using Pacific Scientific 80
oz/in 8 wire unipolar motors wired in parallel on CMD-260 drivers. These
motors are rated at 15.5 volts 1/2 amp, and are running on 38 volts. I will
be upping that to 76 volts this week if all goes well. I know I need better
motors but it works for me and I can live with 12 IPM rapids for now.
Everything works well and I am making parts with it and I am working within
the capabilities of the mill. It is still faster than turning the cranks by
hand and most definitely produces better quality parts than I was ever able
to achieve turning the cranks.

John Guenther
Sterling, Virginia

> -----Original Message-----
> From: Carol & Jerry Jankura [mailto:jerry.jankura@...]
> Sent: Monday, August 19, 2002 8:44 AM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: RE: [CAD_CAM_EDM_DRO] upgrade strategy
>
>
> You didn't mention which G-Code interpreter or operating system you were
> running, but if it's a DOS based controller, make sure that you
> do not load
> either EMM386.EXE or HIMEM.SYS through your CONFIG.SYS file. These drivers
> tap into the computer's interrupt structure and sometimes have enough
> overhead to cause an unstable pulse train. If the pulse train is
> not stable
> (that is, acting as the interpreter would ask it to), the motors
> will stall
> out at speeds lower than what you would expect.
>
> -- Jerry
>
>
> |I have upgraded the power supply to a 36VDC secondary, and reading at
> |the rectified, filtered output showed 59VDC. However the G201 still
> |can only manage 14ipm with the Sherline and 3.2V 2A steppers (half-
> |coil) with set-resistor 18 ohm. Seeing other reporting much higher
> |speed, I can only assume that the following may be the cause of the
> |low performance:
> |
> |1. unshielded 22AWG motor cables (less than 2 feet)
> |2. less than satisfactory pulse train. (deskNC for windows)
> |3. unshielded data cables. (used stranded cables before. Now replaced
> |with solid core twisted pair taken from those cables used for wiring
> |computer network)
> |
> |The problem is getting suitable shielded cables. Supplier only sell
> |such cables in large roll. Any suggestion how I can begin to try to
> |tackle the above?
> |
> |Thanks
> |
> |keongsan
> |
> |
> |
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> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto:
> aol://5863:126/rec.crafts.metalworking or go thru Google.com to
> reach it if you have trouble.
> http://www.metalworking.com/news_servers.html
>
> http://groups.yahoo.com/group/jobshophomeshop I consider this
> as a sister site to the CCED group, as many of the same members
> are there, for OT subjects, that are not allowed on the CCED list.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY
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