I've been researching my control refit for a plasma cutter...

Plasma cutters put out a huge amount of electrical noise, especially when
establishing an arc. Plus there is a twenty-five foot run where the plasma
power, servo power, I/O, encoders, air lines, etc. share the same trough on
my table. Trouble just asking to happen. And from what I've read, many folks
have had a lot of issues.

OK, shielded cable all around grounded on one end. Anything else special for
the cables? I'd like to get the wire ordered.

I've seen a ton of suggestions on encoder and I/O noise reduction but I
think a lot of folks don't know what they are talking about. trouble is, I
don't know who to listen to. In particular attaching small resistors, small
capacitors, and ferrite cores. I plan on using differential encoders from
USdigital and all I/O will be at 24 volt DC with normally closed inputs as
much as possible.

suggestions? In particular is there anything to do with the plasma head to
reduce electrical noise at the source? I'm puzzled that I've not seen
anything on this.

Karl

"Karl Townsend" wrote in message
anews.com...
I've been researching my control refit for a plasma cutter...

Plasma cutters put out a huge amount of electrical noise, especially when
establishing an arc. Plus there is a twenty-five foot run where the
plasma power, servo power, I/O, encoders, air lines, etc. share the same
trough on my table. Trouble just asking to happen. And from what I've
read, many folks have had a lot of issues.

OK, shielded cable all around grounded on one end. Anything else special
for the cables? I'd like to get the wire ordered.

I've seen a ton of suggestions on encoder and I/O noise reduction but I
think a lot of folks don't know what they are talking about. trouble is, I
don't know who to listen to. In particular attaching small resistors,
small capacitors, and ferrite cores. I plan on using differential encoders
from USdigital and all I/O will be at 24 volt DC with normally closed
inputs as much as possible.

suggestions? In particular is there anything to do with the plasma head to
reduce electrical noise at the source? I'm puzzled that I've not seen
anything on this.

Karl





You can wrap the cables in aluminum foil. Cuts down on a tremendous amount
of the radiated and picked up noise.

"Karl Townsend" wrote in message
anews.com...
I've been researching my control refit for a plasma cutter...

Plasma cutters put out a huge amount of electrical noise, especially when
establishing an arc. Plus there is a twenty-five foot run where the
plasma power, servo power, I/O, encoders, air lines, etc. share the same
trough on my table. Trouble just asking to happen. And from what I've
read, many folks have had a lot of issues.

OK, shielded cable all around grounded on one end. Anything else special
for the cables? I'd like to get the wire ordered.

I've seen a ton of suggestions on encoder and I/O noise reduction but I
think a lot of folks don't know what they are talking about. trouble is, I
don't know who to listen to. In particular attaching small resistors,
small capacitors, and ferrite cores. I plan on using differential encoders
from USdigital and all I/O will be at 24 volt DC with normally closed
inputs as much as possible.

suggestions? In particular is there anything to do with the plasma head to
reduce electrical noise at the source? I'm puzzled that I've not seen
anything on this.

Karl

Karl
I suggest you join the Yahoo group Plasmacutting. The moderator Jim Colt is
a Hypertherm rep and is a wealth of info. He has posted good information on
shielding high frequency start plasma cutters. I used a contact start
machine Thermal Dynamics 81 and the electrical noise isn't a problem with
these types of cutters.
Steve

I suggest you join the Yahoo group Plasmacutting. The moderator Jim Colt
is
a Hypertherm rep and is a wealth of info. He has posted good information
on shielding high frequency start plasma cutters. I used a contact start
machine Thermal Dynamics 81 and the electrical noise isn't a problem with
these types of cutters.
Steve

Thanks for the tip. I'll cruise on over search and lurk a bit.

Karl

On May 27, 7:33*pm, "Karl Townsend"
wrote:
I've been researching my control refit for a plasma cutter...

Plasma cutters put out a huge amount of electrical noise, especially when
establishing an arc. Plus there is a *twenty-five foot run where the plasma
power, servo power, I/O, encoders, air lines, etc. share the same trough on
my table. Trouble just asking to happen. And from what I've read, many folks
have had a lot of issues.

OK, shielded cable all around grounded on one end. Anything else special for
the cables? I'd like to get the wire ordered.

I've seen a ton of suggestions on encoder and I/O noise reduction but I
think a lot of folks don't know what they are talking about. trouble is, I
don't know who to listen to. In particular attaching small resistors, small
capacitors, and ferrite cores. I plan on using differential encoders from
USdigital and all I/O will be at 24 volt DC with normally closed inputs as
much as possible.

suggestions? In particular is there anything to do with the plasma head to
reduce electrical noise at the source? I'm puzzled that I've not seen
anything on this.

Karl

The basics of shielding are

1) to make sure power (the gun) and return (ground clamp) cables run
next to each other, as closely as possible.
2) shield that pair of cables within a conductive envelope grounded at
one end only
3) shield everything else within a different conductive envelope
grounded at one end only

Now of course practically applying this to a plasma cutter or welding
application has its own challenges, but that above is the basic idea.


Dave

On Wed, 27 May 2009 18:33:18 -0500, "Karl Townsend"
wrote:

I've been researching my control refit for a plasma cutter...

Plasma cutters put out a huge amount of electrical noise, especially when
establishing an arc. Plus there is a twenty-five foot run where the plasma
power, servo power, I/O, encoders, air lines, etc. share the same trough on
my table. Trouble just asking to happen. And from what I've read, many folks
have had a lot of issues.

OK, shielded cable all around grounded on one end. Anything else special for
the cables? I'd like to get the wire ordered.

I've seen a ton of suggestions on encoder and I/O noise reduction but I
think a lot of folks don't know what they are talking about. trouble is, I
don't know who to listen to. In particular attaching small resistors, small
capacitors, and ferrite cores. I plan on using differential encoders from
USdigital and all I/O will be at 24 volt DC with normally closed inputs as
much as possible.

suggestions? In particular is there anything to do with the plasma head to
reduce electrical noise at the source? I'm puzzled that I've not seen
anything on this.

Karl



Greetings Karl,
The encoders at this link: http://www.amtencoder.com/amtfaq.asp
are supposed to be more immune to electrical noise. That's what Gecko
Drive told me. One of their engineers. Talked my ear off. Anyway, they
are cheaper than US Digital encoders and I bought some from, I think,
Digikey. I was also informed by the same engineer to solder a .01 mfd
capacitor across the two square U shaped loops inside the US Digital
encoder case to help combat noise. Which I did, and it worked.
ERS