Wasn't sure to ask this question here or under worst way of wiring. :)

Is this the proper way of connecting the shielding. When I connect the other shield wire, they will touch. Will this cause a ground loop?

Attachment 1374

Greg,

That's similar to the way I did it. I twisted all of the shielding together and then crimped them. I also heat shrinked them so there were no exposed metal.

That's the part I was wondering about. I'll re-do tomorrow.

Thanks Doug.

Greg,
Normally, when we do shielded junctions at work, we use a conductive encloseure and then terminate all the shields to the enclosure. This way the enclosure becomes the shield around all your joints. Your box looks like a plastic of some sort. Just realize that you lose your shielding in that area. In that case just make sure you have all the shields tied together and they dont short to anything else.

Heath,

Thanks. Yes, the E-stop enclosure is plastic.

I am running a large ground wire for the main structure that ties the Z slide, Y car, gantry, and table together. That main ground will terminate inside the metal control box. The metal control box will be grounded to the incoming supply voltage.

Greg I am not sure what others have done but I sank a ground rod as close to the machine as I could get it and I have my large machine ground wires going straight to the ground rod. My grounds in my control box go to the main breaker box which also has a grounding rod. Not sure if it is necessary or if it even makes any differenc but when I bought my huge squaring shear (it has a control box simmilar to what we are doing) they recomended that I do that, so I did the same with the MM.

Ed having two seperate grounds causes a difference of potential in the ground. I'm not an electrician but I would think that would be a big no-no.

If the electric coming from the control box should contact the frame of the mechmate for some reason it will take the easiest path to ground but if it has two paths then you could have a potential fireball.

That is what you want to happen. Electricity will always flow through the easiest path. As long as you have a good ground path, that is all that matters. :)

Yes but if you have two paths to ground you have a difference of potential. Like I said I am not an electrician but when we ground the boxes for the phone lines on the side of your house we are supposed to ground to the common electric ground so as not to create a difference in potential, everything grounded to one place.

I see what you are saying and that is a good point, when I build amplifiers I try not to create any ground loops and stay with one central ground point for the power supply, as not to inject any noise or interference into the signal.

I can already see though with my MM that there is alot of static electricity around the sawdust and wood chips, as I am working or cleaning. That static electricity will take that shortest path to ground. Which hopefully will not be through the sheilding wire or any control wires, but through the MM frame itself. Which to me is a good reason not to connect any cable sheilding wire to the j-boxes that they run through, thinking the box will sheild the circut inside the box. Unless the jboxes are isolated from the MM, doing this will create a ground loop, (one path through the sheilding to the control box and the other through the jbox itself which is bolted to the MM and then through the MM ground wire).

All circuts on mine that runs off the control box, are getting their ground through the main breaker ground rod, all those circuts are (or should be) isolated to the control box. I didn't ground any sheilding to boxes mounted to the MM ( I connected all sheilding inside my J-boxes to each other and tapped them so that they touch no metal inside the box) , they are grounded in the control box only.

Any static electrical discharges around my MM or directly on the metal my MM will go through the MM frame and to the ground rod close to the MM rather than through the control box or through the shielding wire which is very close to my control wires. When I run a vacume near the MM you can feel pulses of static electricity as the wood chips run through the vacume hose.
I know all the wires on the MM are sheilded and the sheilding should take everything to ground, but I just don't like the idea of that much voltage spikes running a few thousanths of an inch from signal wires, or around the BOB or computer, so IMHO I think it would be the lesser of two evils running the seperate ground rod.

Does this make any sense, or have I totally gone nuts:eek:

I am no expert either but there are alot of folk here including Gerald that are more knowedgeble about this, maybe they will chime in on this subject soon.

That point makes sense to me I was thinking more along the lines of if something catastropic happend and the mechmate frame came into contact with power or the router somehow shorted to the frame. I was not thinking of the static build up. I was planning on grounding back to earth with a seperate ground wire going back towards the control box but picking up the ground on the outside of the box where I planned to install a bus bar for the ground.

As I understand Control box and MM is grounded. My question is -

1. If ground is floating?
2. The MM lies on floor and Control box is mounted wall, which are Earth. Is this causing some electric problem?
3. If Earth of mains power line (Green wire) is to be connected to CB or MM?
4. My router has 3 pin connection, one is for Earth, do I have to provide sepearate line for it through mains Power line Earth?
5. PS ground is common via pin 1 and 12 of G203V (Continuity between PS ground, Alu plate and Pin 1,12), it means all metal is having - 70V (PS Ground), does this provide shielding against interference?
6. I have connected all shieldings to Alu plate, it means they all are having PS ground, is it correct way of wiring?

As I don't want expensive smoke, it's better to ask than to regret later.

Thanks,

Relax, ground problems do not make expensive smoke. They can only make cheap smoke. Ground problems make strange movements, and maybe put the cutter deep into the table....cheap smoke! :)

1. If ground is floating? Don't understand the question
2. The MM lies on floor and Control box is mounted wall, which are Earth. Is this causing some electric problem? No
3. If Earth of mains power line (Green wire) is to be connected to CB or MM? To the control box metal
4. My router has 3 pin connection, one is for Earth, do I have to provide sepearate line for it through mains Power line Earth? For safety, you must connect the router earth to the power supply earth via a route of your choice
5. PS ground is common via pin 1 and 12 of G203V (Continuity between PS ground, Alu plate and Pin 1,12), it means all metal is having - 70V (PS Ground), does this provide shielding against interference? Don't really understand your question. Yes, all metal is connected to the negative side of your power supply out - same as the metal parts of your car being connected to the negative pole of the battery
6. I have connected all shieldings to Alu plate, it means they all are having PS ground, is it correct way of wiring? Yes, it is correct. The other end of the shield (furthest from the alu plate) must not be connected to anything.

WOW That's really fast, while I was still browsing for answer.
Thanks Gerald for you INPUT.

It clears (Sigh) all dark clouds.
My main concern was should I connect Earth with this common ground. Now I don't need lengthy Earth cable for router, I can bolt it to MM.

Floating ground - http://en.wikipedia.org/wiki/Ground_...electricity%29
http://en.wikipedia.org/wiki/Floating_ground

Okay, the ground is definitely not floating.

Yes, you can ground the router to the MM frame, provided that you have grounded the MM frame correctly.

See posts 1 and 2 of this thread. That thick ground wire will take your router's earth to the power supply earth.

That's what I was thinking of, thanks.

Another grounding/earthing question.

I know that the shield for the cables must be earthed in the control panel (preferably to the main ground plane - Gecko heatsink) and that the other end of the shield (i.e. at the motor or switch etc) must not be earthed, but is it okay to tie the shields together (but still not earthed) at some intermediate point such as in a junction box on the gantry.

I have a junction box with cables coming from the control box, terminating into DIN connectors then carrying on to their respective destinations. My thinking is to use one or two DIN connectors to connect the shields together.

Richard, Sean, Gerald any comment?

Ideally, a shield or drain conductor should only be connected at one end. The purpose of the shield is to reduce EMI type interference along the entire length of the cable for that one device. By combining shields at a midpoint, you risk the possibility of negating the good that comes from using a shield.

It is more costly to run separate cables for each electrical device, but, on a CNC machine with low voltage signal lines and high voltage motors and spindles, the need is even greater to separate conductors and isolate electrical noise.

On another forum, some users of the Ascension 1000 control box are experiencing tremendous problems. Those control boxes seemed to all work perfectly until spindles were added to the machines and the weather turned hot. Now, several users are having sporadic stepper problems, which seem to be due to electrical noise from the VFD/Spindles. Last night, the consensus from a group e-mail seemed to be that cabling, line/load reactors and EMI filters would be the next things to check/add.

If it makes anyone feel better, running 30 to 60 feet of cable per electronic device creates problems for all types of machinery. What you have, in effect, is a 30 to 60 foot antenna that picks up every bit of electrical noise from your machine as well as all the other machines running in your entire neighborhood.

So, following the best practices is the best policy.

Alan, "Richard"'s first name is Mike :)

I wouldn't risk tying those shields together. When you bend the "rules" a little here and there, and then find some sporadic movements, it is messy to try and remember which rule was bent where. With the table sizes we are building out here, we have some seriously long cables, or "antennae".

To confirm earthing
 

After reading this thead i just wish to confirm that my thinking is correct on earthing the screen of the signal wires in the control box.
The photo shows the first screen wire in position from my interface board to the Gecko.
The correct way is to twist the screen wire at the gecko end, crimped it to a piece of wire with a connector and lug and then screw it to the heat sink.
The other end of the screen wire must be trimmed short.
Is this correct?

Attachment 3219

Lex, that is about right, but you might be able to crimp a lug directly onto the twisted braiding at the gecko end. (It will be clumsy to have a connector and wire before the lug). You drill and tap the alu plate to suit the lug's position.

Thanks Gerald.
Dankie vir die raad. Ek sal so maak. Ek is lekker dom met die bedraading!:D

Jy vorder goed.

some grounding pictures
 

Hi Thought would share some pictures on the grounding I have done -

Attachment 4451

The above picture shows the grounding done to the main frame - the wire through out is 2.5sq mm.

Attachment 4452

the above pic shows one in and two out - one goes towards the y and z axis where as the other proceeds towards the slave x motor

Attachment 4453

Grounding on the Y car - one in and out goes towards the Z axis and spindle

Attachment 4454

the above is the picture of the grounding near the slave x motor

Attachment 4455

The above pic is of grounding for the Z - the bolt which is used to mount the spindle clamp is used.

I have measured resistances and it varies between 0.2 to 0.3 Ohms - hope this is alright

also is it necessary to provide for grounding jumpers from those done near the motors to the motor mount plates on the gear boxes.?

thats it -

RGDS
Irfan

You grounded both ends of the gantry (pic 2 and pic 4 above), which is something that I have not seen before. Normally we only ground one end. It is not usual to ground the motor plates, but that is technically a good idea.

I don't know if you cleaned off the blue paint under the ground connection, or if you used a star washer, or both?

I scraped the paint using a broken hacksaw on the bolt holes - except for the other side of the gantry - :) I could not reach for the broken hack saw (it was beyond my arm's reach at that time) however I have measured the resistances and 1.2 to 0.3 everywhere.

RGDS
IRfan

Corossion is a grounds worst enemy
 

I happen to play with cars some and an auto elec. told me the worst enemy of of a ground is rust!

His process the 4 "C's" that I always follow is:

• Crimp ends not solder
• Clean all surfaces to bright metal
• Connect surfaces with star washers
• Covering with petroleum jelly

First thing I do on old cars is rebuild the earth circuit, it's amazing just how much better they run.

Just hope I connect the right wires on the MM!:eek:

Its all working!
 

Copied from elswhere:

Maybe it was a little premature to rat out on the SS.
I went over the earthing strategy with our EMI compliance engineer at work and he gave me a number of things to do. (He wasn't all that impressed with the Chinese VFD) I'm sure i'll get a heap of resistance from you guys for this, but he told me earth the motor & spindle cables braid/shield at the motor end. He says the effect of ground loop is insignificant when compared to the shield acting as a large antenna. Without any disrespect to you guys i'm going with him on this. (He is a well experience EMC/EMI engineer who has all the right equipment to measure this stuff)
In addition to that, he told me to add an EMI filter on the power input to the VFD and a toroidal ferrite on the motor output as pictured below.


The IEC cable filter was the only one i could get off the shelf at my local electronics store. I will change this to a normal spade terminal one and neaten the wiring.

But this has fixed my SS problem and i no longer lose comms with it!! It was so much fun driving the table around with the spindle going. I need to finish my water circuit for the spindle but should be cutting in the next couple of days when i get a chance!

Matt, I have also recently started becoming aware of alternative strategies for grounding shields. What is coming through is that power cables (motor or spindle cables) should be grounded both ends, while signal cables (the milliAmp stuff) should be grounded one end only.

We have added ferrite rings on the input and output (2 rings) of our VFD - it is recommended in their handbook. But, what really got our SS going was routing the USB cable far away from anything else.

Anyway, great to hear that you have reliable movement! Now we want reliable sawdust! :)

Update on controller
 

Pics that Robert refers to below

Gerald,
After looking at paul60 ( woodguy) photos on his controller works, (now above) I’m worried about his cable shield connections.
Is it my imagination cross referring some of my zillon post reading . Shouldn’t those Geckos be left alone !
I can’t find the post where I thought I read it was no longer recommended to attached the cable shield to the Geckos heat sink alu plate, minimizing noise among others to those drives ?
Robert ;)

I don't remember any such post, nor do I see anything wrong with the photos above.

I think you may be getting confused with the grounding of the BOB, that was originally connected to the ground plate but later removed (right at the very beginning...)

Copied from another thread:

. . . . . . When the load picked up on the spindle the connection between the Smooth stepper and the BOB was lost. I found that the shield on the cable power supply to the motor from the VFD was connected at both ends which eliminated the shielding and locked up Mach3 and the ss. Only connect one end of the shield cable to ground and it works fine. I'm sure that some one has stated the shielding connection on one end before. That is about as far as I have gotten. Have you had any luck on the breaking resistor?
Buzz

Buzz,

you would usually connect shielding on the end that 'sends' the signal. in this case it would be the VFD, then shield at the motor end would then be left open and not connected.

Ries

Thanks, Ries - I am backward to that. The shield is at the motor end. I will change that tomorrow.
Buzz

EE engineers always say ground the shield at the source, but in fact if you can't do that for any reasons, grounding at the load end works as too. What we need is a Faraday's cage to take effect, the shield being metal conductor hence the cage & grounding at one single point will turn it into a faraday's cage.

I am starting to believe that motors (which don't suffer ground loop problems) should have the shield grounded at both ends. Suggest you try it. (See this post)

Shielding at both ends will not have the Faraday's cage effect, in fact the shield will become part of the EMI transmission antennae...
Faradays Cage
Antennae