about my 48" X 48" X 5" Techno/ISEL woodworking router build

some may remember me from other parts of the LinuxCNC forum... i am working on converting my Techno/ISEL gantry woodworking CNC router from printer port control, to a Mesa 7i80HD-16. the machine is about 48" X 48" X 5" of working area, and currently has a Perske 5HP 3-phase (via Chinese VFD) spindle. it is stepper drive (i prefer the "music" of steppers...), and i will likely keep it that way, until i find the "music" to be a pain. currently, the project has slowed down, with the holiday prep underway, but i expect to be working full-force again asap.
i look forward to sharing pictures in this thread, when i take them, of the whole machine, and how i put it together.
when i first got it, it was just the Techno/ISEL machine itself. the frame, gantry, Perske spindle, and the steel base. it had some servo motors for all 3 axis, but as i could not find any info on them, or their encoders, i opted for steppers, as the motors and drivers were cheaper than servo hardware.
here is an older picture:

it was taken years ago, before i mounted the Perske spindle back onto it (shown with a Makita RF1101 router attached).
the machine resides in the back of a gutted-out old camper. there are some added double doors added to the camper, to the right, so i can put large material onto the machine without having to get it through the camper door. and if i ever have to move the machine out of the camper, they will work for that too.

the control hardware will be mounted in a small rack enclosure i bought just for this reason, and all will be shielded and isolated using adhesive copper foil designed for electric guitar shielding. the power supplies will all be located at the bottom of the enclosure, away from the EMI sensitive parts. i am on the lookout for a plate of copper or aluminum to mount the stepper drivers on as a heatsink, and it will also be tied in to the shielding, to prevent EMI escaping, or entering. stepper driver signal wire will be CAT-5e STP wire, with the drain wire tied to the shielding (one end only, of course). power wires will be twisted in pairs, feeding each driver, and wrapped with shielding foil. the motor wires don't happen to be twisted-pairs, but they are shielded cables.
the power-supply for the logic, and the 7i80HD-16, a computer power-supply, will be partitioned off from the stepper power-supplies.

the reason for all the careful shielding, is my previous setup had a slight cross-talk issue, so this generation will be over-shielded, as much as i can. and taking tips from Best Wiring Practices , i will try and document and label better, this time...

anyway, been meaning to describe my project for a while now, and more updates and pictures will follow as progress is made.

~Travis

travis036 wrote: the reason for all the careful shielding, is my previous setup had a slight cross-talk issue, so this generation will be over-shielded, as much as i can.

You should see people here when i tell them that the plasma turning on is causing some other equipment in their shop to malfunction, they look at me like i just fell from Jupiter !
Sound like a nice plan, thank you for sharing.
Happy New Year, all the best.
Tom.

From the manual the 7i80HD uses 5 volt I/O. This may not have been a good choice for your machine because such a low voltage is more susceptible to noise because the voltage does not need to change much from noise to affect reliability.

If 24 volt is used, the noise has to alter the voltage much more before it misbehaves, about 10 volts or so. Thats why it is the standard voltage for commercial standards.

I would ask some questions on the Driver boards section where PCW is more likely to see it.. I think Mesa have an adapter for 50 pin cards to 25 pin cards so this may allow you to run a 7i76 and upgrade to 24 volt field power. Alternatively swap your existing card for a 7i76e. If more I/O pins are required, you may need to add another daughtercard to increase the number of pins.

conveniently, i just, as in just now, ordered some 5v to 24v optoisolation boards, as well as some 24v to 5v boards for the inputs. my stepper drivers are 24v compatible with the correct resistors in series, so this all works out.

~Travis

Also the LCNC docs on wiring don't mention using a star ground system so that every motor has a seperate ground wire running back to a central ground that in turn is grounded to the electrical system, the cabinet and possibly to a ground rod driven through the slab into the ground. Also ensure that you also run wires from the z axis if necessary. The goal is to ensure there is a path to ground that does not pass through any bearings or linear rails. Hypertherm has a document around this specifically for plasma machines but it would be worth reviewing it.

Also on my machine, I used 5 pin connectors for stepper wiring so the cable shield could pass through into the cabinet and then it was terminated to frame ground right at the stepper controller. Do not connect the shield at the motor end. My latest drivers have a terminal for ground so this worked out well.

interesting, i had heard about a star grounding system, but hadn't thought of it. by your description, i am almost already applying it, in that i am centralizing ground, but i still have to apply a ground stake, and some other steps.
i like the mention of grounding the Z-axis, as i had not considered that either. perhaps the gantry may also be grounded, for consistency. i may ground the Z to the gantry, and the gantry to the frame. and the frame to the central grounding. it may be as simple as a ground wire run through each drag-chain, between each axis.
my stepper cable shield drain wire is connected to the metal shield of the connector, and thus to the chassis. not a dedicated pin connection, but it tests positive for conductivity to the chassis. short of changing the connectors, i could add a grounding tail, and fix it with a sheet-metal screw to the chassis.

something occurred to me, just now. the enclosure for my control box is a "some assembly required" type, with each panel painted at the MFG. perhaps i should not consider this as a grounding location... so the stepper cable shields should continue to a proper ground location. either that, or i need to ground each panel of the enclosure (more of a PITA). i planed on sectionalized shielding inside the enclosure anyway, so the only thing that changes really, is what i can and cannot consider a ground.
with a star-ground connection, i will also have to consider what ties to it. AC and DC grounds generally should be independent. i usually consider shielding to be an AC ground, and the DC logic/control power supplies have their own common ground plane. but the stepper driver PSUs... does the DC ground tie to AC ground, Logic DC ground, or float as it's own ground?

~Travis