Shielded wire for steppers, or not?

[JanHenning]

Hi,

I am about to start my first CNC-project. It's a Optimum BF20L, with Gecko 203V and RS960 steppers @ ball screws. I have 1,5mm2 silicone insulated wire that I want to use from the controllers to the steppers. Max 100cm length.

Will this do, or do I need to buy shielded cable, that is meant to be used with steppers?

Jan

[JanHenning]

I'm buying shielded cables

[LeeWay]

Good choice. Shielded cables will help eliminate a lot of electrical noise and associated headaches. It is really not very costly either. I think I might have paid $20 for 100'.

[gth629e]

Jan Henning,

I suggest you use shielded cable. You never know what you might pick up. You may get by with it and not pick up and interference you never know. It's a small investment that could save some headaches. If you motors start acting up or lose steps and you do have shielded cable, then you can almost rule out interference. Be careful with limit switch cables as well, I have had interference there as well, however, it is less likely.

I am about to do a full writeup about stepper and servo motor wiring selection and sizing at my website cncroutersource.com. If you want to know more.


100 cm is not exceptionally large distance and you might get away with it. It all depends on many variables. Location, distance between cables and other electronics, etc. However, I would still recommend shielded.

Hope this help and keep us posted!!!

[lgalla]

GTH629e,
Another silly idea from Lgalla.
If you mount yer gecos on the steppers may this configuration not pick up as much noise?Yes I know there will be more heat,but some alu heatsinks will keep the cool.Is it worth investagating?Sorry for the spelink errors.
Larry

[zabink]

Larry,
You can in fact buy some stepper motors that have a driver bolted directly to the back. You can buy drivers with NEMA 23, 34 etc. Bolt hole patters for this application. However, you still must provide power and a signal from the PC which should be shielded so you don't really save much. Also its hard to keep them cool as the steppers do get warm and its hard to keep clean. I prefer to keep all the drivers in a ventilated box that has simple filters to keep debris out. If you ever do cut metal or carbon, the dust can short out a board in the right condition. Nice to see you thinking outside of the box though. It can be done, but for most homemade solutions its usually easier to buy or build a box with all your drivers and breakout board etc.

[LeeWay]

I agree. Not really a good idea to put the Gecko's close to a heat source. My 201's with 62VDC running 469 oz steppers only heats the motors just a little, but with the most heat coming from the Gecko, it would heat more. I had a Xylotex running three 270 oz motors and they got just a little warmer.

On the mill I have just got running, I am using the same 270's, but now using 48VDC and 203V's. I barely feel any heat at all.

Another concern might be vibration. I get zero vibration on my Z, but I get a little on my table. It's mounts are fiberglas and aluminum though. I will be ordering some cast iron for the saddle and the table. That should take care of that little vibration some. I still need to put gussets on the column, though that part seems fine. Extra insurance.

[sailfl]

Lee, where did you get your shielded wire that you paid $20 for 100'.

Thanks

[LeeWay]

One of the members here had bought a roll of it and PM'ed me after I posted a thread looking for cable. I looked, but no longer have his PM and don't recall his name. There may be some other members willing to sell some if they have too much. I had enough for three 3 axis machines. Two are built, the third is 3/4 finished, then I want to built a lathe as well. CNC everything. Yeah man. That is the way to go.

[lgalla]

It is common practice in wireing steppers to connect the shield at only one end.ie the Gecko end.If you do this the shield is useless.It was common practice to cut shields in audio to eliminate ground loops.In audio if a star ground is adhered to there will be no"buzz"
Don't know how this applies to stepper drivers&motors,but if only one end is connected you have wasted money on the shield cable.
Here is a copy from an audio site..
"
"Another common solution to hum and buzz problems involves disconnecting one end of the shield, even though one can not buy off-the-shelf cables with the shield disconnected at one end. The best end to disconnect is unimportant in this discussion. A one-end-only shield connection increases the possibility of radio frequency (RF) interference since the shield may act as an antenna. The fact that many modern day installers still follow the one-end-only rule with consistent success indicates that acceptable solutions to RF issues exist, though the increasing use of digital technology increases the possibility of future RF problems. Many successfully and consistently reduce RF interference by providing an RF path through a small capacitor connected from the lifted end of the shield to the chassis."
Larry

[Haydn]

Yes, use shielded cable. If you have four conductor motors then you want five core cable plus a screen/shield. Four of the cores connect to your motors, the fifth is grounding the motor, the shield should only be connected at the controller end or you will induce noise in the system. I had a problem with a gecko once and spoke to Mariss, he asked me how my motors were wired, I told him and he said "at last someone who has done it right!"

Haydn

[Runner4404spd]

i am using shielded cable for my steppers and still seem to be having RF interference issues. do wires in the cables need to have twisted pairs that are individually shielded? i'm not opposed to getting more wire but i need this machine up and running so i need to get a good solution to this problem.