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My 4'x8' machine motor wire length recommendations

Official support for products purchased from the BuildYourTools.com and BuildYourCNC.com sites, and the book "Build Your Own CNC Machine (Technology in Action)" by Patrick Hood-Daniel and James Floyd Kelly.

My 4'x8' machine motor wire length recommendations

Postby Awesomeness » Mon Apr 05, 2010 6:04 pm

I've completed wiring my 4'x8' BlackFoot machine, and I'd like to pass on some insight from my build experience.

Initially, I just needed to guess at how long to make the motor control wires. I bought a 50' piece of 18 gauge stranded 4-conductor "security wire" from Lowes, at about $0.50/ft. I divided this wire in 3, which means each axis would have about 16.6'.

Once you have mounted your electronics to a board or enclosure, I recommend installing a wiring clamp/clip, and after running all the wires through it (including the power cable for the power supply) wrap the wires around the clamp and run them through it again. The reason for this is simple, you WILL eventually trip over the wires, and this will pull against the clamp instead of ripping them out of the electronics and breaking stuff.

About 1'-2' of wire will be consumed by the connections to the drive electronics, and going through the clamp. That leaves maybe 15' of my wire left.

I'll have a more in-depth post later about my method of routing the control wires, Shop-Vac hose, and extension cord for the router to the gantry. For now, just know that it consumes about 8'-9' of wire from the end of the gantry to the router platform (for all 3 axes basically). This leaves about 6' of wire left.

With only 6' of wire left, my only choice was to mount the electronics package in the middle of the length of my table. The table is 10.5' long, so this 6' length of wire is pretty much just long enough to reach from the middle of the table to either end when the gantry moves there.

In conclusion, my recommendation would be to instead use about 25' of [4-conductor] wire per axis. This would allow you to mount the control electronics more conveniently at one end of the table, not the middle. Also keep in mind that I'm only talking about the motor control wires for the axes themselves. You will still need another 50' or so of SINGLE-conductor wire for wiring all the electronics together. This is probably best accomplished by just getting another dozen feet of the same 4-conductor wire, stripping it apart, and using the individually colored conductors appropriately.

One final note, it is smart to get STRANDED wire, at least for the motor control cables. Stranded wire is more flexible, and more resistant to mechanical failure from being repeatedly flexed. You would get away with solid core wire for interconnecting the electronics modules, and you wouldn't have to spend time tinning the ends, but it's probably not worth the effort of dealing with two different kinds of wire.

If you don’t have time to do it right, when will you have time to do it over?
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My 4'x8' machine motor wire length recommendations

Postby bajaru » Tue Apr 06, 2010 3:27 pm

Cabling was a nuiisance when bulding my BlackToe 2.1 (4x8) especially because Keling recommends a maximum of 6 feet for the cable length for their steppers (the ones which Patrick includes with the kit). Trying to make a 10 foot table with 6 foot cables was a real challenge, although it sounds like it'd be easy. I experimented and failed with several methods until I gave up on the official max length and finally settled on affixing the electronics box to the underside the table, along one side of the X axis, right in the middle of its travel. My cables ended up being about 8.5 feet long - nearly 50% longer than the maximum recommendation. So far, I haven't noticed any problems with this set up while using shielded cable.
-Brian

Pa sez: "Keep your flesh away from rapidly spinning metal things."
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My 4'x8' machine motor wire length recommendations

Postby graph4sure » Tue Apr 06, 2010 8:57 pm

You know, I had read alot of posts latelely about these wire lengths, and I know
its all good advise from Kelling, etc.

But on my blackToe v2.1 ( 4x8 ) my wires for each axis is 25' long.
So far I have not had any issues. It's true, at first, when I was working
out my stepping numbers, I had a few grinds on my Z-Axis, but once
Patrick gave me his numbers, everything worked great.

And if you look at Patrick's original blackToe 4x8 demonstration video
you'll notice the long wires on the X-home side down to the floor.
His machine runs like a champ. That video is what sold me.

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My 4'x8' machine motor wire length recommendations

Postby george » Tue Apr 06, 2010 11:15 pm

I guess I got lucky.

I used CAT5e network cable (8 conductor, but I soldered them into 4 wires to increase the current carrying capability. I also put my electronics under the table mid-way - not because of cable length, but to keep the cables short and neat (there's teh luck).

Then I wrapped the cables with 1/4" split tubing (yay harbor freight) and clamped the cabling using cable clamps from the local electronics store (Fry's Electronics).

I was concerned about the current carrying capability of the CAT5 cabling, but by doubling the conductors, everything is fine. I have no hot wires, and I've run the machine for hours at a time.

The end result is a very neat installation with no cables on the floor and nothing to trip over.

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Re: My 4'x8' machine motor wire length recommendations

Postby Huzzah » Wed Oct 20, 2010 12:50 pm

george - did you find stranded CAT5e cable or are you taking your chances with solid core?
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Re: My 4'x8' machine motor wire length recommendations

Postby Awesomeness » Wed Oct 20, 2010 8:40 pm

Honestly, I would recommend AGAINST CAT5 cable. It's way too thin. It's probably like 28GA wire, when you should really be using 18GA or so. You can get nice, neat, 4-conductor 18GA stranded wire at Lowes/Home-Depot/etc.
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Re: My 4'x8' machine motor wire length recommendations

Postby Huzzah » Thu Oct 21, 2010 12:33 am

I'm having difficulty finding suitable cable at Home Depot & Lowe's. I'm on the search for a local electronics store now. The first one only sold the wire in spools of 1,000 feet!
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Re: My 4'x8' machine motor wire length recommendations

Postby SplinterPuller » Thu Oct 21, 2010 3:24 am

4 and 6 conductor wire is used to wire trailers often. 18 and 16 ga. I found a 50 foot spool on ebay pretty cheap.
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Re: My 4'x8' machine motor wire length recommendations

Postby Awesomeness » Thu Oct 21, 2010 5:19 am

Huzzah wrote:I'm having difficulty finding suitable cable at Home Depot & Lowe's. I'm on the search for a local electronics store now. The first one only sold the wire in spools of 1,000 feet!

All the Lowe's and Home Depots around me carry it. They call it "security wire" or "sprinkler system wire". The morons that work there will usually tell you they don't have it, or that they don't know.
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Re: My 4'x8' machine motor wire length recommendations

Postby shawjo » Thu Oct 21, 2010 5:28 am

Sprinkler system wire is usually solid conductor wire. Walmart in their Automotive section has wire for trailer lights. It has 4 wires all put together. It should work perfectly.

-shawjo
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