Please Suggest Strategies for Dealing with DRO Cable Slack in 8 Foot Travel

I do some occasional work and maintanence in a fabrication and repair shop that has been in business since the late 40's. The bed of the reconditioned 1960's Lucas horizontal mill (in truly excellent condition mechanically)there has about 8 feet of travel in the Z axis. So, the cable to the DRO head in that axis has a lot of slack in it most of the time since usually the bed is within a foot or two of minimal travel. Presently the cable is not supported (ya, I know but not my decision) and so it is very vulnerable to damage. Well, the owner noticed a few days ago that the Z readout had stopped working. A little trouble shooting indicates one of the conductors in the Z cable must be cracked.

I am supposed to confirm the crack and replace the cable. I hate to go to the trouble without figuring out a better way to manage the slack cable or else the fix will be only temporary.

So, how to support the slack cable in a way that keeps it off the floor and still allows full travel? At the same time I need to not have any localized area of the cable do all of the bending or it will fail early. Using something like a coarse spring to zip-tie support the cable sounds like a possible solution. The DRO is a long-obsolete but otherwise good Dynamic Research unit. So, no support (like spring-coiled cabling) is available off-the-shelf.

Ideas?

Denis

One way I've seen cables supported is by roller supports running in something like a framing strut. Straps hang down from each roller and are fastened to the cable at intervals of a foot or more. In use, the cable can retract into smooth S curves and the rollers move as necessary. As I recall there was something like a bungee cord fastened to each roller that maintained even spacing.

John Welden said:

McMaster-Carr

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I don't know John those are way more than the $7.00 ceiling that most people on here have for spending on a machine tool.

John Welden said:

McMaster-Carr

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Exactly: cat track.

Managing wire and hose connected to moving machine elements has been a historic PITA. You can loom, festoon, etc but the best, simplest and most easy to maintain is parallel runs through any of dozens of designs of cat track. You can get plastic which is the equal of metal in durability provided heat or solvents aren't involved stainless for corrosive environments, steel for GP where - you get the picture. Lots of vendors, lots of variety.

Naturally you can't slap a cat track system on just aanywhere. The runs and motions have to be considered and often hoses and wiring have to be replaced for it to work properly but once its done, it's done for the life of the machine.

A little forethought will suggest an open design that's easy to clean of chip and dust accumulations and to locate the runs parallel to motions served, away from debris origins, accessible, located to allow access to tank fillers, maintenance points etc.,

What about the cable track, forget the name, cat track, catenary track, used on cnc routers, the black segmented stuff, it's a good cable management option if it can be fitted, also better quality cable might help, there are silicon multi core screened cables available
Another option is the cable rewind unit off a vacuum cleaner, bit of cobbling required though,
Mark

John Welden said:

McMaster-Carr

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I second this. We have large equipment that runs much more than 8' and this is what we use.

only other way would be festooning, which wouldn't be great, or a cable reel, which doesn't make sense for something that short.

bloomautomatic said:

I second this. We have large equipment that runs much more than 8' and this is what we use.

only other way would be festooning, which wouldn't be great, or a cable reel, which doesn't make sense for something that short.

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I'm pretty sure that about 99.9% of modern machine tools use a system like I linked to. (modern as in about 1970's and on)

Thanks all.

Looks like the link-type cable support system is the preferred approach across the board.

I will work up the cost for that setup and see if I can get the shop owner to go that direction. To me, it makes a lot of sense to do deal with this rather than patching here and there.

Denis

John's right. You can buy cheap versions and expensive versions. Plastic and metal. It's the way to go on a Hor Bore long axis.

Regards Tyrone.

Little late to the discussion, but here's the backside of my American with the cable carrier. I mounted a piece of 1½ al. angle for the carrier to rest on. Poke the pic for the Sheldon set up.

I installed linked track cable carriers on all of our larger machines. It works great and lasts nearly forever if installed right.

I guess it is obvious, but the main concern with moving electrical/electronic cables is to keep the radius of the bends to a maximum. Cables will most often break at one end or the other where the flexing will produce the smallest radius.

I like John's suggestion but a few other details should be considered.

First, this is the reason why stranded wire is made: so it can be flexed. Therefore, if you can purchase a replacement cable with a greater strand count for the same effective wire size, that will be better. The amount of stress produced when a wire is bent is proportional to the diameter of the individual strands. So more strands of a smaller size will last longer. This is why automotive, battery jumper cables will have a high strand count: they are made to be flexed often.

Do pay some attention to the two ends which will be fixed to the frames. Make sure that the cable can not bend sharply there. Some form of restraint is needed to prevent this. It can be as simple as making sure that the track that John recommended is firmly fixed to the frame at it's ends. A sharp bend that does not flex is OK. But the cable should not flex right out of the strain relief.

There are other ways in addition to John's suggestion, which is somewhat expensive. Cables can be suspended on springs with holders that keep the radii involved to large values. I have seen pulley systems but the pulley diameter should be large: at least 10 times the diameter of the cable and preferably 25 or 50 times. Gentle curves!

One possible way to construct a less expensive support would to be make a panto-graph style support. But you will need to use something to keep the radii of any turns along it as large as possible. The stiffness of the cable may be able do this if it is held at the mid points of the panto-graph arms.

Whatever you install, do think about chip accumulation. Sharp chips between the cable and any supports can easily abrade into the insulation.

The brand of cable chain I have used before is IGUS but there are probably others.

IGUS are great for cable chains, yeah there not the cheapest.

As to cable, go IGUS, there cables designed around movement usage, nothing touches it and they sell by the meter in damn near any conductor arrangement you want, used in chain you won't be ever having to replace it unless its physically harmed on a application like this.