Measure tension of installed cable tie 1

[Stephan Nelle]

My company is wanting to compare the installation repeatability of nylon cable ties (zip ties, tie raps, ty raps, etc) as installed by hand vs installed with an installation tool (such as:

https://new.abb.com/products/7TAA131790R0001/cable-tie-installation-tool-18-50lb).

The installation tool should (at least somewhat) repeatably tension the cable ties. We want to see how consistent they are tensioned when installed by hand. To do this, we want to conduct a test where a batch of cable ties are installed/tensioned by hand and another batch are installed/tensioned with one of the installation tools, then measure the tension in each and compare the results. My question is, is there a method to measure the tension of an already-installed cable tie?

 

[BUGGAR]

Start with ASTM standards. They cover everything. They are numerous.

 

[Jughandle]

Stress/strain relaxation from temperature/time should be accounted for with polymers. When you find a good tension measurement method, you will probably want the comparisons done in the same environment: a climate controlled area with not too much difference in elapsed time. Note nylons are especially prone to ambient humidity effects.

 

[Stephan Nelle]

Jughandle, good reminder; thanks.

 

[TLHS]

https://www.hellermanntyton.us/products/110-99000/

 

[TLHS]

That's not already installed, but I'm not sure how you would do that unless you are tying around something of a known compressability and then measure the resulting circumference of the tie.

 

[ProEpro]

Use each method to install ties around an object of uniform diameter like a pipe, hose or pool noodle.

Measure the length of the tail that was trimmed from each. This will tell you high tight it was pulled.

One advantage of the tools is they should not leave a sharp edge where the tail is cut. This is a genuine safety improvement.

 

[rb1957]

How about measuring the force applied when closing the cable tie ? Maybe put a loadcell (or a "fish scale") between the cable tie tail and the puller (machine or human) ?

another day in paradise, or is paradise one day closer ?

 

[Stephan Nelle]

TLHS, I have seen this. Thanks for posting. If nothing else, a good way to determine the accuracy of a cable tie gun.

rb1957, I had similar thoughts and seems to be the best option in my opinion.

Thanks all, for replying. I've also thought about measuring the length of the tail and correlating that to tension, but I think there would be a high margin for error with that method as the tail length measurement would have to be rather precise for the change in length vs change in tension.

 

[Strong]

Just an idea:

Cut a solid metal rod into two halves lengthwise. Strap the two pieces together with tie form cylindrical shape. Measure force-displacement to separate the two steel pieces parallel to and/or perpendicular to the flat mating surface. Many ties should be tested for valid statistical results.

Walt

 

[TLHS]

I like the cut in half thing. How about you take a pipe, slice it in half and rig a load cell or two such that they connect the two halves with a bit of a gap for movement. Then when you tension the tie around the pipe it loads the cell.

You could probably rig the same thing by using spring scales, but it'd be fiddly.

 

[btrueblood]

I had a similar thought, but using a short piece of flexible tubing filled with water or oil, and a pressure gage - install and tighten the cable tie and measure the pressure rise on the filled tube.

 

[TLHS]

Yeah, calibrating that might be tricky though.

Here's what I'm thinking. Hatched items are load cells. Bolts are finger tight and just there so that the whole thing doesn't awkwardly fall apart when you take the tie off. The plate I've shown inset in the cut pipe should really be mounted outside for ease of assembly rather than being inset. In retrospect, maybe the bolt should be past the ends of the pipe so you can actually insert it.

Details are left to the imagination of the person getting paid to figure this out

 

[TLHS]

Poor man's version of this would be a grip testing machine... but I'm not sure how you'd calibrate it and I'm not sure they're available in the precision and accuracy necessary.

 

[TLHS]

If you're just trying to gauge consistency, this is fine. If you're looking to put a number to it you're going to have problems. You're going to have to test the exact installation somehow.

The residual tension is going to vary based on the items being attached. The way the teeth on the ties work mean that you have to pull past the tooth and then it relaxes back to sit in it. So if you are attaching on to a reasonably unyeilding surface that doesn't compress then that relaxation might result in basically no tension in the installed condition. You also may get stuck part way up a tooth that represents a lot of installation tension but doesn't translate into residual tension in the installed condition. With really stiff ties and really stiff attachment items, you might not even be able to get it up that first click if the geometry is unfavourable.

In something that is fairly compressible that lets you pull a number of teeth past the point of initial load application, then that relaxation is a small part of the overall strain that was applied and you have a much larger tension.

i.e. if you're only able to pull two clicks past the initial load point, then not being able to get to the third and the relaxation at rest is a large percentage of the total strain. If you can pull ten past, it's not a large percentage and you're going to have a much larger percentage of residual installed tension.

In both cases you may have applied the same installation tension.

 

[robyengIT]

for any type of already in tension cables

https://www.hans-schmidt.com/en/produkte/tension-meter/

 

[TheTick]

The width and thickness will change with tension. It's a matter of whether those changes can be reliably measured.

 

[Stephan Nelle]

A coworker and I came up with the idea of using a piece of tube with a slit through its wall thickness along its length. Put the cable tie around the tube, tighten, and measure the change (decrease) in gap. Could create our own gap vs tension correlation using a load cell. The idea is along the lines of wrapping the cable tie around something of known compressability and measuring circumference like TLHS suggested.

robyengIT, good idea! I hadn't even thought of using a cable tensiometer. Could space two tubes apart such that there is room to use a tensiometer on a section of the cable tie running around/between them. Limit would be available length of cable tie. Again, would probably have to create our own deflection vs tension correlation.

 

[BrianE22]

Wrap 2 ties half way around a cylinder, measure the tension on the ends of the tie. If you mount the cylinder in bearings then the 2 tensions should be equal: