Measuring a very fine wire with 10 µm precision

dan38711: Coils that I have wound very carefully by hand agree almost perfectly, whereas sloppily wound coils deviate significantly.

Where on this spectrum from perfect to useless do ordinary machine-wound coils using simple turn counting fall? Would it not be sufficient to machine-wind one layer of the coil, manually pause it at the end of the layer and note the number of turns, and then program the winder to use the same number of turns for the other layers? This could be a very simple process if your CNC controller was designed to support it, and without needing any exotic measuring techniques. It seems unlikely to me that you would need to deal with variations in the wire thickness within a single spool, and I expect that once you have got it set up for one coil you could then continue to wind multiple similar coils with the same settings.

PeterH: Would it not be sufficient to machine-wind one layer of the coil, manually pause it at the end of the layer and note the number of turns, and then program the winder to use the same number of turns for the other layers?

PeterH,

To me and Dan this seems likes a very good approach to the problem. Although it adds a step in the calibration of the spooling machine to get the number of turns (and consequently the theorical diameter); it seems reasonable to think that from that point on a multitude of coils could be wound using the setting acquired during the calibration run.

I am going to give it a try tonight and report my findings as soon as possible.

Thanks for the idea

Roughly speaking, what is the production volume required? Tens, hundreds, thousands ... ? Also production rate, how many per day, hour, or whatever.

JimboZA: This is a nice diagram explaining the difference between accuracy and precision

In machining we would specify that precision as 'tolerance'. Every cut is to some measure with some tolerance (like +/-0.1 or maybe +0.1/-0.0).

GoForSmoke:

JimboZA: This is a nice diagram explaining the difference between accuracy and precision

In machining we would specify that precision as 'tolerance'. Every cut is to some measure with some tolerance (like +/-0.1 or maybe +0.1/-0.0).

But even the device(s) used to measure that such 'tolerance' is within specification or not is subject to a variation in precision. Accuracy is a poorly understood property in the real world.

Lefty

Where I worked we held close tolerances and sold parts that met them. We had plaques from RCA and Kodak for going a year at a time with zero rejects. We weren't trying to hold any better than we could make but we did precision work within tolerances every day. Part of it is not trying to hold impossible tolerances, but you have to know not only what's possible but what's practical in order to do business. Not just theory, we made the parts.

Why not turn the windings at 1 diameter + (tolerance * 110%) apart per turn? When you come back across the new layer will sit on top. Or is there some reason why the windings have to jam in side to side all along the coil? Does this wire vary thickness by even 10%? You'd get a tighter pack if the diameters set in a hex pattern anyway.

You’d get a tighter pack if the diameters set in a hex pattern anyway.

I hear hands on experience!

robtillaart:

You’d get a tighter pack if the diameters set in a hex pattern anyway.

I hear hands on experience!

I don’t see how they can do, because alternate layers are wound in opposite directions.

They could still be sure how many turns to make per layer without needing to monitor wire thickness. Even the wire should have dimensions and tolerance.

All the automatic or semi-automatic coil winders I've ever seen just relied on a turns counter for feedback and assuming normal tolerances of the bobbin size and wire gage, I would think it would turn out very repeatable induction values, and many of them turned out beautiful looking windings. One could always measure the final induction value and trim if needed. As far as creating a 'perfect' symmetrical magnetic field, I have no idea how critical or difficult that can be nor if wire gauge variation would have an effect, turns is turns.

Lefty