Seeking advice bending micro tubing for LED lighting

[JoeW]

I have some very fine tubing I would to bend and use as conduit for my LED lights.  The tubing is about .02 O.D. (decimal) I am having a hard time a getting consistent radius bend.  Any recommendations?

[narrowminded]

What have you tried?  How sharp is the bend?  What wall tubing?  Are you using a mandrel?  All of these effect how the tube bends.

At minimum you need a round to bend the tube over.  A little bending jig with a pin of the bend diameter and another gapped at the tube diameter to serve as the starting clamp/ holder is easy to make and works well for this as well as wire forms.  If you're going pretty tight an ID mandrel in the form of a wire or such can be inserted to support the tube wall while bending and then pulled out on completion of the bend.  On small ID tube (.01") I've had success with nylon fishing string inside for a pretty tight bend.  Slip fit but not rattling loose.  It needs to fit the ID well.  A little more info should get the answer you need.

[JoeW]

Thank you for the response.  The tubing is stainless, its I.D. is about .012, I am displacing the tubing with .011 guitar string for the bend (I like your idea of fishing line better).  The first try was around the pliers I was holding with (that didn't work).  I have fabed up a mandrel but have not tried that yet.  I still need to figure out how I am going to pinch the tube to hold it for the mandrel bend.  Perhaps I will try putting a piece of larger brass tubing on one side of the pliers and bending around the respective brass tubing.   

[narrowminded]

Forget the pliers.  A scrap block and drills and pins, make yourself something like this but with the sizes you're looking for.  By style, it's the pins in the center that are the idea for your need.     And you can have any size you can drill.  Depending on how "one time use" it will be, select the drill diameter for your desired radius, drill through, remove the drill and slide it through using the drill's shank as your pin.  A second hole of about any size (smaller might be less in the way) spaced over to capture the tubing between the two pins and that's your basic tool.  Make it that simple or as fancy as you'd like.  It might come in handy another day.

http://www.ebay.com/itm/WIRE-BENDING-JIG-TOOL-JEWELRY-MAKING-FORMING-SHAPES-BENDER-FIXTURE-BEAD-WORKING-/201594297294

[JoeW]

Thanks I am off to the wood scrap box and drill index to get started.

[narrowminded]

OK!   Fashion yourself a little "push stick" from... maybe a piece of dowel.  File or sand it to get a flat nose that's appropriately thick for the tube you're bending and perform the bend with the nose of the stick, pushing in right at the bend point and then following the bend around keeping pressure right at the bend point, keeping the tube tight against the mandrel.  You could add a stop or maybe just a pencil mark for repeatability of the bend if you're doing multiples. 

With no reverse bend you could also just use a thin piece of straight wood as your starting/ capturing piece in lieu of the smaller pin that holds the straight starting point.  Once you get the idea let your imagination run wild.  You can make up all sorts of jigs and bends that operate on this basic idea.

[Joetrain59]

See this site, http://www.ngineering.com/tubing.htm
 Joe D

[craigolio1]

You could also try filling the inside of the tube with water and freezing it. Then you bend and let it thaw. Blow it out with a bit of compressed air. The tubing is so small you'd like oh have to pull the water in like you would through a straw as it is likely too small to fill. This way the end doesn't cause a grip on whatever you had inside.



If you plan on using a fibre optic inside you can use that.

Craig

[narrowminded]

If you plan on using a fibre optic inside you can use that.

Craig

I have done exactly that.  But then I needed to remove it for painting and such which lead to the slightly larger fishing line ( +/-.0015").  It acted much like the fiber optic as far as friction when removing but afforded that smallest extra dimension to make final reinsertion of the fiber optic easier.  That was also brass tubing but I suspect the characteristics will be similar in these minuscule sizes. 

The idea of the ice sounds viable too.  Anything that lends support to the ID to hold shape should work.  And as a side note, tube bending in general, the thicker the wall and/ or the larger the radius (relative to tube OD) the better it holds shape while bending.  Much more is available with a search if anybody really cares to become expert in tube bending but these are the most elementary basics.

[Lemosteam]

Actually it kind of makes sense to use the FO as the interior support if you are making a light tube anyway.  Just leave it in there and polish the ends.

[craigolio1]

That's how I've done it. I leave it a couple of mm too long until it's all painted and / weathered etc. Then I trim it and flare the ends.

I've never tried the ice thing. I heard it somewhere and thought it was cool.

Craig

[peteski]

Actually it kind of makes sense to use the FO as the interior support if you are making a light tube anyway.  Just leave it in there and polish the ends.

As I understood, the tube will not carry a fiber optic but magnet wires for the nano or femto LED in the light fixture.

As far as polishing the ends goes, I agree that the light intake end should be polished and as close to the light source as possible. But if the other end is polished then the light will exit the fiber in a highly directional manner so the viewing angle will be rather narrow. In order to simulate a light bulb which emits light in many directions I recommend forming (sanding) the end of a fiber optic into a cone shape and leaving the cone in as rough (unpolished) state as possible. That will scatter the light exiting the fiber optic simulating a light bulb.  It makes a huge difference in the appearance.



Craig,  while using frozen water seems viable, I think that  unless the entire process of bending is done in sub-zero temperature (to keep the water in a solid state, this will not work.  At the tiny size we are dealing with, just few seconds of being in contact with your fingers and/or with the bending fixture will thaw the ice ,even before you have a chance to bend the tube.  Then the process of bending also generates heat within the metal which would also thaw the ice.  At least that is how I see it.

[craigolio1]

Peteski i totally agree about the freezing.

Im very interested in your method with the fibres. This is a bit of thread drift now but would you happen to have comparison pics? I've always thought the melted end looks quite nice. Better is always , well, better. Haha.

[tehachapifan]

I actually thought about starting a thread to discuss how best to prepare fiber optic strands with regards to how they throw light. I found that I sometimes get a narrow beam pattern and sometimes a very wide pattern, but I've never tried sanding the lens end which I typically mushroom slightly into a lens shape with heat from a closely-held soldering iron, leaving a polished-appearing finish. I have, however, sometimes left the inner (light source) end with a total rough-cut, sometimes with a more polished end by briefly applying heat with a closely-held soldering iron, and sometimes with even a slight mushroom shape to it. Unfortunately, I really did not take any notes or track which method did what the best or worst, but there is a definite difference in light appearance with how the light source end of the strands were prepared. I think the rough-cut light source end throws light wider than a polished end but, again, I'm not positive. I have noted that a shorter optic strand and a closer LED will create a wider pattern. I generally prefer a narrower beam for headlights and a wider beam for gyralights, etc.

[craigolio1]

Amazing. I would really enjoy that thread. I'm just happy when I get the LED inside to line up, and actually produce light through the fibre.

Craig