Converting a Star Base LED to a Round Base LED

[PhotonFanatic]

I've always wondered why LED manufacturers insist on making star shaped bases instead of round bases, but have never found a good answer.

TB's post about his turning down a Cree Star to fit the Aleph LE got me motivated to make a jig for transforming any star based LED to a round base. But I was interested only in trimming the base to match the bore for a 20mm reflector, not the Aleph LE diameter; my target diameter: 19.50mm.

First, I made a jig to be used with my collet--a six-pronged jig that would allow the collet to press against the prongs and hold the star in place while it is turned down. But I also needed a spacer block to position the star away from the collet, too. Here are the pieces:

In use, the jig is inserted into the collet:

Then the spacer block is inserted:

And finally, the Star is added:

The star is then turned down in the lathe:

Before and after pic:

No, I didn't lose the LED while turning the base--I started with just the base.

If I want a smaller ending diameter, I would make two new jigs--one with three prongs to hold the star so that the cut-outs for the wires/optic/screws can be made deeper. Then I'd make a smaller diameter six-prong jig for the turning to the desired size. For now, this 19.5mm size is what I want.

 

[Mirage_Man]

Very cool Fred. Great ingenuity!

The only question I have is if the emitter isn't centered on the star then won't it still be after using this method. But I guess there's no way to grab on to a Seoul or Lux like you can with a Cree's metal ring.

 

[TranquillityBase]

Nice fixture Fred!

 

[LukeA]

Very cool Fred. Great ingenuity!

The only question I have is if the emitter isn't centered on the star then won't it still be after using this method. But I guess there's no way to grab on to a Seoul or Lux like you can with a Cree's metal ring.

I tore the ring and dome off of a Cree once with pliers. It came off with relative ease. But the Cree-branded optics I have snap on and off the rings without damaging them, even though I worry about that. YMMV holding a Cree by the ring to turn it.

 

[Mirage_Man]

I tore the ring and dome off of a Cree once with pliers. It came off with relative ease. But the Cree-branded optics I have snap on and off the rings without damaging them, even though I worry about that. YMMV holding a Cree by the ring to turn it.

http://www.candlepowerforums.com/vb/showthread.php?t=182934

Scroll down to post #19

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[PhotonFanatic]

Very cool Fred. Great ingenuity!

The only question I have is if the emitter isn't centered on the star then won't it still be after using this method. But I guess there's no way to grab on to a Seoul or Lux like you can with a Cree's metal ring.

MM,

True, if the emitter isn't centered to begin with, this technique will not help that problem. But with pick and place machines able to work to to such high precision as they can, I don't think we will find too many emitters not properly centered. You can still center it by hand using your favorite method, i.e., some use a stereo microscope, others use the reflector, and then glue the base in place.

TB,

Thanks for the inspiration. :twothumbs

 

[TranquillityBase]

LOL...Those precision pick and place machines must be drinking on the job...I have yet to encounter a Cree emitter that is even close to centered on its MCPCB. Must have something to do with the reflow solder process?

 

[PhotonFanatic]

LOL...Those precision pick and place machines must be drinking on the job...I have yet to encounter a Cree emitter that is even close to centered on its MCPCB. Must have something to do with the reflow solder process?

TB,

No, the problem with Crees on MCPCB's is that they were not done by Cree--those are all made by contract manufacturers working for a distributor. Cree only makes the emitters, which the distributor then ships off to a contract manufacturer who mounts them on their star base. Quality is going to be very spotty in that case. The jobs are too small for the distributor to have a QC guy overlooking the operation, nor is the contract manufacturer isn't going to worry about it too much either.

A manufacturer like Seoul or Lumileds, on the other hand, will be a hell of lot more demanding of the production line to get it done, and done correctly. It really isn't rocket science to center an LED on a PCB.

 

[dom]

OH -how high tech is that eh -haven't you heard of a grinder or bolt cutters.

I don't know -give a man a machine and look what he does!

Top job Fred:thumbsup:

Cheers
Dom

 

[Torque1st]

You could also build a similar six finger fixture with the same ID as the LED body to center on the LED and turn the base OD. Use a center in the tailstock to hold the base in the fixture.

 

[wquiles]

Outstanding job there Fred - very clever!

Will