Mitsubishi ML520G71...Red Holy Grail or Flashlight Fail ??

[dar303]

Very nice work, a manual mill is only as good as its operator!

[CDBEAM]

After much consideration….I have used the ideas of Dave and Logsquared to generate a different design Laser Diode holder. My conclusion is….since we want and need maximum transfer of heat away from the LD….and we want adjustability between the LD and the Collimation lens…have the LD stationary and the collimation lens adjustable !!

With the needs of the Mitsubishi ML520G71 in mind please review the attached pic: LDACL-V 4.0.

It has been my experience with the 445 LD that a larger mass heat sink mount seems to provide a more stable mW output. Considering that the heat flow from the diode OD propagates outward… in varying amounts as a function of modulation…it is my opinion that a larger mass mount acts as a “ Thermal Flywheel “ and to some degree stabilizes the LD core temperature. This in turn stabilizes the mW output and likely increases the MTTF. To that end…the LDACL V4.0 has approximately .72 kg of Brass ( Density:8.4 g/cm^3 ) to absorb the varying thermal output of the LD.

To maximize and balance the thermal flow… from the LD to the mount mass…it would seem logical that the LD should be positioned within the mass centre. To allow for LD radial adjustment, a snug fit…but not a press fit should be employed. Once the optimal radial orientation is achieved, the LD would be held in position by a screw in M9 x .05 retainer sleeve. Of course thermal paste at the LD/Mount interface would further increase the thermal transfer and should be used. So…we now have the LD…snug as a bug… in the Brass mount. The next step…the collimation lens.

To achieve adjustability in the X/Y…the collimation lens is installed into what is labeled “ Collimation Lens Position Disc “ This position disc has movement limited within a recessed bore on the front of the mount. The position disc ( and therefore the lens ) is adjusted X and Y with position bolts labeled C and D. The Position Disc has two small springs …labeled A and B which are secured within pockets bored into the disc perimeter. The springs will apply force towards the position bolts and therefore only two (2) bolts will be needed to accurately centre the Collimation lens.
Finally, the position disc is held to the mount with two (2) bolts labeled CB1 and CB2. These bolts would be installed, but not tightened down during the X / Y lens adjustment. The bore thru holes in the position disc will be oversized to allow disc movement. Once the optimal X / Y lens position is determined…the clamping bolts would be tightened down.
Well…I am now in the process of machining one of these units. I think I have all the bases covered ??? Pics when done !! Thoughts ??? Opinions ??? Thanx Simon…this is all your fault !!!!!!!!!!!!!!!!...and thanx Dave and LS !!!

BEAM

Edit...I see a problem....distance of Collimation lens to LD aperature...being too far !!!...Perhaps lessen over all mount thickness ??? or move the LD forward ??? Must think more on this !! See LDACL V 7.0 LD not as centered...but optical demends trump thermal balance.... ALL engineering is a compromise !!! BEAM

[logsquared]

Nice design. Elegant solution for centering. May be hard to rotate the diode though. I still contend that thermal resistance shouldn't be a problem with the ML520G71. Possibly more of a concern with the 445, as you stated, as its more like 4-5 watts dissipated if run at 1-1.25 amps CW. It would be very easy to test the thermal resistance of any mount. Basically press in a diode that passes current but has no light out (dead diode). Attach the mount to a large heat sink or base. Power the diode and measure the I and V. Multiply to get watts. Wait a bit and measure the temp of the mount and the heatsink. From there you can extrapolate the thermal resistance of the whole mount. With that you can calculate the temp of the diode at any current and ambient temp.

[CDBEAM]

Thanx LS !!! Yea....I thought about how to rotate the diode....down deep in the well ??? Perhaps a small tube/tool....with two small ears that engage the v-cuts in the diode perimeter...
rotate to correct orientation and screw in the retainer.

Any ideas on where to get M9 x .05 threaded Brass tube ???

Concerning the thermal challenge of the ML series ?? mmm ??? Not sure....BUT....I agree with Badger1666...that the LD's output starts to go down....right from the start.....so...Dunno...maybe this is overkill ??? Maybe not ??? I will build one....and see what I get. Thanx !!! You started the fire on how to " dance " the LD'round.

BEAM

Yikes....another thought....scrap the threaded M9 x .05 threaded retainer completely !!! The rotation tool could be used as the backstop/retainer !!! The tube with ears is used to rotate / position the LD...THEN...THAT tube stays in place...and pressure is put on the back of the tube( portion sticking outside the mount) to apply pressure to the back side of the LD....THEN...a simple set screw positioned perpendicular to the tube axis...clamping the tube in place. So...Diode in place...correct orientation...and now held firmly against the mount....tighten the set screw...and done !! Set it, and forget it !! IT COULD WORK !!!

Wheww...Too much thinkin !! Head spinnin !

[kiyoukan]

Im a bit confused with this centering problem.
I make my own m9.05 threaded heat sinks and lens holders and they are very tight and perfectly centered.
So is the fuss only over not properly made threads giving it to much wiggle room?
Also for some of you guys i got a nice array of C-lenses coming.
a new set is on the order a larger version of what the dr has.
6X along with each lens no smaller than 10mm.
but it will make the lens holder kinda long.
around 70mm.
But this is due to the use of larger lenses so getting the beam into the sweet spot on the lens will be better and be able to send multiple threw at once.
But i do have micro setups on the way.

[logsquared]

Concerning the thermal challenge of the ML series ?? mmm ??? Not sure....BUT....I agree with Badger1666...that the LD's output starts to go down....right from the start.....so...Dunno...maybe this is overkill ??? Maybe not ??? I will build one....and see what I get. Thanx !!! You started the fire on how to " dance " the LD'round.

I have noticed the power drop as well. But its only if the diode mount is not attached to a base. If the power is going down very fast (a few seconds) I would guess its the diode body to mount interface. I had the same problem with the 445 in a o-like mount. Almost immediately after turning it on the power would start dropping. Pressing the diode in a different mount stopped the problem. This is the reason I like press in mounts or some prevision to get the diode very tight like dave's mount. And yes, I have been known to dance with diodes

Im a bit confused with this centering problem.

Its not as much an issue with 4mm and up FL lenses. Although I did notice with the 40g-g-1 what looked ok before the tele didn't after.

[polishedball]

perfect on a hand mill, that is talent. id be curious to try one of you mounts these tiny short FL lens show the problem not standard lens. If you ever have time to come up to GR I can show you.

Im a bit confused with this centering problem.
I make my own m9.05 threaded heat sinks and lens holders and they are very tight and perfectly centered.
So is the fuss only over not properly made threads giving it to much wiggle room?
Also for some of you guys i got a nice array of C-lenses coming.
a new set is on the order a larger version of what the dr has.
6X along with each lens no smaller than 10mm.
but it will make the lens holder kinda long.
around 70mm.
But this is due to the use of larger lenses so getting the beam into the sweet spot on the lens will be better and be able to send multiple threw at once.
But i do have micro setups on the way.

[CDBEAM]

LS...yes...a press fit is the best....but we have so many competing demands...rotational adjustment, good heat transfer, and close proximity to collimation lens....Many Gods to serve indeed !! Which is the best path to follow ???

AGAIN...anyone have any idea on where to source threaded tube @ M9 x .05 ???

Thanx.

BEAM

[logsquared]

AGAIN...anyone have any idea on where to source threaded tube @ M9 x .05 ???

Thanx.

BEAM

I can turn you some. you mean M9 X .5 right? How long and what size thru hole?

[steve-o]

/...I have been working on kits that have all the mechanical parts to build two different kinds of dual modules. They are aimed at DIYers that don't have access to a milling machine but want to "get their hands dirty" so to speak.

I'm ready! Prices? Are the lenses included?