JBL 4345 build

[toddalin]

the kenrick -plastic- lens plates are thin (like JBL 2308).

Seems like one would want to go as this as possible until stability(warping) or resonance ruined the party.
Both were addressed somewhat with the inter-plate touch points or with thin wood strips (older jbl).
The self-damping of wood or plastic seems like a good idea (vs metal, ala mccauley).

No, I don't think so. This does not look to be as thin as the JBL offering. Note the rough texture of the edge, indicating ABS sheeting whereas the JBL edges are smooth. In fact, there are only 10 plates here and JBL uses 11.

[ARMED]

do you mind sharing the CNC program for the lenses? Id like to try it...

[toddalin]

I didn't do it in CNC (G-code).

I did the 3D renderings in DesignSpark Mechanical because I wanted to do this on the 3D printer. DesignSpark generates STL (3D), PDF, and Autocad DRW files. But the laser doesn't read 3D files. So, I select a 2D view and output a drawing file of that profile and save it.

The laser runs raster-based and vector-based programs. But all cutting requires vector-based programs. For example, you can do a graphic, but not cut using Photoshop, which is raster-based. So I have to import the drawing file into a program (Inkscape), often cleaning up superflous lines, and save the file as a SVG (vector) file.

The Corel Draw program drives the laser and can read the SVG file to cut the pattern once I import it, scale it, and position it.

[grumpy]

Hmm... That doesn't look -at all- like my kenrick lenses. I'll check when I get home re thickness. Perhaps there was a redesign after the initial run. Not that it matters much, just curious.

[grumpy]

So... different mfg runs on a design iteration, perhaps.
I know the reject rate on the initial run (warped plates) was high... (years ago!)
thicker plates may have been their solution.

[toddalin]

Or..., maybe these aren't Kendrick, even those that's what the post said they were.

[grumpy]

Ah. Those were the Image Communications product... Model L-10 or 11. Makes more sense now

[BMWCCA]

On Kenrick's web page and on Ebay theirs have 11 plates:

[ivica]

do you mind sharing the CNC program for the lenses? Id like to try it...

Hi ARMED,

May be this file can help.

regards
ivica

[toddalin]

Hi ARMED,

May be this file can help.

regards
ivica

"By measurement, the plates are 1/16" thick and spaced 1/4" apart."

It's not right. 11 x 1/16" = 11/16" + 10 x 0.25" = 2.5" + 11/16" = 3.1875"

But the plate actually spans 3.85".

[ivica]

It's not right. 11 x 1/16" = 11/16" + 10 x 0.25" = 2.5" + 11/16" = 3.1875"

But the plate actually spans 3.85".

Hi toddalin,

Yes, but not to forget that , the angle of ABOUT 38 deg has to be included, as 1/cos(38) = 1.269,
so if can be said that (1/16+4/16)*10*1.269 = 3.96", may be 1/16" thickness or 1/4 spacing is not
absolute precise but it is very near the JBL 2308 lenses size.
If You want to be more precise, may be the thickness can be reduced from 1/16" to 1/20"
then it can be get:

(11* 1/20 + 10* 1/4)*1.269 = 3.87"

regards
ivica

[toddalin]

Makes sense.

I guess when one consideres the angle, that my spacing is actually closer together than I thought it was. I figured at ~0.35" vertical spacing (with 1/16" plates) it is good to beyond 19kHz but tighter spacing takes it out past 20kHZ, as if an 075 could go that high.

[ARMED]

I got these in the mail today, we are moving along nicely

do you mind sharing where you got these from?

[quindecima]

Those came from the Sign-Shop on Ebay. Expensive but the only source I know of.

[toddalin]

There is a pair of originals for $250 on the bay.