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ruffrecords

Mechanical Dilemma
« on: December 18, 2016, 04:38:30 PM »
My EZTubeMixer modules originally used standard diecast fixings to attach front panels to PCBs. Problem is, if that is all you use, there is quite a mechanical strain on the on the PCB and the front panel mounted controls when modules are inserted/removed and the only screening between modules is the PCB ground plane.

I now use extruded aluminum cassettes made by Fischer Elektronik. These fully screen the module and and provide more than enough mechanical rigidity. Problem is the extrusions mean I lose nearly 20mm of available front panel width for mounting controls - the old scheme had a 63mm wide space (out of a total 71mm panel width) and the cassettes reduce this to 43mm. If you have few controls this is not a problem but now I am doing more complex modules I cannot approach the density of controls seen in many 500 series products for example.

So I am now toying with the idea of making my own module mechanics. As many of you will know, I have near zero mechanical skills so this needs to be as simple as possible. I am not planning huge volumes so expensive tooling is out  of the question. At present I am considering a scheme based on one I devised for a 35mm module. This adds standoffs to the existing die castings and also to the rear connector to create four pillars to which is attached a 1mm thick rigid steel plate which provides both screening and rigidity. I might also add extra die casings to attach the other side of the front panel to make it even more rigid. This gives me the rigidity I need but only some of the screening (the top and bottom of the module are unscreened).

I don't know if the additional screening is worth it (not having it does mean there is a nice airflow past the tubes) or how to iclude it in  a simple and cheap many.

Any ideas/advice gratefully received.

Cheers

Ian



Re: Mechanical Dilemma
« Reply #1 on: December 19, 2016, 12:07:57 AM »
I don't know if the additional screening is worth it (not having it does mean there is a nice airflow past the tubes) or how to iclude it in  a simple and cheap many.
Screening without blocking airflow suggests... a screen.  ;D

Aluminum window screen is cheap, industrial stainless steel heavy gauge wire screen meant for filtering or sifting can be quite rigid. Copper or brass screen can be easily soldered for grounding purposes.

Industrial wire cloth

Just some ideas, unless, as usual, I missed the point.
Gene

ruffrecords

Re: Mechanical Dilemma
« Reply #2 on: December 19, 2016, 05:15:40 AM »
Screening without blocking airflow suggests... a screen.  ;D


Indeed it does! The early Fischer cassettes I used were totally enclosed but surprisingly they only get warm despite having three tubes inside them. However, I later found a version that had a perforated screen top and bottom which has the nearly the same screening properties but provides better airflow. Thanks for the tip.

Cheers

Ian

Re: Mechanical Dilemma
« Reply #3 on: December 19, 2016, 10:31:42 AM »
Hi Ian

For some reason , I find your first mechanical choice very good, euro rack is professional, industry standard for decade and truly modular, way more than 500 series..., it will be difficult to beat this, especially if your not so good with mechanic.
I personally won't take the 500 series example for control density, over populated knob in this format is just a pain to work with
Maybe have a look at all Fischer sub rack options. IIRC you use the full extruded enclosure, A series. Have a look at F or I series, with shielded side panel made of bended alu,
For example, F series enclosure give you 14(hp)*5.08-16= 55mm, where A series (the one you use) give you 42mm (14*5.08-29.4)
The I series is even better for room, 65 usable mm for 14hp, and 29.5mm for your 7hp (new ???) design.
Combination of I series and small cut at shield panel and/or PCB at front panel side allow you to place control close to edge !

Best
Zam

ruffrecords

Re: Mechanical Dilemma
« Reply #4 on: December 19, 2016, 12:15:14 PM »
Good thinking Zam.  Eurocard format does have a lot going for it and I do not really want to design my own modules. I will look at the alternative Fischer modules. THanks for the tip.

Cheers

Ian

Re: Mechanical Dilemma
« Reply #5 on: December 19, 2016, 01:05:16 PM »
Hi

Have a look here:
http://www.fischerelektronik.de/fileadmin/fischertemplates/download/Katalog/cases.pdf
section N36 to 47 starting page 105
F design page 107
I design page 108
Side note, for your tube PSU sub enclosure there is option with heatsinks extrusion.

Best
Zam

ruffrecords

Re: Mechanical Dilemma
« Reply #6 on: December 19, 2016, 01:41:44 PM »
Hi

Have a look here:
http://www.fischerelektronik.de/fileadmin/fischertemplates/download/Katalog/cases.pdf
section N36 to 47 starting page 105
F design page 107
I design page 108
Side note, for your tube PSU sub enclosure there is option with heatsinks extrusion.

Best
Zam

Thanks, I already have that catalogue but I had not realised it gave the panel space - I had always puzzled those strange nx5.08-something figures and now I know what they mean.

One problem is that nearly all the designs have the top surface of the PCB 14.2mm from the left side of the front panel. I have some modules that I want to make stereo so this severely limits these modules. The 'I' module is the only one where the PCB surface is only 3.9 from the left edge of the front panel which makes them suitable for stereo modules. Unfortunately, the PCB cover is made of plastic!.

Cheers

Ian

Re: Mechanical Dilemma
« Reply #7 on: December 19, 2016, 02:03:03 PM »
One problem is that nearly all the designs have the top surface of the PCB 14.2mm from the left side of the front panel. I have some modules that I want to make stereo so this severely limits these modules. The 'I' module is the only one where the PCB surface is only 3.9 from the left edge of the front panel which makes them suitable for stereo modules. Unfortunately, the PCB cover is made of plastic!.

For the I design, as far as adjacent module face a shielding panel maybe it's not a problem to have only a mechanical plastic protection ?
I don't look deeper but maybe it's possible to have this thin protection made of sandwich plastic/metal, few old studer eurocard I have use this kind of cover at this exact same place.

Best
Zam
 

ruffrecords

Re: Mechanical Dilemma
« Reply #8 on: December 19, 2016, 02:32:14 PM »
For the I design, as far as adjacent module face a shielding panel maybe it's not a problem to have only a mechanical plastic protection ?
I already have a ground lane of the PCB that acts as quite a good shield. My simple design with pillars and a sheet pf steel improves on this so it would be better than the I design. What I really need is an I  extrusion with a modified F type shield.
Quote
I don't look deeper but maybe it's possible to have this thin protection made of sandwich plastic/metal, few old studer eurocard I have use this kind of cover at this exact same place.
That would provide adequate screening but the other problem is I have tubes in these modules and they do not mix too well with plastic!

Cheers

Ian

Re: Mechanical Dilemma
« Reply #9 on: December 19, 2016, 05:12:06 PM »
Not sure to get the point about plastic ? is that heat you anticipate or insulation with leg touching the plastic ?
Maybe drop a mail to vero to have the plastic specification (to me it look like rubber plate), I suspect it's a part made for high stress. High temp (at least 105°) and high insulation (saw them in euro format SMPS, maybe Vero/Eplax)

If you PCB act like a shield at left hand and I design shield panel at right hand, maybe it's enough ?
If it's enough and don't want to introduce plastic in the design, just leave the plastic cover at PCB back.
If plastic spec is fine and shield is not enough, I think you have enough room to ad a thin100x160 metal plate after the plastic. You will then have a full enclosure with small modification.

Anyway, as it is a modular system you can use fully extruded type A enclosure for better shielding when you can (mic pre with high gain), and other enclosure with more mechanical room for less critical modules (regarding shield) like stereo line or EQ at nominal internal console level? Also some versions offer two or more PCB slot if requested ...

Just some ideas...

Best
Zam


Re: Mechanical Dilemma
« Reply #10 on: December 21, 2016, 02:49:21 PM »
Ian, have you tried something like this?

ruffrecords

Re: Mechanical Dilemma
« Reply #11 on: December 21, 2016, 04:40:39 PM »
Ian, have you tried something like this?

No I haven't. Are you thinking this is steel with a separate front panel?

Cheers

Ian

Re: Mechanical Dilemma
« Reply #12 on: December 21, 2016, 06:03:20 PM »
The additional sheet metal will be formed in to an L shape and get sandwiched behind the front panel.

For an example, let's say you use a 1 mm thick aluminum sheet.
Cut to size 222 mm (160 mm + 63 mm - 1 mm) x 100 mm.

at 63 mm away from the edge, v-score a vertical line, this is where you will bend it 90 degrees to form an L shape.
after you bent it, you will have two surface area to work with.

63 mm x 100 mm, for aligned copy the front panel holes/cutout.
161 mm x 100 mm, a base for standoffs and mounting the PCB, and it also serve as a shield.

Re: Mechanical Dilemma
« Reply #13 on: December 21, 2016, 06:04:53 PM »
Example from a prototype case that I made a few years back.

You can see the pencil marked bending horizontal guide lines.
« Last Edit: December 21, 2016, 06:09:55 PM by metalb00b00 »

Re: Mechanical Dilemma
« Reply #14 on: December 21, 2016, 06:06:05 PM »
2nd part of the process.

ruffrecords

Re: Mechanical Dilemma
« Reply #15 on: December 21, 2016, 06:54:44 PM »
Interesting that you make it from 1mm aluminium. Much easier to work with than steel but is it strong enough. Unfortunately I do not have the tools to do this.

Cheers

ian

Re: Mechanical Dilemma
« Reply #16 on: December 22, 2016, 07:54:51 AM »
if you don't have a bending brake...

a workbench table, a scrap of straight edge steel piece (at least 3 mm thick or a steel bar), and some C clamps.

works all the way up to 1.5 mm thick aluminum sheet.

ruffrecords

Re: Mechanical Dilemma
« Reply #17 on: December 22, 2016, 08:56:04 AM »
I don't want to sound negative but I am very mechanically challenged. Accurately drilling holes or making bends I find very difficult. I can do it, but I cannot do it accurately.

Cheers

Ian

Re: Mechanical Dilemma
« Reply #18 on: December 22, 2016, 10:17:24 AM »
I see.

I co-own a gigantic precision laser cutting machine with my buddies, so I don't manually cut or drill holes anymore. When I'm making panels/enclosures, the only manual labor I do besides that is bending, installing nuts/standoffs, and powder coating.
For panel artwork, I just pay another friend of mine who's in the UV printing business.

I could propose a trade or something, but I guess doing so outside the proper channel will probably get myself banned/hated.

ruffrecords

Re: Mechanical Dilemma
« Reply #19 on: December 22, 2016, 11:38:44 AM »
I see.

I co-own a gigantic precision laser cutting machine with my buddies, so I don't manually cut or drill holes anymore. When I'm making panels/enclosures, the only manual labor I do besides that is bending, installing nuts/standoffs, and powder coating.
For panel artwork, I just pay another friend of mine who's in the UV printing business.

I could propose a trade or something, but I guess doing so outside the proper channel will probably get myself banned/hated.

All I can say is you are very lucky. I see nothing wrong with suggesting a trade. I have done quite a few myself. The only problem is I am in the UK and I am guessing you are in the USA.

Cheers

ian