On Topic: Purpose built soldering machine

The elections are over and it is time to get back to some on topic discussions.
I am looking to put together a purpose built soldering machine and I want to
pick your brains.
I have a 6"x8" piece of 16g polished brass sheet and I need to soft solder an 8" brass piano hinge to the polished side. The hinge needs to be moderately well located along one edge, but the tolerances are loose. For reasons of finish and subsequent machining, spot welding or riveting are not feasible.
The polished side of the brass has a thin coat of lacquer and a sheet of protective vinyl on it. I need to protect the polish and the lacquer in the non soldered areas, so heat needs to be very localized and handling kept to a minimum. It is for a production run of 100 pieces.
For prototyping I tinned the hinge with an iron. Then I would remove the vinyl from the sheet in the soldering area. Using the rest of the vinyl as a mask I would sand off the lacquer and flux the area and removed the rest of the vinyl. The sheet was clamped between a couple heat shields and then tinned. The two pieces got clipped together with spring clips, heat shielded and sweated together with a torch.
This worked fine for onesey twosey, but would suck for a hundred pieces.
My plan is this:
I use a strip heater like this,
http://www.mcmaster.com/#die-strip-heaters/=k3s9ef
attached to a hunk of copper buss bar as an 8" long soldering iron.
The pieces will be tinned and clipped into a jig. I have a scrap of architectural bronze extrusion that I think will work well for this. It has enough thermal mass to warm up and not chill the work, but it has enough flanges and surface area to release some of the heat and let the joint solidify in a reasonable time.
The hot 8" iron will be clamped down on the hinge side with a couple of toggle clamps, allowed to heat the pieces up till it sweats and released. The pieces remain clipped in the jig til the solder hardens. (can be sped up with water mist) The next set gets clipped in and the process repeated.
If I am lucky, I would love to eliminate tinning the sheet as well
I have about $400 parts and labor budgeted in for this machine. After that, it's all piecework. My profit depends on being frugal and productive so I don't want to spend a lot of time fiddling around.
If anyone has any ideas or insight or a better way, I would appreciate hearing about it.
Paul K. Dickman
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"Paul K. Dickman" wrote:

Have you considered adhesives? No heat required and with the right adhesive it will be at least as strong as soldering.
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"Pete C." wrote:

ETA: I'm pretty sure there are double sided adhesive tapes that would work and be ultra fast to apply. These days they glue cars and aircraft together, it ought to work for this application and save a lot of trouble. Look to 3M and/or Locktite for top grade stuff.
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I have used some adhesives on metal to metal that impressed the hell out me, but this would be a bad application. In the end the sheet gets slit up into eight 1"wide x 6" long fingers that flip up and rest on the hinge just past a 90 deg swing. That would put 5 1/2" of leverage on a 1/2" wide glue joint. I think that is asking for a peel failure.
Paul K. Dickman
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"Paul K. Dickman" wrote:

3M and Locktite have app engineers that could likely confirm or deny that issue with a phone call or two.
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On Sat, 10 Nov 2012 15:48:50 -0600, "Paul K. Dickman"
[...]

That applies to soft solder also. As the previous poster mentioned the modern adhesives have strengths comparable to soft solder. The limited research I did into this some time ago bore this out and I stopped using soft solder for most applications I did previously.
Michael Koblic, Campbell River, BC
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Sorry, I didn't get back.
Hard drive problems bumped me off line for a while.
I am very familiar with high tech adhesives and as I said before they won't work for this application.
Peel strength is their biggest shortfall. The best of them are rated to 25-40 lbs per linear, inch, a decent solder joint is 10 times that. You can design around this, but that wasn't an option here.
I have a 1"wide joint at the end of a 6" finger with the top of the joint and peak point of pressure 1/2" from the end. That is 11-1 leverage. With glue I could expect that to withstand 2-4 lbs of pressure at the tip before it fails.
I built the soldering gizmo and it works pretty well, but I have to superheat the copper with a propane torch. I may be able to avoid this step with some insulation or perhaps a second strip heater.
It aligns the pieces easily, solders them fully without cooking the lacquer, and minimizes handling of the polished sheet. And I was able to avoid tinning the sheet.
I am pleased.
Thanks to everyone.
Paul K. Dickman
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I seem to recall there was somebody who was doing CNC soldering that was asking questions on the CamBam forums a while back. It was self / shop built application. You might do a search over there and or post a question or two to see if somebody remembers the user and threads who was discussing it. I didn't get into to it heavily, but I think it was just a soldering machine. Not a pick and place machine, but I see no reason you could not build a machine to do both.
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On Sat, 10 Nov 2012 15:06:53 -0600, "Paul K. Dickman"

Greetings Paul, I would try, like many have suggested, glue of some sort. But if that doesn't work what about a resistance soldering unit? Instead of heating the work whay not let the work do the heating? I have a little 100 watt resistance soldering unit that uses carbon electrodes on either side of the work. The work usually brass, heats very fast, And the heated area is quite localized. The unit I have is made by Triton. I'm sure you could build one yourself. Eric
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On Sunday, November 11, 2012 12:34:58 PM UTC-5, snipped-for-privacy@whidbey.com wrote:

We used to use a resistance soldering "machine" made of a large 6.3V filament transformer attached to a fixture with carbon blocks that clamped to the work. You could run the transformer primary through a variac to control the temperature.
Fair Radio has a pretty good selection of transformers. Alternatively, you could use a welder to power this. You ought to be able to jig something up to test the concept pretty easily.
I'd imagine you could skip the tinning of the sheet with a reasonably active flux.
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On Sun, 11 Nov 2012 09:34:58 -0800, snipped-for-privacy@whidbey.com wrote:

I have a heavy..heavy small transformer with a set of resistance heating "clamps" if anyone wants to pay shipping only.
It looks like it was used for something like either musical instruments or perhaps RF connectors based on the cutouts in the clamp.
Probably 20lbs and plugs into 110vtAC. Photo if anyone is interested. Ive had it for years..and have never used it.
Gunner
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On Saturday, November 10, 2012 1:07:00 PM UTC-8, Paul K. Dickman wrote:

Brass (because of zinc content) solders best with some acid flux. Start by cleaning the section (hot blade? wire brush?), then wipe with flux and tin by running an iron over the area.
An iron applying local heat is better than trying for a large heated block in total contact, and if both surfaces are tinned it doesn't need any long application of heat to complete the join.
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