Soldering/Welding Techniques

Thread Starter

cmartinez

Joined Jan 17, 2007
6,440
I just don't think if your going to depend on those micro welds to hold your pin in place that it will work, be strong enough. Those welders are mainly for jewelry not for something mechanical. For strength in a 90 degree joint situation like your doing, you need a fillet of some sort. And to get a fillet you need to add material to the joint.

I forgot all about this stuff before, but thought of it overnight. https://www.riogrande.com/Product/SilverPasteSolderSyringe560ExtraEasy/103101 Using it you would apply to the joint and fixture the parts in position and heat. It's a well respected way of doing jewelry work.
Excellent suggestion, shortbus. I've already bought 3 syringes and they're on their way. Many thanks!
 
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shortbus

Joined Sep 30, 2009
6,968
Glad to be of help. After linking to that I thought of a couple of other things that may help.

Instead of a flame source when using the solder paste, consider something like this, while not inexpensive it is lower cost than the mini arc welder, and can be used for other things. This is just one brand the first to come up, there are others out there - http://www.theinductor.com/induction-heating-products/mini-ductor I saw a demonstration of one and was pretty impressed by it but not enough to get one at my age and already having torches. You tube has videos too. And you can make different size coils.

To hold the parts in arrangement your going to need some fixturing. So here would be my idea on doing that, machinable ceramic. Again just one brand with more out there - http://www.cotronics.com/vo/cotr/cm_machinable.htm Making a piece that would support the rod and the sheet metal part at 90 degrees with a little clearance where the solder would be. Then you would put the fixture in the coil of the induction heater and heat to fuse the parts together. The rod would only be supported on one side of the sheet metal arm so when cooled you would just pull it out and load another. Having multiples would make things go faster. I can make a quick sketch to show what I mean if your interested.
 
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Thread Starter

cmartinez

Joined Jan 17, 2007
6,440
Glad to be of help. After linking to that I thought of a couple of other things that may help.

Instead of a flame source when using the solder paste, consider something like this, while not inexpensive it is lower cost than the mini arc welder, and can be used for other things. This is just one brand the first to come up, there are others out there - http://www.theinductor.com/induction-heating-products/mini-ductor I saw a demonstration of one and was pretty impressed by it but not enough to get one at my age and already having torches. You tube has videos too. And you can make different size coils.

To hold the parts in arrangement your going to need some fixturing. So here would be my idea on doing that, machinable ceramic. Again just one brand with more out there - http://www.cotronics.com/vo/cotr/cm_machinable.htm Making a piece that would support the rod and the sheet metal part at 90 degrees with a little clearance where the solder would be. Then you would put the fixture in the coil of the induction heater and heat to fuse the parts together. The rod would only be supported on one side of the sheet metal arm so when cooled you would just pull it out and load another. Having multiples would make things go faster. I can make a quick sketch to show what I mean if your interested.
That induction heat tool looks rather interesting, I'll give it a closer look. But the machinable ceramics you're suggesting are a real eye opener. So far I've been working on the prototype, and have been thinking about the production process on the back of my head. I knew I needed fixtures, but I still hadn't considered the necessary materials. You've just saved me pretty valuable time, my friend.

Curious fact: the spanish word for an assembly fixture is escantillón ... and it's pronounced "Es - can - tee - yawn" ... there's a huge difference (at least for me) between fluently speaking a language for everyday purposes, and speaking it using technical terms.
 

shortbus

Joined Sep 30, 2009
6,968
So far I've been working on the prototype, and have been thinking about the production process on the back of my head.
If this ends up as a production type thing there are some better ways of attacking things. Like this little part. For making them in the tens of thousands you might want to consider another jewelry process, lost wax casting. Silicone molds for the wax and you would tie many to a "tree" and pour them at one time. This is also done in dental labs on smaller scale and using stainless steel.

Where I served my apprenticeship I learned more in that small 4 man shop than any where I ever worked. The lost wax casting was one thing we made molds for, molds that were used to make the compressor vanes of jet engines.
 

Thread Starter

cmartinez

Joined Jan 17, 2007
6,440
If this ends up as a production type thing there are some better ways of attacking things. Like this little part. For making them in the tens of thousands you might want to consider another jewelry process, lost wax casting. Silicone molds for the wax and you would tie many to a "tree" and pour them at one time. This is also done in dental labs on smaller scale and using stainless steel.

Where I served my apprenticeship I learned more in that small 4 man shop than any where I ever worked. The lost wax casting was one thing we made molds for, molds that were used to make the compressor vanes of jet engines.
Wouldn't the casting stainless steel of such a small part leave a rough/porous surface finish? Or is it a question of the ss alloy itself?
 

shortbus

Joined Sep 30, 2009
6,968
Surface finish is dependent on the wax from the original mold. The jet engine blades I talked about came out of the completely smooth and finished on the blade it's self the only thing machined after casting was the base. This was by design, so they could use the same basic blade in different engines by adjusting the shape of the base. To change the pitch of the blade.

Lost wax isn't like sand or even die casting. The slurry that coats the wax original is changed to fit the part, coarse slurry for things that don't need to be so smooth and the inverse for things that need to be smooth.

Ever had a dental bridge or known someone that has one? Most of them are lost wax cast SS.
 

Thread Starter

cmartinez

Joined Jan 17, 2007
6,440
@cmartinez Here is a short Youtube of them induction brazing/silver soldering carbide tips on a saw blade. Many more of them if you want to look for them.


Beautiful machine :) ... it's impressive how it automatically dispenses the right amount of solder paste.
 

MisterBill2

Joined Jan 23, 2018
3,847
I have made reliable electrical connections to some kind of stainless steel, no clue what alloy, repairing an expensive camera for my son. My secret for getting regular solder to stick to stainless is to heat it and apply both flux and solder, and then scratch the SS under the solder ball and flux, to remove that chromium oxide and get the solder to stick to the steel. It might not work in your application, you may need to braze it using brazing flux, which is different. Getting the metal too hot will form a black layer that nothing will stick to.
 

Thread Starter

cmartinez

Joined Jan 17, 2007
6,440
Everything I ordered is finally here. I had to had the items shipped to McAllen, Tx, because the companies I ordered things from don't deliver to Mexico. I went up there to pick them up this last Monday, stayed two nights with the wife, and came back.

Anyway, the spot welder looks like an interesting machine. When I took it out of the box I noticed that something was moving inside and going clickety-clack when I shook it a little bit... not good. So I removed its cover, and discovered that a small component (a 40V to 5V transformer) that should've been screwed to an internal support had broken a couple of plastic ears used by the screws for attachment... No big deal, what I did was simply remove the screws and used the holes to tie the part to the chassis using zip ties. I also had to solder a cable that had come loose for the same cause to the terminal of a USB port in the back that is used only as a 5VDC supply for a sharpening tool included with the machine.

I took a bit more time inspecting it before putting back the cover and discovered that a couple of spade terminals were a bit too loose for my taste. So I disconnected them, and re-tightened them with a pair of pliers. One of them had a broken insulation jacket, so I replaced that as well using shrink tubing.... problem solved.

Here's a few pics of the internals. The small transformer that I reattached with zip ties can be seen on the right of the first pic. A small solenoid valve for the argon gas can be seen to the left of the toroidal transformer.

14e582a2-9995-49d2-9620-f456c5e4b986.jpg


6263ed91-64be-46de-8f0d-10b8546836f4.jpg


4ef91a64-cc6d-436f-b790-f0e10ac387b1.jpg


490bfe08-4b58-49c1-b8f6-2285ba2657ed.jpg

The capacitor bank is comprised of 15,000 µF @ 63V electrolytics, and the nFets seen on the pics are IRF3205 (55V @ 110A, 200W). Three tungsten electrodes measuring 1mm diam and 150mm long were included in the kit. The argon gas working pressure is 0.1 MPa (14.5 PSI). Fun fact: the controller is using an ATMEL MCU, which is a brand that I'm experienced with and know quite well.

This thing has a 6mm tube quick connect in the back for the argon gas. I'll be connecting the argon thank after I find the proper adapter and start testing this toy today, hopefully.
 

SamR

Joined Mar 19, 2019
1,133
Apparently not... but its specs do state that it has a maximum duty cycle of one weld per second.
Yes with spot welding the repositioning time compared to the actual weld time is very long indeed. Or at least by hand and not in an automated machine it is.
 

jpanhalt

Joined Jan 18, 2008
7,848
Interesting pictures. That main transformer reminded me of the one I modified by winding a second secondary to provide for logic voltage:
upload_2019-9-12_15-59-2.png

I limited mine to 30 V for safety and used about 400 mF for the capacitor bank. Awhile back, I was wondering about using the same CO2/argon mixture used for MIG welding for TIG welding to save on tanks. Some videos convinced me not to do that. The cleansing action of the CO2 did nothing to help, but gave a less stable arc, much more splatter, and a smoke-like deposit. However, for your CD welding, it might be something to consider, particularly if your machine uses a "double" discharge. The first discharge is to clean the surfaces, and the second is for the welding. Mine is just a single discharge, and I do not use any shielding gas. It will tack weld SS tubing, which I follow with silver solder, but the weld spot is quite small.

Do you let the gas flow for a few seconds after the weld?

About those resistors... At first, I thought they might be gate resistors, but I count 8 mosfets and 16 pairs of resistors. What do they do?

I am very interested to see how well it works.
 

Thread Starter

cmartinez

Joined Jan 17, 2007
6,440
Interesting pictures. That main transformer reminded me of the one I modified by winding a second secondary to provide for logic voltage:
View attachment 186042

I limited mine to 30 V for safety and used about 400 mF for the capacitor bank. Awhile back, I was wondering about using the same CO2/argon mixture used for MIG welding for TIG welding to save on tanks. Some videos convinced me not to do that. The cleansing action of the CO2 did nothing to help, but gave a less stable arc, much more splatter, and a smoke-like deposit. However, for your CD welding, it might be something to consider, particularly if your machine uses a "double" discharge. The first discharge is to clean the surfaces, and the second is for the welding. Mine is just a single discharge, and I do not use any shielding gas. It will tack weld SS tubing, which I follow with silver solder, but the weld spot is quite small.

Do you let the gas flow for a few seconds after the weld?

About those resistors... At first, I thought they might be gate resistors, but I count 8 mosfets and 16 pairs of resistors. What do they do?

I am very interested to see how well it works.
I'll let you all know how it went as soon as I have everything up and running. And maybe after I'm done with the immediate needs I'll open it again and make a closer inspection to see how those nFets and the resistors are connected.
 

jpanhalt

Joined Jan 18, 2008
7,848
I'll let you all know how it went as soon as I have everything up and running. And maybe after I'm done with the immediate needs I'll open it again and make a closer inspection to see how those nFets and the resistors are connected.
If you have a MIG welding gas, it would be an interesting experiment to compare that with pure argon. I was surprised (as it seems a lot of people are) with the really poor performance of argon/CO2 with TIG. It was not just "almost" as good, it was really bad.
 

Thread Starter

cmartinez

Joined Jan 17, 2007
6,440
If you have a MIG welding gas, it would be an interesting experiment to compare that with pure argon. I was surprised (as it seems a lot of people are) with the really poor performance of argon/CO2 with TIG. It was not just "almost" as good, it was really bad.
So far, I only have a small 5 lt tank (they're called baby tanks down here) of pure argon. The machine allows adjustment for gas to flow 0.5, 1 and 1.5 seconds of gas flow during welding.
 

jpanhalt

Joined Jan 18, 2008
7,848
5 L? That is something one might buy at a gourmet grocery store for preserving wine. :) I have tried such small tanks for acetylene and switched. The only small tanks like that I use are for soldering water pipe where the tank is attached to the torch. My argon tank is about 8" diameter and 30" tall. It has the standard CGA fitting for all bigger argon tanks. It is easy to handle and keep in the house for wine, but big enough to support a small amount of welding at 15 to 20 cubic feet per hour. While most of my regulators are two stage laboratory type, for TIG or MIG welding or wine, you might be better off considering a single stage regulator with flow meter (metal ball type) and standard CGA fitting. You will never regret it.
 
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