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MOT Spot Welder
#11
Nice going Umar.

I spent quite a bit of time on mine over the weekend. Will take some photos tonight and update the other post.

Are you still planning on zero cross detection, or will you go back to the MOC304x? I have this plan in the back of my head where I want to reduce the power by regulating the on-time of each half wave of the power (like how most light dimmers work). That is one of the reasons I wanted to go for a non-zero cross opto driver.
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#12
Just for interest sake:
http://www.westken.co.za/product/t1ap1-02-square-timer about R2500

In my hunting for decent welding tips (Appears these are somehow linked to being milled from chickens teeth) I found the above company who have everything needed. Their sales rep in JHB comes to you with the spares so I'm expecting a visit tomorrow and hoping to get some decent tips for us to test with.

LIDO is also the cheapest for the cable as well.
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#13
Thanks Org,

Waiting to see your progress. Yes, I'm convinced that zero crossing is essential especially to get your pulses timed correct. However it needs to be implemented on the micro side to ensure your pulse lengths are from the zero crossings. I've decided for now to stick with the Random Phase Optocoupler MOC302x. As you mention power regulation will also be possible using this.

@Gordon, R2500!!! Now we know how much we can sell this thing for if it works. Let us know what tips they have and how much, basically we need something that wont melt too fast Smile

I am actually surprised at the spot welding the unit is capable of doing.
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#14
(2016-10-03, 12:30 PM)admin Wrote: Thanks Org,

Waiting to see your progress. Yes, I'm convinced that zero crossing is essential especially to get your pulses timed correct. However it needs to be implemented on the micro side to ensure your pulse lengths are from the zero crossings. I've decided for now to stick with the Random Phase Optocoupler MOC302x. As you mention power regulation will also be possible using this.

@Gordon, R2500!!! Now we know how much we can sell this thing for if it works. Let us know what tips they have and how much, basically we need something that wont melt too fast Smile

I am actually surprised at the spot welding the unit is capable of doing.

That's just the timer.....The cheapest "normal" handheld spotwelder is still R13k at Addendoffies. So we still well below budget Smile and that DOES NOT do batteries Smile also I think its limit was 4mm in total so 2x 2mm which we should be able to do as well with the MOT's. Or like some have done with 2 or more MOT's together and gotten over 2000amps'.
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#15
I had a random idea that may be worth a try... what about using High Speed Steel (HSS) drill bits for our electrodes?
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#16
(2016-10-03, 04:47 PM)admin Wrote: I had a random idea that may be worth a try... what about using High Speed Steel (HSS) drill bits for our electrodes?

Spent some time with the chap from Westken (About the only guys that can help with the electrodes etc). Very nice guy (Elwyn) and very very helpfull. Will ask if I can "publish" his cell etc.

The common electrodes are made of copper, chromium and zirconium. Pure copper obviously as we know has issues with melting and dirtying up too quickly and is not a good solution. This is expensive stuff but I have bought some rod and some tips for testing. Copper will work but melts away quickly and HAS to be cleaned after every single weld.

They start at 12 or 13mm for the normal spotwelders as with 7000amps/15KVA for a "baby" welder that's just whats needed. Obviously this includes gaps for the holders and air or water cooling as well which is why I ordered some 10mm road as it seems to be the smallest available so we can make our own smaller tips for the battery tab welding and water/air cooling isn't on the plate yet.

The four 6mm tips I bought cost R400 so they had better last!

Another 'tip' I got was to use brass for the tip holders or arms as that's what the pro machines use as its cheaper and works perfectly well.

The timers are really expensive and the timer I got quotes on won't do the job for our needs either so its more like R5k+ for the timer which coincides with ACDC's timer at R6k albeit his timers have nice face plates and buttons on etc already so easy to integrate into a pro looking project while ACDC's isn't very user friendly.

Checking around the internet I see others have tried Tungsten TIG tips and all sorts of other metals and alloys to varying degrees of success but obviously those in the industry know the copper alloys work cheapest and best. Obviously because we send our copper overseas to get the alloys added and then re-import it its an expensive setup.

Personally I think its a question of testing and going with what works for the weld needing done but there is quite a bit of help out there to guide if pro welds are needed. The tips I got today hopefully cover most of them.

The pressure exerted on the welds is also important and also differs dependent on materials being welded but most of the machines I looked at seem to exert the same pressure which is quite high. Obviously the bigger more specialised and more industrial machines use pneumatic and or hydraulics rather than lever force to "clamp".

Some info:
The electrodes are one of the most important factors in the resistance welding process but often the most abused. It is important to consider the electrode material, shape, size, tip profile and cooling.
Electrode materials are covered by ISO 5182. These are mainly copper alloys with a small percentage of alloying element to improve hardness, while maintaining good conductivity.
The most common materials are Class 2 (e.g. copper/chromium or copper/chromium/zirconium) and may be used for low carbon and high strength steels in general. Higher conductivity alloys, such as copper/zirconium and dispersion strengthened copper, show some benefits when welding coated steels as they provide less surface heating because of their low contact resistance.
When welding harder sheet materials, such as stainless steels, much higher electrode forces are required but lower welding current. These materials are better welded with the harder Class 3 electrodes such as copper/nickel/silicon. This is replacing the superior copper/cobalt/beryllium alloy because of the potential beryllium hazard (mainly as a dust from machining or dressing operations).
Refractory electrode materials, such as tungsten/copper, tungsten, or molybdenum are used for applications such as projection welding inserts, where the electrode contact area is at least three times the weld size. These materials have higher hardness but lower conductivity than the Class 2 electrodes. They are unsuitable for spot welding as they suffer localised heating at the tip contact, which can lead to cracking of the electrode. The exception is for joining high conductivity metals such as copper wire or foil, where heat is generated mainly within the refractory electrode tip and conducted into the materials to be joined.
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#17
Got the 1m long 10mm rod so now I need to build my welder and test as well. Org's is really working well from the demo's the other night so really good job there! I'm basically cloning his electronics but with less amps and smaller tips.

(2016-10-06, 12:34 PM)Gordon Wrote: Got the 1m long 10mm rod so now I need to build my welder and test as well. Org's is really working well from the demo's the other night so really good job there! I'm basically cloning his electronics but with less amps and smaller tips.

So if anyone needs tips for testing gimme a shout for a piece of my copper stuff Smile
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#18
https://youtu.be/6mqcQjDSoWc
Nice looking but I actually think more expensive than Org's version? as well as a lot bigger.
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#19
My timer is built! Thanks to Org for many many many hours of suffering with me and helping me learn some electronics, circuitry and arduino. I'm building the transformer over the weekend with some 75mm2 cable so hopefully some successful welds soon.
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#20
Well done! You need to start a thread and post some pictures of your build and learning's.
I've been sidetracked with studies for some work related certification so have had no time to work on my build. I have not forgotten though and will get back to it asap.
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