Spot Welder at PA

[Doggggboy]

I see the 240V spot welder at PA will be on sale again next week. I'm trying to decide if I should get one or try building my own. I'd like to have one like Dan Gelbarts! But then considering I've never used one before maybe the 240V PA model would be a better starting point? What think you all???

Dan Gelbart knows way too much about EVERYTHING!

 

[Canadium]

Hey I've been trying to justify buying that one also, but it hasn't been on sale in the time I've decided that I "need" one.

With not buying it ON regular price, made me consider making one also. The building of one looks fun and interesting but the examples of homebuilt ones appear to loose a functionality of the commercial ones and that is portability. I would think that being able to manover one into awkward positions is key to its versatility. Now there are probably homemade versions that do allow this feature but the ones I've seen are basically bench mounted units.

Do you have a particular need for a spot welder? I sure don't, but like to try to think of where I would need one.

I would try building one for the adventure and fun of it. I imagine it would be just another machine that I would use to build and repair other machines. I would like to be able to make custom enclosures for other DIY projects. Need to learn more about sheet metal work!

Theoretically seems to me spot welders are pretty simple machines. A big transformer, a power controller and some thick copper electrodes. But the devil is always in the detail! Based on cursory searches of Youtube the common spot welder DIY begins with a transformer from a junked old microwave oven. One build even uses two such transformers together. I'm still trying to wrap my head around how these things are rated for power. Dan Gelbart recommends machines in the 15 to 25 KVa range. As far as I can tell the PA welder is far lower than that.

 

[kevin.decelles]

I bought the 120V one on sale at PA...... takes me back to 10th grade shop class. Works ok, I've used it to fix a few things..... if I fix 100 more it will pay for itself.

I agree on the DIY version starting with Microwaves...... seems to be a common design.

 

[Janger]

Why don’t people use welders as the power source? They are already low voltage high current with adjustable output ??? More current than even two microwave transformers. All you need are some electrodes and a mechanism to bring them together with pressure? Some welders even have a 'spot' setting for an automatic brief power engagement. What am I missing?

 

[Tom Kitta]

I also have spot welder for few years now - some use but has not paid for itself. Used less then 10 times. Most of the use is not actually for the shop, but for either decorative stuff that disintegrates or for things like expensive pot handle breaking off. Also used it for some thin sheet metal that holds some bird houses to the tree. Need to fix 90 more things to get it to pay for itself.

 

[DPittman]

I chuckle that we talk about how a $250 welder hasn't or won't likely pay for itself but say nothing about the thousands of dollars of other equipment in our hobby that probably is the same.

 

[Tom Kitta]

I chuckle that we talk about how a $250 welder hasn't or won't likely pay for itself but say nothing about the thousands of dollars of other equipment in our hobby that probably is the same.

Problem is no one is really counting $ or $ is relative as far as hobby is concerned. I mean most work is making things for other machines or cool jigs etc.

 

[DPittman]

Why don’t people use welders as the power source? They are already low voltage high current with adjustable output ??? More current than even two microwave transformers. All you need are some electrodes and a mechanism to bring them together with pressure? Some welders even have a 'spot' setting for an automatic brief power engagement. What am I missing?

Good question. Is the lack of a brief power engagement the biggest hold back on most welders? Surely such a device such as that could be easily incorporated into an accessory electrode contraption that could be used on almost any electric welder?

 

[Canadium]

Why don’t people use welders as the power source? They are already low voltage high current with adjustable output ??? More current than even two microwave transformers. All you need are some electrodes and a mechanism to bring them together with pressure? Some welders even have a 'spot' setting for an automatic brief power engagement. What am I missing?

I was wondering the very same thing. Was thinking a person could probably get a cheap used crappy tire welder on Kijiji. But I'm having trouble doing the engineers rough calculation for power output. Wouldn't the limitation really be the same in both cases, ie the household power supply? P(KVA) = VA/1000 where P(KVA) is power in KVA, V is voltage and A is current in amperes. For example, if V is 240 volts and A is 10 amperes, P(KVA) = VA/1000 = (240)(10)/1000 = 2.4 KVA.

 

[Tom O]

I wonder if I could do it with my Miller It looks like it might be able to.

 

[Janger]

The PA ones are pretty basic. If the electrodes have a current path the current flows. Move the electrodes apart and it stops. Dan Gelbert's has a much fancier control - I think it works like this: push the electrodes together on the part then press the foot switch which delivers the preselected current / time etc. set from the dials on the machine. I'm not that familiar with these tools - what is the usual amount of control?

I think your miller there Tom would work with the spot timer. My everlast mig also has a setting for a spot weld. I bought some copper bar with making something like that in mind - another project in the backlog. I ended up buying the PA 240V one with Dabbler. For some reason it gets to hang out in my garage mostly. Have not done much with it yet.

 

[DPittman]

I see the 240V spot welder at PA will be on sale again next week. I'm trying to decide if I should get one or try building my own. I'd like to have one like Dan Gelbarts! But then considering I've never used one before maybe the 240V PA model would be a better starting point? What think you all???

@Canadium
I'm curious how you knew the sale was coming up. I just got the PA flyer today and see the sale start on Feb15th. We are usually a few days later receiving the flyer than the big cities, but not usually any later.

 

[YYCHM]

@Canadium
I'm curious how you knew the sale was coming up. I just got the PA flyer today and see the sale start on Feb15th. We are usually a few days later receiving the flyer than the big cities, but not usually any later.

I just got that flyer today.

 

[Canadium]

@Canadium
I'm curious how you knew the sale was coming up. I just got the PA flyer today and see the sale start on Feb15th. We are usually a few days later receiving the flyer than the big cities, but not usually any later.

I usually get 2 sets of PA flyers, one via Canada Post the other in a weekly junk mail bag. The junk mail bag arrived today but this time the one from Canada Post arrived several days ago. Can't remember exactly when but it could have been the 4th. sometimes one of them fails to show up but I usually get at least one. I find them greatly entertaining and always spend way too much money there!

 

[DPittman]

I usually get 2 sets of PA flyers, one via Canada Post the other in a weekly junk mail bag. The junk mail bag arrived today but this time the one from Canada Post arrived several days ago. Can't remember exactly when but it could have been the 4th. sometimes one of them fails to show up but I usually get at least one. I find them greatly entertaining and always spend way too much money there!

Yes my wife was just reminding today about how many "damn fliers I get from PA". It seems to me I get to addressed to me, one to my business and then a general unaddressed mailer. I need to contact them again I guess. I love getting the PA flyer.

 

[Former Member]

All I can say considering we are DYI'rs

 

[DPittman]

Well I couldn't resist the sale, I bought a 220volt machine at Princess Auto today. $190.
What is heat sink compound and how important is it? The manual states to apply the stuff to the electrode tip threads when installing.

 

[combustable herbage]

Heat sink compound is used for better transfer of heat between two mating surfaces normally its used in computer cpu's and is available at most electronic suppliers or amazon. Its important in cpu's so they don't overheat, maybe better heat transfer in your situation.

 

[mikefrost]

Spot welding is resistance welding.

The idea is that you have a path for the electric current that is very very low resistance, i.e. the transformer secondary and the heavy copper bars / tip.
The piece to be welded is (supposed to be) much higher resistance i.e. 2 thin pieces of sheet steel.

Apply the current and the thin pieces get so hot that they melt together, hence the need for pressure to squish the parts together. Also that's why you need to make sure the pieces to be welded are really clean and are tightly held (clamped) together.

The secondary voltage is usually in the range of 1 V, the current is in the range of 1000 - 1500 A ( albeit for 1 or 2 seconds) . The input current on my 110V MOT welder is about 12 - 13 A. On a regular household circuit, anything more will pop the breaker.

Most industrial spot welders have water cooled tips.
The portable ones will get quite warm after a while.

I found that I use mine more often that I thought I would. If you do make one using a MOT , get the biggest honkin' one possible - bigger is better.
Mike

 

[Susquatch]

I am not sure I can really help here other than to add a very important caveat on the overall reliability of spot welds.

I am no welder, but I do have considerable experience with spot welding in an automotive assembly setting and I have a patent for electronically controlling a spot welder in that environment so its not like I'm clueless like I am with other welding processes. It's really that spot welding a car body together in a factory setting with giant spot welders is on a whole different scale than a hobby level machine.

I agree with @mikefrost's comments. At least for the big machines, the challenge is controlling the timing and the current so that the spot weld process itself doesn't just send a molten nugget flying around the area with a hole in the part. Pressure needs to be enough to allow high current but not so much as to pinch the molten nugget out.

In my mind, the biggest problem with hobby spot welding is prolly the same one as in the big factories - quality control of the nugget. In particular, how do you know the nugget is a good one? In the factory setting with repetitive welds, we did destructive testing of an entire car body every so often - every two hours or so. It had to be often enough to catch problems but not so often as to waste production. My invention monitored the weld nugget formation in real time to avoid the need for inspection and destructive testing. This can't be done in a hobby setting.

Another way to address the quality control issue is to have 4 times as many welds as needed so you can afford to have a few bad welds.

Anyway, the only real value I can bring to this discussion is this: Don't assume that a good looking spot weld on the surface is actually a good weld at the part to part interface. Cold spot welds are a fact of life in the best of environments even under very carefully controlled conditions. By all means, test them to the extent that you can, but on mission critical joints, I'd prolly recommend a more traditional welding method where you can trust your eyes to assess the weld quality reliably.

Just my two cents for what it's worth.