Poor penetration.... Car welding

[Ben g mon]

morning!
I'm currently doing repairs/resto to my bmw e30 318IS....
I'm halfway round it all the front end welding repairs are done ..however...
Since I've moved from outside/ driveway into a lock up (and gone from domestic mains to generator power) I can't get the welding right..it looks like gorilla welds and when I was plug welding the inner sill reinforcement repair plate it won't stay on..

Generator is Honda 3kva in good order

Welder is a Clarke pro 90 which requires 2.6kva MAX

Am using gas also

Mig wire is a type than can be used on slightly rusty steel and I have been grinding it clean.

Did have wire feed issues and that's now coming through fine

Is it normal to get white deposits on the steel you are welding?

Any ideas? I really want to get the welding done over winter then the upgrades!

Thanks for reading, I can get pics if needed

 

[cumbriasteve]

White deposits are usually a sign the sheet has a protective coating on it and not heard of a wire that is suitable for rusty steel, happy to be proved wrong though.

Photo's of the problem areas/welds and the white coating will help other's to give advice.

 

[steveo3002]

if it all worked at home on mains power and not with the genny i think that points towards the problem

 

[octo0072000]

by the sounds of the genny is not big enough inrush current on welder could be double the max Kva of the mig well in excess of your genny is the genny max 3 kva or peak 3kva 2.6 max kva
if it all worked at home on mains power and not with the genny that's the problem

Welder is a Clarke pro 90 which requires 2.6kva MAX
Generator is Honda 3kva in good order

 

[Richard.]

White deposits to me sounds like your welding on galv. If that's the case don't breathe in the fume.

 

[Ben g mon]

White deposits are usually a sign the sheet has a protective coating on it and not heard of a wire that is suitable for rusty steel, happy to be proved wrong though.

Photo's of the problem areas/welds and the white coating will help other's to give advice.

This was the wire I was using

http://www.ebay.co.uk/ulk/itm/311117387256

 

[Ben g mon]

by the sounds of the genny is not big enough inrush current on welder could be double the max Kva of the mig well in excess of your genny is the genny max 3 kva or peak 3kva 2.6 max kva
if it all worked at home on mains power and not with the genny that's the problem

Welder is a Clarke pro 90 which requires 2.6kva MAX
Generator is Honda 3kva in good order

Wow, so I need a unit like 4.5 KVA?

 

[Ben g mon]

White deposits to me sounds like your welding on galv. If that's the case don't breathe in the fume.

I went over the steel with a knot wire wheel so I thought it would take off the coating.... I recognised the steel had a galvanised coating

 

[Ben g mon]

if it all worked at home on mains power and not with the genny i think that points towards the problem

Thanks, didn't know if it was this or a change in wire type, or if welding with a generator welds in different ways....

 

[Ben g mon]

It's ER70S-6 wire, so nothing 'special' about it for 'welding rusty metal' - except for the sales description of course...

Ime, a 3kva generator is likely to be more like a 2.6kva for continuous use, with a 3kva peak. I'd say it's not big enough by a fair way.

Could you please recommend a KVA rating?

I'm welding with 0.6mm wire and the metal used is 0.8-1.0mm thick car panel steel

Looks like my generator may be for sale soon then...

 

[steveo3002]

why not drag the welder home and see how it goes with a bit of scrap same as youre using,,,will confirm if the genny is the problem if it works fine

 

[Richard.]

I went over the steel with a knot wire wheel so I thought it would take off the coating.... I recognised the steel had a galvanised coating

Takes more than a wire wheel to get galv coating off.

 

[Ben g mon]

Takes more than a wire wheel to get galv coating off.

So just a cleaning disc like 36 grits and keep going until bright/ noticeable colour change?

 

[Ben g mon]

I can't say if the generator is the cause of the problem you are experiencing, especially the 'white deposits' and considering you're apparently using swp wire, but the one you have is too small...

Ok, I'll test the welder on mains electric first and start hunting a more powerful generator...

 

[Ben g mon]

There's more to choosing a generator than a lot of people think there is, if I could get 'real' figures then I could give an accurate number...

As it is, your average 'consumer' generator output figure is usually a 'peak' figure (for sales headline) and is based on a purely resistive load (like a lightbulb). To be fair, that's really the only consistent thing they can use.

Because a transformer is far from a purely resistive load (it's inductive/capacitive), the figures on the generator become 'wrong'. A transformer could have as 'bad' a power factor as 0.4 when it's starting up - which means for a "1kva" transformer you could be needing a "3kva" generator just to get it going.

I have a "3kva" generator, which is actually a 2.6kva unit, which doesn't have a hope of starting an old 1hp (760w, or 0.76kva (yeah, alright, figures be stoopid)) motor. -- A motor is a little like a transformer electrically in that when it's starting the voltage and current are not in sync

So - my recommendation...

Take the figure written on your machine and double it (or maybe even triple it if you want to be 'really safe') and that's what you want. For your "2.6kva" load, well, a 5-6kva would be alright, a 4.5kva might actually be borderline, especially if you're anywhere near the higher settings.

Point taken, thank you for the guide

 

[agrimog]

you are going to need a welder in the region of 6-7.5KVA to run your welder, and it will require a voltage regulator on it as well, the inductive load every time you strike the torch is huge. if your getting a white powder on your welds, or white fluffy smoke coming off, its galvinised sheet, be very carefull or you'll find the joys of galvy flu, change yor steel to something more sutible and get a good quality weld through primer

 

[chris y]

I have some experience with using small generators with a welder, quite a bit really, recently finished a vast amount of welding on an extremely rotten car, I used about 2.5 bottles of Argoshield to give you an idea. (X or Y size, cant remember)

Machine - SIP 150A, I know I know but very old and better than a SIP should be and easy to transport

Initially I started the project after a friend offered his 5.5KVA diesel generator if I fixed it, big mistake, it was a wreck and when we got it started it ran on its own oil and is now dead.
I had done some cutting by then so needed to weld and knowing what the result would be in anger plugged into my own budget 2.3KVA generator.
The welding was no problem at all, no different to mains power although I never used settings 5 and 6. Predictably after at a guess a metre of weld over various tasks I cooked the generator, shorted the windings, very dead now.

The next day I had the chance of a bargain Loncin 3800 (3.8KVA) generator so bought it, theory being that its a lot bigger than the 2.3 so with plenty of cooling time it was worth a try.

Well that worked brilliantly, the car is now welded and has 188 new pieces of metal welded in over 18 months.
I only used setting 5 for 2mm chassis work and have penetration on the back side. Generally I kept it to settings 2, 3 and 4 and let it cool regularly.


What I'm saying is that in my experience the risk is mainly one of cooking the generator, it didn't make any noticeable difference to the welding experience.
While the large generator sizes being suggested are definitely sensible and correct it is very possible to work with something much smaller with care.

I would guess that either the generator being discussed is particularly poor or the zinc is the real problem.

In my garage away from home I added a digital voltage meter, about £3 from ebay, so I could keep an eye on any generator output, welding didn't cause significant voltage drop, that might be a wise thing to do so that you can see if any generator you use can deliver under load.

 

[Kent]

I don't think smaller than say 5 kva should be used generally 240 v mig plants require 6-8 kva
Who knows to be fair without looking but it's a fair bet it's to do with your power into the set

 

[Ben g mon]

Thread revival!

Been looking at 4kva units units used and fairly local to me, but currently got my hopes up for a 8kva unit as I have a lot of welding to do!

Not as much as 188 pieces as one chap has mentioned more like 30 (did 13 on the driveway, sloping of which put me off the back end welding!)

Thanks for all the hints etc and I hope you all enjoyed Xmas and new year......