Welder

Discussions about techniques for rocket building. Leave your tips and tricks to making the perfect rocket.

Moderator: Moderators

User avatar
CATO
Mr Smiley
Mr Smiley
Posts: 1957
Joined: Thu Dec 24, 2009 6:20 pm
Location: Sydney, NSW
Contact:

Re: Welder

Postby CATO » Sat May 25, 2013 11:04 pm

Hi Nic,

Have you managed to update your welder yet?
"In thrust we trust"

AMRS 21 L3
TRA 07459 L3

Impulse:
2018: 14,767 Ns (44% N)
Ns 17: 5,973; 16: 34,558; 15: 35,955; 14: 6,016; 13: 10,208
PB - Gorilla N2717WC, H: 10,260', S: 1.14M

User avatar
ROCKet STAR
Astronaut
Astronaut
Posts: 1724
Joined: Mon Mar 16, 2009 1:40 pm
Location: Blue Mountains, NSW
Contact:

Re: Welder

Postby ROCKet STAR » Sat Apr 12, 2014 3:02 am

I have a question for those of you who weld, and figured I would tag on to Nic's thread, to save starting a second welding thread.

I need to put together a test stand for testing a couple of motors (hybrids) up to approximately 1000N thrust, and am looking at getting myself a MIG welder for the job. I am thinking I will construct it from steel box section that would have somewhere between 3-5mm wall thickness. I was hoping I could get peoples opinions on what sort of welding current I should be aiming for?

Most of the MIG welders I have seen online, that operate at above 120A welding current, use require a 15A mains circuit.
While I don't currently have a 15A outlet, I have just removed an old heat bank from my house, which was on a 32A circuit, that is now unused. As such it wouldn't be a big deal to get a decent power outlet installed if necessary.

It is not something I am going to use very regularly, so don't want to spend too much on it if I can avoid it, but by the same token, I don't want to skimp and end up with something gutless, that will result in welds that could fail.

Also, the idea of getting a gasless MIG is appealing given it's simplicity.

Would any of you knowlegable people have any suggestions?

Cheers :)
Chris Barnes

AMRS# 29 - L3

UKRA - L3

User avatar
OverTheTop
It's only money...
It's only money...
Posts: 2636
Joined: Sat Jul 21, 2007 2:20 pm
Location: Melbourne, Australia

Re: Welder

Postby OverTheTop » Sat Apr 12, 2014 10:44 am

I did a MIG course a few years back. It was interesting at the time as I was soldering 0.4mm pitch components during the day and gas-axing and welding 12mm steel plate at the TAFE course...

From my course notes (there is a table with lots of useful stuff) for 3mm steel currents in the region of up to 170A are specified. I depends on the type of weld (butt, chamfered, tee, angled etc). There is usually some leeway on the numbers and I usually run lower, just because I don't get much practice.

Here is an example:
3mm T weld, 0.8mm wire:
Two passes needed
Electrode consumption 0.1kg/m
Deposition rate 1.9kg/hr
Wire feed rate 8.3m/min
Current 130A
Welding speed 19m/hr

A similar butt weld would take only 125A.

If you run 1mm wire the current jumps up to 170A. The welding speed goes up about 25% also.

Wire speed is generally proportional to current, so when you are learning you will probably use lower current till you get confidence.

Gas welds seem to come out better looking than gasless for me. I do use gasless more often as I don't like the costs associated with hiring cylinders from BOC. Strength is probably similar. Gasless makes SO MUCH SMOKE. Do it outside and in a gentle breeze from behind if possible. A fan blowing gently on you (not the workpiece, as it disturbs the shielding gas) is good for keeping the smoke out of your face.
TRA #13430
L3
"Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

strud
Engineer
Engineer
Posts: 917
Joined: Thu Oct 02, 2008 7:37 am
Location: Central Tablelands, NSW

Re: Welder

Postby strud » Sat Apr 12, 2014 5:19 pm

Quite some time ago I used a MIG for almost everything, but 4 years ago I bought a 180A inverter Stick/TIG unit and must say I would only bother with MIG now if there was a lot of weld length to do.

TIG is awesome for fine stuff and stick is great for the more agricultural ie heavier material.

The unit I bought is something like this :

http://www.machineryhouse.com.au/W163

CS

User avatar
ROCKet STAR
Astronaut
Astronaut
Posts: 1724
Joined: Mon Mar 16, 2009 1:40 pm
Location: Blue Mountains, NSW
Contact:

Re: Welder

Postby ROCKet STAR » Sun Apr 13, 2014 3:20 am

Thanks for the response, guys.

My inclination to go for a MIG was based on this video of Adam from Mythbusters, describing it's simplicity: http://www.youtube.com/watch?v=EA1jeViV4l8

I am thinking that doing a basic welding course may be a good idea, in order to get a feel for it.

I have also been looking into TIG welders, as I would like to learn to weld aluminium eventually, however I am now thinking that I may start off with something in the order of a 150A MIG, for learning purposes. I'll go for one that can accomodate both gas and gasless, so I have both options. I have seen that there are small disposable argon bottles available which while relatively expensive, are probabbly cheaper than renting a bottle from BOC for occasional use.

I'll likely then back it up with a stick welder for where the MIG starts to struggle. From what I have seen, stick welders look to be fairly cheap in comparison to MIG and TIG welders, so would probably make a nice addition.

I'll probably look for a decent TIG setup when I have little a bit more experience.
Chris Barnes

AMRS# 29 - L3

UKRA - L3

User avatar
OverTheTop
It's only money...
It's only money...
Posts: 2636
Joined: Sat Jul 21, 2007 2:20 pm
Location: Melbourne, Australia

Re: Welder

Postby OverTheTop » Sun Apr 13, 2014 10:12 am

MIG is good if you have a lot of welding to do. TIG is good for more fancy stuff but is quite slow.

The stick welder is what gets the most use at my place. Small and portable it is quick to get out and running. I can weld down to about 25A with it so even the thinner stuff comes out ok for what I need.

If you are learning to weld, start at a higher current and work your way down as you skills improve. My dad used to say "Any mug can weld good at 100A!"
TRA #13430
L3
"Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

b-h
Engineer
Engineer
Posts: 536
Joined: Thu Apr 26, 2007 9:32 pm

Re: Welder

Postby b-h » Wed Apr 16, 2014 8:16 pm

Chris,
A small gas mig will weld your test stand fine ,3-5 mm easy. Avoid the gasless wire if possible, It leaves a messy weld and takes a some heavy wire brush work to clean it up especially before painting. Use a quality gas shield . CO2 is cheaper and in some applications it is perfect e.g.: welding reo bar together to be buried in concrete, but again it leaves a messy splatter cold looking weld to clean up. Good quality gas shield = clean strong weld
I have 5 different welders in the shed, all of them can nearly do everything but each of them can weld some jobs better than the others.
"We're going in with the oxy and out with the mig"

User avatar
ROCKet STAR
Astronaut
Astronaut
Posts: 1724
Joined: Mon Mar 16, 2009 1:40 pm
Location: Blue Mountains, NSW
Contact:

Re: Welder

Postby ROCKet STAR » Fri Apr 18, 2014 3:17 am

Thanks for the tips, Steve. I have purchased a 155A machine that is capable of both gas and gasless operation. It sounds like gas operation is the way to go with it. Looking at different gasses, I see that other than straight CO2, an 80% Argon 20% CO2 mix is widely available, as well as straight Argon. Would you have a preference for one over the other for welding steel?

Also, if anybody here has used the disposable cylinders, what is your opinion? Looking at them they are going to be at a lower pressure compared to a cylinder from BOC, and hence contain less gas for their volume. Do you think they are worthwhile for infrequent use?
Chris Barnes

AMRS# 29 - L3

UKRA - L3

User avatar
OverTheTop
It's only money...
It's only money...
Posts: 2636
Joined: Sat Jul 21, 2007 2:20 pm
Location: Melbourne, Australia

Re: Welder

Postby OverTheTop » Fri Apr 18, 2014 10:01 am

The gas welds are far nicer than the gasless.

The disposable cylinders I have used (and also built into a spectrometer I designed!) hold one litre at 60 bar. So that is 60 litres of argon. If you know your flow rate when on the MIG you can work out your run time on the bottle. For very infrequent use it is the way to go.
TRA #13430
L3
"Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

b-h
Engineer
Engineer
Posts: 536
Joined: Thu Apr 26, 2007 9:32 pm

Re: Welder

Postby b-h » Sat Apr 19, 2014 10:46 am

Chris,
I have used straight Argon in the mig on mild steel, It didn't work too well. I only used it because we ran out of mig shield so we pinched a bottle off the Tig.
Argon/CO2 for mild steel apps
Argon/O2 for s/steel
Argon for aluminum
OverTheTop wrote:The gas welds are far nicer than the gasless.

The disposable cylinders I have used (and also built into a spectrometer I designed!) hold one litre at 60 bar. So that is 60 litres of argon. If you know your flow rate when on the MIG you can work out your run time on the bottle. For very infrequent use it is the way to go.
I agree

Small handy disposable bottles are uneconomical except in a case of a small exotic job that requires a different gas .
Small spools of wire can also be obtained along with Spool guns
"We're going in with the oxy and out with the mig"

User avatar
ROCKet STAR
Astronaut
Astronaut
Posts: 1724
Joined: Mon Mar 16, 2009 1:40 pm
Location: Blue Mountains, NSW
Contact:

Re: Welder

Postby ROCKet STAR » Mon May 05, 2014 3:21 pm

I was able to have a play with my new MIG welder yesterday. I cut some short lengths of steel box section, and tried to run some welds along them. The first few tries were terrible! All spatter and porous. A bit of experimentation with current, wire feed and gas flow, and they started to improve. I'm going to need some more practice, but I think I'm getting there!


weld.JPG
weld.JPG (84.05 KiB) Viewed 2221 times
Chris Barnes

AMRS# 29 - L3

UKRA - L3

rocket_troy
Engineer
Engineer
Posts: 1005
Joined: Thu Oct 09, 2008 9:30 pm
Location: Melbourne Australia
Contact:

Re: Welder

Postby rocket_troy » Mon May 05, 2014 3:33 pm

and for those in QLD who are serious about their rocket projects :P
http://www.dominiongroup.net.au/cms/webroot/send_file.php?file_name=ON145+BROCHURE.pdf

TP
ERG #02


Return to “How to's”

Who is online

Users browsing this forum: No registered users and 1 guest