Welding Tips and Tricks

I've started a college course to refresh my mig skills. I realise getting the right wire speed and voltage combination is vital.
The set uses 0.8mm solid wire (which I think equates to 0.035" wire). The material is 1/4" steel plate and the gas is 95% Argon and 5% CO2, I believe.

Having Googled to get some advice on setting up, my procedure - which Ill try next time I'm at college - would be as follows, if I've understood things correctly

Obviously, with experience one would soon set the machine up for dip transfer "sizzling bacon", but until then I guess you have to do some sums to get to the right start point.


1 Amp per 0.001" of workpiece - in my case this would be 250 Amps, but I see that 0.035 wire has a range of 50-180 Amps, so I guess one would want 180 Amps (being unable to use thicker wire). The burn rate for 0.035 wire seems to be around 1.6 inches/Amp . 180 x 1.6=288 inches/minute.

Using the tip on this site, I would aim to set up for 29" of wire feeding in 6 seconds.

Then I'd aim to set the voltage so that with this wire speed, I got the ideal weld bead - and sizzling sound.

This all sounds good in theory but I'd really be grateful to know if it's the proper way to go about things. (So far, under guidance, I've been starting off with a voltage - around the high 20s or even 30V) and then adjusting the wire speed accordingly, but I'd like to be more methodical about setting up.

Comments please.


Many thanks

Martin

Is there any reason you are either not using the various set up recommendations supplied with/on the welding unit or that are available through referencing the many tables available on the Net? The information available through those means would get you into a good start position and then you could adjust accordingly.

martinr,

That gas ratio seems incorrect. I typically use Ar-75/CO2-25.

Wob

Im pretty sure the 1 amp for every .001 thickness rules is only for single pass welds, so keep that in mind. Im also kinda sure that that rule only applies to the lower guage metals, but I could be wrong on that. It would also depend on the joint configurationan and type of metal too.

Keep in mind too that your amps will vary with your voltage, and visa versa. Basic electrical theory(about all i know lol)= (Volts x amps)=watts(power, or in the case of welding, heat). Ohms (resistance) figures into that somehow, which is why yuo need to add more voltage if your running longer welding leads (because more resistance)

1/4" plate @ 30v is to high. Set machine to 23 volts @ 380 and adjust from there. 75/25 gas .035 wire. mage sure you have no oil or dirt or other crap on the plate. All doors to shop closed and fans off, wind is your worse enemy. let me know if this helps. good luck.
Anthony

Anthony is right. 30v. is too hot even for .045 dualshield on 1/4" His recommendation is a great starting point, and your final settings will vary by machine. On carbon steel in 3g/3f, I commonly use about 22.2V and 350 ipm and push the weld (for uphill--for downhand, the gun angle is the same, but appears as dragging). In 4g/4f, I'll increase wire speed to about 380 and push the weld.

Most dedicated MIG machines are CV, or "constant voltage", meaning the weld current is a function of wire speed. Higher speed (short-circuit welding) equals higher welding current.

Good luck,

Steve