HF start question

[CRS51]

Hello all have been doing quite a bit of welding with my new Rtech welder but have come up against a problem. When using the hf start on very thin aluminium the first second or so seems too strong a current and melts the material or blows a hole in it.
Also can't manage to use the 1mm tungstons on aluminium as when using the hf it melts the tungston to oblivion and the tip ends up inside the ceramic.

Have been trying 1mm tungston on .75mm sheet using 1mm filler rods, gas is 8lpm, amps have been set to 46 max and have tried down to 10 (lowest setting) also using the foot pedal, have tried pulse on and off but to no avail. Manages to use the 1.6 tungstons ok, have tried both zirc and lanth tungstons.

Is 10 amps too much for a 1mm tungston or is it the machine is giving out too much current on start up for the hf start ?

Any advce welcome

Chris.

 

[hotrodder]

A 1mm tungsten should be able to handle from 40ish to 60A (maybe a touch more) max depending on AC balance settings. You haven't said what your balance settings are but IIRC R-tech do things backwards to conventional in that turning the balance up (higher number) increases the %EP. With most inverters for most scenarios less than 65% EN (or more than 35% EP) just gives the tungsten a harder time with no improvement to weldpool cleaniness

Sub 1mm ally is the wrong way to go while learning. Besides being frustrating you're more likely to end up getting bad habits which'll hold you back/slow down the learning process. With 2 or 3mm material everything happens slower... instead of worrying about/constantly blowing holes you can concentrate on reading the weldpool, maintaining a consistant arc length etc etc

 

[CRS51]

Thanks for the tips hotrodder, I have tried altering the balance on the machine - you can set it from -30% to +30% on my machine and I have tried it at both extremes and many settings inbetween, best thing is for me to get some pics up tomorrow for everyone to have a look at.
Also need to take a trip to the local scrap merchant for some more plate
thanks
Chris.

 

[Paul G]

Hi Chris.

I'm not familiar with your welder but I assume it has a soft start / slope in, or whatever it's called by RTech.

On my Miller I can set start amps, time to ramp up, main amps, time to ramp down, and finish amps.

I wonder if you have this set correctly as on the Miller I can in theory set the start amps higher the the welding amps.
(The _/-\_ button.)
If I use the foot pedal this over rides these settings however.

The pics show a welding current of 50 amps but a start current of 70 amps. ( relevant LED's arrowed ">" )
For welding at 50 I would normally set the start amps at around 20.
If you can set the RTech in a similar way this may help.

Cheers,
Paul G

 

[CRS51]

Thanks Paul, will have a look into it the next few nights.
Have taken some pics from this mornings attempts,
.75mm aluminium and also found a few bits of 3mm aluminium too. Now someone has been in and borrowed the wire brush
The thicker material was done with wp26 and 2.4 tungston at 150 amps (max) the thinner material was done with the wp9 and 1.6 tungston at 45 amps (max) no pulse and hf start.
You can see particularly on the start of the thinner material runs that the hf start gives quite a big push of energy for the first second or so and then settles down. Is this how it works or am I doing something wrong ? Have been using the foot pedal so I can reduce the amps as I get closer to the edge of the material.
Third picture down, near top centre, is where I tried a 1mm tungston and it just melted and dissapeared up inside the ceramic.
Is it better not to use the foot pedal and hf start together ?
More practise needed !!
Cheers Chris.

 

[hotrodder]

You can see particularly on the start of the thinner material runs that the hf start gives quite a big push of energy for the first second or so and then settles down. Is this how it works or am I doing something wrong ? Have been using the foot pedal so I can reduce the amps as I get closer to the edge of the material.

The white area is the 'etched zone' that results from the 'cleaning' effect of the EP phase of the arc. There's various reasons for the larger etched zone surrounding the starts including technique and base metal cleanliness.

Is it better not to use the foot pedal and hf start together ?
More practise needed !!
Cheers Chris.

Most TIG sets won't do lift start in AC. HF start + pedal is normal, if you barely press the pedal when starting then the HF can end up running for longer and/or the arc can dance around some while it's trying to establish itself.

First thing i'd suggest is re-reading the TIG tutorial and following it's advise. The welds on the thin ally look for the most part as though you're melting the wire with the arc. The welds on the thicker material look a lot better but you're not doing yourself any favours with the material- tiny offcuts that are manky/heavily oxidised. New material and larger pieces will make life MUCH easier. One way of avoiding loads of wastage is to cut a bunch of small strips and tack them together to make two larger coupons...


which you can then switch between as a means to control heat build up. Buy yourself some 25 - 50 x 2 or 3mm flat bar (cheap as chips from your local metals stockholder in steel or ally and easy to cut into manageable lengths with a hacksaw in the carpark) and it'll be very easy to make the coupons. Can tack them up in a kinda W shape to practice fillets/outside corners too

 

[Drains]

Are you starting the weld by pressing the button on the torch, then using the pedal? If so, you're starting at maximum amps then bringing it down. Just weld with the pedal.
FYI, the HF is present throughout on AC (although probably not on your set as it'll be using a square wave), but even on DC, if you are using the pedal, nothing else is required to start/stop or control the current.

If you are only using the pedal you need to check there's not some minimum current setting or suttin. You should be able to bring in the amps from the set's minimum level of what, 5A or so?

 

[CRS51]

The white area is the 'etched zone' that results from the 'cleaning' effect of the EP phase of the arc. There's various reasons for the larger etched zone surrounding the starts including technique and base metal cleanliness.


Most TIG sets won't do lift start in AC. HF start + pedal is normal, if you barely press the pedal when starting then the HF can end up running for longer and/or the arc can dance around some while it's trying to establish itself.

First thing i'd suggest is re-reading the TIG tutorial and following it's advise. The welds on the thin ally look for the most part as though you're melting the wire with the arc. The welds on the thicker material look a lot better but you're not doing yourself any favours with the material- tiny offcuts that are manky/heavily oxidised. New material and larger pieces will make life MUCH easier. One way of avoiding loads of wastage is to cut a bunch of small strips and tack them together to make two larger coupons...

View attachment 28097
which you can then switch between as a means to control heat build up. Buy yourself some 25 - 50 x 2 or 3mm flat bar (cheap as chips from your local metals stockholder in steel or ally and easy to cut into manageable lengths with a hacksaw in the carpark) and it'll be very easy to make the coupons. Can tack them up in a kinda W shape to practice fillets/outside corners too

Hotrodder, thanks for the help, I'm getting some new material this weekend so more practise pics will be up soon.

Are you starting the weld by pressing the button on the torch, then using the pedal? If so, you're starting at maximum amps then bringing it down. Just weld with the pedal.
FYI, the HF is present throughout on AC (although probably not on your set as it'll be using a square wave), but even on DC, if you are using the pedal, nothing else is required to start/stop or control the current.

If you are only using the pedal you need to check there's not some minimum current setting or suttin. You should be able to bring in the amps from the set's minimum level of what, 5A or so?

Drains, thanks also for the reply, when the foot pedal is plugged in it overides everything else so yes it's pedal only. The minimum current on my machine is 10 amps.
Have tried pressing the pedal fully down when starting and also just enough to get it started but it always gives out a pile of energy which see's off the 1mm tungstons.
Cheers Chris.

 

[chevy2]

I've a 200amp r-tech machine and find that 1.6mm white tungstens are fine for thin sheet ali,
Maybe go up a size to 1.6mm?