Long stick-out...

[Davek0974]

Hi all,

i'm teaching myself MIG on a MigMate 170 Pro with 0.8mm and pub Co2.

After trawling this site, i realiser that these budget machines have flaws mainly related to the wire feed, and mine is indeed 'variable' which is a pain, i have tweaked the controller settings but it seems to be just bad/cheap design or poor regulation of voltage etc.

A drop-in replacement upgrade board would be a good seller.

Anyway, what i'm asking is this...
When i reach the end of a run and release the trigger, i am left with a long stick-out (3/4" - 1") which needs to be trimmed back to the 1/2" i like to start with. Is this caused by the unit or me?

If i release the trigger before moving the torch away, it usually welds the wire to the job which needs flashing off and then trimming. If i leave the long point and then start a run, i get a lot of spatter at the start.

Any suggestions mauch appreciated. I will post some pics soon.

Dave

 

[weldequip]

You may be running too much wire speed, although it is normal to have some wire stick out after finishing a run. Some of the higher end machines have "Burn-Back" control which burns back the wire for a split second, so you don't need to keep snipping it back manually.
So I wouldn't worry too much (although the SIP's erratic wire feed doesn't help!)
weldequip

 

[shenion]

Sounds like the wire feed does not have good braking so it does not stop quickly.

I could do a board for these SIP's. But unless I could get enough quantity, they would be too expensive. Don't know the replace mt costs of the boards, might be worthwhile considering the markup they charge.

Yes, it is a poor design.

There is posts here about changing the pot inthe SIP's for a bit better wire feed.

 

[Davek0974]

Thanks for the quick reply, great forum.

I tried setting the wire speed by holding the torch against a lump of scrap and twiddling the knob with the right hand. It seems happiest about 1/4 turn up from bottom.

I probably need a fair bit more practice but i am very happy so far, i'm building push along order picking trolleys at work using 25x25x2mm tube and they turn out great, self design, prep, build and paint, its very satisfying and makes a change from the normal day job of production manager

Off the shelf units are about £230, i can knock these out for about £50 so it saves them a lot of money and i get a nice welder

Dave

 

[Davek0974]

Sounds like the wire feed does not have good braking so it does not stop quickly.

I could do a board for these SIP's. But unless I could get enough quantity, they would be too expensive. Don't know the replace mt costs of the boards, might be worthwhile considering the markup they charge.

Yes, it is a poor design.

There is posts here about changing the pot inthe SIP's for a bit better wire feed.

Hi,
I did read somewhere about changing the trim pot to a 100ohm unit to improve bottom end control, might try that.

Thinking about it, the feed motor does tend to slow down rather than stop dead when i release the trigger.

Surely a replacement board would just give the same fault? If you get the time, try pricing up a new board, it might be acceptable. I dont know yet but i would happily pay £20-£30 to get good wire control.

Dave

 

[shenion]

A good controller will short out the motor when it turns off. That will act as the brake as the motor acts like a generator.

To get that kind of price I would need to make dozens of boards. Bare boards cost me $33US/each for the first 10 or so. Then they get cheaper, probably $10/100. Add the parts and assembly costs and they would be above what you would pay.

 

[Davek0974]

How about a kit form of upgrade then.

You supply the board and parts list, wiring diagram, installation instructions etc. The builder orders the parts locally and assembles it themselves. I would definately go for that as i've probably got most of the parts.

Dave

 

[Alex]

Fiberglass UV exposed and then ferric etched will suffice, I can do all of that and tin plate the copper for long term use. I know its not silked screened production quality but its just as robust.

That being said the real problem with the SIP is the physical wire feed assembly, maybe somebody could CNC a motor wire feed unit from solid aluminium, or get a wire feed unit from Clarke and modify it for use on an SIP, however in reality your best off cutting your losses and losing the SIP all together.

Have you noticed on Northerntool USA they sell top brand Hobart, lincoln etc and on UK Northerntool they sell Sealey type quality?? Plus they charge nearly twice as much for a Honda GX340 in the UK northerntool compared to USA.

http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200325745_200325745


http://www.northerntooluk.com/products.asp?partno=6065E

 

[Davek0974]

Everything is more expensive in the UK

Anyway, how about a wiring diagram for the controller?

Making a complete wirefeed should not present much headache. Simply a geared motor driving a pinchwheel. Once the feed chassis is set, the motor can be any size.

Hmm, i feel a project coming on here.

Question one, how does the standard setup alter the basic wirefeed rate in sync with the power settings?

How about a continuously running geared DC motor (I'm thinking car wiper motor - plenty of torque) coupled to the pinchwheel via a small magnetic clutch/brake unit as used in photocopiers etc. This would give instant start/stop. If the motor was a decent size in the first place, the speed should be pretty constant without feedback or loop control, i dont think the load on it varies too much when welding.

Sorry, im getting carried away

Still, i'll add it to my pile of projects

Dave

 

[Alex]

Adding an improved wire feed controller is not going to make a huge difference, its physically a poor mechanism.

A good motor would be something like a Schumacher or Trinity or Orion 540 size, though not really necessary.