New user with Cosmo 170 (SIP) and a headache

[malcolm]

I'm not convinced it's a control issue. We tried my SIP 130 which still has the PWM controller fitted and it had the same problem. Takes a number of seconds to get to speed - maybe 3 seconds - you can hear the whine as the speed changes.

Don't know what the problem is though. Would a voltage measurement over the start help?

 

[R Kraft]

It would be good to know the voltage that they run at various speed.

Without decent feed back from the motor,it would be like driving a car with one gear.
Robert

 

[BChild]

It would be good to know the voltage that they run at various speed.

Without decent feed back from the motor,it would be like driving a car with one gear.
Robert

Hi Robert

Explain to me (for the benefit of those in the cheap seats) how I would go about measuring the voltage and I'll use my multi meter to get some readings accross the range of the motor speeds

 

[shenion]

Measure the voltage on the motor terminals with the speed set to minimum and max.

 

[Robotstar5]

I'll use my multi meter to get some readings accross the range of the motor speeds

A digital meter will probably be all over the place, try to use an analogue meter if you have one

 

[BChild]

Now getting hacked of with it..............

right so I needed to do some heavier work 5mm thick angle iron to make some frames

I'm still using Co2 (10-12 L/min)
I've changed the welder over to 0.8mm wire (tip, roller and wire)

I've done nothing to the welder since the training session so based on what I learnt at Malcolms I needed to run it fairly near the max or at max

(I have of course done a few bits of welding but I'm finding the thin stuff frustrating without Argoshield light so I'm using up my CO2 on a couple of heavier projects and the difference between argo and CO2 on heavier stuff isn't much)

I tried Max but that was quickly rules out cos it popped the fuse in the plug and after that it popped the fuse in the garage supply so Power five was my max

Started with a guestimate of 35% wire speed and damned if it wasn't quite close to the mark right from the off (I'll use percentages cos it's a 10 turn pot so 350 in number or 3.5 turns)

Welded a few bits up and then something strange happened - I could feel it pushing away from the work - dropped the wire feed to 30% and carried on - little bit later it started pusshing again - dropped the wire speed to 25% and then the thermal overload put paid to progress for a while

After a break to cool I went straight into it but had to drop the wire speed again as I could feel it pushing.

In a nutshell after a night of constant adjustments I ended up finishing the task with a wire speed of 5%

I tried a test piece of 20 guage and had to turn the wire speed down to min and on min power I got the unstable arc on CO2 I've always had but it improved on the next power up and I was able to do some nice runs on power two with wire speed on minimum

I went back to Power 5 and 5% wire speed and on some scrap left over and results were just the same - any increase in wire speed resulted in a lot of pushing

So I'm now very confused and a bit tiddled off

I know the zero point has shifted and the wire speed is a bit quick at zero (need to change the trim mpot to a 100 ohm one)

I know my transformer is 24V which is a bit high so my wire speed is biased to the bottom end of the range

Why on earth is a good setting becoming a bad setting after a short time

The only factor I can think would influence the settings is heat rising in the work means you need lower wire feed (lower amps) but from 35% down to 5% just doesn't make sense.

I wouldn't mind betting now I've come in and had a cup of tea and done some other stuff I could go out again and with the same settings as I left it on it'll burn the wire back to the tip if I try to weld with it and I'll need to replace the tip and turn the wire speed up to 35% again (then the process with happen all over again)

I'll try it tommorrow instead so I've had enough tonight!!!!

 

[BChild]

I wouldn't mind betting now I've come in and had a cup of tea and done some other stuff I could go out again and with the same settings as I left it on it'll burn the wire back to the tip if I try to weld with it and I'll need to replace the tip and turn the wire speed up to 35% again (then the process with happen all over again)

I'll try it tommorrow instead so I've had enough tonight!!!!

Sod it I went out and tried it - seriously welded the wire to the tip on the previously used settings had to remove and replace

Kept increasing the wire speed untill I got pushing (30%) and ended up at 25% wire speed laying down nice runs on 5mm steel - same as before it started pushing again shortly after a couple of runs and before a short space of time I was back to 5%

Something isn't right and I can't believe the heat built up in the steel would have that big an effect

 

[R Kraft]

It could be that the drive transistor is heating, the heating would make the bias on the transistor change.
The warmer a transistor is, the less bias it needs.
In some uses it would be called thermal run away.
Robert

 

[malcolm]

I had a similar thing once - the wire speed would double after running about 10m, and it didn't need to be welding at the time, just feeding. That was a faulty capacitor.

It'll be the speed control circuit. You'd not normally need to change the wire speed while welding.

 

[BChild]

I had a similar thing once - the wire speed would double after running about 10m, and it didn't need to be welding at the time, just feeding. That was a faulty capacitor.

It'll be the speed control circuit. You'd not normally need to change the wire speed while welding.

I've slept since yesterday and I think I need to establish if the wire speed is actually changing

Stop watch and tape measure time

I'll power up the welder - set it to 30% measure the wire feed speed m/min and then change it to 5% and measure it there without having sparked up.

Then I'll go thro the same excercise as last night (should take long about 15 mins of welding activity) and then measure the wire feed speed when I've been forced to drop it down to 5% and it's still welding. Then I'll change it to 30% and measure it there too

Should have a good comparison to look at

If it's not wire feed speed changing it will be a WTF moment

 

[Jake SS]

Had a customer bring in a SIP 100. I immediately broke out in a sweat!

Anyway got it going.
Thought I might have a play with it.
.8 wire
corgon 5/2 gas, equiv boc light I think
Max open circuit 33vdc
Welded with it, pretty good actually, fairly smooth considering.
19vdc load @ 71amps was sweet spot for material

Added a 10,000uf cap.
Max open circuit 44vdc
Same load volts 19, @ 71amps
But had to reduce wire feed a notch.
Wave forms were interesting, may have a play with the inductance, the cap smoothed out the wave forms but it seemed to be a bit course when welding.

I was on my own when doing this so had to operate camera, watch meters, etc. so was a bit difficult. I did not have it on my load bank which makes it more difficult.

I am not real flash with the pics part but see how it goes!

1 motor no cap
2 motor with cap
3 open circuit no cap
4 open circuit with cap

 

[R BEADLE]

hi to change you pollarity you you change the wire from your torch from the + to the- and vice versa . thats the quick release coupling on the front of your machine .

 

[BChild]

I've slept since yesterday and I think I need to establish if the wire speed is actually changing

Stop watch and tape measure time

I'll power up the welder - set it to 30% measure the wire feed speed m/min and then change it to 5% and measure it there without having sparked up.

Then I'll go thro the same excercise as last night (should take long about 15 mins of welding activity) and then measure the wire feed speed when I've been forced to drop it down to 5% and it's still welding. Then I'll change it to 30% and measure it there too

Should have a good comparison to look at

If it's not wire feed speed changing it will be a WTF moment

OK Some Data

Cold welder power on no welding just wire speed measurements in m/min

0% - 1.56 m/min
10% - 3.96 m/min
20% - 5.04 m/min
30% - 6.00 m/min

Start welding

5mm Angle Iron
welder set to power 5 (one down from max)
Wire speed 30%
Shielding gas CO2

5 inches of welding fine nice pool good sizzle happy days and then as expected it started to push

Drop to 20% and another 6 inches of welding and soon into push again

Drop to 10% and 2 x 5 inches of welding run and here comes the push

Drop it to 5% and I got a short distance till I remembered this is about the time when I trip the Thermal overload so stopped

Tape measure and stop watch

0% - 2.88m/min
10% - 5.28 m/min
20% - 6.36 m/min
30% - 7.20 m/min

So now I know it's wire speed changing as opposed to power level changing - next question is it related to welding activity or is it related to time the welder spends switched on (as suggested in Malcolms post a page or so back)

Only thing I can do to establish that is leave it to cool overnight and then tommorrow switch it on and leave on for say 30 mins and then measure the wire speeds at the same settings as before

Now I really feel frustrated

 

[BChild]

Am I out of my mind to continue persevering with this bloody SIP/Cosmo?

I am beginning to wonder is I have had this problem all along and if the modifications have accentuated the issue or I've caused the issue with the mods and damaged part of the control board?

At least I know Gas choice isn't the problem working on thicker steel (cold starts are still an issue on thin stuff although I actually notice it less on 0.8mm wire (I do make more holes with 0.8mm!!)

Still it's one of the longest running threads in the SIP section - even if the machine is still less than perfect!!

 

[BillJ]

Am I out of my mind to continue persevering with this bloody SIP/Cosmo?

You must be close now. Mine doesn't do this and despite mine being regulated and yours not, I can't see anything in your mod that should cause this behaviour as long as you haven't made any mistakes in the wiring.

The next step should be to measure the output voltage of your rectifier before it enters the motor control board before and after the speed has drifted. This will tell you if the voltage from your mod is drifting. If so, there's something wrong with your mod. If not, then it must be the control board. Confirm this by measuring the output voltage of the board (across the motor) before and after the motor speed has drifted.

 

[BChild]

You must be close now. Mine doesn't do this and despite mine being regulated and yours not, I can't see anything in your mod that should cause this behaviour as long as you haven't made any mistakes in the wiring.

I wish I felt the same.............. but for the house boiler dying last month and the inevitable £1200 replacement costs I'd have bought a portamig and said sod it - can't make a silk purse and all that

I don't think I've made any mistakes with my wiring but electrickery ain't my strong point

The next step should be to measure the output voltage of your rectifier before it enters the motor control board before and after the speed has drifted. This will tell you if the voltage from your mod is drifting. If so, there's something wrong with your mod. If not, then it must be the control board. Confirm this by measuring the output voltage of the board (across the motor) before and after the motor speed has drifted.

Right - you've lost me already - Transformer mod measure the voltage supplied to the control board then measure the voltage after (accross the motor) Please excuse me for being really thick here but you can't generate electricity in a control board can you?

What goes in surely comes out doesn't it

Like I said - electrickery..............

 

[BChild]

I hate being less than positive so in other news it's nice that I can feel when things aren't right and I now know how to correct the problem but the frustration stems from knowing I shouldn't need to "correct" anything.

Malcolms training session was a hugely usefull exercise I'm just not moving up the learning curve cos nothing stays constant - adjusting the welder to get consistant results when nothing is changing just piddles me right off

Sorry on a serious downer when its stable and warm it works OK for a cheap welder certainly better than when I got it out of the box

 

[BChild]

Right - you've lost me already - Transformer mod measure the voltage supplied to the control board then measure the voltage after (accross the motor) Please excuse me for being really thick here but you can't generate electricity in a control board can you?

What goes in surely comes out doesn't it

Like I said - electrickery..............

Ahh having slept

So it could be my transformer changing it's output voltage - as a result the voltage to the board changes and so the output from the board changes the motor speed

Thats what we need to bottom out whats changing where - OK tonight I'll have another look at the damn thing

 

[BillJ]

Right - you've lost me already - Transformer mod measure the voltage supplied to the control board

Just to check that the voltage supplied to the control board remains constant as the motor speeds up. If not, something is wrong with the mod (not just the wiring, maybe a faulty part) and this would be the cause.

then measure the voltage after (accross the motor) Please excuse me for being really thick here but you can't generate electricity in a control board can you?

What goes in surely comes out doesn't it

No. The control board's job is to reduce the voltage by an amount controlled by the knob on the front. If, say, it were to reduce the voltage by a lot initially but then over time (a component warming up?) reduce it by less and less, that would give the symptoms you describe.

This could also depend on the load presented by the motor, though. If the motor (or the mechanism it is driving) were stiff initially and then freed up gradually, again you could have the symptom described. Thick grease warming up in the gearbox or something like that?

All speculation but...

 

[BillJ]

Thats what we need to bottom out whats changing where

Exactly!