Welder mods.

[Dave Plowman (News)]

I've successfully managed the repairs on the Rover wheel arch liners - not a tidy job, but strong and you can't really see it anyway.

So am thinking on modding my SIP MigMate 130 Turbo. A method of changing the polarity for gasless wire, and improving the wire feed.

I've not even opened it up for a look yet, so these are just thoughts.

Presumably the gas/gasless models use a switch? Can't seem to find one aftermarket anywhere, and SIP spares are expensive. So I was wondering about using terminals and jumpers.

Looking for large insulated posts for panel mounting has drawn a blank so far - something like a larger version of a panel mounting loudspeaker terminal is what I want, but in 10mm or so, and with insulated nuts.

As regards the wire drive motor I was thinking along the lines of converting it to PWM drive. Assuming it's not already.

[Andy Dingley]

If it's anything like SIPs I've previous done battle with, it's not the motor that's the problem, it's the roller drive's inability to grip the wire.

[Dave Plowman (News)]

That bit seems ok on mine - you can adjust the friction between the drive wheel and wire. But the actual speed varies dramatically at the slow end which is where it's critical for me. You can here the motor speed changing on its own.

[Dave Plowman (News)]

^^^^

[Andrew Mawson]

liners - not

changing

thoughts.

wondering

loudspeaker

Dave,

Ask on

the forum there will have someone who has already done it !

AWEM

[Jules Richardson]

Hmm, give Matty F from here a prod - he was making his own insulators for tram work and doing a really good job. You could maybe make your own to take a regular bolt to use as a terminal and provide the insulation barrier between the bolt and surrounding metalwork. Drill a hole through the bolt to take the wire.

For the nuts, perhaps there's some form of plastic you could heat and dip them in to cover them (then just lightly drill either side and remove the plastic from the threaded section once it's set) - or cast something to take the nut using the same insulating material as for the bolts.

(why do the nuts need to be insulated? If they're securing thick wire, I'd be concerned that you couldn't get them tight enough by hand - would a regular old nut, tightened by a spanner, and with a flip-up insulated cover not do? Tie a bit of rope to the spanner and hang it on the machine so it's always nearby)

cheers

Jules

[Mark]

Some time ago someone on that forum completely redesigned the speed control for that welder using a separate 24v ? transformer and circuitry. Unfortunately its such a busy forum, i now cant find any reference to his web page which had all the construction details.

[Dave Plowman (News)]

I did do a Google, but found some dreadful bodges. Since those were the first hits, decided I'd probably better going my own route.

[Dave Plowman (News)]

One of my cars has exactly what I need - it brings the battery cable through the bulkhead. Sadly. it's an old car and I can't find that bit as a spare. But it seems to me it would be a common stock part - if only i knew where. Couldn't find it at RS or any of the car wiring specialists.

I was hoping for something which didn't need a tool to use. I have a disconnect device on the car battery which is simply a thumb wheel and that handles the same sort of current.

[Bill]

In message , "Dave Plowman (News)" writes

Marine supplies? Similar to these?

[Dave Plowman (News)]

That sort of thing, but it would be easier to make up something similar than import from the US. ;-)

[Jim K]

my old mission speakers have chunky screw terminals on them - wire goes though the boly bit and secured by plastic coated nut....in red and black too ;>)

Jim K

[Dave Plowman (News)]

Drawn out the circuit, and it's crude in the extreme. It basically uses the same volts as the welding side to drive the motor via a simple one transistor controller, with no regulation. So unless the welding part is drawing constant current, the drive to the motor will vary with that. So I'm going to drive it off its own PSU. A quick test shows that PWM drive increases the torque at low revs dramatically.

[Jim K]

when my sh1tty draper mig's wire feed slipped (s*1t rollers too) the motor sound/pitch would change too....

Jim K

[Andy Dingley]

Slower (dodgy motor / drive)

or faster (slipping roller) ?

[Dave Plowman (News)]

Presumably it slips because of increased drag somewhere on the wire? There is a mod said to help which involves a steel strap between the roller bearing arm pivot and a drive roller housing fixing screw - said to stop the plastic flexing.

However, if you remove the wire and run the motor at slow speeds, you can slow it down easily by gripping the drive wheel. Much more difficult with PWM drive.

Thing is I had all the bits lying around for this mod. Buying new might not make it cost effective. I should finish it tomorrow and will report on whether it actually makes welding thin stuff easier.

[Dave Plowman (News)]

My guess is not enough torque from the motor at slow speeds.