replacing wire pushing motor

[kibodwin]

When welding I can hear the motor that pushes the wire changing
pitch. I think (but this could also be due to inexperience..) that this
change in pitch also makes a change in wire speed feed rate, if only
ever so slightly.
I have not opened the welder but is it possible to open up the welder
and change the motor out for a replacement part? Are there any precautions
needed when opening the welder? Is there something else I should be looking at
before opening up the welder?
It is a cheap chinese knock off but I should be able to find a like for like replacement
motor.
K.

 

[GrahamGKD]

I think I’d be inclined to check whether the change in pitch / wire speed is caused by some other factor before changing the wirefeed motor – e.g. is the wire clean (not rusty) and running freely out to the torch. The change you are hearing could be caused by varying load on the motor because of friction in the liner or the torch itself?
Regards opening up the welder – the obvious precaution is to unplug it from the mains beforehand!

 

[kibodwin]

Hi Graham,
I would have unplugged it first. I presume there are no capacitors or similar in
the welder looking to hurt me!?
The wire is new and rust free and the liner seems ok. I put some compressed air through it and the wire runs freely through it so I dont think its the liner.
I can weld with it but I though that for the price of a replacement motor it might be worth
the upgrade and it might even improve my welds! The change on pitch varies during
welds and is not constant this is why I suspect the motor.
I will take a look inside the welder tonight and see if the motor has a serial no.
Thanks for the reply.
K.

 

[GrahamGKD]

Hi Kibodwin,
Just thought I’d mention the unplugging thing – no doubt we have all done it!
There could be capacitors inside but they should be fairly easy to spot (shaped like cans). If there are you can discharge them with a resistor or similar load.
I’m sure I’ve read somewhere that less well specified machines use a crude tapping from the welding output to provide the source to drive the wirefeed motor – hence you will see threads on here about SIP owners modifying their machines to use a stabilised supply for the wirefeed. Is this something that used to be fine with your machine and has now become a problem or could it just be a design feature of the machine?

 

[kibodwin]

Hi Graham,
I suspect it is going to be a 'design feature' of the machine!! =)
I can live with it for now but it will end up getting looked at.
As I am a bit wary of poking around in something that produces large
amounts of Amps I will not attempt ant modifications.
The machine has been like this since I got it. I am upgrading from flux
core to gas in the coming weeks so this will get fixed after this.
You mention others use a stabilised power supply to the motor, would it be worth
or safe to put a multimeter on the positive and negative of the motor to see
the fluctuations in power supplied? I would then see if it is the motor or its power supply.
K.

 

[the snooper]

with a lot of the smaller cheaper machines the wire feed motor is connected to the welding transformer so it changes speed when the voltage (power)setting is altered so when you arc up it will affect it, its a known problem on SIP machines

 

[kibodwin]

it sound dangerous to mess around with, I will take a look and see but if it is as you say
then I am leaving it alone and living with it. At least I will know what to look for when I get a new mig welder!
thanks for the pointer.
K.

 

[mike 109444]

Kibodwin Be aware that the motor will be DC so make a note (or pic) of which way round the two motor connections go, you don't want the motor running backwards!

 

[kibodwin]

I hope they are the standard red and black but being a cheap
knock off this might not be the case. I will keep an eye out for the polarity,
thanks for the heads up though.
K.