Motoman SK16X wire feed alway feeding at high speed

  • Hi everyone, I'm new in this robotic world. I own a motoman SK16x since december and I now have a problem with the wire feeder. The welder is a motoarc 350i ( model Arc-master 351 ( 350i) . No matter if I start a job in play or if I try to feed out manually, it always comes out at the highest speed. Is anyone has ever seen that issue ? Thanks in advance for any help provided !

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  • What welder interface do you have on that robot a UWI or a HUWI. It will be mounted on the inside of the controller door.

    When the feeder is running at full speed all the time, with no speed control, it is an indication the tachometer my have gone open. Can you test the voltage back from the tach?


  • Thank you for the quick reply ! I didn't found electrial diagram yet. Do you know where I could find it ? Also, how can I find the info if it's a UWI or a HUWI ? If it can help to pinpoint the problem, I did some test yesterday. I've retry to retract the wiring and then make it feed out, the speed returna to normal. How does the tachometer works exactly ? Is it a mechanical part inside the feeder motor itself ?

  • Is there something mounted on the inside of the door? If yes, post a picture. It's very hard to describe the differences between UWI and HUWI.

    A tachometer is part of the motor. It can be optical or like a little generator that sends a reference voltage back to the the speed control circuit. In the case of an optical tach it sends a pulse stream to the speed control circuit. Either way, if the tach is bad, or the cable to the tach goes open or the motor control circuit is bad the motor will run full speed "thinking" the tach is not giving the correct voltage or signal. With some of the REALLY OLD systems (known as PWF) the tach has brushes that grind away and fill the bottom half of the tach enclosure causing a short to ground and the motor runs full speed.


  • To update this post, I've reopen the feeder motor and by doing so, I've notice that 1 brush for the tachometer wasn't properly doing the contact ( the spring wasn't properly in place) So the problem at first was exactly what you told me. ( the tach brush has a build up of " brush dust". Thank for all your help !

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