Many years ago I was an engineering co-op with a set of chores that included keeping track of motor rebuild projects, mostly for rewinding and new bearings. Spending capital on new motors wasn’t even a gleam in the management’s eye.
The rebuild company was local, and I had an occasion to see the job firsthand. I recall lots of manual winding and a lot of scrap.
I remember being surprised at how they stripped insulating varnish off the stators prior to rebuild. They doused them with kerosene, lit them on fire under a big exhaust hood and burned off the varnish — without apparent concern about pollution implications.
Actually, the whole varnishing function surprised me. Once stators were wound and retested, they were transported to a varnish holding tank, dipped in the resin several times and then transported to an oven where they baked for about 12 hours. That was a long process time, but had to be done right. The insulating varnish increases a motor’s thermal conductivity and mechanical stability, and it protects against voltage transients.
As with the varnish burn, I would have thought, with all the improvements in resin technology over the years, that process had been greatly streamlined.
Fast forward to November 2007, and why I mention this becomes apparent: I spent a day at Baldor’s new, medium-size motor plant in Columbus, Miss.
This is a well-run factory. The employees exhibit genuine enthusiasm toward customer service and have an appetite for satisfying rush and custom orders.
The machining centers, some new, are versatile and Ethernet-linked for program downloads from within or from company headquarters. The factory has both automated and manual stator-winding stations.
But much to my surprise, the insulating varnish step is pretty much as I saw it all those years ago. The stators are automatically transported, dipped and swirled in resin pots 10 or 11 at a time, and then baked and cured for seven hours.
Local management is moderately aware of other varnish application alternatives, and I’m sure there are faster-curing resins, but they are comfortable with the resultant quality in what is a critical step. The varnish application process is a clear production constraint, but I don’t think anybody can argue with end product quality. Baldor smokes its competitors every year in the industrial motor category in our Readers’ Choice study, which asks which supplier provides the best value in a given product category.
Some of you know more about this process. Is there a better way?
Maybe, though just because there’s a more sophisticated method out there, it doesn’t always mean it’s right for you or your customers. That’s a lesson for machine controls, too.