Heat Related Failures in Rexroth Indramat Drives

Summer brings us warm days, balmy nights — and heat related failures in Rexroth servo drives.

The most common cause of heat-related problems with drives is the failure of the powered fan found on almost all drives and power supplies. This fan is typically on the underside of the drive, centered in depth on the unit. You can usually see it if you look at the underside.

If the fan fails, the drive will start to age at an accelerated rate. Essentially, your unit will become a year older in drive years each week. If the unit is in a controlled environment, like a sealed, air conditioned cabinet, the aging won’t be as severe, but it may still be as though your drive became a year older every two weeks.

My recommendation for longevity is twofold:

  1. First, put the fan on a fairly regular inspection schedule. The machine operator should verify fan operation on each startup of the machine. This is easier than it sounds — an inexpensive mirror on a stick available at any automotive parts store helps here, but don’t stick it on live wires. If the machine is never shut down, conduct a preventative maintenance check every week or two.
  2.  Second, if the machine is more than ten years old, start thinking about replacing the fans as a preventative measure. 10 years is quite a bit of life for a fan running all the time, and you have got your money out of it. Call us at (479) 274-8422 for replacement fans.

Think about your cabinets, too. I go into plants all the time and see cabinets with doors open and fans blowing into them. If you take a look at the cost of downtime and repair, putting a sealed air conditioner on a cabinet and keeping the doors closed is one of the cheapest long term PM items you can do. Putting regular fans on the cabinet to circulate plant air just will not cut it: you aren’t cooling
your father’s relay panel here.

In plants with closed, air conditioned cabinets and with checks on fans, it is not uncommon to see original Indramat TDM drives from the 1980s running along quite happily. In plants using cabinets with open doors in hot and/or moist environments, it is not uncommon to see them shell out an entire row of drives in under 10 years.

A cool servo is a happy servo!

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