How to maintain or tell if a commercial grinder is in good health?

Grinders are one of the keys to exceptional espresso. Discuss them here.
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#1: Post by cdneddy »

recently got a nuova simonelli MDX for a great price from a seller. It was in good physical shape, the doser said 7000 uses but i when i tried everything it still work quite well.

Burrs have been replaced. but what is some good tips on keeping this running for the next 5-10 years ahead? I will be using it at my office, so about 10-15 cups per day.

What are signs that the motor is fading?


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#2: Post by allon »

These commercial grinders are very heavy duty, built for commercial service. Ignore the counter, it wraps frequently and is only there for tracking coffee usage, not grinder usage. And it only really works if the doser is kept half full, a situation that should never happen in home/light use.

There are a couple things that can fail.

If you turn it on and it hums but the motor doesn't spin, and there is nothing blocking the burrs, then the culprit is likely the motor start capacitor. This is a relatively inexpensive part that can be replaced. An easy way to confirm the diagnosis is to gently spin the motor (carefully! No fingers, maybe a chopstick?) and if it starts up, it's confirmed.

Another failure mode is total failure - no hum. This could be a fuse but could also be the contactor (relay) that is used in some grinders. The motor draws a high current and some grinders have an option for automatic operation, which keeps the doser full. This uses a sensor switch which has a low current handling capacity so they use the low current switch to driver a high current relay which drives the motor. The relay can fail. This can be fixed by replacing the defective relay.

A general appliance repair shop can probably do these repairs for you but it will cost labor. A buddy who knows electrical stuff can be helpful.

Bearings on the motor can fail. These are often very hard to replace, depending on the grinder design. Symptoms include horrible noises, failure to spin by hand, wobble.

Other failures include sluggish operation from build up of coffee sludge or lack of lubrication. For example the doser handle may fail to drive the dosing mechanism if the pawl that engages the ratcheting gear doesn't spring back due to sluggishness, or if a spring breaks.

Springs do sometimes break. Replacements are available for most grinders.

Breaking other parts while disassembling for cleaning can happen. Be careful. Don't apply excessive force. It is even possible to bend the motor shaft if suitably abused.

Hopefully this gives a picture of what to look for when buying a used grinder, as well as some tips on what could go wrong with a commercial grinder (though seldom really does).
LMWDP #331

cdneddy (original poster)
Posts: 30
Joined: 11 years ago

#3: Post by cdneddy (original poster) »

Thanks Allon for your input. It was helpful and gives me something to refer to if something does happen in the future *touches wood*