Hello HB members,
I went to check out used mazzer robur today. I have never seen or carry one before. Oh boy! was it heavy. What i noticed is that after 1/4 - 1/2 lb of beans, the ground coffee feel quite warm. Is this typical that robur create this much heat? The seller of the machine doesn't know much about the grinder :/. He had it in garage since earlier this year and i can see he didn't take care of it real well which is so sad. I'm about to purchase mazzer robur so i need some advice.

Thank you all for your opinions!

Suthee

All grinders heat the grind. People used to attribute this to the motor being stopped and started; but it also happens when the motor is separated from the burr. When you break something, you release heat. The coffee bean gets broken a lot, and steel is a poor conductor of heat, so the grind gets hot.

It is actually less of a problem for the Robur, since it runs at 300 RPM, not the 1600 to 1800 that is common to most grinders. However, if the whole housing got hot, indicating that the motor or bearings overheated, you have a problem.

Roburs overheat.
Did you grind a 1/4lb through without stopping? If not, what was the cycle?
People have vented Roburs, attached fans, etc.
But a Robur should not overheat under normal home use.

yes, 1/4 lb of beans in single go. I have never used commercial grade grinder before so I have no clue and I have never grind that much beans at a time before. So this is normal, right?

Sounds like it's probably normal as everyone else is saying. Have you ever tried grinding that much coffee in the Rocky listed under your equipment? It should orient you.

Normally we home users do about 15-20g at a time with at least 30s to 2 minutes in between shot grinding, so heat is really never an issue on most grinders, least of all titans like the Robur.

There are warnings about how long to leave the Robur running for a single grinding session and how long to wait in between. I don't have my manual here but I remember reading it. Also, my Robur is vented with a fan that automatically engages after I start grinding and continues for some time afterwards. Did your Robur have this fan and did it run?

mitch236 wrote:Did your Robur have this fan and did it run?

This rear fan is a Robur-E only feature. It's not on the doser-Robur.

another_jim wrote:It is actually less of a problem for the Robur, since it runs at 300 RPM, not the 1600 to 1800 that is common to most grinders.

Is this correct? Presumably the same work is done breaking 100g beans, be it at 300 or 1600RPM. A higher RPM may have the benefit of more cooling due to higher air flow. A low RPM that grinds very quickly releases all the heat in a short interval.

The efficiency of the burrs in turning beans to powder will affect the total heat due to friction between the incomplete grind and the burr.

A more powerful motor has more torque at the same RPM and is thus less subject to overload. A slower motor has more torque at the same power. A reduction gear increases torque by reducing RPM, but also reduces overall power due to friction losses in the gearset. hp = t * f / 5252.

The Mazzer Robur and Kony are designed to function in higher-capacity bars without having heat issues (compared to Minis and Super Jollies at least and I believe Majors as well). Dave's data in TGP: does burr heating grounds affect taste of espresso? seems to bear out that, whatever the reason, big conical burrs heat less than their smaller flat burr counterparts. Seems like it was also not that big of a deal, at least for the amount that Dave tested, which was way beyond home use anyway.

The OP talked about the grounds, not the motor or housing. Grinding heats whatever is ground, since the energy used to break the large bits into smaller bits turns to heat -- even a hand grinder, when turned fast enough, will heat the grinds. The Robur heats grinds no worse than any other grinder.

So, if the grinds are warm to the touch, probably the grinder is OK; if you can smell them baking; probably not so good.