Hi ,

I'm owner of MCR-10 since Dec 2023

allow me to share my experience on few of your points

for your issue on the gap try to let your roaster on 220 C for around 20 min to 30 min and try to reduce the drum rotation I usually use 57 HZ so I set it to 45 HZ and "keep the gap as large as possible "after that try to reduce the gap slowly till you hear the grinding sound then you turn to clockwise very slowly to let the grinding sound disappear.

in this way, only the chaff will be on the burner chamber.

on batch size, I feel that the sweet spot is 8 KG, not 10 KG

I'm on the MCR-20 with similar warm up protocol and origin variety. I've also had this issue not long ago where it got pretty bad - every now and again beans would load up in the gap and then it'd be a delicate game of trying to close the gap while trying to let the drum cycle the beans down the waste chute without stalling.

These days, it's been better with me only having to make minimal adjustments until the beans hit yellow and then it's stable from there. When charging, I only open the hopper gate about halfway or so to slow down the amount of beans. I think this gives the bean mass enough time to spread out evenly throughout the drum and also reduces amount of heat loss from the front of the drum.

We spoke with support, initial recommendation is to increase charge temp.

We bumped up to 460F and ran a batch of Honduras (pretty easy bean to roast, large screen size). No issues, no gap adjustment.

Next we'll try a smaller screen Ethiopia Guji and see if it handles well.

Overall only very minor adjustments to our profile were required. These large batches don't seem to mind the 35F increase in charge at the same gas and air.

@theroastery said:

We have maintained the grease on the front and rear drum bearings, so that is unlikely to be a culprit. The drum itself does appear to have a small amount of visible imperfection (undulation) during rotation, which causes uneven rubbing/grinding sounds when the gap closes too much (it has a rhythmic/pulsing effect to the contact with the front wall). We addressed this on a video call with Aziz about 9 months ago and he assured us it wasn't a concern or was at least within margin of error as far as the actual drum is concerned.

Any thoughts would help, going to troubleshoot this a bit longer then probably setup another call to support.

Has this been a constant issue or was it something that developed over time? I had a similar issue on my 3k that I fought for months and it ended up being the bolt that is inside the front drum bearing had worked itself loose and eventually fell off. Beans went everywhere. Might wanna check that and make sure it’s torqued. I think it was a combination of the heat cycles and vibrations.

@bassmasteraj said:

Has this been a constant issue or was it something that developed over time? I had a similar issue on my 3k that I fought for months and it ended up being the bolt that is inside the front drum bearing had worked itself loose and eventually fell off. Beans went everywhere. Might wanna check that and make sure it’s torqued. I think it was a combination of the heat cycles and vibrations.

Thanks for the input! It was an issue on our 10K pretty much from the beginning. The bolts seem secure across the front so I don't *think* that is the issue in our instance.

UPDATE

For the past couple months we've had all sorts of different coffees and roasts on the 10K machine, and although the issues seem to be partially resolved by increasing the drop temp as recommended by the support crew at Mill City (see previous post of Feb 9), there are still issues with the gap allowing smaller screen sizes (Ethiopia Guji, Sidamo...also decaf coffees) to fall into the gap. In many instances, we can adjust the gap one or two times on a roast and that's it. Other cases, the gap fills with beans and throttles down to a halt, requiring us to dump the batch. As previously observed, larger screens have no issues, since they aren't subject to falling through the gap even at it's wider settings.

When we get a slow week I'm going to take a look at possibly removing the front of the drum, although I haven't quite figured out the best way to do that yet. My suspicion is that something else must be going on inside there. The biggest question mark for me at this point, is that when we do experience drum gap closure during a roast, the resulting sound is cyclical (1 per rotation) which means the drum isn't even/flush to begin with. My guess is that the drum gap issue allows beans to fall through the "weak spot" (uneven spot) in the drum rotation.

Of course, if that is the case, I don't really know what the fix will be at that point, but at least it will help me narrow it down.