Grinder Burr Wear Diagnosis
A café's espresso grinder (Mazzer Super Jolly) has been in service for 5 years, grinding about 20 kg per week. Recently, baristas report that shots are inconsistent: sometimes they gush, sometimes they choke, even with the same grind setting and dose. The grinder's burrs have never been replaced. The grinder is cleaned weekly with Grindz tablets. The motor sounds normal. The hopper is kept full. The espresso machine is a Nuova Simonelli Appia II, which was descaled 2 months ago. The water hardness is 150 ppm. The baristas use a scale and timer, and they distribute with a leveling tool. The inconsistency is more pronounced with light roasts. The café uses a mix of beans, some dark, some light. The grinder setting is adjusted frequently.
1. What is the most likely cause of the inconsistent shots, and how would you confirm it?
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The most likely cause is worn burrs. After 5 years at 20 kg/week, total throughput is about 5,200 kg, well beyond the typical burr life (around 500-1000 kg for espresso burrs, depending on burr type). Worn burrs produce more fines and inconsistent particle size distribution, leading to variable extraction. To confirm, inspect the burrs: look for rounded edges, wear patterns, or damage. Also, check for consistency by grinding a sample and using a sieve analysis if available. Another test: grind at a setting and pull multiple shots; if time varies significantly with same dose and distribution, burrs are suspect. Also, check that the grinder is calibrated and that the burr carrier is clean. The fact that inconsistency is worse with light roasts (harder beans) supports worn burrs, as they struggle to cut hard beans uniformly.
2. What maintenance actions would you take, and how would you prevent this in the future?
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Replace the burrs with new ones (preferably OEM or high-quality aftermarket). After replacement, recalibrate the grinder and dial in. Implement a burr replacement schedule based on throughput: track weekly usage and replace after a certain weight (e.g., every 1,000 kg for espresso). Keep a log of burr changes. Also, perform regular maintenance: clean burrs monthly with Grindz or similar, and check for wear. Consider upgrading to a grinder with easier burr access if frequent changes are needed. Train staff to notice signs of wear (inconsistency, longer grind times). Additionally, ensure the grinder is not overloaded and that the hopper is not causing popcorning. For now, replace burrs and monitor shot consistency.