Streamlining Coffee Grinder Maintenance with Remote Wear Classification

In a paper published in the journal Applied Sciences, researchers introduced a remote access server system designed to classify coffee grinder burr wear accurately. Users upload photos of their ground coffee granules through a chatbot interface and receive the wear classification result within a minute.

Study: Streamlining Coffee Grinder Maintenance with Remote Wear Classification. Image credit: Tony ton/Shutterstock
Study: Streamlining Coffee Grinder Maintenance with Remote Wear Classification. Image credit: Tony ton/Shutterstock

The system utilizes image processing to analyze the granules' size distribution and then trains a deep learning model to classify burr wear into initial, regular, or severe with over 96% accuracy. This mobile-friendly service is beneficial for both coffee chains and enthusiasts.

Related work

Past studies have shown that the sharpness of coffee grinder burrs significantly impacts coffee flavor consistency in chain coffee shops. However, precise measurement methods are costly and impractical for daily use. In response, a collaborative effort with experts from a major coffee chain led to the development of a manual wear classification method. However, concerns arose regarding the scalability and reliability of this manual method across numerous chain coffee shops.

Additionally, the reliance on subjective assessments and qualitative analysis raised doubts about its consistency and accuracy. Moreover, the need for continuous employee training and supervision added to the operational challenges faced by the coffee chain.

Methodology Overview: Deep Learning and Image Processing

The paper presents a comprehensive approach for classifying coffee grinder burr wear using deep learning models and image processing techniques. Initially, a dataset comprising 600 images of coffee granules, each with a reference coin for size comparison, was collected from various grinder burr wear levels and grinding settings.

Coffee shops employed a simple method involving a mobile phone camera and a white paper surface to standardize image acquisition. Researchers applied image processing techniques to extract granule size distributions. These techniques involved morphological operations such as erosion, dilation, opening, and closing to handle image noise and overlapping granules, followed by segmentation and size estimation using reference coin proportions.

Furthermore, the researchers meticulously designed the image processing flow to minimize numerical errors propagating through morphological operations. They utilized metrics such as mean squared error (MSE) and peak signal-to-noise ratio (PSNR) to evaluate the fidelity of processed images compared to their preprocessed counterparts.

The results indicated acceptable levels of distortion or noise, particularly in the closing and opening operations and the subsequent watershed transformation. These techniques effectively isolated coffee granules and reference coins, enabling accurate size estimations despite potential propagation errors.

In conclusion, the proposed methodology offers a practical and robust solution for remotely assessing grinder burr wear using readily available equipment and standardized image processing techniques. By extending the expertise of coffee professionals to remote users through a chatbot interface and deep learning models, coffee chains can maintain consistent coffee quality across their establishments. The meticulous evaluation of image processing steps ensures reliable size estimations, which is crucial for the accurate classification of grinder burr wear levels.

Researchers devised a method to ensure adequate input data preprocessing for the deep learning model by standardizing the input vector length and addressing the issue of varying granule sizes. They generated a uniform input vector with N entries by dividing all granule area sizes into N intervals and counting the number of granules falling into each interval. This approach enables the deep learning model to operate efficiently without being influenced by the number of granule sizes. Additionally, min-max normalization was applied to the input data to prevent potential convergence issues, ensuring stable model training.

Researchers carefully considered balancing model complexity with data availability in the design of the deep learning model to avoid overfitting or underfitting. Researchers constructed a sequential model architecture utilizing Keras and TensorFlow frameworks, incorporating appropriate activation functions, hidden layers, and neurons per layer.

They employed the Adam optimizer for efficient model compilation and fine-tuned hyperparameters such as learning and dropout rates through grid search. With a focus on multi-class classification for grinder burr wear, suitable activation functions, and loss functions were selected to facilitate accurate predictions. They also implemented dropout regularization to mitigate overfitting concerns. Through systematic experimentation and optimization, researchers developed a robust deep-learning model architecture to classify grinder burr wear levels effectively.

Experiment Results Summary

In the experiment results section, the researchers detailed their process for training and testing data preparation, emphasizing the collection of 600 images across different burr wear levels and grind settings. They highlighted the concentration of coffee granule size distributions based on grind settings, noting the potential for misjudgment in assessing burr wear levels due to similar distributions across different settings.

Through building and verifying the deep learning model architecture, the researchers utilized techniques such as Adam optimization and rectified linear unit (ReLU) activation functions to achieve high prediction accuracy. They conducted grid searches to fine-tune hyperparameters and experimented with different interval numbers and activation functions to optimize the model's performance.

Furthermore, they employed dropout mechanisms to prevent overfitting and conducted a Monte Carlo dropout analysis to assess model robustness. Additionally, integrating a live interactive network experience (LINE) bot provided a user-friendly interface for remote users to access the classification system efficiently. Through these steps, the researchers demonstrated the effectiveness and reliability of their approach in classifying grinder burr wear levels accurately, facilitating practical applications in coffee industry settings.


To sum up, the approach involves utilizing mobile phone-captured coffee granule images for analyzing grinder burr wear levels through image processing and a compact deep-learning model. A LINE bot interface facilitates remote user interaction, ensuring convenience and accessibility. Performance analysis indicates minimal errors in image processing, robust model prediction consistency, and high accuracy exceeding 96%.

The system's low implementation and operating costs, rapid response, and user-friendly features suit commercial coffee chains and enthusiasts. Furthermore, its adaptability suggests potential applications in predicting tool wear for various machinery and broader contexts.

Journal reference:
Silpaja Chandrasekar

Written by

Silpaja Chandrasekar

Dr. Silpaja Chandrasekar has a Ph.D. in Computer Science from Anna University, Chennai. Her research expertise lies in analyzing traffic parameters under challenging environmental conditions. Additionally, she has gained valuable exposure to diverse research areas, such as detection, tracking, classification, medical image analysis, cancer cell detection, chemistry, and Hamiltonian walks.


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