In electronics manufacturing, part attrition refers to the loss or rejection of components during the assembly process, particularly when using SMT (Surface Mount Technology) pick & place machines. This attrition, also known as part wastage, occurs due to various factors such as machine imperfections, component packaging, and production batch size.
- Machine Imperfections: SMT pick & place machines, while highly precise, are not perfect. During the assembly process, some parts may be lost or rejected due to machine errors or inconsistencies in the picking and placing of components.
- Tape Leader Requirements: Many electronic components are packaged on reels with tape. The mechanical construction of tape feeders in pick & place machines requires a certain length of tape, known as the "leader," to be present before parts can be automatically picked up. This leader tape contributes to part attrition.
- Component Characteristics: Attrition rates can vary depending on the specific component being used. Factors such as size, shape, and packaging type can influence the likelihood of a part being lost or rejected during the assembly process.
- Production Batch Size: The size of the production run can also impact part attrition. Larger production batches may have different attrition rates compared to smaller runs due to factors such as machine setup, component handling, and overall process efficiency.
PartsBox provides a flexible way to define and manage part attrition on a per-component basis. Users can set two key parameters for each part:
- Percentage-based Attrition: This parameter represents the expected percentage of components that will be lost during the assembly process. Attrition rates typically range between 0.1% and 3% for production runs, depending on the factors mentioned above. For example, setting a percentage-based attrition of 1% means that for every 100 components, 1 additional component will be allocated to account for potential loss.
- Quantity-based Attrition: This parameter specifies the minimum number of extra components that should always be reserved, regardless of the percentage-based calculation. This is often related to the length of the leader required to feed a reel into the pick & place machine. For instance, setting a quantity-based attrition of 10 means that at least 10 additional components will be allocated, even if the percentage-based calculation suggests a lower number.
These attrition parameters can be set individually for each part or applied to multiple parts simultaneously, providing flexibility in managing attrition across different components and projects.
Impact on Project Building and Pricing
When building or pricing Projects/BOMs (Bill of Materials) in PartsBox, the software takes part attrition into account. This means that the actual number of components taken from stock or ordered will be higher than the strict requirements of the BOM.
For example, let's consider a project that requires 500 resistors. If the percentage-based attrition for resistors is set to 1% and the quantity-based attrition is set to 10, PartsBox will calculate the total number of resistors needed as follows:
- Percentage-based attrition: 500 × 1% = 5 additional resistors
- Quantity-based attrition: 10 additional resistors (minimum)
In this case, PartsBox will allocate 510 resistors for the project (500 + 10), ensuring that there are enough components to account for potential attrition during the assembly process.
By accurately accounting for part attrition, PartsBox helps electronics manufacturers optimize their inventory management, avoid shortages, and ensure smooth production runs. This feature streamlines the process of building and pricing projects, taking into consideration the realistic requirements of the manufacturing process.