Understanding FMS Production Lot Sizes

Flexible Manufacturing Systems (FMS) represent a significant advancement in production technology. An FMS is designed to combine the flexibility of job shop manufacturing with the efficiency of mass production. It typically involves a group of processing workstations (usually CNC machine tools) interconnected by an automated material handling system, all controlled by a central computer.

Applicability of FMS based on Production Volume

The choice of a production system depends largely on the variety of products to be made and the production volume or lot size for each product. Different systems are suited for different scenarios:

• Job Shop: High product variety, low production volume (small lot sizes, often custom).
• Batch Production: Medium product variety, medium production volume.
• Flexible Manufacturing System (FMS): Medium product variety, medium production volume (often higher than traditional batch but lower than mass production).
• Mass Production/Transfer Line: Low product variety, high production volume (large lot sizes).
• Continuous Flow: Very low product variety, very high production volume.

FMS is particularly effective when dealing with a range of part types that need to be processed in batches or mixed flows, requiring flexibility in machine routing and scheduling. The setup times are often reduced or eliminated, making it economical for smaller batches compared to traditional systems, but still requiring a certain minimum volume to justify the high investment cost.

Typical Lot Size Range for FMS

Considering the balance between flexibility and automation efficiency, FMS is best suited for intermediate production volumes. While the exact range can vary depending on the specific industry and FMS configuration, a commonly cited range for the lot size of a product applicable to FMS production methodology falls between 100 and 500 items. This range allows the system's flexibility and automation benefits to be economically realized for different product variants produced in these batch sizes.

Larger lot sizes might lean towards dedicated mass production lines, while much smaller lot sizes might still be better handled by job shops or less automated batch processes unless the product variety is very high and setup times are critical.

Therefore, the FMS production methodology is typically applicable where the lot size of a product is neither extremely small nor extremely large, finding its sweet spot in the medium volume range, such as 100 to 500 items per batch.