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Placement speed-Feeder breakdown-PCB

Date:
2017/02/27 00:00
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Placement speed-Feeder breakdown-PCB

Placement speed

 

The placement speed is influenced by many factors in the placement process.

Feeder breakdown

The placement speed is affected by the line downtime. Since feeder problems are the a major source of downtime, the repair and maintenance of feeders are crucial for the component placement operations. Here are the common ways to detect feeder problems:

  • The feeder doesn't achieve the desired output or the output drops after being at the desired level. The feeder has low or reduced output.

  • The feeder operates noisily only during certain periods.

  • The feeder operates but has reduced output.

  • The feeder operates noisily but achieves normal output.

  • The feeder's amplitude gradually fades or slowly decreases.

  • The flow of material discharging from the feeder is turbulent, creating inconsistent flow to the process.

  • The feeder output is inconsistent, creating feed rate fluctuations.

Placement system set up

All on-line setup reduces the capacity and improper setup procedures could also create additional line downtime. No boards could be produced if the placement system is not set up. Due to the complexity of the feeder set up and changeover process, it is important for operators to be aware of the variety types of feeder mechanisms. There are additional tools that could be implemented to assist the placement set up, such as roll-up feeder carts, just-in-time (JIT) methods and smart feeders.

Placement speed derating

In practice it is not possible to obtain the quoted theoretical maximum throughput rate for machines in a placement system. It is necessary to derate the theoretical numbers to obtain realistic values, due to unexpected downtime, board load and unload time and machine configuration. Other factors include PWB size, component mix, and the requirement for more complex vision recognition for fine-pitch components. There are many techniques of derating. Global derating considers system-wide stops, slow-downs and set ups as well as machine factors. To calculate the amount of global or system derating, one should take the average of the number of total components placed per hour in a long period (i.e. an entire product shift). Regularly scheduled stops should be included when determining the level of global derating the system requires. Rigorous derating, which considers each piece of equipment in service for a particular product individually, must be conducted by specific machine model for the line balancing. Rigorous derating values are necessary for full optimization of the process.

 

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