Process engineering Standard times

Objectives Standard times are used to gauge how long each element/step of a process takes to complete. Standard times are measured against the actual time man and machine takes to complete a process. If there are time deviations over standard times the operation cycle time needs to be assessed.

Standard time Standard time is unique to the: fixture operation man power environment.

Standard time Definition The total time in which a job should be completed at standard performance This will also include: work content allowance for delays unoccupied time interference allowance.

Standard performance Definition The output rate of a qualified worker without over-exertion as an average over the working day/shift. Providing that the operator: is trained in the operation understands and adheres to the procedures is motivated applies themselves to their work.

Cycle time Definition The total time taken to complete the combination of elements or steps which make up the work cycle. This includes man and machine time.

Actual time Definition The observed time taken to perform an element or combination of elements of work, obtained by direct measurement. Actual times of process steps that are over the given takt time and/or standard time, are assessed to identify where improvements can be made to increase cycle times.

Elements of a process Spot welding The expectation is one spot weld is completed in the standard time of 4 seconds. Hold position 1 second Squeeze position 1 second Apply spot weld/current 1 second Hold/cool position 1 second.

Estimating Example: To apply 100 weld spots to a plate at 4 seconds each (regardless of gun positioning times) should equal 400 seconds of spot welding only. Both man and machine time need to be assessed to confirm the overall process time meets customer requirements.

Elements of process Machine element Standard time Actual time Hold position 1 second Apply spot weld Squeeze position Hold/cool position Total time 4 seconds In this example the machine times meet the process requirements.

Elements of process Operator element Standard time Actual time Position gun 1 second 1.5 seconds Squeeze trigger 0.8 seconds Remove 1.7 seconds Total time 3 seconds 4 seconds In this example the actual time does not meet the process requirements. The actual time is one second longer than the standard time which will affect the number of units produced over a shift.

Cycle time results Element Standard time Actual time Machine 4 seconds Operator 3 seconds Total time 7 seconds 8 seconds Time deviations may occur due to one operator being slower than another. To reduce cycle time the operator movements and work environment are assessed to identify where improvements can be made.

Standard performance criteria When assessing standard performance of operators the following factors need to be addressed. Physical strength Stamina over an 8 hour shift Is the operator trained Operators level of understanding Ergonomics Environment Age (maintaining an efficient pace) Selecting the right person for the job.

Other time deviations Some time variations are outside the operators control. These may include: Variation in the quality of material used Changes in operating efficiency of tools or equipment Changes in methods or conditions of the operation Variation in the operators focused attention that is required to perform certain elements Change in temperature or lighting.

Improving performance A manufacturing process needs to be designed at a base level so the majority of workers understand what is required. The process must be user-friendly. Use operators who are physically suited to the work. Increase operator skills and understanding through training.

Improving performance Questions to ask can include: Is there another way to perform the operation and still maintain the quality? Have the conditions changed since the operation was added to the process? Could the operation be combined with a previous or a subsequent operation? Would changing the sequence improve the operation? Can the racks be moved closer to the work station to reduce material handling time? If the operation is modified, will subsequent operations be affected?

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