Formulas

Estimated Production Time

The planned production duration is calculated as the difference between the estimated finish time and the estimated start time of the production item (PI) at the moment of production start to ensure that the calculation takes into account the right number of operators during production.

Formulas:

Estimated Production Time = Estimated Finish Time - Estimated Start Time

Estimated Start Time = Estimated Finish Time (of previous item in queue) + Changeover Duration

Estimated Finish Time (per produced unit) = Estimated Start Time + (Quantity x tact time* ) + Production breaks duration + time between shifts**

Estimated Finish Time (any quantity) = Estimated Start Time + Tact Time + Production breaks duration + time between shifts**

*from parametrization for current number of operators on shift

**if the item is produced over more than one shift

Actual Production Time

Actual Production Time represents the total active production time of a specific production item. This metric reflects the net time during which the item was actively being processed. The timer starts when production begins, and it is paused whenever the item is placed on hold or sent to "Redbox" due to any interruptions. Time is resumed only when production is restarted. This ensures that the Actual Production Time only includes periods of uninterrupted production and excludes any downtime or pauses.

Formulas:

Actual Production Time = sum of times when item in status “In Production”

Any periods during which the production is paused, sent to "Redbox", or otherwise not actively progressing are excluded from the calculation. Only time intervals when the status is explicitly "In Production" are considered.

Actual Duration Time

Actual Duration Time tracks the net production time for each individual declaration within a production item. Declarations occur when units are completed and recorded during production. This value represents the time it took to produce the declared quantity, considering only active production time between declarations (or between the start of the order and the first declaration). Just like with Actual Production Time, any pauses, interruptions, or transitions to "Redbox" are excluded, providing a clean, downtime-free duration.

Calculation:

• For the first declaration: Actual Duration Time is calculated from the start of the production order to the time of the first declaration.

• For subsequent declarations: It is the net production time between the previous declaration and the current one.

• If production is paused or interrupted, the timer pauses and resumes when production is restarted, ensuring only the clean, active time is recorded.

Formula:

Actual Duration Time = Time between [start of production or last declaration] and [current declaration]

Any periods during which the production is paused, sent to "Redbox", or otherwise not actively progressing are excluded from the calculation. Only time intervals when the status is explicitly "In Production" are considered.

Example:

Production Efficiency

Production efficiency is calculated as a percentage based on the estimated production time versus the actual duration.

Formulas:

Efficiency = (Estimated Production Time / Actual Production Time) x 100

Scrap Ratio

The scrap ratio is calculated dynamically when the production item (PI) changes.

Formulas:

Scrap Ratio = (Scrap Quantity) / (Quantity + Scrap Quantity + Bad Quantity)

OEE (Overall Equipment Efficiency)

The OEE (Overall Equipment Effectiveness) metric is a crucial tool for measuring production efficiency. In our software, the OEE calculation is fully aligned with the traditional formula, offering insights into the production system by breaking it down into three main components: Availability, Performance, and Quality.

Overview

The OEE is calculated as follows:

OEE = Availability × Performance × Quality

This calculation allows users to track and optimize production by focusing on these key aspects. Each component reflects a different dimension of the production process, and their combination gives a comprehensive view of production effectiveness.

For users interested in diving deeper into each parameter, the sections below provide detailed breakdowns and calculation methods.

1. Availability

Definition:

Availability measures how much of the planned production time is actually available for production, accounting for unplanned downtime within scheduled production shifts.

Calculation:

Availability = (Planned Production Time − Unplanned Downtime) / Planned Production Time

Detailed Calculation:

• Planned Production Time: This refers to the total time scheduled for production between the start and end of a shift.

• Unplanned Downtime: Includes unexpected stoppages of the production line that occur within the scheduled shift. If a Line stoppage occurs outside the shift time, it is not considered in the availability calculation.

Example:

If the planned production time for a shift is 8 hours, but there is a 30-minute unplanned downtime during the shift, the availability would be calculated as:

Availability = (8 hours − 0.5 hours) / 8 hours = 93.75%

2. Performance

Definition:

Performance evaluates how efficiently the production is running compared to its theoretical maximum output. It compares the actual quantity produced to the ideal quantity that could have been produced in perfect conditions.

Calculation:

Performance = Actual Production Output / Theoretical Production Output

Detailed Calculation:

• Theoretical Production Output: This is calculated based on the total available production time and the ideal tact time for the specific material being produced. The ideal tact time is the shortest possible time required to produce one unit of the material, based on its parameterization in the system.

  Theoretical Production Output = Total Production Time / Ideal Production Time

• Total Production Time is the sum of Actual Duration Time produced on the line over the selected period.

• Actual Production Output: This includes both finished goods and scrap produced during the shift.

  Actual Production Output = Quantity Finish + Quantity Scrap

Example:

During selected time period was produced many items, from which 10 were for Material A. All items for Material A took 100 minutes to produce and totaly 45 units was finished. Therefore actual tact time was around 2 minutes 15 seconds. If the ideal tact time for a material is 2 minutes, the theoretical production output would be 50 units.

Performance of material = 45 / 50 = 90%

3. Quality

Definition:

Quality measures the proportion of correctly produced items (good parts) out of the total production, including scrap and defective products.

Calculation:

Quality = Quantity Finish / (Quantity Finish + Quantity Scrap)

Detailed Calculation:

• Quantity Finish: The number of defect-free products produced during the shift.

• Quantity Scrap: The number of non-repairable defective products (scrap) produced.

Example:

If 100 units were produced in total, 90 of which are good products and 10 are scrap, the quality would be:

Quality = 90 / (90+10) = 90%

4. Specific Cases and Their Impact on OEE

Downtime and Line Stopages

Downtime that occurs within the scheduled production time affects Availability. However, downtime outside of this window does not impact OEE calculations.

Scrap vs. Discard

The system differentiates between scrap (which cannot be repaired and is excluded from finished quantities) and bad quantity (which requires future processing but is included in finished products). Here we encounter the question of what to consider as defective units – whether just scrap or also bad quantity. Therefore, in the Settings - Main section, there is a select-type switch called "OEE Production line scrap / discard" with options:

• scrap

• bad quantity

• scrap + bad quantity

Depending on what is selected here, the corresponding quantities of scrap, bad quantity, or both are included in the calculation of defective units.