Whiteboard Metrics Calculations - Machine Level Hourly View
The purpose of this article is to explain how to calculate and describe the significance of values in the Machine Level - Hourly View on the Whiteboard.
Table of contents
OEE Metrics Calculations
OEE=Availability*Performance*QualityAvailability=Uptime/Planned Productive TimePerformance= (Number of parts produced) / (Machine rate*Uptime)Quality= [(Number of parts produced) - (Number of parts rejected)] / (Number of parts produced)
OEE=Availability*Performance*Quality RatioOEE=Good Production (pcs)/ (Expected speed (parts/hr)*Scheduled Time (hr))
Examples
Example 1: All grey period (idle status)
In this case, the machine has a 1-hour unscheduled period (from 23:30 to 00:30) shown in grey - where does the number “189” come from?
This is the Expected Production (Parts), which represents the number of parts that could have been produced if the machine was running. It is calculated as follows:
Expected Production (Parts) = Runspeed (Parts/Minute) * Duration (Minutes)
Furthermore, the job details can be found through the job list view or just by clicking on the job column on the current page. A pop-up window similar to the one below should show up.
Next, substitute the specified number (e.g. Runspeed) into the equation.
Expected Production (Parts) = Runspeed (Parts/Minute) * Duration (Minutes)
189 (no decimals showing up by default) = 3.158 (parts/min) * 1 (hr) * 60 (min/hr)
Example 2: Mixed uptime and downtime periods
In this example, you can see multiple machine statuses in the first hour. Similar to example 1, Runspeed (Parts/Minute) can be found in the Job pop-up window. The value is 3.158 in this case.
The following table shows how items in the quick view are calculated:
Quick View | Machine Status | Key Numbers (Parts) | Duration | Equation | Math Calculation | Description |
|---|---|---|---|---|---|---|
| Uptime | 97 | 30.1 mins |
| 97 = 3.158 * 30.1 + 3 -1 | Produce 97 parts in running state/uptime. No downtime issues happening in this duration |
Downtime | 76 | 24 mins |
| 76 = 3.158 * 24 | It should have produced 76 parts but failed. Micro-stoppage and idle status are triggered in this period | |
Unscheduled | 18 | 5.9 mins |
| 18 = 3.158 * 5.9 | Unscheduled production values (18 parts) | |
| Opportunity | 77 | 24.3 mins |
| 77 = 3.158 * 24.3 | It shows the extra capacity (77 parts) which can be considered to maximize the total production |
Scrap | 1 | 18 sec | Scrap values added manually | N/A | Bad parts, reported by customers |
Technically, we assume Runspeed is a fixed value for all periods.
The following table shows how the values in the OEE gauge and the Cycle Gauge are calculated.
Gauge Type | Quick view | Description |
|---|---|---|
OEE |
| Numerator = 97 = 3.158 * 30.1 + 3 -1 Denominator = 171 = 97 + 77 - 3
57% = 97 / 171 |
Cycle | Numerator = 18.5 = (30.1 / 97) * 60 Denominator =
|
Example 3: Production without Jobs
If a machine is not running on a job, the way calculations are done changes. In this case, the Machine Rate (prod/min) can be found in the PEConfig settings. For this example, the Machine Rate (prod/min) = 180
Quick View | Machine Status | Key Numbers (Parts) | Duration | Equation | Math Calculation | Description |
|---|---|---|---|---|---|---|
| Uptime | 5632 | 55.7 mins |
| 5632 = 180 * 55.7 - 4387 | Produce 5632 parts in running state/uptime. |
| Downtime | 781 | 4.3 mins |
| 781 = 180 * 4.3 | It should have produced 781 parts but failed. Idle status are triggered in this period. |
Opportunity | 781 | 4.3 mins |
| 781 = 180 * 4.3 | Opportunity production values (781). |
Gauge Type | Quick view | Description |
|---|---|---|
OEE |
| Numerator = 5632 = 180 * 55.7 - 4387 Denominator = 10800 = 180 * 60
52% = 5632 / 10800 |
Availability |
93% = 56 / 60 | |
Performance |
5632 = 180 * 55.7 - 4387
56% = 5632 / 10019 | |
Quality Ratio |
5632 = 180 * 55.7 - 4387
100% = 5623 / 5623 |
Different approaches to OEE calculation in this case
OEE = Availability * Performance * Quality Ratio = 93% * 56% * 100% = 52%
OEE = Good Production(pcs)/(Expected speed(parts/hr)* Scheduled Time(hr)) = 5632 / (180 * 60) = 52%
Generally you can choose either of them to calculate OEE. They both work in SLX system.
Briefly, in OEE gauge, Expected Goal can be concluded as below:
Expected Goal = Running + Opportunity + Running (Type)
Please note that for Running (Type), if it gains parts, Expected Goal=Running + Opportunity - Running (Gain). Otherwise, Expected Goal=Running + Opportunity +Running (Loss).
In addition to Running (Type), some cases include other components such as Production During Errors, Blocked Parts, Starved Parts, etc. We should add them to the equation as well. See Example 4.
Example 4: Production with complicated machine status
In this case, we have multiple machine status.
Apparently, the calculation formulas are the same as in the previous examples. But due to different machine types, the Expected Goal ( denominator of the gauge) is the most confusing part. Let’s look into it.
Starting from the basic equation in Example 3, we can expand it by adding some specific terms as below:
Expected Goal = Running +Opportunity + Running (Type) + Production During Errors + Blocked Parts + Starved Parts
360 000 = 103 109 + 127 744 + 128 967 + 11 + 35 + 54 + 25 + 43 + 12
With the addition now of faults and Late Start (which would also include Early Departure and Break Creep) we can simplify the equation to the following:
Expected Goal = Running + Opportunity + Running (Type) + All parts added by Type
Example 5: Special case with small error
According to our equation, Running + Opportunity + Running (Type)=Expected Goal
494 314 + 599 020 + 45 958 = 1139 292
But in this case, 1139 309 – 1139 292 = 17. Where did we gain 17 parts?
You can see a setup gain of +16 on the 10th line down that accounts for missing parts.
Yes, there is an error here in 1 part; a 0.00009% error is acceptable.
There is production hidden under Test Run that does not show up in the Goal Column.