Help Manual

Contents






Sigma Magic Help Version 15

Time Study

Overview

The time study tool can be used to perform a time study analysis. The inputs to the time study are the individual times for each step in the process and the outputs of the time study are the expected total time for the entire process set and the confidence interval calculated at the given level of confidence. Time study can be used anytime you need to determine the amount of time each step in the process takes. These studies are usually conducted to develop work standards. In a Lean process, time is an important element and time studies can help capture the amount of time each step in the process takes so that they can be used to set the standard and then continuously improve the standard over time. The cycle time for each step in the process can also be compared to the TAKT time to determine if a process has any bottlenecks.

To add this tool to your workbook, click on Lean and then select Time Study.

Inputs

Click on Analysis Setup to open the menu options for this tool.

Setup

A sample screenshot of the setup menu is shown below.
Time Study
1
Analysis Type: Specify the tool format for this analysis. This selection is not enabled since there is only one format available.
2
Num Rows: Specify the number of rows of data you would like to enter on the worksheet. This information is used to format the worksheet. Note that any data below this formatted area will be cleared.
3
Num Observations: Enter the number of repeat observations for each step. Repeat observations help you capture the amount of variation you have in your process. Try to measure each step at least 3 times.
4
Time Calculation: Specify how you want to calculate the total process time. The different options are:
OptionDescription
AverageUse the average value for the overall time.
MedianUse the median value (good option if you have outliers in your data).
Average (excluding min/max)Use the average value which is calculated after eliminating the lowest and highest values.
CI BoundsUse the 95% confidence interval (lower or upper bound)
MinimumUse the minimum value (if you want to set aggressive targets)
MaximumUse the maximum value (if you want to set a conservative target)
5
View Example: Click on this button to open the example file. You can view the example to get an idea of how to fill out this tool or you can use the example as a starting point and modify it to meet your project needs.
6
Help Button: Click on this button to open the help file on this topic.
7
Cancel Button: Click on this button to exit without saving any changes.
8
OK Button: Click on this button to save changes and update your analysis results.
In the worksheet, enter the details of your process.
  • Enter the number of the process step (or just an index)
  • Next enter the description for each step in the process.
  • For each step in the process, enter the observed time. The units are not specified, so you can enter in any units (minutes, hours, seconds, etc.), but make sure you are consistent in your data entry. If one value is entered in minutes, then all values should be entered in minutes.

Charts

If you click on the Charts button, you will see the following dialog box. Charts
1
Title: The system will automatically pick a title for your chart. However, if you would like to override that with your own title you can specify a title for your chart here. Note that this input is optional.
2
Sub Title: The system will automatically pick a subtitle for your chart. However, if you would like to override that with your own subtitle you can specify a subtitle for your chart here. Note that this input is optional.
3
X Label: The system will automatically pick a label for the x-axis. However, if you would like to override that with your own label for the x-axis you can specify a different label here. Note that this input is optional.
4
Y Label: The system will automatically pick a label for the y-axis. However, if you would like to override that with your own label for the y-axis you can specify a different label here. Note that this input is optional.
5
X Axis: The system will automatically pick a scale for the x-axis. However, if you would like to override that with your values for the x-axis, you can specify them here. The format for this input is to specify the minimum, increment, and maximum values separated by a semi-colon. For example, if you specify 10;20 then the minimum x-axis scale is set at 10 and the maximum x-axis scale is set at 20. If you specify 10;2;20, then the x-axis increment is set at 2. Note that this input is currently disabled and you will not be able to change this setting.
6
Y Axis: The system will automatically pick a scale for the y-axis. However, if you would like to override that with your values for the y-axis, you can specify them here. The format for this input is to specify the minimum, increment, and maximum values separated by a semi-colon. For example, if you specify 10;20 then the minimum y-axis scale is set at 10 and the maximum y-axis scale is set at 20. If you specify 10;2;20, then, in addition to minimum and maximum values, the y-axis increment is set at 2. Note that this input is optional.
7
Horizontal Lines: If you want to add a few extra horizontal reference lines on top of your chart you can specify the values here. The format for this input is numeric values separated by semi-colon. For example, if you specify 12;15 then two horizontal lines are plotted at Y = 12 and Y = 15 respectively. Note that this input is optional.
8
Vertical Lines: If you want to add a few extra vertical reference lines on top of your chart you can specify the values here. The format for this input is numeric values separated by semi-colon. For example, if you specify 2;5 then two vertical lines are plotted at X = 2 and X = 5 respectively. Note that this input is optional.

Verify

If you click on the Verify button, the software will perform some checks on the data you have entered. A sample screenshot of the dialog box is shown in the figure below. Verify The objective of this analysis as well as any checks that are performed is listed in this dialog box. For example, the software may check if you have correctly specified the input options and entered the required data on the worksheet. The results of the analysis checks are listed on the right. If the checks are passed, then they are shown as a green-colored checkmark. If the verification checks fail, then they are shown as a red-colored cross. If the verification checks result in a warning, they are shown in the orange color exclamation mark and finally, any checks that are required to be performed by the user are shown as blue info icons.

Outputs

Click on Compute Outputs to update the output calculations. A sample screenshot of the worksheet is shown below.
outputs The total time for all process steps is shown in the figure. The excel table also shows the value of the cycle time for each step depending on the methodology you have selected. The figure plots this data in a bar chart and then plots the confidence intervals for each step as whiskers. If you work with the average value, then it is expected that half the time your times would be greater than the average and half the time less than the average. To pick a conservative time, use the maximum or minimum value from the confidence interval rather than the average value.

Notes

Here are a few notes regarding this analysis:
  • To handle missing observations, you can leave the fields blank in case you don't have the values for any reason. Note that you need at least 2 values to calculate the standard deviation. If you have less than 2 observations, the standard deviation is set at 0.0.
  • You can choose the default confidence level of 95%. This means that you are 95% sure that your total process time will be less than this value. You will be wrong only 5% of the time. As opposed to being wrong half the time if you work with the average value.
  • Currently, for this version of the software, you can have up to 10 observations per step.
  • Note that the value you specify under options is only used when you create a new worksheet. After that, if you specify or override the value in the Time-Study worksheet, the software assumes that you want to use this new value for this spreadsheet.

Examples

Following examples can be found in the Examples folder within the software.
  • Data was collected for one zone of assembly of TVs. Use the data in the reference file to do a time study at a 95% confidence level (Time Study 1.xlsm).