Warranty Analysis Folio Setup

 

To add a warranty analysis folio to a project, choose Home > Insert > Warranty, or right-click the Warranty folder in the current project explorer and choose Add Warranty on the shortcut menu.

In the setup window, select a format to use with the folio. You must select the format that is appropriate for the type of warranty claims data you have available. If you select the Nevada chart format, click Next to go to the next step to configure your analysis; otherwise, click OK to immediately create the folio.

Converting Formats

You can convert the format of an existing warranty analysis folio to a another format. To do so, open the existing folio and choose Warranty > Tools > Convert Data, and then choose the format to convert to. (The data in the existing folio must already be analyzed in order for the command to become available.)

Converting formats creates a new folio and does not overwrite the contents of the existing folio. It is an automatic process, except when converting from the dates of failure format to the Nevada chart format, and vice versa. In that case, you will be prompted to define the time unit of each period (e.g., dates, month or years) in order to proceed with the conversion.

Below is a summary of the data conversion options:

From	Convert To
Nevada Chart Format	Dates of Failure Format
	Times-to-Failure Format
Dates of Failure Format	Nevada Chart Format
	Times-to-Failure Format
Times-to-Failure Format	N/A
Usage Format	Times-to-Failure Format

Control Panel Settings

This section focuses on the warranty folio control panel, which contains most of the tools you need to perform a warranty analysis. For more information about control panels in general, see Control Panels.

The warranty control panel consists of the following pages:

• The Main page contains all the tools you will need to perform a warranty analysis. These tools are described in the next section below.

• The Analysis page contains the settings that are also displayed on the Main page of the control panel.

• The Comments page allows you to enter notes or other text that will be saved with the folio.

• The Statistical Process Control page is available only for the Nevada chart format. It contains optional tools for monitoring warranty returns data.

• The Suspensions page is available only for the usage format. It contains the settings for estimating the amount of usage for fielded units.

Control Panel Main Page

• The Life Data Model area contains the options for performing life data analysis. When you click Calculate, Weibull++ converts the warranty claims data into failure/suspension data and then performs a life data analysis based on the settings you specified in this area.

• Use Subsets gives you the option to analyze multi-population data sets. To use this setting, you must first assign each subpopulation group in your data sheet to a specific subset ID. Select the Use Subsets check box, and then use the drop-down list to switch between the subset IDs and alter the analysis settings (i.e., distribution and parameter estimation method) for each one. When you click Calculate, the software will separately analyze each subset of data. You can view the parameters of each subset ID by choosing the subset ID from the drop-down list or by clicking the Results Report icon in the Analysis Summary area.

• The Suspend After check box allows you to specify a period beyond which the data are considered incomplete. For example, consider a shipment that has been in the field for 14 months. If the warranty period is 12 months, then the failures entered in the data sheet for months 13 and 14 are taken into account, but all remaining units in that shipment period are suspended at 12 months. Note that:

• In the Nevada chart format, the warranty period uses the same time units used in the Nevada chart data sheets.

• In the dates of failure format, you can specify the warranty period to be in days, months or years.

• In the usage format, you have two options: a) specify the warranty period to be in days, month or years, or b) consider a warranty period based on usage (e.g., 100K miles or 10 years, whichever comes first).

• This option is not available for the times-to-failure format.

• The Analysis Summary area displays the results of the life data analysis. This includes the parameters of the selected distribution, the rho and/or LK value (when applicable), and the number of failures and suspensions in the converted data set (includes failures at t = 0, but excludes suspensions at t = 0). Click the Results Report icon  to open the Results window, which shows the results in a worksheet that you can copy or print.

• The End of Observation Period setting is available only in the dates of failure format and usage format. It is used to determine the time in service for each unit that had not yet been returned by the end of the observation period (i.e., the suspensions). The date is typically set to the last day the warranty data was collected.

• The Suspensions Estimation Method area is available only in the usage format. It displays information about how the product usage is defined. Clicking the link will take you to the Suspensions page of the control panel, which contains the options for estimating the amount of usage accumulated by suspensions.

Folio Tools

The folio tools are arranged on the left side of the Main page of the control panel. Use these tools to manage data and experiment with the results of your analysis.

  Calculate converts the warranty claims data to failure/suspension times and then estimates the parameters of the chosen life distribution based on the converted data. If you select the Use Subsets option on the Main page of the control panel, the parameters of the distribution of each subset ID will be calculated. This tool is also available by choosing Warranty > Analysis > Calculate.

  Plot creates a new sheet in the folio that provides a choice of applicable plot types. In warranty analysis folios, this includes plots such as expected failures vs. period, reliability vs. time, probability plot, etc. You can plot the data in the warranty analysis folio either with or without generating a forecast. This tool is also available by choosing Warranty > Analysis > Plot.

  Distribution Wizard opens the Distribution Wizard, which helps you select the distribution that best fits your data based on the selected parameter estimation method (i.e., RRX, RRY or MLE). In warranty analysis folios, the ranking in the Distribution Wizard is based on the converted failure/suspension times. This tool is also available by choosing Warranty > Analysis > Distribution Wizard.

  QCP opens the Quick Calculation Pad, which allows you to calculate life data analysis metrics. It uses the same calculations that you can perform in a Weibull++ life data folio QCP. This tool is also available by choosing Warranty > Analysis > Quick Calculation Pad.

  Forecast opens the Forecast Setup window, which allows you to specify the time periods at which you wish to estimate the number of expected warranty returns. Clicking Forecast before the parameters have been calculated will automatically calculate the parameters and open the Forecast Setup window. This tool is also available by choosing Warranty > Tools > Forecast.

  Folio Setup is available only for the Nevada chart format. It opens the Nevada Chart Setup window, which allows you to change the time periods of the warranty claims data in the current data sheet.

  Change Units opens the Change Units window, which allows you to select the units to use in the data sheet. This tool is not available in the dates of failure format. The units that are available in the drop-down list are defined at the database level. Note that:

1. • In the Nevada chart format, this tool is available only when you choose to label the sales and returns periods in terms of numbers during the setup process. See Nevada Chart Setup.

   • In the usage format, only the units that are related to usage (e.g., cycles, miles, etc.) are available in the drop-down list.

   • In the times-to-failure format, all the time units that were defined at the database level are available in the drop-down list.