Measure Phase Blog

Containment to Prevent Automotive Steering Column Electrical Failures

Measure Phase

Date: 21 February 2016

Introduction 

The first step we undertook as a team was to measure the number of field failures annually as a result of electrical failures in the steering column electronic(SCE). These failure were as a result of foreign metal debris causing short circuits in the SCE.

At an average cost saving of  €5300 per field failure , any reduction of same would have a significant cost saving for our company .
         Because of the issues we were having with insufficient conformal coating on our SCE , it was decided to carry out a CMK evaluation on our Nordson coating machine .Analysis of CMK will be performed in the next phase of the DMAIC process, ie the Analyse Phase. CMK was measured using 50 continouous samples produced on our machine , in this case the X, Y and Z axes, keeping all influences other the machine parameters constant. The data was then input into Minitab software to calculate the CMK values for each axes . The industry specification is a CMK value of greater than or equal to 1.67 . CMK values greater than this value indicate that the machine is capable and also that a stable process is achievable .

The most significant part of our Measure Phase was the Design of Experiments(DoE) we carried out to determine the optimum levels for all variables of the conformal coating process, thus giving best possible results, namely sufficient coverage with no delamination (splitting or separation into layers), cracking or bubbles.

The first stage of the DoE process was to screen out the significant variable.See Table2. All machine variables were listed at their low and high settings and the results entered into Minitab software.This generated an array of runs for us to complete (DoE1)and present for analysis. See Table3. The aim of this Design of Experiments is first to identify the significant variables by means of our screening method in DoE1 and secondly to provide an understanding of the significant variable settings and the effect they have on each other. DoE analysis will also be carried out in the next stage of the DMAIC process , ie the Analysis Phase.

Both tools , ie CMK and Design of Experiments were invaluable to us as a team in order to first prove that our machine was capable and also that it was being operated at optimum settings.

Define Phase Blog

Containment to Prevent Automotive Steering Column Electrical Failures

Define Phase

Date: 7 February 2016

Introduction 

The aim of this project is to put a containment in place to prevent foreign metal debris in a steering column assembly causing short circuits on the steering column electronic. The issue the team are focusing on is one related to several field failures as a result of shorts within the steering column electronic (SCE). Detailed analysis and investigation revealed that the root cause was determined to be foreign metal debris from the steering column assembly which was attracted in particular to the two Hall IC's on the electronic. Their close proximity to magnets located on the bottom side of the printed circuit board was the main reason for this.The Hall IC's have conformal coating protection applied to them, however this was not sufficient, primarily on the bend of the leads to protect against metal debris causing shorts. Hence the need to come up with a containment solution as soon as possible to prevent further field failure, and also to ensure that this design flaw would not reoccur in any future redesigns.

Conformal coated Hall IC's                    Metal debris short across Hall IC

The first step in the Six Sigma process was to form a project team , the one chosen was one individual from each relevant department ; each would bring invaluable knowledge and experience to the table.

The next step was to create a project charter which was an invaluable tool in that it gives a simple
overview of the complete project from start to completion .

Project Charter

A SIPOC diagram was generated to chart the process flow of product through the conformal coating stage .

SIPOC diagram

Subsequently , I went on to hold a brainstorming session with the team members to go through the potential causes of the lack of conformal coating in the steering column electronic(SCE).From this information I then created a Cause and Effect diagram to visually display all potential causes of this problem. I found this an exceptional tool for organising all the possible causes of a known effect in a clear and organised way .I also found the brainstorming session itself to be a very positive experience as it gave much more insight into the process than I would have previously encountered .

Cause and Effect diagram

A Gantt chart was formed to display project milestones ie define, measure, analyse, improve and control in a much more visible format. This six sigma tool also helped identify all essential tasks and whether they could be performed parallel to each other or had to be performed sequentially .

Gantt Chart