Control Phase

Control Phase

Daily Yield Pareto – monitor the yield on a daily basis to ensure issues are not re-occurring. Action as appropriate

Process map – if the line yield drops below 85% yield

Team meetings - weekly updates on yield to Product Builders to keep the focus

The control phase of the project kicked off on the 18^th March. All the tools used in the earlier phase enabled us to improve our yield from a Rolled Throughput Yield of 22% to 69.68%. From the below Pareto coil issues and kinks had reduced but we had another issue, delamination. Our focus was then on the lamination station and the horizontal laminator. The air pressure on the laminator was at 20 psi when it should have been at 25 psi which meant the units were getting too much heat.

The next issue we encountered was fibres on the units which we noticed at the mandrel removal station. For this issue we cleaned all material before using, cleaned the trays the units were being stored in before using and we also cleaned the bench tops before each lot was started.  The Pareto will be of huge benefit to us as it is a visual reminder of the issues we will see going forward.

Daily Pareto

Process Map

The process map we conducted at the Hub Attach station proved to be a vital tool for us in hi-lighting the issues being caused at that station with regard to kinks. This tool will be used going forward to enable us to resolve any issues we may encounter in the process.

Weekly Team Meetings

Team Meetings are conducted by me weekly. Going forward the Engineer for the line will present on the issues from the Daily meetings to the Product Builder team. In the past we have hi-lighted issues of concern to this group and have found that they respond very quickly to help solve the issues but then once the initial reaction has died down we tend to see some of the same issues come back again. We feel that a weekly update will keep the focus for this team and improve the yield and output of the line.

Improve Phase

The Improve phase of the project kicked off on Feb 24^th. The team gathered all the information from the various tests that were conducted and decisions were made on the implementation of the fixes. We found that the tools in the Improve Phase were not as abundant as they were in the other 3 phases. Our issues did not suggest we conduct  a DOE so we opted for the following tools:

1. Chart of Condition - to graph the results for "channels in the Hub"

2. Bar Graph - to graph the differences between the flaring mandrel and the tapered mandrel

3. Box Plot - to show there was no difference in mandrels using tensile at 10 N

Channel in the Hub

We started working on the biggest issue on the line "channels in the hub". The PD Engineer worked with the team to solve this issue. A series of tests were conducted on the station with the Product Builders and the testing proved to be quite a long process.  The confidence graph below shows that when the units were not put through the plasma step there was on average 75%  failure rate whereas when the plasma was applied to the units we had a 100% pass rate. Following implementation of the plasma process on the line the scrap rate for "channel in the hub" dropped from 75% to 0%. (sample of one test conducted below)

Glue in the flow path 

In parallel  with the channel issue we also worked on the issue of "glue in the flow path". Below is a production inspection form filled out by the Product Builder conducting one of the trials on the line. These inspection forms are used in my company to record information. It is a controlled document which is printed with a date stamp and reviewed by quality. (omitted names for this purpose)

The bar chart below shows the difference between the flared mandrel and the tapered mandrel for a sample of 15 units. As shown below the flared mandrel had a scrap rate of 60% for glue in the flow path and the tapered mandrel had a scrap rate of 0%.

The box plot below also shows that there is not a significant difference between the flared mandrel (balloon tubing mandrels) and tapered mandrel for tensile hub performance.   
The samples built with both mandrels were tensile tested to ensure they were not having an adverse effect on the tensile performance of the product. All units passed tensile testing and had a higher tensile force then the product hub tensile specification of 10N. 

Kinks

In conjunction with the other two yield issues on the line we looked at the kink issue. A number of fixes were put in place for this issue. After conducting a Process Flow of station 6 we were able to high light area's for improvement. Below are  sample photos of before and after to help with this issue. We also in produced two improvements to the process,removal of balloon tubing and hooping units at station 5 and securing the hoop unit at station 6. 

Before - Old Rack heads. Hubs sitting on top of rack

After - New rack heads. Units fitting snugly on racks

All the tools we used in this phase were quite easy to use and they gave us the results we required. The improvement in yield has been significant and the line has gone from being at a RTY of 22%  to a RTY of 79%. ( there is only 1 type of product now running on line,the CE product) Further improvements are being implemented  in the form of a new plasma machine which will give an additional improvement of 3-4%. (currently the plasma machine is on another line) 
Our overall experience with the DMAIC process has been enlightening and has taught us that the tools we used in this process enabled us to reach the improvements we have seen to date. 

All improvements have been updated in the relevant procedures.

The final step in the process is the Control Phase. 

Daily Yield Pareto – monitor the yield on a daily basis to ensure issues are not re-occurring. Action as appropriate.

Process Map - if the line yield dips below the 85% yield 

Team meetings - weekly updates on yield to Product Builders to keep the focus

Analyse Phase

Brainstorming

The Analyse phase of the project commenced on the 20th Jan. The above tools were agreed upon and then we kicked off with a Brainstorming session with the PB's from the outer line and included the PB's in the Generic area. Our reason for including the second group was because they had a lot of knowledge when it came to the types of issues we were seeing on our line. The manufacturing engineer,the BPI person and myself conducted the session. We started the session by explaining to the PB's what we were doing and what expected outcome we required which was to get as many ideas as we could on the issue of kinks.  We agreed a half hour time slot for this session and we decided to go with a structured process. Everyone in the room took a post it and a biro and wrote down what they thought could be causing the kinks on the units. The structured process of Brainstorming proved to be the better way to go because the PB's in the room had never done this before and we knew that we would not get as many ideas from them if we opted for the unstructured process of Brainstorming because they would not have been as forthcoming. All the information was gathered and most of the PB's had written 2 or 3 ideas which was then added to the below Brainstorming diagram which is currently used by my company. 

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Affinity Diagram 

The next step in the process was to look at all the ideas and group them in to categories. We came up with five categories and inputted them into an Affinity Diagram. The below diagram shows the areas that are causing the most kinks on the product which is handling and the second biggest area is the method of which the product is being processed. These were the areas we agreed to work on in the Improve phase of the project. Both of these tools were easy to work with, unlike the process map which was time consuming, and both tools delivered the expected outcome which was to point out the areas in the process to work on.

FMEA 

Below is a snap shot of station 6  of the FMEA. This FMEA was constructed by the team and we  included the Product Development team. This station had to be carefully assessed because it was new to our business. We had to ensure that we captured all failure modes. Each failure mode was then assessed for root cause and a decision was made by the team on the effects it could have on a patient. We also  incorporated the ideas from the Brainstorming session when considering the failure modes for this station. This tool took quite a long time to construct and although there are FMEA's for other products in our company this product is quite unique to our business. The FMEA was constructed from the start of the process right through to the end of the process which was beyond the scope of this project.

Measure Phase

Measure Phase

The measure phase of the project, as agreed by the team, included the following.

Process mapping:

We conducted a map of the process that was causing us the most issues on the line, the plasma station and the hub attach station. This tool proved to be a very important tool for us when dealing with the kink issue on the line. While monitoring the plasma station we found that a piece of balloon tubing which was put on at the previous station to help prevent kinks on the end of the unit was actually causing the units to kink. The Product Builder at the plasma station puts the units into a hoop to carry the units to the plasma station. While putting the units into the hoop the balloon tubing was getting pushed and logged into the hoop by the Product Builder. When the next unit was pushed into the hoop it was getting caught on the tubing and kinking the unit.  The product builder told us that they see this from time to time, but this was never reported to us before this. We were able to inform the product builder at that stage to ensure that they check the hoops before putting units into them and to discard the hoops that had tubing stuck in them. We found 25 out of 50 with balloon tubing in the hoops at the time of the observation. 

When we looked at the hub attach station we found  that after Hub attach the units are removed from the hoops and placed on a rack to hang. Unless the units are removed carefully there is a potential to kink the unit. A unit was kinked during our observation of this step in the process. We also found that there is also the potential for kinking units when the balloon tubing, which is inserted on to the units at mandrel removal, needs to be replaced back on the unit before removing the full lot to the next station. Below is a Map of the Hub Attach process. This tool is very visual but can be time consuming when mapping out on Mini tab.

We then looked at the biggest issue with that station which was the glue issues with the 2 different types of mandrels. Neither of the mandrels we were using was going to improve our gluing process so we decided that we would look at alternative mandrels and trial these mandrels on what we call shorties. This trial is in process at this time.



Data Collection

For data collection we opted for a p Chart. The reason we opted for this tool was we felt that it had the best visual indicator. These charts enables the user to pull out each scrap reason code and it allows the user to see if the process is out of control with that particular scrap issue See below p chart for 8 lots of IDE units showing the kink issue on the line

Rolled throughput Yield

We now knew what issues were causing the biggest issues on the line but we also wanted to see how the overall line was performing and to do this we took a snap shot of both IDE units and CE units to see how the yield was performing on both types of products. Below is a snap shot of the CE units and the rolled throughput yield for that product.

CE Snap shot of 240 units (RTY)

Station                            Yield   

Station 1                            100%          

Station 2                            99.2%         

Station 3                           99.12%       

Station 4                           100%          

Station 5                           94.5%         

Station 6                           23.7%         

RTY =                              22%

Six Sigma Yield Improvement Project

                                            Six Sigma Yield Improvement Project 


Define Phase 

My name is Ann Coughlan. I am working in a Multi National medical device company and I am the Team Leader for a new product introduced in January of this year. The project is still in the development phase but we have deadlines for various builds and one of our biggest challenges is yield.

 The overall project objective was to achieve a 20% improvement . A team was assembled by me to look at the best way to complete this goal and the first meeting took place on Tuesday 12th Nov 2013 to discuss the plan.

In the Define phase the team agreed to  complete a Project Charter. The team agreed on a Project Charter (see figure1 below 2nd page of project charter)  as a visual reminder of what needs to happen in each stage of the DMAIC process. This,we felt,would guide us through each stage and it would also allow us to add or subtract if necessary as the project progressed.  

Figure 1 Project Charter

From there it was decided to map the process (see figure 2 below "process flow chart") and highlight the area's of concern so that we could focus our energy in those area's. A process map is a visual aid used by the company as part a "work content graph"  which is continuously up dated when a line is asked to produce more units or if for some reason it introduced a step on one of the stations. The high lighted area's on the chart are the stations we looked at from a yield  perspective. We needed to know which stations were causing the poor yield on the line. The chart shows where the issues originated from. 

Figure 2 Process flow chart

Yield

We also decided on a pareto chart (see below figure 3&4) to see what the biggest issues were on the line. It became very evident where the issues were on the line. We were using a gluing method to glue our hubs to the units. The first chart shows a straight mandrel being used and the second one shows a tapered mandrel being used. As you can see from the charts both gave very different  outcomes. There were other issues on the line, but from a pareto stand point our main focus was the  hub gluing station. Th pareto was a very useful tool because it enabled us to focus on the problem area. 

Figure 3 Straight Mandrel

Figure 4 Tapered Mandrel