Project:  Reduce Number of Returns

Define:
_x_ Assign a trained project team and Team Champion to oversee the team.
_x_ Team members understand the Six Sigma Implementation (checklist).
_x_ Schedule developed for meetings.
_x_ Team / management make a record of the scope of the team, goals, and issues.
      _x_ What was done in the past? _x_ What support is needed? _x_ Final goal?

In the past, more and more effort has been put into inspection.  At first it seemed to work, but in the long run the return rate actually started to raise.  So, the entire process needs to be looked at.  The owner will provide support as necessary, mainly time to gather data and materials for improvement tests.  The final goal is to eliminate returns caused by defects in manufacture or the parts used.

 

SIPOC Chart for Audio Mixers

__Suppliers__	__Inputs__	__Process__	__Outputs__	__Customers__
_ Parts Suppliers	_ Parts	1. Parts Assembled	_ Packed unit	_ Dealers
_ Flux & Solder	_ Flux	2. Flux Dip & Solder Dip	_ OEM unit	_ Distributors
_ OEM	_ Solder	3. Trim & Clean	_ Paperwork	_ OEM
	_ OEM parts	4. Inspect & Test Board		_ Inventory
	_ Orders	5. Assemble Unit		_ Warranty
	_ Expected demand	6. Inspect & Test Unit
		7. Pack

The customer simply wants a unit without any preventable defects.  Preventable defects need to be controlled.

_x_ Verify that all of the deliverables have been recorded.

Measure:
_x_ Determine necessary CTQ measurements in the process, the Metrics, and where to measure.
      _x_ Inputs _x_ Process _x_ Process Variables and Output functions (y=?)

Inputs are the type and condition of parts, flux, solder, and cleaning agents
The CTQ process steps are assembly, fluxing, soldering, cleaning, inspection, and testing.

(The final number of defects is significant in the returned unit repair cost, and justifies in-house repair - Ir & Tr .  However, there is a cost to in-house repair that may be eliminated by better defect prevention - Dp)

Verified that current methods of measurement were satisfactory, when work instructions were followed.  To ensure the quality of the results, only trusted workers were allowed to make the measurements to be collected.

Analyze:
_x_ List possible sources of variation seen in the measurements.
      _x_ Cause and effect diagrams 

_x_ Make list of Vital Few factors that fit data.

1. Flux and solder issues causing bad connections and shorts.
2. Undefined clipping methods causing bad connections when leads pulled.
(Testing was not causing a significant number of defects.)

 

Best Solutions for Improvement

Improvement	Costs	Benefits	Savings
1. Better work instructions	low	stop destructive practices	high
2. Monitor that work instructions are being followed	medium	prevent "forgetting" work instructions - prevent defects	high
3. Make a fixture to better hold the circuit boards for fulx and soldering.	medium	Easier handling, more even flux and soldering.	medium
4. Flux & solder adjustment based on number of defects found in inspection and testing.	low?	Reduce defects caused by changes in the environment impacting the process.	medium
5. Determine environmental effects and methods on the fulx/soldering process, make better work instructions.	medium?	Better defined process and less uncertainty related defects.	medium

Improve:
_x_ Test possible solutions.
      _x_ If anything limits testing, consider options and management support.

Improvement #1 - better work instructions, plus Improvement #2 - monitoring that the work instructions were being followed caused an immediate impact, reducing defects over 50%.  Did tie up several additional hours of supervisor time per day.

Improvement #3 - make a fixture to better hold the circuit boards for fulx and soldering had only a minor effect with the prototype fixtures.  Only significantly stopped defects due to parts shifting while being soldered.

Improvement #4 and #5 did not provide any significant results, perhaps an issue for later study.

Full scale implementation resulted in no returns due to preventable defects after implementation!

Control:
_x_ Document the improved process and ensure work instructions meet requirements.
      _x_ Provide training as necessary for the new process _x_ Verify process owners are ready.
_x_ Ensure process continues to be monitored for changes and effectiveness.
_x_ Review that project is complete.
_x_ Recognize employees who helped make the project a success.
_x_ Verify that all of the deliverables have been recorded.