CHAIR LOCK

Rajko Šrimpf, Black Belt Six Sigma, Design for Six Sigma, Applied Reliability, Triz Level 3, March 2016

The DFSS project, designed with the Acclaro DFSS, CATIA and TRIZ.

IDENTIFY

Project name: Chair lock

Project overview:

The scope of this project is to design new wheels for chairs. The main function will be locking the chair while seated and unlocking while not seated.

This is especially visible in the baby chairs market. Put the baby in the chair and will lock, take it out and the chair will unlock. Lift the baby in chair and the chair will unlock and can be moved in x-y direction.

Problem statement:

Current wheels don‘t lock. Have to use very expensive one to do this.

Customers/Stakeholders:

The solution as described will adress the market for baby chairs. Market is huge and with the many players. I will work as little hours as possible.

Goal of the Project:

Will do the slick design, and ouf course with the main point on the cost of material and processing equipment. So to use as little as possibble.

Scope Statement:

Some sort of 3D model prints? Cant‘t tell for sure if I‘m gona make them.

Project financial benefits:

This is DFSS project. I will go with this project as it is and not change Acclaro DFSS when the changes come. We will see how good I have predicted the outcome.

Some old design even with the lock and some new development in this field. Basically the same principle but different design. Don‘t know the name of the developers. Isn't my intention to copy their design, only want to show different approach designing this products. And by the way, I like this new design.

Wheels are 3 Stage product

We hit developement limits.Products sell on design apeal and price.Recomendation: COST REDUCTION!But how? Everbody looks almost the same and uses the same solutions.Can we find another? Can‘t do cost reduction, rather I will add a feature customer is willing to pay for.

Sandard wooden chair for babies. We will add wheels with the lock on the base of the chair.

DEFINE

Solution of thw wheel

Solution of the locking mechanism

Covering the product

Category

Covering the product33,3%

Solution of the locking mechanism33,3%

Solution of thw wheel33,3%

CTQ of the CHAIR project

DESIGN

So we got here 1.1.3 Standard solution from TRIZ. Nice Su-Fields thou. They rule and seems like we have got here the working Principle 1: Segmentation to use.

FIRST DESIGN

Axiom 1: The Independnce Axiom: Maintain the independance of the functional requirements.

Axiom 2: The Information Axiom: Minimize the information contect in a design.

We have decoupled design, so it is than more likely that we will achive Six Sigma quality level.

So, I would be happy even with the 5 Sigma level.

CTQ 1

CTQ 2

CTQ 3

Top level FR statement

- Locking the chair with the puting the baby into the chair- Don‘t need to do lifting the chair when moving without baby.

Moving in X-Y direction with ease even when the chair is heavy

SECOND DESIGN

Axiom 1: The Independnce Axiom: Maintain the independance of the functional requirements.

Axiom 2: The Information Axiom: Minimize the information contect in a design.

We have decoupled design, so it is than more likely that we will achive Six Sigma quality level.

So, I would be happy even with the 5 Sigma level.

CTQ 1

CTQ 2

CTQ 3

Top level FR statement

- Locking the chair with the puting the baby into the chair- Don‘t need to do lifting the chair when moving without baby.

Moving in X-Y direction with ease even when the chair is heavy

Damm it, I got jet another version of the working principle. So that takes actually 3 versions. CAD times 3x. Damm.

1. 2. 3.

THIRD DESIGN

Axiom 1: The Independnce Axiom: Maintain the independance of the functional requirements.

Axiom 2: The Information Axiom: Minimize the information contect in a design.

We have decoupled design, so it is than more likely that we will achive Six Sigma quality level.

So, I would be happy even with the 5 Sigma level.

CTQ 1

CTQ 2

Top level FR statement

- Locking the chair with the puting the baby into the chair- Don‘t need to do lifting the chair when moving without baby.

Moving in X-Y direction with ease even when the chair is heavy

So Kano is the same for all 3 solutions. Let‘s do now Pugh matric to choose the best one.

So we got a winner solution 3. Close call but its ok. CAD cyclus will go only into solutions 3. Why waste time on others if theyare not up to the task?

OPTIMIZE

ISO 2009 SCREW M3x6 STEEL GRADE A COUNTERSUNK SLOTTED FLAT HEAD

01

02

03

04

05

07

08

10

ISO 7089 WASHER 8x16 STEEL GRADE A PLAIN NORMAL SERIES

09 SAME NOT SYMETRY PART

BILL OF MATERIAL01 – RUBBER02 – PIN03 – BASE04 – SPRING05 – RING07 – PLATE08 – WHEEL09 – WHEEL10 – AXL

Putting the baby into the chair LOCKS.

Lifting the baby or the chair UNLOCKS.

Guess you wondered what kind of spring to use? This chair weights about 11.2 kg. So 4 springs should hold this weight and compress additionaly when put the baby into the chair.

RPN 1 13 3 2 2 2 1 1 1

Percent 5,9 5,917,6 17,6 11,8 11,8 11,8 5,9 5,9 5,9

Cum % 94,1 100,017,6 35,3 47,1 58,8 70,6 76,5 82,4 88,2

Item WheelSpringScrewRingPinWasherPlateAxlRubberBase

18

16

14

12

10

8

6

4

2

0

100

80

60

40

20

0

RP

N

Pe

rce

nt

Pareto Chart of RPN parts

This is DFMEA for all parts. I think that comercial part will do ok. The base should have proper plastic material to whitstand all the tear and wear in a liftime of the product. Seriously, babies don‘t weight several 10 kilos anyway.

VALIDATE

So I worked as little hours as possible and didn‘t change Acclaro DFSS in anyway even when changes came. Bad predictions maybe, but the last solution is the optimal.

I have calculated the working hours, less then 60 I may say with the ppt included. Acclaro DFSS with the traces really cuts time in design. When traces are not ok, you may have a problem and do not forget about the bad coupled designs, thay are not that rare.

So the solution works and I am really thinking on doing another project.

Patent application is not calculated in the working hours. It‘s better to spent there more than to little and have later enormous problems.

Rajko Šrimpf, 28.3. 2016