Wednesday, December 11, 2019

SPC | Statistical process control | QSQTECH.COM

STATISTICAL PROCESS CONTROL (SPC) :

Hello friends, Today, we are talking about SPC.

Topics that we are covering today:

INTRODUCTION
BASIC TERMS OF STATISTICAL PROCESS CONTROL
VARIABILITY: TYPES OF CAUSES
QUALITY MEASURES : TYPES OF DATA THAT USE IN SPC TERM
CONTROL CHART

So friends lets start without wasting time.

INTRODUCTION:

SPC means Statistical process control. It means that we control and monitor our process based on data.
From the data, we find out what are the trends of our process and how many variations in the process or where is going our process. It is monitored and if any defect is being generating in it then identify their causes and try to improve the process.

Definition:

Statistical process control (SPC) is a scientific visual method which is used to monitoring and controlling the manufacturing processes by eliminating variations of special causes to improve the quality.

BASIC TERMS OF SPC:

1. Statistical process control:

In this, we monitor the production process to detect and prevent poor quality.

2. Sample:

A single item which is taken from a lot of items for inspection to know that the lot is acceptable or not.

Control chart:

Process is within statistical control limits.

VARIABILITY:

There are two causes of variation in any process.
1. Random causes
2. Non Random causes

1. Random causes:

It includes common causes.

Common causes are inherent in process and generally are not controllable by process operator. For example: variation in raw material, Variation in ambient temperature and humidity.
It can be eliminated only through improvements in the tools or system.

2. Non Random causes:

It includes special causes.

It clearly identified what the cause of defect generation.
It can be modified through operator or help of management team action.
For example: tool wear, gross changes in raw materials, and broken equipment. Sometimes, it is also called assignable causes.

QUALITY MEASURES:

There are 2 types of data :

1. Attribute

2. Variable

1. Attribute:

This type of product characteristics that can be evaluated with a discrete response.

E.g. Yes - No, Good - Bad etc.

2. Variable:

This type of product characteristics that can be measures.

E.g. Weight - Length

CONTROL CHART:

The control chart is a graph in which the control limits are defined. Control limits are the upper limit and lower limit.

Process control chart

The process control chart is shown in pic.

In this, number of samples are showing which is from 1 to 10. The lower control limit and upper control limit are shown which is the lower specification and upper specification and a centerline is the mean or also called as a target line. The process must be at the target line or around it.

In this, all the points are around the target line but the second last point is outside the upper control limit. Where the point has gone beyond the upper limit, this means that there will be generate defects in the process.

Similarly, we are able to monitor the data with the help of control chart. We can also detect & control the defects in the process.

Below points are shown that process is under control:

A process is in control if:

The points of reading of the sample will not be outside the control limit.
Most points will be near the target or average line.
There should be equal number of points in the above and below the center line.
The number of points should be appear randomly distributed.

TYPES OF CONTROL CHART:

1. Attribute control chart

p chart
np chart
c and u chart

2. Variable control chart

Range (R- chart)
Mean (x- bar chart)

1. Attribute control chart:

Attributes control charts are used for discrete or count the data. There are several scenarios where the classification of measurements in only one category has quality characteristics of interest. Those variable that are defined as

Good/bad
Yes/no
Acceptable/not acceptable
Ok/ng

And typically it measures the defective by counting.

The following attributes control charts will be discussed:

Types of Attribute control chart

The p chart (Fraction nonconforming control charts)
The np chart (Number nonconforming control charts)
The c and u chart ( Control charts for non conformities

2. Variable control charts:

Type of Variable control chart

In this, two charts are include;

Mean (X bar chart): It is also known as average chart or x bar chart.

Mean / X bar chart of data

As shown in above pic,

Here,
Given, LCL = 42.88 and UCL = 52.52
Then, we find out x̿ = 47.7
Here, x̿ = Average/mean of points

Range (R chart): It is also known as R chart and is used to shown the variation in range in the process.

Range/R bar chart of data

As shown in above pic,
Here,
Given, LCL = 0 and UCL = 17.65
Then, we find out R̿ = 8.35
Here, R̿ = Average of the points of Range

We hope you will understand this topic.

Thank you 😊

Some of related question that help to improve your basic knowledge.

To know about Defect analysis

What do you mean by Quality control?

What is Quality assurance? Available in hindi also.

Wednesday, December 4, 2019

PPAP | Production Part Approval Process | QSQTECH.COM

PRODUCTION PART APPROVAL PROCESS (PPAP):

Hello friends,
Today, We'll discuss on Production Part Approval Process (PPAP). Hopefully, you'll understand this topic.
First of all, thanks for visiting.
Now, below topics that are covering today.
Introduction
Necessity of PPAP
PPAP Documents
PPAP Process Requirements

INTRODUCTION :

PPAP is the way to prove that the supplier will meet the customer's requirements.

Training on PPAP- pdf in hindi click here to download pdf

It is generally formed by the AIAG (Automotive Industry Action Group) in 1993. He had taken input from BIG3 ( Ford, Chryslers, GM) and based on that, he developed this guide. The recent version of PPAP is the 4th edition which is currently running. It was publish on 1 June 2006 by AIAG.
Initially PPAP was adopted by the automotive industry but understanding the benefits of its concept all other industries have adopted this concept.

PPAP is the process for the supplier not for the customer.
PPAP submission is an event for the customer to review and approve.
It is the one in 5 core tools of Quality management system.

In this, 19 documents including which the supplier submits to the customer, which are related to the drawing.
Then the customer starts reviews and Approval process for running the new parts.
The customer comes to the supplier to review and see if the supplier is following the standards of the documents or not.
If customer feels everything is right that the supplier can meets the customer requirements then the customer gives approval for the production of new part.

Necessity of PPAP:

PPAP states that supplier is ready for production and will fulfill the customer's requirements and provide quality products to the customer.
PPAP provides evidance that the customer engineering drawing records and required specification are clearly understood and supplier is ready to fulfilled their requirements.
It ensure that a suppler can meet the required production ability and quality that is given to customer.

PPAP Documents:

There are 19 documents that are given to customer in PPAP.

Design Record
Authorized Engineering Change (note) Documents
Customer Engineering Approval
Design FMEA
Process Flow Diagram
PFMEA
Control Plan
Measurement System Analysis Studies (MSA)
Dimensional Results
Material / Perfomance Test Result
Initial Process Capability Study
Qualified Laboratory Documentation
Appearance Approval Report
Sample Production Part
Master Sample
Checking Aids
Customer specific requirement
Part Submission Warant (PSW)
Bult Material Requirement checklist

1. Design Record:

The supplier shall have the design records for the product (such as drawing given by customer or design approved by customer) that including the design and description of saleable parts.

If the customer is responsible for design then it will be in the form of customer drawing.
If the supplier is responsible for design then it will be in the form of supplier released drawing.
In both the cases, when design record is in the electric form, produce a hard copy and a printed copy of drawing must be submitted.

Note:

There will only one design record regardless of design responsibility.
Design record may refer to other documents that making part of design record.
Enter the date the original drawing or design record was initially completed.

2. Authorized Engineering Change (note) Documents:

Usually this is called " Engineering Change Notice".
It is the document that shows the detailed description of the changes during part development or before mass production.
Organization shall have the document "Authorized Engineering Change Note" for these changes note yet recorded in design record but incorporated in the product, parts or tooling.

Lets assume,

The customer issue an ECN to the supplier via mail but the same ECN is not implemented in customer drawing then before supply the part to customer, supplier attach ECN copy. This ECN copy is called Authorized Engineering Change Document.

At the time of developing the part, it is not applicable if the customer not given ECN.

And if the customer has implemented it in the drawing after the ECN, then this document is not applicable.

3. Customer Engineering Approval:

When specified by the customer, the supplier shall have evidence or Engineering Change Approval. The Customer Engineering Approval section is relatively new and was included in the latest AIAG PPAP.

Taking approval of the customer, Wherever you have made engineering changes, then you also have to submit the evidence.

For example,

If the supplier is not capable to make any dimension, then supplier takes deviation from customer for it through mail or in MOM. This mail or MOM (if customer approved) is called Engineering Change Approval.

Deviation:

Any approval from customer, regarding changes in part dimension is called deviation.

4. Design FMEA:

If supplier is responsible for design, then it is necessary to make Design FMEA (Failure Mode Analysis).
After that Documents of Design FMEA is submitted to customer.

5. Process Flow Diagram:

The supplier shall have a Process Flow Diagram that clearly describe the production process steps and sequence.
A copy of Process Flow Diagram is submitted to customer.

6. PFMEA:

The supplier shall have a Process FMEA developed in accordance with the customer requirements.
Its evidence is submitted to customer.

7. Dimensional Results:

The supplier shall provide evidence that dimensional verification required by the design record and the control plan have been completed and results indicates compliance with specified requirements.
The supplier shall have dimensional results for each manufacturing process.
It means if supplier is producing parts from multiple cavity / die of the mould, then the resultant result emanating from each of the parts are to be given to customer as evidence.

8. Measurement System Analysis studies:

It is also known as in short MSA studies.
The records submits to customer of MSA studies, e.g. gauge R & R, bias, linearity, stability studies in PPAP.

9. Qualified Laboratory Documentation:

The supplier shall have a laboratory scope and documentation showing that laboratory used is an accredited laboratory.
And its evidence is submitted to customer.

10. Control Plan:

There are 3 types of control plan : 1. Prototype, 2. Prelaunch, 3. Production and supplier is submits the documents required control plan by the customer.
Control plan defines all controls used for process control and complies with IATF 16949 : 2016 requirements.

11. Material / Performance Test Result:

In this 2 types of Test Results :

Material Test Result
Performance Test Result

1. Material Test Result : In this, the supplier shall perform tests for all parts material when chemical, physical, or metallurgical requirements are specified by the design record or control plan.

2. Performance Test Result : In this, the records of test results of functions in the parts also submitted by the supplier as per requirements.

12. Intial Process Capability Study:

If Index value > 1.67 = The process currently meets the customer's requirements, after approval, begin production and follow control plan.
If 1.33 > (Index value) >1.67 = The process is currently acceptable but may require some improvements.
If Index value < 1.33 = The process does not currently meet the acceptance criteria.
If Unstable process = Depending upon the nature of the instability, an unstable process may not meet customer requirements.
Process with one - sided specifications or Non - normal distribution= The supplier shall determine with the customer an alternate acceptance criteria for processes with one - sided specifications or non - normal distribution.Strategy when acceptance criteria is not specified then the supplier shall contact the customer if the process cannot be improved.

13. Appearance Approval Report:

A separate Appearance Approval Report shall be completed of each parts that are easy to visual on outer side (External parts)

for which a submission is required if the part had appearance requirements on the design record.

14. Sample Production Part:

The supplier shall provide the sample product as requested by the customer and as defined by the submission request.

15. Master Sample:

The supplier shall retain a master sample for the same period as the production part approval records.

The supplier shall retain a master sample for each position of a multiple cavity, die & mould etc.

16. Checking Aids :

If requested by the customer , the supplier shall submit with the PPAP submission any part - specific assembly or component checking aids.

17. Customer Specific Requirements:

The supplier shall have records of compliance to all applicable customer specific requirements.

18. Part Submission Warant (PSW):

After the supplier submits all the documents and activities, the final observation or summary is to be summarized into the Part Submission Warrant (PSW).

A saperate PSW shall be completed for each customer part number unless otherwise agreed to by the customer.

19. Bulk Material Requirement Checklist:

For bulk material, The Bulk Material Requirement Checklist shall be jointly agreed upon by the customer and supplier.

PPAP Process Requirements:

For production parts, products for PPAP shall be taken from a significant production run. This production run shall be from 1 hour to 8 hours and with the specific production quantity to total a minimum of 300 consecutive parts.

Unless otherwise specified by the authorized customer quality representative.

This run shall be manufactured at the production site using the tooling, gauging, process, materials and operators from the production environment.
Parts from each unique production process e.g. each position of a multiple cavity / die shall be measured and representative parts tested.

We hope you will understand this topic.
Thank you.