Takt time & Cycle time

TAKT TIME VS CYCLE TIME DEFINATIONS & CALCULATION WITH EXAMPLES

          Normally many of us get confused between Takt time & Cycle time. There is a big difference in    

          both the terms. Let us find out the Difference in their definition first.

                                                     TAKT TIME:

Takt time is the maximum amount of time in which product need to be produced to meet the customer demand. Or in other words Takt time is the speed in which product need to created or manufactured to satisfy the needs of customer.

          So TAKT TIME Formula 

                 = (Net Time Available for Production)/(Customer’s Daily Demand)

          Let's us consider the example from manufacturing industry.

         Example:

         Company A require 350 pcs to be manufacture in a day.

        Based on the requirement Company B will calculate the Takt time for the same.

        Let us say  available time for production is 7 hours 30 minutes (excluding rest time & lunch  

        time) that is 450 minutes, but from this also you need to minus the 5s time or start up time if any 

        during start of shift or end of shift. So let us say 5 minutes time is used for 5s or start up during 

        start of shift & 5 minutes of 5s at end of shift.

        So, Net available time = 450-10= 440 minutes

        Takt time  =  440⁄350  =  1.25 min/pcs

        Takt time assumes a constant daily demand during a day, if daily demand changes Takt time need 

        to be adjusted.

       So, basically above calculation of Takt time gave us the idea that we need to manufacture a part in 

        1.28 minute to meet the company A demand.

  

                                                    CYCLE TIME

        Cycle time: It is the actual time spent on working for manufacturing an product, measured from 

        start of first task to the end of last task. Cycle time includes both Value added time as well as non 

        Value added time.

        

       Let us understand this with the help of example:

       

       Company B produces 180 pcs in 7 hours 30 minutes ( one shift time net production time) ,we 

       assumed that there is no line stoppage

       

       Cycle time =   Total run time or net production time/ number of unit produced

                         =    450/180 = 2.5 minute/pcs

      So, now if we compare with our takt time calculated above, you will not be able to feed the  

     Company A , Assembly line as our cycle time is more than the Takt time.

     for this either need to run 2 shifts for meeting the company A demand or either you need to process 

    improvements  in company B assembly line so that Company A requirement can be met.

    By proper calculation of Cycle time & Takt time we can attain lot of benefits:

   1) Primary benefit of calculating Cycle time of your product is that you can determine if you are

       going to meet the customer requirement or not.

   2) Proper calculation of cycle time allow you to proper set up of the processes, it is important for

    understanding how many machines, stations or personnel are required for meeting the Takt time so

     that requirement can be met.

   3) Cycle time help you to identify if there are some improvements or LCA can be done to achieve 

       Takt  time.

   

Thank you for reading the article.

If you have any query please mention in comment box.

    

   

PPAP

Introduction to PPAP (Production Part Approval Process)

Introduction

Production Part approval process is used in the Automotive & Aerospace industry to establish the confidence in suppliers & their production process.

The PPAP process is designed to demonstrate that a supplier has developed their design

and production process to meet the Customer requirements, minimizing the risk of failure by

effective use of APQP

Why PPAP is required

The purpose of any Production Part Approval Process (PPAP) is to:-

• To ensure that the processes used to manufacture parts can consistently reproduce the parts at required/stated production rates during routine production runs
• PPAP is to determine that all customer requirements are understood & to demonstrate that supplier process has the capability to produce the parts that consistently meet customer requirements
• Ensure that a supplier can meet the manufacturability and quality requirements of the parts supplied to the customer

WHEN PPAP IS REQUIRED

• A PPAP is required when production of a new product or part is planned and when there is any significant change to a product or process

• A customer may request a PPAP at any time during the life of a product. PPAP may be required for all components and materials incorporated in the finished product, and may also be required if components are processed by external sub-contractors.
  For suppliers, this means they need to maintain & develop a quality system that documents all of the requirements of a PPAP submission, no matter if you have been asked to deliver PPAP or not, it is must. Customers are not responsible for creating PPAPs, suppliers are responsible for creating & maintaining the PPAPs.
• There are five Phases in APQP & PPAP is required in Phase-4 of APQP

PPAP APPROVAL PROCESS

• PPAP is a series of documents gathered in one specific location (a binder or electronically) called the "PPAP Package". The PPAP package is a series of documents which need a formal certification / sign-off by the supplier and approval / sign-off by the customer

• The form that summarizes this package is called PSW (Part Submission Warrant). The signature in the supplier certification area of the PSW indicates that the supplier-responsible person (usually the Quality Engineer or Quality Manager) has reviewed this package and that the customer-responsible person (usually a Customer Quality Engineer or Customer Quality Manager) has not identified any issues that would prevent its approbation

ELEMENTS OF PPAP PACKAGE

There are 18 elements included in the PPAP Package

1. Design record with all specification
2. Authorized engineering change number (AECN)
3. Customer Engineering Approval
4. DFMEA (Design Failure Mode and Effects Analysis)
5. PFD/PFC (Process Flow Diagram/Chart)
6. PFMEA (Process Failure Mode and Effects Analysis)
7. Control Plan
8. MSA Study (Measurement System Analysis)
9. Dimensional Results
10. Material, Performance Test Result
11. Initial Process Studies/SPC (Statistical Process Control)
12. Qualified Laboratory Documentation
13. Appearance Approval Report (AAR)
14. Sample Production Parts
15. Master Sample
16. Checking Aids
17. Customer specific Requirements
18. Part Submission Warrant (PSW)

Now, we will briefly understand the meaning of each document

Design record with all specification

• A Printed copy of drawings need to be provided. If the customer is responsible for designing it is the copy of customer drawing latest revision. If the supplier is responsible for designing it is the copy of Supplier latest release drawing in system.
• Each & every feature must be “ballooned”  correspond to inspection results (Inspection report/PDQA report) 
• Part matrix must be included which shows the revision history of drawings with the latest revision   ( Part matrix is the document which record the model, drawing part number, its release date & event for which the drawing is released)

Authorized engineering change number (AECN)

• A document that show detailed description of the change. Usually this document is called as “ Engineering Change notice”

So, basically ECN must be done for both internal change or External change “Change requested by customer” & its record should be maintain in ECN control register for that particular product

Customer Engineering Approval , if Required

• This approval is usually the Engineering trial with production parts performed at the customer plant. A "temporary deviation“ usually is required to send parts to customer before PPAP.
• Customer Engineering Approval usually refers to (a positive outcome of) a trial at the
  customer’s facility conducted with production parts from the supplier.

DFMEA (Design Failure Mode and Effects Analysis)

• This is only Applicable when the Supplier is design responsible

PFD/PFC (Process Flow Diagram/Chart)

• Process Flow Diagram, also known as a process flow chart, shows the document and clarifies all steps required in the manufacturing of the part. The process flow diagram must match both the control plan and the Process Failure Mode and Effects Analysis (PFEMA). The process flow diagram must include all of the main steps in the processing of the part and also all offline activities such as handling, measuring, inspection etc.The diagram/chart also needs to show the flow of non-conforming materials (rejects/rework)

PFMEA (Process Failure Mode and Effects Analysis)

• A PFMEA is a structured technique that helps a team think through “everything” that may go wrong in a process
• The severity or impact of each failure is rated, the potential that a specific failure may actually occur is factored in and the probability that the failure can be prevented or at least detected is considered.
• The intent is to identify risks that are unacceptable and initiate corrective plans that mitigate those risks and help make the process more robust

Control Plan

• A copy of the Control Plan, reviewed and signed-off by supplier and customer
• The Control Plan follows the PFMEA steps, and provides more details on how the "potential issues" are checked in the incoming quality, assembly process or during inspections of finished products

MSA Study (Measurement System Analysis)

• MSA usually contains the Gauge R&R (repeatability & reproducibility) for the critical or
  high impact characteristics, and a confirmation that gauges used to measure these
  characteristics are calibrated.

Dimensional Results

• A list of every dimension noted on the ballooned drawing. This list shows the product characteristic, specification, the measurement results and the assessment showing if this dimension is "ok" or "not ok".
• If any parts do not meet the correct specification for a valid reason which could continue into mass production then the supplier should create an exception report & submit to customer with reason why the part is not meeting the correct specification.

Material, Performance Test Result

• Material Tests refer to chemical, physical or metallurgical requirements specified by the Design Record or Control Plan.
• A summary of every test performed on the part. This summary is usually on a form of DVP&R (Design Verification Plan and Report), which lists each individual test, when it was performed, the specification, results and the assessment pass / fail.

Initial Process Studies/SPC (Statistical Process Control)

• Initial Process Studies are used to evaluate whether a (supplier’s) process can meet
  Special Characteristics or (Critical Characteristics) defined by the customer.
• Objectives of Initial Process Studies are to determine if production processes are
  stable, will yield acceptable outputs for critical or special characteristics and are ready
  to begin process validation builds.

Qualified Laboratory Documentation

• If testing is performed in a supplier’s internal lab, they must provide a copy of their quality certification
• When submitting test results, include documentation showing that the laboratory is qualified or accredited.
• Inspection and testing is to be performed by a lab qualified (or accredited) to conduct the types of tests and measurements.

Appearance Approval Report (AAR)

• Complete an Appearance Approval Report (AAR) for each part (or series of parts) that have appearance requirements noted on the Design Record.
• If the part or product does not have appearance requirements, the AAR is not required

Sample Production Parts

• The supplier must provide the customer with a sample of the subject part (or parts) for approval.
• The part(s) must come from a significant production run and be the same part(s) referenced in the PPAP package.

Master Sample

• A Master Sample is to be signed off by both the customer and the supplier when they agree that the sample part meets all the design requirements and any special customer requirements. It is often used as the benchmark for future production runs

Checking Aids

• When special tools are used they should be photographed, documented and included in this section, and this should also include the calibration records of the tools and the dimensional report from the tools

Customer specific Requirements

• All requirements over and above the standard PPAP documentation level specified by the customer are included in this element.

Part Submission Warrant (PSW)

• The PSW is a summary of the PPAP submission complete with all applicable data for the 18 Elements.
• A PSW is required for each of part or part number. This form shows the reason for submission (design change, annual revalidation, etc.) and the level of documents submitted to the customer. There is a section that asks for "results meeting all drawing and specification requirements: yes/no" refers to the whole package. If there is any deviations the supplier should note on the warrant or inform that PPAP cannot be submitted
• PPAP requirements are typically distinguished by level as follows:

Level 1 – Part Submission Warrant (PSW) only submitted to the customer.

Level 2 – PSW with product samples and limited supporting data.

Level 3 – PSW with product samples and complete supporting data.

Level 4 – PSW and other requirements as defined by the customer.

Level 5 – PSW with product samples and complete supporting data available for review at the supplier's manufacturing location. Complete documentation


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