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Injection Moulding Technology - Part 3 CoWC 0410 Injection Moulding Technology Part 3 Quality.

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Presentation on theme: "Injection Moulding Technology - Part 3 CoWC 0410 Injection Moulding Technology Part 3 Quality."— Presentation transcript:

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2 Injection Moulding Technology - Part 3 CoWC 0410 Injection Moulding Technology Part 3 Quality

3 Injection Moulding Technology - Part 3 CoWC 0410 To improve the delegates understanding of quality issues, relating to injection moulding and how the process can be optimised and monitored. Session aim

4 Injection Moulding Technology - Part 3 CoWC 0410 By the end of the session you will be able to: Calculate Cm and Cmk values. Explain how weight can be used to monitor the process. State 3 Quality Improvement tools. Session objectives

5 Injection Moulding Technology - Part 3 CoWC 0410 The manufacturing process MethodsPeopleMaterial EnvironmentEquipment Output Information on quality Decisions taken Quality control - Detection systems

6 Injection Moulding Technology - Part 3 CoWC 0410 Improve Designs Update Performance DoE Information on quality SPC FMEA The manufacturing process MethodPeopleMaterial EnvironmentEquipment Output Decisions taken Quality assurance - Prevention systems

7 Injection Moulding Technology - Part 3 CoWC 0410 Quality tools A combination of trials to identify optimum process conditions. e.g. L8 – 7 variables with 2 levels. DoE (Design of Experiments) Step-by-step approach to identify all possible failures in a design, manufacturing or assembly process. FMEA (Failure Mode & Effects Analysis) SPC (Statistical Process Control) A mathematical technique to measure and improve performance.

8 Injection Moulding Technology - Part 3 CoWC Process function – Capability study on m/c. 2. Potential failure modes – Zero cushion position 3. Potential effects of the failure – High scrap rate 4. Potential causes of the failure – Worn/damaged check ring 5. Current process controls – None 6. Recommended actions – a) Barrel tolerances +/ C. b) Monitor cushion position c) Visual check every 6 months (Abrasive polymers) PC & GF grades Failure Mode & Effects Analysis

9 Injection Moulding Technology - Part 3 CoWC 0410 SPC - More detail Collecting, representing and analysing data, developing and understanding patterns. A sequence of operations, not only the machine cycle. Statistical Process Control Measuring performance, taking action on the data.

10 Injection Moulding Technology - Part 3 CoWC 0410 Target Bottom Limit Top Limit Total Tolerance x x xx x x x x x Terminology xx

11 Injection Moulding Technology - Part 3 CoWC 0410 Measured sizes Target piston diameter = 60 mm (+/- 1mm) Case study 60.0 x xxxxxx xxx x x x x Target Total Tolerance x x x xx x x x xx x x x x x x x x x x x xxx x xx x x x x xx x x x Total Variation in Sample

12 Injection Moulding Technology - Part 3 CoWC 0410 Normal distribution curves x

13 Injection Moulding Technology - Part 3 CoWC 0410 Normal distribution curves x 6 x std dev (6 Sigma) = %

14 Injection Moulding Technology - Part 3 CoWC 0410 Why choose 6 sigma? x 1 sigma = 691,462 DPM or 30.9% Defect free 2 sigma = 308,538 DPM or 69.1% Defect free 3 sigma = 66,807 DPM or 93.3% Defect free 4 sigma = 6,210 DPM or 99.4% Defect free 6 sigma = 3.4 DPM or % Defect free

15 Injection Moulding Technology - Part 3 CoWC 0410 Machine capability Total tolerance 6 x Sigma Cm Cm = Cm Cm = Measure of the variation present, in relation to the available tolerance.

16 Injection Moulding Technology - Part 3 CoWC 0410 Capability = Cm = Total tolerance = 1.2 = 3 6 x Sigma 0.4 Curve fits into tolerance 3 times. High capability Tolerance = +/ Sigma ( = 0.4 )

17 Injection Moulding Technology - Part 3 CoWC 0410 Curve does not fit inside the tolerance. Low capability Capability = Cm = Total tolerance = 1.2 = x Sigma 1.6 Tolerance = +/ Sigma ( = 1.6 )

18 Injection Moulding Technology - Part 3 CoWC 0410 LSLUSL Cm = 1.67 or greater Minimum capability

19 Injection Moulding Technology - Part 3 CoWC 0410 LSLUSL Cm is still = 1.67 Minimum capability but some samples are outside limits. Target

20 Injection Moulding Technology - Part 3 CoWC 0410 Targeting Cmk Cmk = Difference between the Avg. and nearest limit 3 x Sigma Cmk Cmk = Measure of the variation present in relation to the available tolerance, combined targeting of the set-up.

21 Injection Moulding Technology - Part 3 CoWC 0410 LSLUSL Worked example TARGET Avg.(Mean) Cmk = Difference between Avg. and nearest Limit 3 x (Sigma) = Cmk = 1.67 or greater or greater x sigma =

22 Injection Moulding Technology - Part 3 CoWC 0410 Injection Moulding Technology Part 3 Quality


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