injection moulding technology
DESCRIPTION
Injection Moulding Technology. Part 3. Quality. Session aim. To improve the delegates understanding of quality issues, relating to injection moulding and how the process can be optimised and monitored. Session objectives. By the end of the session you will be able to:. - PowerPoint PPT PresentationTRANSCRIPT
Injection Moulding Technology - Part 3
CoWC 0410
Injection Moulding Technology
Part 3
Quality
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
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
Injection Moulding Technology - Part 3
CoWC 0410
The manufacturing process
Methods People Material
Environment Equipment
Output
Information on quality
Decisions taken
Quality control - Detection systems
Injection Moulding Technology - Part 3
CoWC 0410
ImproveDesigns Update
PerformanceDoE
Information on qualitySPC
FMEA
The manufacturing process
Method People Material
Environment Equipment
Output
Decisions taken
Quality assurance - Prevention systems
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.
Injection Moulding Technology - Part 3
CoWC 0410
1. 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 +/- 100C. b) Monitor cushion position c) Visual check every 6 months (Abrasive polymers) PC & GF grades
Failure Mode & Effects Analysis
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 themachine cycle.
Statistical
Process
Control
Measuring performance, taking action onthe data.
Injection Moulding Technology - Part 3
CoWC 0410
TargetBottom
LimitTopLimit
Total Tolerance
x x xx x x x x x
Terminology
xx
Injection Moulding Technology - Part 3
CoWC 0410
Measured sizes
Target piston diameter = 60 mm (+/- 1mm)
Case study
60.0
x x x x xx xx x xx
xx
x
61.2
60.8
60.6
60.4
60.2
61.0
58.8
59.8
59.4
59.2
59.0
59.6
Target
Total Tolerance
xx
xx xx
x xx x
x
x
xx
xx
xx
x
xx
x x x
xxx
xx
x
xxx
x
xx
Total Variation in Sample
Injection Moulding Technology - Part 3
CoWC 0410
Normal distribution curves
x
Injection Moulding Technology - Part 3
CoWC 0410
Normal distribution curves
x
6 x std dev (6 Sigma) = 99.9997%
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 99.9997% Defect free
Injection Moulding Technology - Part 3
CoWC 0410
Machine capability
Total tolerance6 x Sigma
CmCm =
CmCm = Measure of the variation present, in relation to the available tolerance.
Injection Moulding Technology - Part 3
CoWC 0410
Capability = Cm = Total tolerance = 1.2 = 36 x Sigma 0.4
Curve fits into tolerance 3 times.
High capability
Tolerance = +/- 0.6
6 Sigma
( = 0.4 )
Injection Moulding Technology - Part 3
CoWC 0410
Curve does not fit inside the tolerance.
Low capability
Capability = Cm = Total tolerance = 1.2 = 0.756 x Sigma 1.6
Tolerance = +/- 0.6
6 Sigma
( = 1.6 )
Injection Moulding Technology - Part 3
CoWC 0410
LSL USL
Cm = 1.67 or greaterCm = 1.67 or greater
Minimum capability
Injection Moulding Technology - Part 3
CoWC 0410
LSL USL
Cm is still = 1.67
Minimum capability
but some samples are outside limits.
Target
Injection Moulding Technology - Part 3
CoWC 0410
Targeting
CmkCmk = Difference between the Avg. and nearest limit
3 x Sigma
CmkCmk = Measure of the variation present in relation to the available tolerance, combined targeting of the set-up.
Injection Moulding Technology - Part 3
CoWC 0410
LSL USL
Worked example
TARGETAvg.(Mean)
Cmk = Difference between Avg. and nearest Limit
3 x 0.035 (Sigma)=
Cmk = 1.67Cmk = 1.67 or greateror greater
0.215
0.105
3 x sigma
= 2.04
0.215
Injection Moulding Technology - Part 3
CoWC 0410
Injection Moulding Technology
Part 3
Quality