3. Product History
• The product is called as OPM Double & it is used in the assembly
of the water treatment system. First the component was developed
in metal. The product cost was too high.
• The part was made by assembling two parts to form one parts
• The component should withstand the continuous operating
pressure of 100 psi & it should pass all the product approval
procedures like leakage test, bursting test, etc
• It was a very challenging task to convert the thick walled
component (thickness around: - 8mm) into plastics & that to which
needs to be manufactured by injection molding process.
•After doing the product engineering we successfully injection
molded the component defect free.
4. Objective
• Metal to plastics substitution of the product & to make it feasible
to mold with the injection molding process.
• Product Re-Engineering using Moldflow & Structural Analysis
softwares.
• Plastic Product Design validation to match the customer’s
requirement.
• Process monitoring to ensure consistency in the quality of the
part.
5. Approach
• Studying the existing metal design & re-designing the component
considering plastic product design guidelines.
•Material selection considering customer’s requirement.
• Validation of product design & process parameters optimization
using Moldflow Software.
• Validating the design with structural point of view using FEA
Software.
• Mold-Design of the component.
• Mold-Trials to freeze the process parameters i.e. flow rate, cooling,
packing profile, mold temp, weight of component, etc.
• Process monitoring for achieving consistency in the quality of the
part.
• Part approval from the customer.
• Project Sign-off.
6. Component Application.
The image shows the assembly of the water treatment system.
The part is assembled in the area marked in the plot.
Filtration System
OPM (Part).
7. Material Selection Criteria
• The component should withstand the pressure of 100psi & it should
qualify for the bursting pressure as per the product requirements given by
the customer
• The component is used in water application hence the plastic material
should have lower water absorption.
• Good Dimensional Stability.
• The component will be in contact with water, so the material grade should
comply to the FDA & ROHS regulations (i.e. material grade should be NSF
approved & it restrict the use of lead,cadmium,mercury,etc).
• Component should be light in weight
8. Material Details
General Details
Physical Properties
Material Description
PA-12, 43% glass reinforced. NSF 61listing in several colors. FDA compliance. Low water absorption.
Hydrolytic stability. Dimensional stability. Suitable for fluid engineering applications including pump
housing, pump impellers & water meter components.
11. Challenges
Following were the challenges faced during the Product
Development: -
1. Being a thick walled component, molding the part defect free with the
injection molding process was a challenge. There was a problem of porosity
& sink marks in the thick areas which was affecting the quality of the part.
2. Longer Injection molding cycles due to higher cooling time.
3. As the length of the part was long, core-deflection was a major concern
4. High Level rejections of the product in production.
5. Optimization of the Process-parameters used for Injection molding of the
part.
12. Value Engineering
Old Metal Design
Modified Design in Plastics
12
Initially part was designed in metal by the client as shown in the top most image. Polysmart
studied the product application in details & designed the entire system in Plastics in two
parts without affecting the end application of the part.
13. Product Optimization
Further research was done on the part & finally the two plastic parts were combined together
to form one single part finally benefiting the client on the product cost without affecting the
end application.
Sr.no Description Metal
Design
Plastic
Design
1. Part Weight
(gms)
2175 344
2 Part Cost
(INR)
Above
800/-
Approx
443/-
3. Manufacturing
operations
3-4 1
4. Assembled
Parts
3-4 1
14. DFM Study
After optimizing the product design, the part was studied in detailed with respect to mold
construction & ease of manufacturing. The part was simplified & tool was manufactured
resulting in drastic reduction in the tool cost.
15. Moldflow
Gate Selection Criteria : -
1.Balance Filling at both the extreme ends
2.As there were longer core in the slides, uniform distribution of the injection pressure
is main requirement to control core deflection.
3.As it is a thick walled part, gate was placed in such a way that there should be
sufficient packing provided in the thicker region to overcome the problem of porosity
& sink marks.
16. Core Deflection Analysis
In the core deflection Analysis the constraints were assigned to the core As the side
cores were cantilever & longer in length the main concern was of core deflection
due to injection pressure. The process-parameters were optimized by Moldflow & the
part rejection due to wall thickness variation was reduced drastically.
Core Constraints
Uniform wall thickness observed
in the molded part after optimizing
the results using Core-Deflection
Analysis in Moldflow.
Core Deflection results with
different gating options.
OK Part
17. FEA Analysis
The product was Analyse for thermal loads & as well as structurally to comply to the rule &
regulation specified by the client
21. Causes of Porosity & Sink
Marks
Major aspects considered for Porosity & Sink mark Issues
• MATERIAL
-Discharge gases while molding
- High Moisture Content
- High Shrinkage
- Glass Fiber
Vital & Trivial
Variables
affecting
porosity & sink
marks
• PROCESS
- Shrinkage after Molding
- Material Too Hot
- Injection rate too fast
- Insufficient packing pressure
- Mold temp too high
• DESIGN
• PART • Tool
- Thick Wall Section
- Geometry variations
causes low probability
of the fiber alignment causing
porosity.
- Gate Design
- Gate Location
- Mold Temp
- Mold cooling
- Air Vents.
22. On line Sampling NSF/nonNSF grade Competency
Predrying of material Grinding %age Training
preventive maint of mold & machine Type of grinding
Product Design (*) Percentage of Glass
Annealing Mold Design (*)
Purging
Fiber orientation
Shot weight
Functional Testing Injection rate
dust/dirt Tonnage
ambient temperature Measurement system Barrel temperature
ambient humidity Hold on pressure
Gate type
Mold temperature
MOTHER NATURE Cooling efficiency
Screw-barrel gap
(*)- constraint
Variables in red above are significantly affecting porosity
METHOD
MEASURMENT
Porosity
& Sink
Marks
MACHINE
MATERIAL MAN
CAUSE AND EFFECT DIAGRAM FOR
POROSITY
23. DOE on Shop floor
DOE was done on the shop floor & the finally the optimised process-parameters were
identified by which we were getting the parts defect free.
By conducting DOE
We were able to
optimize the injection
Pressure which was the
main factor for
Core deflection.
24. Process Capability Study
(SPC)
11.511.010.510.09.59.0
USLLSL
Process Capability Analysis for CTQ
PPM Total
PPM > USL
PPM < LSL
PPM Total
PPM > USL
PPM < LSL
PPM Total
PPM > USL
PPM < LSL
Ppk
PPL
PPU
Pp
Cpm
Cpk
CPL
CPU
Cp
StDev (LT)
StDev (ST)
Sample N
Mean
LSL
Target
USL
1.23
0.94
0.29
1.23
0.94
0.29
0.00
0.00
0.00
1.59
1.67
1.59
1.63
1.56
1.59
1.67
1.59
1.63
0.255996
0.255996
30
10.28
9.00
10.20
11.50
Expected LT PerformanceExpected ST PerformanceObserved PerformanceOverall (LT) Capability
Potential (ST) Capability
Process Data
ST
LT
Variation (Before) Variation (After)
After doing the DOE on the shop
floor & deriving the optimised
process setting, Process Capability
Study was used to monitor the
consistency in the Quality of the
part.
27. Conclusion.
Product was re-engineered with respect to plastic product design
guidelines.
Product Design was optimised by combining two different parts to
form one single part, leading to cost saving in Material,
Manufacturing cost & Assembly processes without affecting the end
application.
The longer cycle time was addressed by cooling the 90% of the
part in mould & remaining outside the mould by putting part in water
bath to save on the cycle time & increase productivity.
By applying various methodology of Six Sigma, FEA & Moldflow
we were able to solve the chronic issue of porosity & sink marks
which was affecting the quality of the part.
Process Capability Study was used to precisely monitor the
consistency in the quality of the part.
