Hello and welcome to this blog post. Today's topic is plastic part design, and as a helpful resource for your upcoming project, I have included my material selection checklist.
Polymer material selection - an important step in the plastics part design process
Unlike the typical process of finishing the design and then searching for a suitable material, material selection is best done in tandem with the design development.
Design can adjust to material restrictions and capabilities when material selection is developed concurrently.
Technical data sheets (TDS) and material selection tools can be used to compare potential materials to design criteria and component service conditions. The data can be entered into a checklist, highlighting qualities that are not relevant.
A checklist is useful since it makes sure that no manufacturing detail, property, or service requirement is missed.
Covering effectively the product requirements, a combination of functionality questions and selection factor questions can support you to achieve this. The functionally and selection factor questions can be found here.
A Polymer Part Design Checklist, I published together with design engineer Vatsal Kapadia here.
Polymer Material Selection Requirements Checklist
My checklist consists of 12 sections and next we have a detailed view on all the sections. You can download the Material Checklist here. The checklist is in line with Step 1 of my Polymer Funnel methodology.
In this first stage we map out the true part functions and material requirements. After this we translate the requirements into material selection factors (Figure 1).
This can be done with the support of questions (summarized in the checklist) such as what load does the plastic part need to carry? Or/and will the part be exposed to chemicals?
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| Figure 1: Designing with plastics - Polymer Material Checklist as support tool for Funnel stage 1. |
1. General
-Performance requirements (structural, etc.)
-Combining multiple parts or functions
-Structural load (static, dynamic, cycling, impact, etc.)
-Environment (Chemical, temperature, time)
-Tolerance requirements
-Lifetime of product
-Quantity of product vs. manufacturing process
-Secondary operations
-Packaging and shipping
2. Environment
-Temperature
-Time
-Load
-Chemicals, water, humidity, etc.
3. Engineering Design Data
-Type of load
-Frequency of load
-Stress rate (compression, tensile, flexural)
-Strain amplitude
-Load deformation (tensile, compression, shear, etc.)
-Apparent modulus (includes strain due to creep)
-Direction of load
-Correlating test data with end use
-Safety factor
4. Part Geometry Data
-Part volume
-Size restrictions for design?
-Thickness restrictions for design?
5. Material and Process
-Directional layout of reinforcements
-Regrinding
-Pre-drying
-Prototyping (machining, moulding, additive manufacturing)
6. Appearance
-Style
-Shape
-Colour
-Surface finish/ weld lines / flow lines/ parting line / gate location
7. Tests (UL, SAE, ATIM, etc.)
-Tension
-Compression
-Creep
-Dynamic/ fatigue/torsion
-Impact
-Poisson’s ratio
-Continuous service temperature / UL temp. index
8. Economic Factors
-Cost of present part and cost aim
-Cost estimate of part with plastics
-Faster assembly and elimination of finishing operation
-Redesign part to simplify product
9. Sustainability Factors
-Use of regrind
-Post industrial recycling (PIR)
-Post consumer recycling (PCR)
-Biosourcing
-Lifecycle assessments (ISO 14040)
10. Temperature Range of Part
-Short term and long term heat exposure
-Heat aging - retention of properties over time and temperature
-Dimensional stability at elevated temperature
-Hydrolysis stability needed
11. Flammability and Electrical Requirements
-Parts needs flame rating (UL 94 - V0, HB, etc.)? If yes, at which thickness?
-Glow wire or unattended appliance requirement?
-Electrostatic Discharge Shielding (ESD)
-Electro Magnetic Interference (EMI) shielding
12. Special Requirements
-UV exposure?
-Chemical exposure
-Additional approvals and RoHS
-Material restrictions (halogen, copper, etc.)?
-Special environments (nuclear protection needed)?
-Overmoulding concerns
-Warpage concerns due to mating with another part
-Laser welding needs?
-Special colorability?
-Conductive requirements (thermal conductive and electrical isolating)?
You can download the Material Checklist here.
I offer to select the optimal polymer for your project, doing the polymer material selection together with you, and also teaching polymer material selection as a training in a group - let me know how I can help you here.
Thanks for reading and #findoutaboutplastics
Greetings
Herwig Juster
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Literature:
[1] https://www.findoutaboutplastics.com/2020/08/what-is-difference-between-industrial.html
[2] https://www.hardiepolymers.com/knowledge/designing-with-plastics/
[3] https://www.findoutaboutplastics.com/2022/08/polymer-material-selection-defining.html
[4] https://www.polymermaterialselection.com/online-selection-tools
[5] https://www.polymermaterialselection.com/contact-me
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