THE ADVANTAGES OF PLASTICS
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MATERIALS AND TECHNICAL CAPABILITIES
VALVES & PUMPS
Is plastic always injection molded?
Injection is a widespread process for producing thermoplastic parts in series, but the choice depends on the material and the drawing. Rubber and elastomers may require molding and vulcanization; conventional PTFE uses specific cycles, different from ordinary thermoplastic injection. For some geometries or quantities, CNC machining of a semi-finished product may be suitable. EDR assesses injection, vulcanization, overmolding and CNC according to the component’s needs. The injection process described here applies to thermoplastics and should be distinguished from the cycles for rubber and PTFE.
How is the material selected for the application?
Besides stiffness and strength, temperature, contact with fluids, outdoor exposure, friction and dimensional stability must be considered. Among thermoplastics, PP and ABS can be evaluated, for example; for technical functions, PA, POM or PC, with compatible fillers and reinforcements where needed. The family name alone does not identify performance: grade, formulation and operating conditions matter. EDR verifies the material with the manufacturer, asking for the functional properties and the documentation needed for the component to be defined.
When is it worth investing in a mold?
The mold must be assessed together with the number of parts expected over the product’s life. Geometry, material, cavities and finish affect its cost, while cycle time and scrap affect the series price. Undercuts and areas that are hard to eject may require additional mechanisms. EDR compares these elements with the quantities and frequency of supply; where appropriate, it assesses a different process. Batch size, sampling, ownership and management of tooling are defined in the proposal.
How are part tolerances and stability assessed?
Shrinkage, cooling and polymer behavior affect dimensions. Humidity and operating temperature can alter them further. Tolerances and measuring conditions must be agreed for the specific material, checking samples in the intended condition.
Which drawing details affect part quality?
Uneven wall thicknesses, massive ribs and insufficient draft can cause sink marks, warping or ejection difficulties. Gate locations, weld lines and ejector marks must be assessed on functional and cosmetic surfaces.
Can parts for food contact be produced?
Food use requires verification of the grade, the contact conditions and the documentation applicable to the finished part. The polymer name is not enough. Requirements must be stated before the material is chosen.
Are inserts and overmolding possible?
Inserts and overmolding can integrate different materials or functions, if design and process allow. Compatibility, adhesion and thermal expansion must be assessed. Color, texture and any subsequent operations must be defined and verified on samples.
What should be checked before starting series production?
Sampling makes it possible to verify dimensions, assembly, appearance and functional requirements. The control plan identifies critical characteristics and acceptance criteria, linking them to the material and drawing revision.
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