Technical parts in engineering plastics: machine or injection-mould? The choice whether one should realise an engineered part in plastics by way of injection moulding or through machining is not merely to be traced back to the issue of serial quantities.
Technical requirements, engineering of the part itself design considerations. service in supply as well as economic factors come into consideration.
It is very worth while indeed, to weigh both production methods' con's and pro's, as well as considering the part's dimensions and performance requirements.
Parts machined from stock shapes
Pros
- Economic for small or medium call-off orders
- Flexibility in production
- Short-term delivery
- High precision possible (narrow tolerances)
- Excellent material properties (thanks to higher grade of cristallinity) Thicker sections and wide difference in thickness possible
- No "release draft angle"
Cons
- Machining expertise required
- Material selection limited to stock shapes availability Loss of material through machining
- More frequent control
Injection-Moulded parts
Pros
- Economic for large-series orders
- High grade of reproducibility
- Far reaching automation possible
- Coloured parts possible
- Saving material and weight
- Glossy aspect of part's surface
- Wide variety in material selection (specialities, even tailor made)
Cons
- Mould cost considerable
- Long pre-production time
- High engineering costs
- Thermal degrading of material possible
- Post-matching sometimes required
- "Release draft angle"
- Material properties may be negatively influenced by production method
Far from being exhaustive, we believe that above parameters of selection will be a good help in guiding you into selecting the best production method, being either machining or moulding.
