Prioritise functional characteristics
Not every dimension is equally critical. The decisive characteristics are those that determine assembly, sealing, movement, bearing function, electrical performance or installed position.
Precision Injection Moulding
Precision Injection Moulding for Dimensionally Accurate Functional Parts
When precision injection moulding is the right solution
Precision moulding is required when a part must guide, seal, snap into place, support, position, insulate or fit precisely during assembly. In these applications, meeting drawing dimensions alone is not enough; the function-critical characteristics must remain controlled in production.
This requires material, geometry and tooling to be aligned early. Wall thicknesses, flow paths, gate position, parting line, demoulding and access for inspection all influence what tolerance level remains realistic and economical.
What influences dimensional accuracy in injection moulding
Plastic parts change during and after moulding. Shrinkage, post-shrinkage, moisture absorption, fibre orientation, temperature control and warpage can affect fits and functional surfaces – sometimes by hundredths of a millimetre.
BERGER therefore does not treat precision as an isolated drawing dimension. The entire technical chain matters: cavity design, mould inserts, cores, sliders, gating, venting, mould temperature control, ejection, process window and inspection strategy. Only when these factors are aligned can tight specifications be met reliably in production.
Tooling details determine repeatability
On precision parts the critical points are often details of the mould: parting lines across visible or sealing surfaces, core shift, flash, slider position, ejector marks, local overpacking, or weld lines in functional areas.
BERGER therefore aligns the tooling concept and mould trials with the part's final function. The goal is not just a dimensionally accurate first sample, but a process that remains stable from cavity to cavity, batch to batch and after mould restarts.
Typical precision requirements
Assess tolerances realistically
Tight tolerances must be compatible with the material, geometry, mould design and measuring method. Where necessary, the tolerance concept and inspection strategy are refined before mould manufacture begins.
Match tooling and process
Tooling details determine whether function-critical contours can be reproduced consistently across cavities, batches and production restarts.
Define an efficient inspection scope
Inspection characteristics should be selected so that function-critical deviations can be detected with a technically and economically appropriate level of effort.
From critical characteristic to stable production process
The focus is the function of the production part. Critical characteristics are identified early, addressed in the tooling and process, and monitored systematically throughout production.
1
Clarify part function and installation conditions
BERGER reviews the drawing, 3D data, samples and the application together. That shows which dimensions, surfaces and contours matter for function or assembly.
2
Develop a production-ready tooling concept
The number of cavities, gating, parting line, cores, sliders, venting, mould temperature control and demoulding are matched to the critical characteristics.
3
Safeguard mould trials and production
Process windows, correction loops, approval criteria and measuring methods are defined so that dimensional accuracy and function can be verified not only on samples but throughout ongoing production.
Precision is proven in the finished part
Precision is not judged by the tightest individual dimension, but by how the function-critical areas work together. Fits, sealing surfaces, guides, snap features and thin-walled geometries must remain stable across production runs and batches.
Questions about precision injection moulding
For plastic parts with function-critical geometries, close fits, sealing or guide surfaces, snap features, thin-walled sections or other characteristics where dimensional accuracy affects function.
Part geometry, material, tooling concept, gating, mould temperature control, demoulding, measuring method and process stability. The drawing defines the target; whether that target is production-capable depends on the engineering of the entire process.
Many later corrections are necessary because material, geometry and tooling concept were not considered together early enough. Early assessment identifies risks before tooling costs are incurred or the production ramp-up is jeopardised.
Yes. Existing moulds and parts already in production can also be assessed for dimensional accuracy, process window, inspection characteristics and correction needs. Critical characteristics can then be reviewed systematically and stabilised where necessary.
Through function-related inspection characteristics, defined approvals, stable process windows and in-process checks. The focus is on characteristics that matter for assembly, function and the application.
