Think Plastics

Think Plastics answers common questions about injection moulding: what a mould costs, how long it takes to make and how long it lasts, and how to design a part so that it moulds well. It is written for product designers, engineers and buyers who are getting a part made for the first time.

Each article opens with a short answer, then gives the published figures behind it. Every figure is credited to the supplier, design guide or standard it comes from, so you can check it and judge it for yourself. Figures are typical planning values, not specifications. For a real part, the material supplier's data sheet and the toolmaker's review always come first.

Articles

How much does an injection mould cost?: Published price ranges for injection moulds, the features that move a quote, and how to compare two quotes fairly.
What production volume suits injection moulding?: How tooling cost spreads across a production run, where published break-even points fall, and how to run the sum for your own part.
How long does an injection mould last?: SPI mould classes, published shot counts for aluminium and steel tools, what wears a mould out, and what to ask for in writing.
Should I choose an aluminium or steel injection mould?: When an aluminium tool is enough, when steel earns its higher price, and the bridge option in between.
How long does it take to make an injection mould?: Published build times for prototype, bridge and production moulds, what the quoted date really covers, and what stretches it.
How many prototypes do you need before manufacturing a product?: The prototype stages most products pass through before tooling, what each one must prove, and how to choose the right prototype method.
What is the minimum wall thickness for injection moulding?: Published wall thickness ranges by resin, why flow length sets the real floor, and why uniformity matters more than the minimum.
How much draft does an injection moulded part need?: Published draft angles by surface finish, texture depth and feature, where the sources disagree, and how to check a design.
What causes sink marks in injection moulding?: Why thick sections sink, the published rib and boss proportions that help prevent it, and what the moulder can and cannot fix with process settings.
What tolerances can injection moulding hold?: Published commercial and fine tolerance values, why resin, size and the parting line limit them, and how to put tolerances on a drawing.
How much do injection moulded parts shrink?: Published mould shrinkage by resin from three sources, why they disagree, and why the shrink value is built into the mould itself.
What is the most common injection moulding plastic?: Why ABS and polypropylene are the default choices, how they compare on fit, finish, hinges and cost, and how to choose between them before the mould is cut.
What size press does my mould need?: How to estimate clamp tonnage from projected area, with worked examples, plus the shot-size and mould-fit checks that also decide the press.