5 Tips for Saving Time and Money on Your Mould Tool

By Saleem Shariff

It is completely unacceptable in today’s world of rapid product development and just in time manufacturing, that it can take up to eight weeks to produce a mould tool for injection moulding.  The problem is even worse for those manufacturers who are prototyping new products or parts, for those who need a supplier to bridge a gap between launch and full manufacturing, those who need to cover a short-term peak in demand or who want to launch a new product who are unable to predict demand.

cnc machine

So, with product development and manufacturing lead times constantly shortening, what can design engineers do to reduce the time and cost involved with making a mould tool?

1. Feature by Feature review

Begin by analysing what you must have in your design and what you should avoid; and then consider the best method of achieving this from your mould tool.

Try and eliminate undercut features, these complicate and in some cases prevent part injection.  If that’s not possible, perhaps because you need a side action, sliding shut off or pick off, then consider an alternative solution such as sliding shutoffs, pass through cores or change the parting line and draft angles to provide an easier mould build.

2. Choose your finish carefully

Do you really need a high mould polish, textured surfaces or moulded part numbers?  Sometimes, if you are supplying the aerospace or military applications, then your answer may be yes.  If not, then they can add to the cost of your mould tool.

3. Don’t dodge the draft

There are some features that you need to design into your mould and in this instance an injection moulder would tell you not to dodge the draft. What does this mean?  If we look closely at an ice cube, they have tapered edges, or a draft, so that you can get them out of the tray.  It’s the same for injection moulded parts, you need to allow for some draft to make it easier to eject the parts.

mould being removed from a machine
4. Plan for modifications

Getting your mould right first time for the finished part may not always be possible.  If you are prototyping a part, then you may need several iterations of the design to test before coming up with a final version.  To plan for change, you need your design to be metal safe.  This means that you can remove metal from the mould, but not add it.  Or in reverse you start out with less plastic and can add it into the later designs.  So, you may be able to thicken a wall, but not make it thinner, you can add features such as bosses, raised text, or ribs but not remove them and you can reduce the diameter of a hole or even eliminate it - all by adding plastic in later versions.

5. Consider Aluminium moulds

Aluminium moulds are more affordable than steel, plus they’re easier to modify. Steel moulds are traditionally made up of several smaller pieces that fit together like a jigsaw – which means that if you want to make a modification you’ll have to get the whole tool remade. Aluminium moulds are normally produced in just two parts – the A side and the B side, so modifications can be made (within reason) by machining on top of the existing mould. It’s also worth asking your supplier whether they offer a lifetime guarantee for your mould – so you can be sure the mould will last the duration of your project.


Want to know more about injection-moulding at Protolabs? Request your free interactive quote and you’ll have it returned within 24 hours – and we’ll provide a design for manufacture analysis.