Eight Ways To Save Money On Moulded Parts

We’ve never met anybody who said, “My parts are manufactured too cheaply. I need to make them more expensive.” Sourcing quality parts at the lowest possible cost is almost always a priority for businesses. Here is a countdown of the eight most important keys to ensure the lowest cost per part when it comes to injection moulding.

8. Reduce part size wherever possible

The bigger the part, the larger the mould. Not only does this require more mould-grade metal like aluminium or steel, but it also involves more machining to make the mould. Since mould cost is amortised by the number of parts produced, expensive moulds can drive up costs significantly, especially on short part runs. Besides, large moulds call for bigger moulding machines and more raw material, which translates to higher shift rates and input costs. Reducing the size of the part goes a long way towards avoiding all this.

Reducing part size can help save costs in more ways than one.

7. Stay metal safe

There’s a saying in mould making: you can add plastic, but you can’t add metal. This refers to the fact that it’s very complicated to add metal to a mould, but comparatively simple to subtract metal from it. Smart mould design plans for this by starting with the smallest possible design – this allows the same mould block to be re-machined a few times over to accommodate design revisions, instead of starting with a new block each time.

It’s easier to add plastic than metal. Stay metal safe by erring on the smaller side for part dimensions.

6. Put function before form

Everyone likes shiny parts, but the tooling to deliver stylish aesthetics and surface finishes may require spark machining (aka electrical discharge machining), abrasive blasting, diamond buffing, and even polishing and craftsmanship by hand. These processes drive up costs significantly, as do the addition of logos and part numbers that have to be machined into the mould. So unless such features are absolutely essential, avoid them.

Parts with high-gloss surface finish and lettering / logos tend to increase tooling costs.

5. Cut out undercuts

The design feature that most commonly increases tooling costs dramatically is the undercut. Undercuts are recessed surfaces that make it impossible for a part to be moulded with a single pull mould. Undercuts drastically drive up costs by necessitating complex geometries, removable / collapsible cores, or multi-plate construction. In most cases, designs can and should be modified to avoid undercuts, and doing so translates to big dollar savings.

Avoiding undercuts wherever possible makes tooling simpler, faster and cheaper.

4. Simplify, simplify

With CAD tools and software becoming more accessible and user-friendly, practically anyone can create a 3D model – but it takes a skilled, experienced designer to know what not to do, and how to design for excellence. Modularising parts to make them interchangeable, standardising sizes, maximising self-mating hinges / attachments, and reducing the total number of parts are all important methods that add up towards cost saving.

Simplifying part design through a good DFMA review process saves time and money on the part and downstream operations.

3. Choose the right material

Material selection impacts not only input raw material cost, but also costs such as inventory carrying cost, and moulding costs due to cycle time. When designing a new part, most people prefer to stick with materials that they’re already very familiar with, but it’s important to evaluate whether that’s really the best option.

A material or grade that’s commonly available in one region can often be difficult and expensive to source in another region, or a manufacturer may be able to offer better rates with an alternative material thanks to economies of scale. Exotic, hard-to-source materials can be expensive, and new materials are continually being released, so it’s prudent to explore whether material substitution can offer cost advantages – with or without a trade-off in part performance.

Choosing the right material can make the difference between a cost-effective, quality part, and an expensive, bad part.

2. Match mould and volume

Probably the area with the highest potential to deliver savings is planning production volumes. Having a road map in place with clearly chalked out volumes is the best way to ensure maximum ROI on tooling. Depending on the exact design of your parts and the volumes required, your manufacturer can help you decide whether or not to use a family mould, a multi-cavity mould, or a mould with removable inserts. While opting for the simplest single-cavity mould may seem inexpensive at the outset, inadequate planning can lead to hugely expensive retooling costs when you want to scale up later.

A higher grade tool with 100% more yield can often cost just 30% more than a lower spec tool.

1. Maximise volume

It sounds obvious, but increasing volume for a part’s planned in-production lifecycle is by far the most effective way to lower costs per part. While a mould made of an intermediate grade of steel may deliver up to 500,000 shots, moulds constructed of higher grade, hardened steels can often yield in excess of 1 million shots. This 100% increase in output generally requires just a 30% increase in tooling cost. Of course, there are also benefits thanks to the efficiencies of scale, such as better rates on raw materials, and optimised loading and batch times.

Bonus: Yes, the headline promised only eight tips, but in the spirit of getting more for less, here’s another pro sourcing tip.

Location, location, location

When choosing a contract manufacturer for prototypes, small-volume parts, or full series production parts, keep in mind that your supplier’s physical location is often a major cost influencer. Finding a supplier who is closest to you may sound like it’s the most convenient option, but it’s not always practicable or cost-efficient. Huge industrial cities like those in China, Europe or North America bring with them expensive overheads for land and manpower – which the manufacturer passes on to you. Engineering Plastics’ facilities are located in Mysore, India, one of the world’s most cost-effective manufacturing centres, that also enjoys a highly skilled, English-proficient workforce.

If you’d like quotes, suggestions or advice on your next project, we’re always happy to hear from you. Ask for a free manufacturing assessment and quotation, or write to us at enquiry[at]engineeringplastics[dot]in, and we’ll get back to you.