After the design prototyping stage of product development is complete, clients need to decide on their manufacturing strategy. For plastic products, they have a few options-
- Injection Moulding- the most common type of manufacturing method which includes creating a metal mould and injecting the chosen plastic into it repeatedly. For large quantities (>10,000 pieces) this is the most economical manufacturing method.
- Thermoforming/Blow Moulding- this method is used in certain cases where hollow items need to be created. This also involves using a metal mould and using hot plastic and air (pressurized or vacuum) to form the product into a particular shape. This is economical when the quantities are large.
- Silicone Moulding and Resin Casting- this is most commonly used in small batch production. It includes creating a master (using CNC or 3D printing), and then making a silicone mould based on it. The mould is then poured with a resin to make solid plastic products.
In the case of injection and blow moudling, the main downside is the mould cost and time. Depending on the shape of the part, the mould can cost upwards of $2000 for small parts. Moulds for larger, more complex parts would cost significantly more. Additionally, these moulds take multiple months to prepare. The moulds are generally long lasting and can be used to manufacture over hundreds of thousands of parts with minimal maintenance. Thus, it is really viable only when the quantities to be produced are high. However, after the mould is created, the per piece cost is extremely low and each piece is often produced in under a minute.
Thermoforming is only possible for certain part shapes and this also involves creating a (less expensive) mould.
Silicone moulding and resin casting is viable for smaller quantities because making the silicone (instead of metal) mould is much quicker (moulds are made in a few days) and cheaper (silicone is cheaper than metal). The downside is it is fairly labour intensive, each part takes hours to be formed, and depending on the materials used, moulds have a much shorter lifespan (usually 50-100 pieces per mould).
There is a large market for clients who want to create between 100-1000 pieces of their product before committing to the costs and timelines involved in injection moulding.
There are also many clients who don’t need tens of thousands of pieces of their product but are forced to make them because of the minimum order quantities of many injection moulding manufacturers. Producing larger quantities than required also stifles innovation and product upgrades because sales teams are incentivized to sell off old inventory of outdated products.
There is also the case where spares and parts are required for repairs through the lifecycles of products. Companies often commit to manufacturing and warehousing spares and other parts in case of requirements by customers. Large customers also commit a certain project cost towards buying and storing spares in case the manufacturer isn’t able to supply parts in the future after they deem products to be outdated.
All these issues can be mitigated by 3D printing. Only the master 3D file would be required to produce on demand manufacturing without having to worry about investing and maintaining expensive moulds. Warehousing and transportation costs would be significantly reduced as a result of on demand manufacturing.
Case Study 1
Assuming an order for 500 of the following ‘reset’ buttons is received.
In order to complete the order, we can compare the costs and timelines between using either 1 filament 3D printer (most filament 3d printers, 1 resin 3D printer, a moulding and casting setup with 5 silicone moulds (assuming each mould can handle 100 casts), or 1 metal injection mould.
Overall project timeline for 500 pieces assuming 1 3D printer/ 5 silicone moulds/ 1 metal mould
This shows that resin 3D printing should be chosen by the manufacturer because it would produce the parts at the lowest cost and in by far the quickest amount of time with probably the highest part quality.
A reduction in quantity would increase the competitive advantage of 3D printing even more. In order for injection moulding costs to fall below that of resin 3D printing, the order quantity would have to be 3000 pieces. And even then, the timeline would not be comparable (16 days for resin 3D printing vs 2.5 months for injection moulding).