Injection Moulding
Injection moulding is a manufacturing process where molten material is injected into a mould to form a part. Some of Oltó’s made to manufacture (MTM) components will be produced via injection moulding. All of these parts have been designed with injection moulding principals and limitations in mind. 
Here is part 45 (top plate), a clear example of injection mould friendly design. There are no over hangs, draft angles are used for easy part removal, everything has an appropriate radii and the average wall thickness is 2mm. The recommended wall thickness for using ABS is 1.143 – 3.556mm (Protolabs, 2020).
Above are examples of what the steel mould tooling is likely to look like.
Careful consideration was put into the development of each injection moulded part, making sure they were appropriate for tooling. Some parts were even split into two to achieve this. Above shows parts 8 and 9 (exit pipe left and right).
Technical Implications: One mistake I made was not using chamfered edges for flat walls and holes. I had planned to put chamfers in at the end of the design process, however I learnt that for intricate parts, this can be very complicated. In the future, I will design in chamfered edges as I go.
Alternative methods to Injection Moulding (SLS)
Selective Laser Sintering (SLS)
SLS 3D printing is a rapidly growing market for manufacturing products. Unlike previous 3D printing methods, SLS does not require support material as it is self-supported by its powder additive. This allows for high quality finishes straight from the print bed. An entry level injection moulded part is going to be significantly more expensive to produce than it would be in a 3D printer (Rogers, 2015). This is because of the expensive custom tooling that is required for injection moulding.
SLS printing was however not chosen for the following reasons:
- Although SLS printing is cheaper at first, injection moulding is cheaper in the long run once the cost of tooling has been paid off.
- SLS printing is a lot more time consuming than injection moulding meaning it will slow down production.
- Powder needs to be removed from SLS parts once printed. This job is more time consuming than inspecting an injection mould meaning more staff will be required. This will increase costs.
Rotational Moulding
Rotational moulding produces hollow parts, making it the ideal process for making products such as bins and kayaks (Spence, 2018). This means that components such as the exit pipe would not need to be split in two parts, reducing costs substantially.
- It is challenging to include extruded holes in the design.
- The wall thickness cannot alternate throughout the part.
Laser Cutting
Laser cutting is a manufacturing process that slices sheet material into specified shapes using a laser. Some of the smaller MTM components in the design will be laser cut.
Above shows part 17 (gear cover one). This is a good example of a laser cut component.
Technical Implications: One of the flaws of laser cutting is the waste material produced. Parts will be aligned in the most efficient layout to reduce this as much as possible, as shown above. Despite the waste material, laser cutting was chosen because it is cheap and fast.
Alternative Methods To Laser Cutting
CNC routing
A CNC router in some circumstances can provide a better finish than laser cutting. It is also much faster than a laser cutter when cutting thick material. When using acrylic, CNC machines do not provide the same smooth edge as a laser cutter would, but for this product, one could argue that this is not an important feature as all the laser cut components are for engineering purposes and will not be seen by the consumer.
- The smallest standard drill bit for a CNC router has a radius of 1mm. As some parts are being cut to fit to a 3mm D shaft, the 1mm radius corner will cause implications to the fit, meaning design changes will be required.
- CNC routing is more labour intensive than laser cutting. Clamping down material, for example, and the care that needs to be taken in doing so, takes time and effort (Oshkosh, 2017). This will increase costs.
Tig (Tungsten Inert Gas) Welding
Tig Welding works by melting the face of the two steel components being joined. The heat is generated by an electric arc formed between the base metal and the tungsten electrode. Tig welding can be completed with or without filler metal.
Tig Welding will be used to alter OTS steel tubes into MTM parts. Notice the overhangs that have been welded to part 55 (main body unit 2) shown above. These features are vital for the final assembly of the product.
Production Mistakes (Technical Implications)
Despite the quality of the production line, it is always plausible that mistakes may be made. All products should be electrically tested at the factory to ensure that only quality products get shipped. This saves time and cost by allowing correction or rework of a failing product before shipping (Crotti, 2018).
